Condensing vs Modulating / Condensing

jt3

Gentlemen,



 After suffering through the cost of heating oil for the last couple of years I’ve finally decided to switch to a gas boiler.  Found “The Wall” while trying to research

residential gas boilers.  I want to thank Dan for hosting the site and everyone in and out of the trade who answer questions, especially from those of us who “haven’t got a clue.”  This is one of the few forums I have read where there seems to be good give and take on the discussion without things getting heated. (no pun intended).  You can disagree without being disagreeable. It’s a nice change from some other types of forums I’ve read.



 After reading the Wall for about a month and researching boilers I had kind of narrowed down my prospects to 4 or 5 mod/con boilers in the 95 / 96 percent range.  The final deciding factor would be the installer and which ones he preferred to work

with. 



 Yesterday one of the contractors I had called got back to me and after asking a few questions about my house and current system, through a monkey wrench into plans and suggested a non modulating condensing boiler.  (He was talking Weil McLain boilers at 91% efficiency so probably a GV90+)  His reasoning was:



It would probably save me $1,000 to $1,500 on the installation



Boiler is easier and cheaper to service & maintain



Life expectancy is almost double the mod/con boilers



While the mod/con would be a little cheaper to operate, the difference would not be significant.



Between the difference in the initial cost and higher service costs, the mod/con boiler probably won’t last long enough to reach a break even point in the investment.



The more I thought about it, the more I wondered if he was correct.  If the mod/con could be setup to provide 96% efficiency all of the time (which it probably wouldn’t) and the straight condensing boiler provides 91% efficiency (which it should if I

understand the concept correctly) it is a maximum 5% difference in efficiency.  If I spend $100 on fuel, the mod/con boiler would save me $5.00 over the non-modulating boiler.  Based on this years cost for fuel, I’m figuring around $1,800 if I convert to gas.  If that is anywhere close it would mean that the mod/con boiler would save me about $90 a year over the straight condensing boiler ($5.00 x 18). 



 Two questions:



Are the reasons for NOT going with a mod/con boiler valid?



Is my thought process on the $5.00 difference per $100 spent

valid or am I missing something major?



 I won’t go into all of the details of the heating system unless someone wants them but it is a 100 year old  2 story NE Colonial with 2 zones for heat, (approx 65’ total SlantFin baseboard split 40’ & 25’ for the heating zones) and a zone for an AMTROL 40 gallon indirect hot water tank.  Current boiler is a Weil McLain P466 HEWT,

144,000 BTU.  Going with a mod/con I was figuring around 105,000 BTU input. 

(Rough heat loss calculation from an Excel spreadsheet I found on line

came out to just under 45,000 BTU/hr which doesn’t include anything for the

DHW.  Might be a little low but I figured the 105,000 BTU should handle it.)



 Thanks for any input you can provide.

Paul48

105

That would be way over-sized for a mod/con. Your baseboards total are under 40000 btu's. You'd short cycle like crazy.Not to mention, that load is split between 2 zones.

PeterNH

oversized - short cycling

Hello JT,

Sounds like you have a clue.

 

Are you sure there is only 65 feet of baseboard?

If it is typical stuff, it can only put out about 40,000 btu's max.

Unless you have massive needs for domest hot water, it would seem that your boiler choices are way, way, massivly oversized.



Which gets me to the problem of short cycling.

The big boiler that can not modulate, especially in mild weather, will be turning off and on canstatn;y over and over and over again.

This is where, i believe,  the best part of the mod-con is the modulating part.

Where it has the ability to reduce the fire to natch the load.

Otherwise, i agree with the cost assements.

Just don't overlook short-cycling or consider adding a bufer tank.



Peter

Paul48

If

there are any cold spots in the house, now is the time to address those issues.How many people in the home? Huge hot water demand? If everything is good....for size, you need to look at something like the Munchkin MC50

04090

Decisions

I sent you a message about expenses and operating expenses for our house, which is similar in age and size to yours.



We chose not to go the mod/con route for the exact reasons you question, and discussing with neighbors that have mod/con feel we made a very good decision.



Once some new install things were worked out, thanks in part to the experts on this board, the new system works great (although I'm still trying tweaks) and gas consumption is way below expectations.

jt3

Update

Hi Guys,



Thanks for the answers. 



1.  Yeah, there is only 65’ of baseboard (plain old ordinary Slant Fin).  Used to be 69’ but remodeled the kitchen last year and put in a pantry which necessitated shortening the one in the kitchen so I could put in a door.  After talking to someone yesterday I may see if I can add a little more on the first floor to make up for the loss in the kitchen.  Upstairs has plenty of heat with the possible exception of the bathroom where I may see if I can put in a short piece.  Like a lot of old houses, the biggest problem is access and open wall space. 



One question I asked the contractor who was here yesterday was about the basement.  Being an old house it is fieldstone with a concrete floor.  Currently the only heat in the basement is heat loss from the boiler and hot water tank and a second refrigerator.  I haven’t actually put a thermometer down there but it normally is

probably between 55 and 60 in the winter unless we get a really cold, windy spell when it may drop down to 50 degrees or so.  Replacing the old oil fired boiler with a gas fired one will significantly reduce the amount of “lost” heat since there will be very little loss from the gas boiler.  His recommendation was to get on old radiator and plumb it on a by-pass to the return lines from the two heating zones.  Put a zone valve on the return line that would close and force water through the radiator when a cellar thermostat called for heat. 



This should do two things.  Keep the cellar warmer and help to keep the return water temp low enough to stay in the condensing mode.



2.  Peter, define “massive” needs for hot water.  There are 4 adults.   My wife, 2 adult daughters and myself.  All of the females like long, “hot” showers.   Redid the showers a couple of years ago so both now have anti-scald valves which allow 2 people to take showers and both to have hot water.  It’s much nicer than being in the middle of a hot shower and having it go ice cold.  Shower heads are both 1.6 gpm heads with valves that let you reduce the flow at the head. 



Not in my original post but one contractor had suggested I get a small, instant type hot water heater to feed the AMTROL and said it would be cheaper than running a DHW zone on the main boiler all summer.  The contractor yesterday said the first one

needs to learn about mod/con boilers.  The mod/con boiler should be in condensing mode almost constantly since the AMTROL is set to 125 degrees.  The tankless

units usually run at a lower efficiency.



This is getting long so will cut it here but will keep the board updated as things progress.

Zman

Mod con

I think your idea of a 105 mod con is perfect. A non modulating boiler will short cycle excessively. The mod con will likely have a low end of 20,000 btu. It will run at peak efficiency at this rate. It looks like this is almost a perfect match with one zone calling.As for the DHW I think the 105 will work well. If you measure the GPM of your showers and you know the temperature of the water coming out of the ground this can be easily calculated. I would recommend a firetube style modcon like the Triangle Tube. They are lower maintenance and require less energy in circulators. Lochinvar,Dunkirk and others have similar designs. 

PeterNH

Massive ? possibly.

Hello Jim,

How long is the typical duration of the hot female type shower?

Is it common for 4 showers to occur 2 at once and then 2 more right away?

While doing laundry at the same time?

I think 105 is rather large.  Depending on the above answers.

As ZMan mentioned, Any idea of the water temp. coming into the house?



Peterr

Zman

Quick math

A boiler with 105,000 input running at 88% efficiency at sea level will have an output of 92,400. If you assume a shower will be 100 degrees and the incoming water from the city will be 50 degrees the numbers look like this: 92,400/500= 182.8 GPM per degree. 182.8/50 degree delta t= 3.65 gpm of warm water to the shower. With 1.8gpm low flow valves you can run 2 showers forever without running out. With old high flows maybe just one shower. The 40 gallon tank can act as a buffer for when the loads are greater. Yes your system is oversized for heat but unless you plan on putting in a larger DHW tank, I think it is pretty close for DHW.

Zman

Short cycling

To answer the 5% efficiency question. A non modulating boiler in your application will short cycle to the point where it will greatly reduce efficiency.

jt3

2nd Update

Thanks ZMan & Peter



Have a proposal / quote coming in the next week or so from a contractor that stopped by the other day. He says they use primarily Utica and Triangle Tube boilers.  He likes the Utica SSC condensing boilers.  Will see what he recommends when I get the info.  He checked the current boiler and hot water setup.  I gave him all of the info on the room dimensions, insulation, number, size and type of windows in each room, ceiling height, current baseboard etc. so he should be able to do his own heat loss calculations.  Will be interesting to see what he comes up with.



On the DHW aspect I should have mentioned that the AMTROL is, in theory, a backup to a closed loop Solar hot water system.  I say in theory because the solar system is

antiquated and not too efficient at this time.  It is one of the “King” solar systems that Sears was installing back in the early 80’s.  Two 4x8 panels with a 110 gal Sepco Solar Tank.  Tank had been replaced once under warranty and I replaced it with an 80 gallon how water tank with external heat exchanger about 3 years ago.  Unfortunately, I wasn’t familiar with flat plate exchangers at the time and went with a small shell and tube heat exchanger which works but not as well as it could.  I am in the process of deciding what size flat plate exchanger to go with and will change that,

hopefully this spring.  On a nice clear sunny day I probably get a tank full of water in the 90 to 100 degree range.  On a cloudy, 35 degree day like today it probably brings the temperature up 10 degrees or so.  Glycol gets drained every 3 or 4 years and

the system gets flushed with fresh water until everything runs clear.  It then gets refilled with Cryotek (sp?) 100.  Replacing the heat exchanger should help but I’m not sure how much longer the panels will last.  They have to be getting near the end of their “life cycle.”



With the old Sepco tank we used to run out of hot water.  Since changing over to the AMTROL I don’t think we ever have but it is the difference in electric backup which

had slow recovery and oil fired backup through the AMTROL which is much quicker.  It is just getting to the point that I can’t afford the oil and I don’t see the price dropping and staying down in the future.



Question on mod/con theory since I had never heard of this until a month or so ago.  Is the idea that in a perfectly balanced system that the output from the radiators (used generically) will perfectly match the buildings heat loss thus maintaining a constant temperature?  Since “short cycling” is inefficient, the idea is to have the boiler run almost constantly but at a much lower rate, just at or very slightly above the heat loss calculated from the outside temperature? 



Thanks again for this board and all of the information you provide.  As a homeowner I have done a lot of my own maintenance and repairs over the years but messing around with gas is not going to be one of them.  That doesn’t mean I don’t want to know how things work.  I want to know if a contractor I hire is doing things properly and I think this board has helped in that respect.  I will at least  read the installation manual for whatever boiler gets installed, something I wouldn’t have thought of doing before reading posts on this board.  And the good thing is, I might even understand what I’m reading. : )

PeterNH

You got it

Question on mod/con theory since I had never heard of this until a month or so ago.  Is the idea that in a perfectly balanced system that the output from the radiators (used generically) will perfectly match the buildings heat loss thus maintaining a constant temperature?  Since “short cycling” is inefficient, the idea is to have the boiler run almost constantly but at a much lower rate, just at or very slightly above the heat loss calculated from the outside temperature? 



===================

Yes. That's it

The idea is to have just enough gas flame, to heat the water just enough, to match the heat loss of the house to the heat generated by the boiler.



Some guys here like to use an automobile cruise control analogy.



I like to think of it like a pot of pasta boiling on a gas stove. Keep adjusting the gas, exactly perfectly, so the pot is boiling at the max but it never boils over.



Peter

gennady

mod con

WM GV+ not modulating , does not have outdoor reset, it is just cast iron weil mclain with stainless steel cooler on the side, why bother, just install regular hot water standard efficiency boiler , they prove to be easy sell, proven 50 year old design, and very cheap. WM come up with GV series as a mockery of high efficiency , just to give cheap boiler, with high efficiency rebates possibilities from utility company, so unqualified contractors could sell it under 90+ % efficiency to uneducated consumers. This puts a shame on formerly reputable boiler manufacturer.Just my 2 cents.

jt3

Followup on Install

Gentlemen,







New boiler installed about a month ago.  Went with a Triangle Tube Prestige Solo

110.  Made sure it had the new control

unit.  Had a problem finding a local TT

installer so I went with a local company with a good reputation.  After I had hired them and the boiler was

installed I found a local person who has been to the TT classes so I had him

check out the install and fire off the boiler when the gas company finally got

around to installing the gas meter and turning on the gas. He pointed out

several things that he would have done differently but not anything that will

cause a problem.  So far everything seems

to be OK although at close to 100 degrees for the last 3 days, I don’t really

need a boiler right now.





 After reading the manual, looking closer at the install (and

reading the board) I do have several questions.





1.     

On my old boiler, the circulators were on the

return (cold) side of the zones.  If I am

looking at the piping correctly (water flow is from the bottom to the top of the

heat exchanger), the new circulators are on the output (hot) side.  Does it make any difference and is there an

accepted standard or is it up to the installer?





2.     

The AMTROL is labeled “Boiler Return” and “Boiler

Supply.”  I would interpret Boiler Return

as going to the boiler and Boiler Supply as coming from the boiler.  If that is correct, the installer plumbed it

backwards.  (Hot water from the boiler is

pumped into the Boiler Return)  Where it

is feeding a simple coiled heat exchanger will it really make any difference?





3.     

Somewhere on the board I read that hot water

tanks should be maintained at 140 degrees to prevent possible “legionella”

  Is this really a problem for

residential tanks (Town water not private well water) that get a complete water

change daily or does it apply more to commercial applications.  Should the setting on the AMTROL be at 140

degrees.  (Which would make my wife happy

since if she can’t scald her hands, it’s not hot enough.)





 Thanks again for the help and once I get into the heating

season I’ll try and post info on how its running.





 Jim

gennady

picture

is this a picture of unfinished job?

jt3

3 Zones Plumbed

Yes, these shots show the 3 zones before the main water feed and the condensate drain were installed. Figured these pictures would show the plumbing better than the ones I took after the job was done and all the black foam insulation was in place. In those shots the insulation makes it difficult to follow the piping.



Jim

gennady

dhw temperatures

I alwais set tank temperatures over 140F, like 150-160F, to deal with legionella first, then it increases thermal capacity of the tank. In NYC domestic hot water mixing valve must be installed according plumbing code, so domestic water temperature is tempered to 120F anyway. Also, on the system side of the circulators shut off valves have to be installed, so if repair needed in the future, you do not have to drain whole system.

gennady

pumps

what model # of pumps installed?

what is length of longest run of the zone? what is load on each zone?

how is flow trough the zone controlled?

was outdoor reset sensor installed and activated?

jt3

Gennady,

The AMTROL has a plastic liner (poly?) with a recommended max temperature of 150 degrees.  Didn’t have a mixing valve on it because it was only set to 125.  Will have to install one and boost the temp to 140. 



 Pumps are Taco 007 F5 7IFC

House is an old 7 room NE Colonial. Boiler is in the basement. Estimate the first floor zone to be between 100 and 110 feet in length with 45 feet of standard Slant Fin baseboard.  Second floor zone is about the same length with 25 feet of Slant Fin Baseboard.



There is a Taco pump for each zone plus one for the indirect hot water.  Thermostats are Honeywell Electronic Heating and Cooling ($25 to $30 at Lowes 2 years ago) wired for heating only.  (no central air)



Outdoor reset was installed and activated (which brings up another question I forgot to ask).



 If I understood the manual correctly there is a setting where you can have the boiler shut down once the outside temperature reaches a certain point.  I believe it stated that the default setting for this was disabled.  Once we no longer need heat I set the thermostats to hold at 55.  (This happened prior to new boiler installation.  When the boiler was fired off the tech did have me kick the thermostats up to make sure they activated the boiler.)  To the best of my knowledge, the boiler has only run for hot water.  When I checked the pump model a few minutes ago, the boiler was in Standby with output and return temperatures of 78 and 76 degrees.  Would there be any advantage to setting a shut down temperature of say 50 degrees (outside temp) or is this system only going to come on when there is a call for heat?



 Example: Outside temperature 40 degrees.  Thermostats set at 68.  Due to solar gain through windows and other internal heat sources (refrigerator, stove, electronics etc.) the inside temperature is 70.  Will this boiler maintain a minimal water temperature based on the outside temperature and the programmed “heat curve” or will it remain off as long as the thermostats are not calling for heat?



Thanks,



 Jim

gennady

pump

WWS warm whether shutdown function , when this function is turned on and set to certain outdoor temperature, it shuts down heating operation of the boiler upon reaching this temperature. some boilers like Viessmann vitodens 200 have much more complicated WWS function, but most of condensing boilers do it this way.



Regarding your pumps , there is more issues with the way it is done.

Condensing boilers work best when temperature of return water is below 130F, and lower return water temperature improves efficiency. At 132F boiler condenses partially and at 120F or 110F boiler condenses better. So it is best to bring water temperature as low as possible.

It means that delta T (difference between inlet and outlet baseboard temperatures) has to be as high as 40F. In standard baseboard heating applications it is 20F.

In worst case scenario @dT=20F and 1 gallon per minute water flow, heat rejection from 1 foot of baseboard will be 510 BTUHR @170F water temperature (because 170F is a medium water temperature when entering temperature is 180F, and leaving temperature 160F and dT20F) Total heat rejection from 25 feet of baseboard will be 25x510=12,750 BTUHR

Boiler minimum load is 23,000BTUHR, So on coldest day of the year when one zone only is activated, boiler will short-cycle, and efficiency will be lower then standard efficiency boiler done right. on warmer day it will be a disaster.

But on pumping issue, to get 12,750 BTUHR to baseboard, you need to pump 1.27 gallons per minute.

As per pressure drop, 135 feet total run (baseboard and piping length combined), and unknown diameter and fittings , we get 6x1.35=8.1 feet of head

Lets take a look at taco 007 curve http://www.taco-hvac.com/uploads/FileLibrary/101-029.pdf

At 8 feet of head we see 8 gallons per minute pumping.

You have to install limiting device on circulator outlet. And/or combine 2 zones into 1, and/or install buffer tank.

I do not know your heat losses room by room and ratio of radiation to load, but if you do those calculations, you might find the need to upgrade your baseboards to bigger and high efficiency to allow for lower water temperature of return water. there is much more to that.

gennady

termostat

Outdoor reset control is a space temperature control. it means you do not need thermostat. This is my opinion, and many will disagree. i see situation, where outdoor reset is used in conjunction with thermostats as driving a car with 2 people fighting for the driver wheel. one wants to turn left, another wants to turn right, one wants to stop , another one wants to speed up.. you not going to go far driving like this. loose your thermostats. problem is that outdoor reset curve for most boilers must be calculated, based on heat losses at different outdoor temperatures, and system must be balanced ( flow must be set for each loop),

you not going to get it from you plumber and definitely not from engineer

gennady

duplicate

duplicate

Jean-David Beyer

many will disagree

I do not disagree, and I believe it is the proper foundation for an understanding of outdoor reset. I have a mod-con with outdoor reset. However, I have the two thermostats (one in each zone) set to the desired temperature, but I treat them as upper-limit switches. In other words, the intent was that they would always be calling for heat unless the zone got too hot.



I then set the reset curves (one for each zone; different because one is radiant slab and one is finned-tube baseboard that is oversized, but not enough to use the same reset curve as the slab does). I set the reset curves very closely to the heat load so in cold weather, the slab zone runs almost continuously. The reset curves for my boiler are essentially straight lines, not curved (or not  very much).



In really warm weather, the thermostats will shut off. Another reason I cannot quite go with just outdoor reset is that it makes no allowance for outdoor wind speed, and the leakage of my house, though low, varies with wind speed. I have wondered about getting an electric anemometer and hooking it in with the outdoor sensor, but I am afraid that would be too much trouble. So I set the outdoor reset very slightly too warm, and let the thermostats stop the boiler if it is warm and not windy.

gennady

wind load and infiltrations

In my installations I do insist on TRV and VFD circulator, it corrects all issues with wind loads variables.

For radiant. very important to have floor surface at 85F, and space temperature has no relevance to comfort. Thermostats in radiant floors applications are nonsense in my opinion

j a_2

peternh

Peter   As in salesman/installer/serviceman all in one I think along the lines as you...Not all systems, as they are, are a good fit...I have been very hesitant at times to install mod/cons...sometimes I flat refuse...Why, because I don't want the call in the winter saying this is so much different than my old system,does not seem warm enough.  My wife/husband hates it..That is something I cant easily fix...Can I, yes, but at what cost...Cant tell you how many times I have been to homes of complaints like this..Stick in the analyzer and cant even get a good reading without short-cycling,unless I lock it in a mode...That is not correct...If a couple has lived in the house for 20 yrs with nice warm rads or emitters of any kind and you go in and cool them down chances are you will get the call,if someone never lived in the house and its there first heating season they may be o k with it..I agree a completely correct installed system will work, but at what cost..When push comes to shove I go with cast iron,and a boiler bypass,a poor mans outdoor reset if you will....This subject can go so deep with all new ideas...But as Dan always says we are in the business of comfort...I continue to seek the perfect answer but as of yet only with steam is that obtainable..Size it pipe it vent it..How easy is that...I know not all will agree but I truly think we as a whole are not as prepared as we should be with the mod/cons yet...I have read report after report and still have questions...j a

jt3

Gennady & J-D

Gennady,



 Not disagreeing with anything you said.  I’m sure you know a lot more about this

subject than I do.  However, I think you may be coming at it from a different direction. 

I replaced a 26 year old oil fired boiler that, when new, ran at 80% efficiency on a good day with a gas fired unit that can theoretically provide 96% efficiency.  While I plan to tweak the system and make changes (when funds allow) to get the best efficiency possible, my main reason for going with the new system was to cut overall

costs.  With the difference in fuel oil and gas prices, even at the same efficiency as the old oil burner (using the same number of BTU’s to heat the home) my fuel bill will be cut in half. 



You explained what WWS is and I have worked in buildings where thermostats were disabled and the system was controlled by the outside sensor.  If installed and programmed correctly it is probably a great system.  In the two buildings I was in, not so great.  (Uninsulated cement block / brick veneer buildings in New England don’t have the same heat loss characteristics as insulated wood frame buildings. -Grin- ) 

You didn’t say whether the WWS would make any difference in a normal residential system using thermostats for control.  (If thermostats are set for 55 degrees, once

the minimum temperatures are above 55 degrees does it make any difference

whether you are in WWS mode or not?)



 As to the circulators, you got me thinking.  The 25’ zone is the second floor bedrooms which is the least used zone.  With the old system thermostats would start calling for heat around 5:00 in the morning (68 degrees) to about 8:00 when they drop back to 62.  Around 4:00 in the afternoon they would again go back to 68 and stay there until 10:00 at night when they would drop back to 62.



On a sunny winter day with little or no wind, that zone probably has very little call for heat. Reasonable solar gain along with some heat from the 1st floor keep the temperature in the low to mid 60’s depending on the outside temperature and wind conditions.   (Did actually do a quick measurement and count of elbows on that zone and it is longer than I thought.  From output of circulator back to the boiler is approx 180’ with 19 – 90 degree elbows. That includes the 25’ of baseboard.) 



First floor zone which is the zone that would call for heat more often is probably a little longer than the 100’ to 110’ I originally thought.  Without measuring, 135’ to 150’ would probably be more accurate (including 45’ of baseboard).  If I counted correctly, there are 27 – 90 degree elbows.  That thermostat comes up to 70 at 5:00, drops back to 68 at 9:00, goes back to 70 at 4:00 and down to 62 at 10:00 in the evening.  There is almost always someone on the first floor with the second floor not occupied during the day.  I had considered going to the higher output baseboards but with close to $30,000 in expenses this year (heating system, electrical system upgrade and Title V septic) I decided to hold off on the additional expense and see how the current baseboards work out.   When your retired on a basically fixed income, that kind of puts a dent in the budget.



If the output from the Taco's is too high, what would you suggest?



 J-D



 If I understand you correctly you wire the thermostats so the circulators run constantly, keep a low boiler water temperature and only shut off the circulators when the temperature exceeds the thermostat setting.  The way I see it is you are basically doing the same thing as Gennady except you are keeping the thermostats to compensate for the unexpected increase in heat loss such as caused by strong winds.  I am assuming that both of you are setting the system to maintain a constant temperature throughout a 24 hour period.  While I am comfortable at 68 to 70 degrees during the day when I am up and around, I prefer 60 to 62 degrees when I’m sleeping. (Actually I prefer it even colder but that is about the minimum my wife will tolerate. -Grin- ) 

My only question would be: If your system is balanced out so that the circulators run almost constantly, your baseboard output has to be very close to your homes heat loss.  If that is the case, how does the system compensate for the increased heat loss on a windy day?



 Thanks,



Jim

CMadatMe

Efficiency

Your boiler system was not 80% efficient, that was your combustion or burner efficiency. A more realistic number is 65-70% and maybe even less. A condensing boiler isn't 95% efficient every day if at all either.



Constant circulation when utilizing outdoor reset is not the place for someone that wants to set back unless, the control function or heating plant has some type of boost feature to overcome deep setback. Personally I would prefer the use of indoor reset such as using this http://www.hydronicalternatives.com/getattachment/4d7f735b-c4d9-4f35-9413-e167424235ec/EM-32-Electronic-Room-Responsive-Control.aspx but would also make sure I'm installing it in the right application.



This job here in particular is pretty basic and you could do constant circulation, here I would do a Vitodens 200 with a Vitotrol 300 that provides indoor feedback back to the boiler so I am now doing outdoor, indoor reset based on real time conditions. Since this boiler utilizes a LLH or supply side temp sensor constant circ can be done easily and effectively.



You mentioned the magic word, budget and you aren't going to get this without spending some money. An option here may be a Vitodens 100 with a Como-Ot using an Alpha or a Bumble Bee zone it with Zone Sentry's, set the right ODR curve, find the sweat spot over the winter and call it a day...

Jean-David Beyer

J-D

First of all, if you think I am disagreeing with Gennady, then I was not clear enough. He is a professional, and I am just a homeowner whose experience with a mod-con is just one boiler from one manufacturer in one house. I did a lot of reading and learning, much of it here. I also have an engineering background that makes it easy for me to understand cotnrol systems, but none of it related to home heating.



"If I understand you correctly you wire the thermostats so the

circulators run constantly, keep a low boiler water temperature and only

shut off the circulators when the temperature exceeds the thermostat

setting."



That is my goal.  It works pretty well with my downstairs (radiant slab) zone that is my largest zone. About 24,000 BTU/ hour when it is 0F outside. It works less well with my upstairs (finned-tube baseboard) zone that is tiny: about 6250 BTU/hour when it is 0F outside. And it "never" gets that cold here in New Jersey where I am. Design temperature around here is 14F and it almost never gets below 10F. I calculated my heat loss because the installing contractor was too lazy to do it properly. My calculations were plenty accurate to size my boiler, but no where near good enough to calculate the reset curves.



On really cold days, my downstairs zone runs up to 18 hours a day, uninterrupted. On warmer days it gets interrupted during the day because the outdoor temperature rises faster than the slab can cool off, so the thermostat cuts off the heat. I use no setback at all in the radiant zone. For an on-grade slab, it would make no sense.



I do use about 2F setback upstairs because I am not usaully up there at night, and baseboard heat can recover from setback in 2 to 4 hours where the slab takes between 4 and 24 hours, depending on how much setback is used. If I ran 180F water in the baseboard, it would probably recover much faster than that, but I wanted it to run condensing all the time, so I put in about triple the amount of baseboard that would normally be used. It runs at 110F when it is over 50F outside, and gets up to 135F when it is 0F outside. That way, it condenses all the time, but not very much when it is 0F outside. As I said, it never gets that cold around here.



"The way I see it is you are basically doing the same thing as

Gennady except you are keeping the thermostats to compensate for the

unexpected increase in heat loss such as caused by strong winds."



I look at it the other way around. I use the thermostats to compensate for "unexpected" decrease in heat loss when the sun shines in, or the wind is less than usual. In such cases, the thermostats stop the circulators (and, indirectly, the boiler) from running when less heat is required that would be obtained because of the reset curve.



"I am

assuming that both of you are setting the system to maintain a constant

temperature throughout a 24 hour period.  While I am comfortable at 68

to 70 degrees during the day when I am up and around, I prefer 60 to 62

degrees when I’m sleeping. (Actually I prefer it even colder but that is

about the minimum my wife will tolerate. -Grin- ) "



I will not speak for Gennady. I set my main downstairs radiant zone at 69F around the clock. My radiant zone is really made up of five circuits, and there are five rooms there and five ball valves on the supply to the slab. I assume each circuit is under exactly one room. That is not quite true, but close enough. It took a lot longer than I expected to determine which valve went to each room. My kitchen, bathroom, and my living room have their valves fully open. My bedroom is partway off and runs about 1F cooler than the others. My computer room has its valve almost completely off; I can hear the water rushing through it. That room needs very little heat because one of my computers uses 400 watts and the other computer uses about 125 watts. That is about enough to heat that room except on very cold days. I could shut that circuit off, but I do not dare because I do not want to freeze the pipe. I do not need to chill the bedroom any further because I sleep alone, and am getting old.





"My only question would be: If your system is balanced out so that the

circulators run almost constantly, your baseboard output has to be very

close to your homes heat loss.  If that is the case, how does the system

compensate for the increased heat loss on a windy day?"



The reset curve is "off" a tiny bit too hot. So it puts out just enough to heat on the cold windy day. It is on the sunnywarm days with no wind that the thermostats compensate by turning off the (excess) heat. The reason I can get the circulators to run so long is that the difference between when I need more heat or less heat at the same outdoor temperature is only about 1 degree. 



I think if my house had greater heat loss, I could get it to run the circulators all the time. But I do not really want to do that. My guess is that if it got really cold out, the downstairs circulator would really run 24 hours instead of just 12 to 18. And if running 24 hours a day was not enough, I would just diddle the reset curve for that zone to provide a little more heat in that part of the reset curve.

gennady

EM 32 Electronic Room Responsive Control

Actually EM 32 Electronic Room Responsive Control uses constant flow as well, it just modulates temperature as more advanced thermostat

gennady

radiator temperatures

To j a

I do tell customers upfront, their radiators will not be hot as usual, and most of the times will be warm. And this brings up funny story. I had to service some boiler plant belonging to one of the New York City Agencies this winter. So here what the fellows telling me . Some of the tenants did not see their radiators hot all the time. They started to complain about it. Any attempts to explain principals of outdoor reset on steam systems to them failed. They went all the way up to mayor and comissioner. So the order went out: get the radiators hot all the time. Then all windows got opened in this project, and they run out of budget on heating in january.

gennady

pump

Not disagreeing with anything you said. I’m sure you know a lot more about this

subject than I do. However, I think you may be coming at it from a different direction.

I replaced a 26 year old oil fired boiler that, when new, ran at 80% efficiency on a good day with a gas fired unit that can theoretically provide 96% efficiency. While I plan to tweak the system and make changes (when funds allow) to get the best efficiency possible, my main reason for going with the new system was to cut overall

costs. With the difference in fuel oil and gas prices, even at the same efficiency as the old oil burner (using the same number of BTU’s to heat the home) my fuel bill will be cut in half

=============================================

Bills to be cut in half. Why not 3 times? I m not kidding. I did have 75% bill reductions on my jobs. When after installation of condensing boiler bills only reduced by 50% there are some issues with installation. Do not pay attention to AFUE number. It is meaningless and has nothing to do with real efficiency. Real efficiency is in the proper sizing, proper settings, design, set up and layout

==============================================



You explained what WWS is and I have worked in buildings where thermostats were disabled and the system was controlled by the outside sensor. If installed and programmed correctly it is probably a great system. In the two buildings I was in, not so great. (Uninsulated cement block / brick veneer buildings in New England don’t have the same heat loss characteristics as insulated wood frame buildings. -Grin- )

You didn’t say whether the WWS would make any difference in a normal residential system using thermostats for control. (If thermostats are set for 55 degrees, once

the minimum temperatures are above 55 degrees does it make any difference

whether you are in WWS mode or not?)



======================================

Actually WWS function is based on outdoor temperature. If you set it up to 60F then this function will stop boiler and system pumps from supplying heat to house when outdoor temperature reach 60F. It has nothing to do with indoor temperature. or thermostats

======================================



As to the circulators, you got me thinking. The 25’ zone is the second floor bedrooms which is the least used zone. With the old system thermostats would start calling for heat around 5:00 in the morning (68 degrees) to about 8:00 when they drop back to 62. Around 4:00 in the afternoon they would again go back to 68 and stay there until 10:00 at night when they would drop back to 62.

=====================================

you cannot do night or any type of set backs on high efficiency systems. it robs you from all savings

=====================================



On a sunny winter day with little or no wind, that zone probably has very little call for heat. Reasonable solar gain along with some heat from the 1st floor keep the temperature in the low to mid 60’s depending on the outside temperature and wind conditions. (Did actually do a quick measurement and count of elbows on that zone and it is longer than I thought. From output of circulator back to the boiler is approx 180’ with 19 – 90 degree elbows. That includes the 25’ of baseboard.)

========================================

if your piping is 3/4" and you have regular sweat els installed, each el is equal to 1.2 feet of straight pipe. 19 x1.2=22.8 feet of straight pipe

23+180=203 feet

at dT20F your load of 12750btuhr, require 1.23 GPM (gallons per minute)

dictates 1.34 feet of head loss and from pump curve, we see that at this head loss this pump is not pumping 1.23 GPM, but actually pumps more.

please see attached screen shots

=========================================



First floor zone which is the zone that would call for heat more often is probably a little longer than the 100’ to 110’ I originally thought. Without measuring, 135’ to 150’ would probably be more accurate (including 45’ of baseboard). If I counted correctly, there are 27 – 90 degree elbows. That thermostat comes up to 70 at 5:00, drops back to 68 at 9:00, goes back to 70 at 4:00 and down to 62 at 10:00 in the evening. There is almost always someone on the first floor with the second floor not occupied during the day. I had considered going to the higher output baseboards but with close to $30,000 in expenses this year (heating system,

=============================

you might not need higher output.baseboards. All you need is properly sized baseboards. you might be surprised if you do proper heat loss calculations.

=============================================



electrical system upgrade and Title V septic) I decided to hold off on the additional expense and see how the current baseboards work out. When your retired on a basically fixed income, that kind of puts a dent in the budget.



If the output from the Taco's is too high, what would you suggest?



===================

install circuit setters on each zone, reduce flow to proper level, loose one pump and all thermostats. If you do not feel comfortable without thermostats, go for what Chris offered. see link in his post.

================================

CMadatMe

Exactly

Consumers like control of a thermostat so when you have to use them why not this. Everyone gets their way. It works like a champ...

Paul48

?

That boiler has its own circulator.Where's the primary/secondary piping?

j a_2

Gennady

Thanks for sharing that story....Just last evening, I went on a lead/sell job and the customer thanked me for being up front, about my thinking on why and why not mod/cons...I like most have no good reason to install something that I know wont deliver what they are cracked up to be...I do care about people spending there hard earned money when they don't really need to....Don't get me wrong I have and will install mod/cons but only if it fits the home...other wise I walk away...Going with cast iron boilers on last nights sold job....3 units all 3/4 copper 900 sq ft each...heat loss 32k btu per unit...removing one big oil thingamjig installing 3 new nat gas boilers...low use upgrade...domestic hot water by gas existing...ja

jt3

Chris

Interesting looking controller.  Also looked at some of their baseboards and panels.  Very nice equipment.  I especially like the baseboards, just couldn't afford them.  As to the boiler, I just had a Triangle Tube Solo 110 installed so won't be in the market for a new boiler for a while.



Thanks for the info and I'll keep it in mind if I hear of anyone else looking to upgrade.



Jim

jt3

J-D

Sorry, I must have given you the wrong impression.  I think you and Gennady are doing the same thing.  You have just added the twist with the thermostats.



You have a great way to heat with a radiant slab.  A builder up here was building homes on slabs back in the late 50's and early 60's.  Nice even heat. Very economical.  Only problem was they used copper pipe in cement.  Apparently copper and cement don't play well together.  If I remember correctly, most of the systems were converted to baseboards within about 15 years due to leaks in the slabs.   Done correctly however, using modern materials I don't think you can beat it. 



Thanks for the info and I may hit you up for info on how you adjusted your reset curves once we get into the heating season.



Jim

Jean-David Beyer

Only problem was they used copper pipe in cement.

My slab is copper tubing in concrete. My house was built in 1950, and it does not leak yet, so 62 years. It does not leak, at least, based on my simple test of turning off the makeup water and watching the pressure gauge every day for several months. There are very small pressure changes, both up and down. depending on things like the outdoor temperature causing the system to run warmer or cooler, for shorter or longer times. and such. These changes I can determine only because there is a little red tell-tale needle on the pressure gauge, and I set it to point exactly where the real pressure needle is when I turn off the makeup water. The changes are about the thickness of the needle; i.e., far less than the spacing of the indications on the dial. And the changes all average out so the needle mostly points to where the red tell-tale points. I usually turn the makeup water valve on a little because if it is off, my maintenance contractor gets upset: he belongs to the always-on school. I dare turn off the makeup water because the controller is smart enough to detect low water condition. But my AHJ does not trust that, so I have an M&M low water detector on there as well (probe type): belt and suspenders.



So even though I very much doubt my slab is insulated, they must not

have used fly ash in the concrete mix. I hope it lasts as long as I do.

I will be 74 in less than a week.



"I may hit you up for info on how you adjusted your reset curves once we get into the heating season."



OK. I have described how I did it before. There were two problems doing this. 1.) My heat loss calculations are not accurate enough to set the reset curves accurately enough. 2.) I cannot adjust the outdoor temperatures to suit my convenience, so I have to wait until mother nature does it. It took me a couple of years to get the reset curves as I want them.



The controller permits me to have two reset curves and I use one for my slab zone and the other for my baseboard zone. I was surprised that, when I was done, I run my supply temperature very low (75F for the slab zone) and it stays there until the outdoor temperature gets down to 50F. It then slopes up until the outdoor temperature gets down to 6F at which point the supply to the slab is 120F. If it gets any colder than that outside (I have never seen that happen: design temperature here is 14F), it levels off at 120F. This makes the slope pretty much agree with the actual heat loss, even when it is windy out.

jt3

Gennady,

Bills to be cut in half. Why not 3 times? I m not kidding. I did have

75% bill reductions on my jobs. When after installation of condensing

boiler bills only reduced by 50% there are some issues with

installation.

===========================

I'll settle for half to start with.  My wife is one of those people who would wonder why the baseboards aren't getting hot even if the room is up to temperature.   Planned on watching the output and return temperatures this winter and see how low I could get them while still maintaining a comfortable temperature in the house.  May also have to add something to the return line of the first floor loop to supplement heat in the basement since there will be minimal heat loss from the new boiler.  That could also help increase the spread between output and return and get the return water down to condensing range.

==================================

Actually WWS function is based on outdoor temperature. If you set it up

to 60F then this function will stop boiler and system pumps from

supplying heat to house when outdoor temperature reach 60F. It has

nothing to do with indoor temperature. or thermostats.

=================================

But, if you set your inside thermostat to 55 degrees and the inside temperature never drops below 60 degrees, wouldn't that accomplish the same thing? (Boiler not coming on because there is no call for heat.)

===================================

you cannot do night or any type of set backs on high efficiency systems. it robs you from all savings



=====================================

Guess I'll have to close the bedroom door and close down the top of the baseboard at night so I can sleep.  Just don't sleep well in a warm room.

===================



install circuit setters on each zone, reduce flow to proper level, loose

one pump and all thermostats. If you do not feel comfortable without

thermostats, go for what Chris offered. see link in his post.



================================

Wasn't familiar with "circuit setters" so I looked them up.  Other than the fact that they can be set very precisely, are they doing basically the same thing you could do with a ball or gate valve?  If the taco pump is flowing 7 to 8 gpm and you reduce the flow to 1.5 gpm, are you stressing the pump?  (should the pump be replaced with a lower volume pump?)

I looked at the "32" units that Chris talked about.  Interesting.  The company also has some nice baseboards and radiators.  After seeing the prices on the baseboards and radiators however, I don't know if I could afford the temperature control unit. (Grin)



Thanks,



Jim

gennady

pump

I'll settle for half to start with. My wife is one of those people who would wonder why the baseboards aren't getting hot even if the room is up to temperature. Planned on watching the output and return temperatures this winter and see how low I could get them while still maintaining a comfortable temperature in the house. May also have to add something to the return line of the first floor loop to supplement heat in the basement since there will be minimal heat loss from the new boiler. That could also help increase the spread between output and return and get the return water down to condensing range.

==================================

you have to decide for yourself what do you want, hot radiators or comfort



==================================



But, if you set your inside thermostat to 55 degrees and the inside temperature never drops below 60 degrees, wouldn't that accomplish the same thing? (Boiler not coming on because there is no call for heat.)

===================================

WWS is used because you do not have thermostat to shut system down

heat loss is based on assumption that temperature of the wall on outside of the house is 55F and when outdoor temperature reaches this temperature, there will be no heat loss, and no need to run heating system. Has nothing to do with thermostat.

==================================



Guess I'll have to close the bedroom door and close down the top of the baseboard at night so I can sleep. Just don't sleep well in a warm room.

===================

the room must not be warm. actually it can be as low as 69F and you will feel very comfortable. Body reacts to temperatures swings, as it happens when thermostats are used to start and stop circulators with fixed 180F water temperatures. you get rid of those swings, you get comfort at lower temperatures. Also you will cut heating bill 3% for each degree of temperature of the room you lower. so going from 74 to 69, you will save 15% right there on the top of everything else





==================================



Wasn't familiar with "circuit setters" so I looked them up. Other than the fact that they can be set very precisely, are they doing basically the same thing you could do with a ball or gate valve? If the taco pump is flowing 7 to 8 gpm and you reduce the flow to 1.5 gpm, are you stressing the pump? (should the pump be replaced with a lower volume pump?)

I looked at the "32" units that Chris talked about. Interesting. The company also has some nice baseboards and radiators. After seeing the prices on the baseboards and radiators however, I don't know if I could afford the temperature control unit. (Grin)

==================================

No you are not stressing pump. You make it work as it was intended. Ideally you need pressure differential bypass, but it is expensive. Cheaper to install VFD circulator. i would recommend for your application taco dT ones. but you will need 2, one per circuit. Cheaper one pump and 2 circuit setters. Unless you slow down water ride, you will not condense at anytime. give water time to cool down. Yes, you can use ball valve as rude flow control, but not a gate valve. Still you do not know what is the flow when you use ball valve. It is a good if you have time to play with it. Not when you are contractor and do not want have few call backs for adjustments. Also it has to be on discharge side of the pump, and you have none there.



Regards

Gena

gennady

this is how we do it

this is still work in progress

jt3

Paul48

Paul,





Sorry for the delay in responding.  Boiler got put in and too many other summer

and fall projects so logging onto “Heating Help” got put on the back burner.



The attached picture shows the primary loop.  Hot water comes down out of the front of the boiler and at the “T” goes to the right into the heating loop.  Water from the heating zones comes in from the left and returns to the rear of the boiler. 

Distance between T’s on the primary loop is 5 ½ inches on center.  Can’t remember at this point if it is supposed to be a maximum of 4 or 6 pipe diameters.  Piping is 1 inch copper so it is either a little too much space or just under the max. 



The company that installed the system put in 3 Taco 007 circulators. (2 heating zones plus Indirect DHW) I changed the circulator on the main heating zone to a Taco 008 Delta T circulator and set it to a 20 degree differential.  That is about all I

can afford to do this year.  Next year I would like to add some high output baseboard which should help all around, change the other circulator, and consider a buffer tank which would help increase cycle times.  (right now not enough volume / baseboard output and cycle times are running really short)  Also want to see about using the main heating zone return line to add some heat to the cellar.  That may allow me to set the delta T higher for better efficiency and keep the chill off the cellar.  Will have to see what is available or what I can put together.



Even though the efficiency isn’t what it could be, it is better than the old oil fired system.  Normally I would get the oil tank topped off in late April or early May.  Boiler was used year round as backup to an older solar hot water system.  Winter

settings were 160 / 180 but in the summer I would drop them back to 140 / 160.  It would get filled again around Dec 1st.  Fill would be in the 160 to 180 gallon range or roughly a gallon a day.  At $3.50 per gallon that was a good chunk of change.  So far I have received 6 gas bills and the total is just under 30% of what I would have paid for oil.  The efficiency might not be perfect but it is sure better than what I would have paid with oil.  Now, as long as the price of natural gas doesn’t skyrocket . . . . .



Jim