Maintaining minimum flow w/o P/S -differential bypass? bypass zone? flow switches? ideas?

hot_rod

Gordy said:

Hot rod are these commercial, or residential applications? A little detail on why a direct piped had issues.

It was a larger sized boiler with a Magna pump. Although many homes in the resorts would qualify as commercial, I suppose.

One issue was the boiler would ramp down, burner went off and post purge enabled. But a 10VDC signal was still going to the pump contact. It involved the programmer changing some code in the control, then flashing the fixes onto other test site applications.

I agree with Hatt that you need to first, know what you want the system to do how and when.
Then program those into the control and or pump.

Then observe the operation for a period of time through all conditions. If you plug it all in and walk away, how do you know what actually goes on.

I doubt a homeowner often catches these control error or glitches, and it really take all the parties to design, identify, confirm, and make adjustments. With everyone understanding the goal. Often the programers back in an office don't have the ability to get data that allows them to make code corrections, or even understand the designers intent.

So it is easy to see how with so many variables out there in regards to piping and distribution, types of emitters and mixes that making a simple one size fit all control, or boiler/ pump package is a challenge.

Working with the BAC folks it is easier to write the correct logic from the start instead of modifying two separate component software trying to make them get along. I don't think the average small size residential installer will have the skill set to program this deep and have the time and $$ in a job to observe and correct program glitches.

Most mod cons already use PWM to operate the fans, so another PWM for the pump might make some of these control options easier to manage. There seems to be more more PWM options in the small circ pump offering than 0-10 stuff.

The product manage I spoke with at the boiler manufacturer see the pump being able to send data back to the control, the control can respond and adjust as one of the key components missing on the smaller residential circulators.

The boiler manufacturers feel the squeeze to stay price competitive. Hard to build a boiler and control that can manage all this and compete with the import product with smaller HX, less powerful controls, etc.

Viessmann is a classic example, they entered the US with state of the art product and the market keeps asking them to dumb it down and get price competitive.

Paul48

There was mention of 1 gpm as minimum through the HX. I find 4.6 gpm with a reasonable expectation of a 35* DT temperature rise through the HX. To me, that means 4.6 gpm has to go to the system, and the system has to shed the btus. A 35* temperature rise is the highest they provide for in the I&O. I understand this is at high fire, and the boiler may be firing at 10%, but you still require the system to shed the btus.

I see the 1 gpm minimum at low fire. Forget zoning anything smaller than the minimum firing rate of the boiler. At minimum firing rate, you still have to maintain a 16-17* DT on the system side, or the boiler climbs to high limit. With a baseboard system, there is little chance of maintaining that DT. Zoning will put you at a greater disadvantage.

hot_rod

Paul48 said:

There was mention of 1 gpm as minimum through the HX. I find 4.6 gpm with a reasonable expectation of a 35* DT temperature rise through the HX. To me, that means 4.6 gpm has to go to the system, and the system has to shed the btus. A 35* temperature rise is the highest they provide for in the I&O. I understand this is at high fire, and the boiler may be firing at 10%, but you still require the system to shed the btus.

I see the 1 gpm minimum at low fire. Forget zoning anything smaller than the minimum firing rate of the boiler. At minimum firing rate, you still have to maintain a 16-17* DT on the system side, or the boiler climbs to high limit. With a baseboard system, there is little chance of maintaining that DT. Zoning will put you at a greater disadvantage.

Also below 1 gpm the flow would be laminar and pick up little or any energy in it's trip through the boiler.

This is the same issue with heat emitters, at some number (gpm) the flow goes laminar and heat exchange plunges until it completely stops at 0 gpm.

This examples shows flow through 12 feet of fin tube and about where that transition to laminar occurs.

Rich_49

Hot Rod , what text is that from ? I'd like to see 3-6 and the rest of the text .

hot_rod

http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_16_na_0.pdf

Paul48

That agrees with the output ratings for 1 and 4 gpm that baseboard manufacturers give.

Paul48

Hey......They actually give equivalent length of Monoflo Tees in there.

keyote

Thanks been out town couple days i need to settle this now.
I see pauls comment but not sure how to interpret this its at high fire and ill be at low fire with radiant i think i will be using ramp if need be to enforce this but have still to read the service manual.
HOTRODs comment seems more germane my biggest worry is on a 65 degree day when my flows are .5- .85 gpm @ 1.7 -2.2 feet head [above laminar flow i think] but since the btu are below the 8500 low mod. I am thinking i will have to combine at least two manifolds into one zone to get enough btu absorption.
But no one has explained the following. Hat says the pump simply can not pump less than 1.6 gpm and possibly much more at those low heads and modulation. well that would be great regarding the low flow problem if i am absorbing 8500 btu,but i don't understand where the extra flow goes. Does that mean that the boiler will give the floors 3 or more times flow than they require, or that the excess will be routed back to the boiler through a bypass loop? if it goes to the floors what happens to the calculation loop cad gave requiring lower flows? does the heat call simply get satisfied quicker, or does something else happen?
If i am combining manifolds into one zone or using boiler controls to manage calls to avoid single zone calls i assume the combined flow is the new flow number and while it would be closer its still under 1.6gpm.

Rich_49

Laminar may be just what you need on the system side during conditions like this . I still can't fathom the notion that you need transitional or turbulent flows during times of lesser heat requirements . Repeat after me , on the system side , the flow needs to be what the load requires , nothing more , nothing less . We do not need to maintain turbulent flow to do the job .
This and this alone is repeatedly ignored and is what determines whether a system can be direct piped or requires P/S piping . The boiler must have enough flow to carry away the heat produced or at least a place to store any excess heat that the system cannot deliver . The system should be able to shed the heat at the rate it is needed to fill the reservoir .

hot_rod

Rich said:

Laminar may be just what you need on the system side during conditions like this . I still can't fathom the notion that you need transitional or turbulent flows during times of lesser heat requirements . Repeat after me , on the system side , the flow needs to be what the load requires , nothing more , nothing less . We do not need to maintain turbulent flow to do the job .
This and this alone is repeatedly ignored and is what determines whether a system can be direct piped or requires P/S piping . The boiler must have enough flow to carry away the heat produced or at least a place to store any excess heat that the system cannot deliver . The system should be able to shed the heat at the rate it is needed to fill the reservoir .

True, but if the boiler is cycling off, and the room is falling behind on temperature, with emitters properly sized, it leaves only one bottleneck, that being the lack of turbulent flow being able move energy from the fluid to the wall of the heat emitter.

The whole concept of Reynolds Numbers was developed to calculate and show where the potential exists.

Defining that exact point in every system out there would be a task, the numbers, formulas and simulation get you close. IBR testing has shown that point in some emitters like fin tube. It is quite obvious heat transfer stops a 0 flow.

Or sit on a bucket and observe what is happening in real time.

keyote

Ok guys you are all making some deep points im trying to keep up.
I think Hat has said the minimum of that pump is going to go through the loops faster and come back warmer. that i imagine may cause a problem for the boiler already on lowest modulation. "Unless " he says i throttle; which i take to mean adjust the flow meters on manifolds. Which i would think would have an undesired effect when i am no longer on a design day that requires less flow and would cause me to again wonder where is that extra flow going if im choking it with flow meters and the pump cant flow less?

keyote

Rich is referring to Hot rods laminar comment, and seems to be confirming what i read about laminar flow but frankly was so surprised i was sure i was misunderstanding. That at low flows the flow stratifies and has difficulty picking up and releasing heat.
However looking at the chart that was posted it seemed that my required flows .5- .85 were higher than laminar levels anyway and since i will have to combine zones the combined flows of two zones would be higher still at 1.2 gpm @ 1.8 ft hd.

Rich i think what you most were trying to say was that the bottom line on the P/S or not question is whether or not a zone can absorb the lowest modulation output. since two zones combined do require 8500 on 65 degree day im good.However if i am interpreting all this I am basing this 8500 by combining two zones btu loads and their gpm and if the gpm combined is still a bit under what Hat says is pumps minimum i think the BTu changes a bit with the flow change? If i remember the lower flow will require me to lose more btus but the combined zones while low on gpm are over 8500 so i may be ok.

keyote

I dont think the vt2218 has a flow readout i would like that on commissioning to help figure out whats happening.

so reading your very deep level comments has made me think of a question so naive its scary at this point i dont know the answer.
looking at my loopcad flow requirements by manifold for 17 and 65 degree days i have of core different flow requirements. And I noticed when in the program it would show different dt on the various loops some way way off from the dt i thought was locked in for the design. i assumed it was telling me that it was setting the ideal water temp for the entire manifold and that i would have to adjust the flows for the needs of the individual loops loads.That once i had done that the sum would equal the flow it was showing as the manifold [zone] total.
Now i am wondering if i set flows on 65 degree day how can the change when it gets colder?does that just work out that as the pump pumps harder to maintain dt the flows through the meters set on 65 degree day also work on 17 degree day ?

keyote

I think Ironman has disillusioned me of any meaningful zoning possibility and since half the house would not give me any real advantage over simply zoning the entire house as a single zone that's what i will do eventually. But i still have the problem in the interim since only the top floor is looped, I do have have an abandoned copper fin tube system in the cellar i think i could adequately flush and gang with the top floor radiant and get above 8500 btu.
Am i understanding correctly that if im demanding over the lowests mods output i wont still need a buffer tank, id really really like to not use one but if im going to need one id rather not find out the hard way. or is it that im too close to call?

keyote

Thanks Hat yes its the 65 degree day that im worried about i reran loop cad with that design temp and is what i have been referring to as the lowest possible call. any single zone on that day is only about 2-6k but if i combine them im even safer. I think the boiler has a feature where it gangs zones reading install manual now. think i will give this a whirl without the buffer.

But wait 91 degrees is what loopcad calls for on that 65 degree design day.So what are you saying it cant really do that without shortcycling and high limiting? so set the temp higher and what will happen, the calls will be satisfied quicker and it will cycle a bit but thats life? or it will overheat the room a bit and actually cycle less?

Gordy

You will need to aggressively setup the ODR function so the water temps will match the load. The thermostat becomes a high limit device. Compensating for othe influences such as solar gain, cooking, wood burner, many occupants etc.

If you need heat on a 65 degree day something is wrong. Rarely do I need to fire up the system until highs in the mid to upper 50's lows in the 40's. Depending on solar gains.

Gordy

Hatterasguy said:

keyote said:

Am i understanding correctly that if im demanding over the lowests mods output i wont still need a buffer tank, id really really like to not use one but if im going to need one id rather not find out the hard way. or is it that im too close to call?

The lowest output on the warmest day...........not the design day.

In reality, if the lowest output on the warmest day is 1/2 the boiler's low firing rate, you can still manage without a buffer tank. You don't have to push the reset curve all the way down in the weeds. Since the boiler is going to cycle anyway, raise the floor a little bit and allow the zone to satisfy and shut the boiler down.

This whole effort to get the SWT down to 90F on a 60F ambient is an exercise in futility as NO modcon can ever get down that low.

Raise the floor to 115F. Satisfy the zone and let the boiler shutdown for a few hours.

Why not?

Bet my system could make it behave easily.

Gordy

keyote said:

I think Ironman has disillusioned me of any meaningful zoning possibility and since half the house would not give me any real advantage over simply zoning the entire house as a single zone that's what i will do eventually. But i still have the problem in the interim since only the top floor is looped, I do have have an abandoned copper fin tube system in the cellar i think i could adequately flush and gang with the top floor radiant and get above 8500 btu.
Am i understanding correctly that if im demanding over the lowests mods output i wont still need a buffer tank, id really really like to not use one but if im going to need one id rather not find out the hard way. or is it that im too close to call?

Apparently you are not so easily disillusioned.
This has been preached on many of your threads. But maybe ironman made it more palettable....

Gordy

It's really about more than mass. As Rich said its the ability to dump the btus which comes down to emitter selection. When speaking radiant tube density matters.

Being able to conduct the btus out of the water in the tubing matters.pex compared to copper pex is at a disadvantage. Pex without plates more yet. PEX in concrete better. Pex hanging in a joist bay stinks.

Harvey hit the nail on the head a while back with my system the copper embedded in plaster, and concrete sucks the btus out of the water delivery very efficiently. So long as the mass can suck it up.
However those days are gone unless you have money. So plates, drywall, and wood substitute in the conduction process.

Rich_49

Here is a solution and another was mentioned By Hot Rod earlier in one of your numerous threads . The Veissmann with the 13 gallons of mass . Or this , when short cycling is short is not short cycling .

http://www.htproducts.com/literature/versahydrobrochure.pdf

Looking at gas bills right now for a highly zoned house in Ann Arbor Mi that went online in November 15

Gas bills

Dec 58.32
Jan 79.80
Feb 95.07
Mar 61.52
Apr 57.44
May 44.55
June 44.03
July 34.08
Aug 29.01


56.04 average gas bill . 3,800 sf ranch , slab , 14 zones , 4 occupants , lots of showers . Garage is heated . Zoning for comfort does not have to kill system efficiency , there are ways to do it . Just have to be willing to do what you need to and spend what you need to spend or CHANGE the plan . Why 14 zones ? Individual comfort , period

keyote

Rich thanks Gordy actually suggested that htp with built in buffer last week, the suggestion struck me as good but i have to get over my feeling that the lochinvar is a superior machine. I am going to look at it before i pull the trigger, another issue is i have already installed the smart 50 and while re piping it to a differnt boiler is a pain doing away with it is a big deal

Harvey Ramer

Hat mentioned something earlier that I do on almost every Modcon/ODR installation. Cut off the bottom of the reset curve. Or in other words, limit the minimum Supply temp. You must have a temp difference between the water and the floor/emitter for heat transfer to occur. It comes at almost zero sacrifice to condensing efficiency and more than makes up for it by allowing longer run times on the boiler.

Gordy

Hatterasguy said:

Rich said:

Looking at gas bills right now for a highly zoned house in Ann Arbor Mi that went online in November 15

Gas bills

Dec 58.32
Jan 79.80
Feb 95.07
Mar 61.52
Apr 57.44
May 44.55
June 44.03
July 34.08
Aug 29.01


56.04 average gas bill . 3,800 sf ranch , slab , 14 zones , 4 occupants , lots of showers . Garage is heated . Zoning for comfort does not have to kill system efficiency , there are ways to do it . Just have to be willing to do what you need to and spend what you need to spend or CHANGE the plan . Why 14 zones ? Individual comfort , period

The Versa Hydro essentially puts the buffer tank, the indirect, and the boiler into one package. It's a neat solution.

The data for the house is somewhat meaningless without:

a) Cost per therm
b) Heatloss


With those values, the total consumption per degree day can be calculated and the overall system efficiency can also be calculated.

Then you'd have some worthwhile data.

Ann Arbor Michigan, and 3800 sf ranch......

keyote

Gordy you're perfectly right, ironman was simply the last straw and i guess phrased something right,maybe the bit about our imposing american expectations on european technology. I mean sure its obvious we have been basically talking about absorbing heat for a month, and mass is well massive in that discussion. But for years prior i have been reading about radiant heat and zoning yada yada so it was really hard to accept that something that had been so widely purported to be so simple was indeed so difficult, particularly after i bit the bullet and committed to a new boiler with the lowest modulation available.

Been wondering about radiant ceilings and sprayed concrete.
Been away a few days started the service manual today

Gordy

Most Americans are glutinous. Especially in the minds of Europeans. It's what happens when fuel is cheap. Even when fuel went through the roof. It was a minor taste of what Europe has dealt with for decades. Hence there fore their habits. Down to municipal transportation.

hot_rod

Gordy said:

It's really about more than mass. As Rich said its the ability to dump the btus which comes down to emitter selection. When speaking radiant tube density matters.

Being able to conduct the btus out of the water in the tubing matters.pex compared to copper pex is at a disadvantage. Pex without plates more yet. PEX in concrete better. Pex hanging in a joist bay stinks.

Harvey hit the nail on the head a while back with my system the copper embedded in plaster, and concrete sucks the btus out of the water delivery very efficiently. So long as the mass can suck it up.
However those days are gone unless you have money. So plates, drywall, and wood substitute in the conduction process.

Here is a pic from about a month ago. This company in Il has been making copper radiant loops since around 1960 maybe. Most or their work now is repair loops for jobs damaged in reno work.

They recently flushed their files, keeping all the bend data back to 1980's






I'm sure they would bend up an entire job for you. The price may be a bit higher that this 1980 job.

ry

Rich_49

Hatterasguy said:

Rich said:

Looking at gas bills right now for a highly zoned house in Ann Arbor Mi that went online in November 15

Gas bills

Dec 58.32
Jan 79.80
Feb 95.07
Mar 61.52
Apr 57.44
May 44.55
June 44.03
July 34.08
Aug 29.01


56.04 average gas bill . 3,800 sf ranch , slab , 14 zones , 4 occupants , lots of showers . Garage is heated . Zoning for comfort does not have to kill system efficiency , there are ways to do it . Just have to be willing to do what you need to and spend what you need to spend or CHANGE the plan . Why 14 zones ? Individual comfort , period

The Versa Hydro essentially puts the buffer tank, the indirect, and the boiler into one package. It's a neat solution.

The data for the house is somewhat meaningless without:

a) Cost per therm
b) Heatloss


With those values, the total consumption per degree day can be calculated and the overall system efficiency can also be calculated.

Then you'd have some worthwhile data.

3440 degree days @ base temp of 55* . Nov through Present

Just e mailed client to provide therms used . Will provide .

hot_rod

keyote said:

Gordy you're perfectly right, ironman was simply the last straw and i guess phrased something right,maybe the bit about our imposing american expectations on european technology. I mean sure its obvious we have been basically talking about absorbing heat for a month, and mass is well massive in that discussion. But for years prior i have been reading about radiant heat and zoning yada yada so it was really hard to accept that something that had been so widely purported to be so simple was indeed so difficult, particularly after i bit the bullet and committed to a new boiler with the lowest modulation available.

Been wondering about radiant ceilings and sprayed concrete.
Been away a few days started the service manual today

There are a bunch of nice interactive rsimulators at Lochinvar U..

Play around with the control on that Knight KHN before you buy. Size buffer tanks, calculate mixed fluid temperatures, and ODR programming.

it is sometimes easier to understand the simulators than the manuals.

I'm hoping they offer a table top trainer version of that control, like they do with then others. then you could connect pumps, valves, etc to the tool and run through different arrangements.

keyote

Thank you hotrod i watched a couple training vids but did not notice this simulators stuff except the buffer sizing app elsewhere on their website.

Gordy

The versa hydro is a nice unit. Integrate with solar. I believe keyote mentioned that solar was in future plans.

keyote

Rich that's interesting data,the house is about 75% of mine but i see you have about 33% more more tube length more loops and I guess that accounts for your lower heads. I see something i also noticed in my loop cads i didnt understand that difference between SWT and required water temp?

The viessmann is too expensive, This unit you used here i would have thought oversized for my house butyour job a has lower load, thats because of the 55 gallon buffer? And the buffer allows the zones too, But it isnt losing efficiency with all that water standing by?
The graphs gordy posted made me think operating the KHN 085 between 10 and 60% mod was ideal, i thought a buffer would be heating at higher mods shorter burns and have little RWT drop across buffer so less condensing advantage so less efficiency. Im thinking from this maybe i was wrong to assume that, which would be good since i guess adding a buffer will be plan B.

you seem to like this HTp brand, I had bad experience trying to find and price their buffer tank, then the Hat controversy seemed to imply they were not a premium product compared to lochinvar, then the thread about them being a rebrand has all prejudiced me. But i also gathered maybe they were utilizing some import parts but building their own tech on top, and this unit seems a different idea altogether kind of like my tribufferator idea, is it expensive?

Gordy

The graphs I posted may not be quite the same for the versa hydro it's a different animal with built in buffer.

As far as the negative comments twords htp. I will let Rich address your questions. They have many different product lines as you may have noticed. The more complex the comtrol strategy on the boiler the more costly. The KHN, and uft are an example. Htp has given a 10:1 TDR with controls, but not as deep as the khn's. Nor is the cost. You have to know the equipment, and your options when designing. Do I need the uft, or a KHN. Do I need the extra control options etc.

The westing house brand is more of a similar line that is sold in big box, and Internet portals. I'll let Rich elaborate.

As you noticed with one of many of Rich's designs he is fluent in compiling home owners needs, budget, and making it all work with detail to the emitter end as economically as budget allows.

keyote

Thank you gordy its good to know you think this unit is a good value; its unique design kind of obviates the need for deeper controls in my situation. i have to admit it kind of addresses my concerns and those gas bills are pretty good evidence its efficient.
I get the hint but this is the last thing i need to do for phase one of renovation [tenants are occupying renovated top floor blissfully ignorant they have no heating system] and I have taken off the last year of work to get it finished so am running on fumes and credit cards and cant afford a designer. I may consult one before i do any further system work which wont be until i am back to work and in better shape, but I have to get a boiler installed and tested before fall. tick tock