new vito200 wb2b coding question

JED_5

Hi all, have lurked for some time and am astounded by the knowledge here.  Have a 3 mo old Vitodens 200 that I'm loving so far.  



My question. To increase the supply temp/boiler water temp from my Vito200 I'm going to Coding level 2, and address 06, correct?  





I'm a homeowner, and want to make sure I've got the manual understood. We've got some low temp's arriving and during the last bout of cold air one zone didn't quite stay warm even at Max supply temp.  The older (1950's Fitzgerald built-the-house-around-it-torched-it-out-monolith) put out 180-190F, which I think did the trick with the original fin tubes.  

I have no DHW or radiant...just fin tubes everywhere.  System is on a external thermostat.   Was running evening and at work setbacks but this caused comfort issues (wife was not thrilled with the new boiler).  No setbacks now and seems to have little impact on total heating bill..woo hoo!   

Basically in the fine tuning stage of new boiler technology (quite shift from 1950 to now!).  

Thanks! 

CMadatMe

Quick Question

What is the room temp setting in the boiler? Was is left at the factory 68. If so, raise it and it will boost the boiler water temp. Just turn the dial to raise that. It will boost the boilers curve. Another note...The low loss header sensor when used dis-engages the boilers supply temp sensor. The boiler only wants to make the hot water that the system needs based on the temp in the low loss header. 



Coding address 6 is to limit the maximum boiler water temp. You cannot raise it any higher than 176 degrees. We generally use it as a high limit if the boiler was our mixing valve for a radiant application.



To change the heating curve I would strongly suggest you read begin at page 31 of the attached manual and go from there. You can seriously screw the boilers brain if you start just pluging in numbers you may not understand.



I would recommend that you just change the room setpoint if your uncomfortable. It's the simplest way for a homeowner to boost the curve without causing any coding glitches. Have the installer come back and double check all the coding.



How did the installer come up with his heating curve from the get go. Did he leave you a room to room heat loss?



If you attempt to play with the curve and get lost call Viessmann's 24hr 7 day a week tech support hotline at 1-888-484-8643. Make sure you have the boilers complete model number and serial number. That is going to be the first question they ask from you. The serial number is on the lh side of cabinet on that white bar lable. It's not the serial number on the heat exchanger plate.

icesailor

Vitodens 2000:

I could be wrong but I think that the maximum high limit setting on your boiler is 170 degrees. At least that is so on the Vitodens 1000.

Your comments on your operations and failures just reinforce my concerns about limiting yourself in flexibility to get the job done. Heat is heat. A BTU is a BTU.

No matter how hard you worked to convince your wife what a good thing this new UHE boiler will be and how much money you will save, it is all for naught if she is cold and you can't get the house warm enough to get her warm. Life will cease to exist as you knew it before the boiler change.

I have a Weil-McLain WTGO-3 boiler and a 50 gallon storage tank. I have set back thermostats on 5 zones with Taco zone valves. The house has never been cold and it has hit the 0 degree temperature I designed it for many times. It never failed. Even with the 10 degree setback, it still comes right back on the coldest days. I recently replaced my Taco 007 circulator with a Wilo variable speed circulator. I set it at a speed that seemed it would work for what I was doing. When it was 2 degrees out and the living room zone came on, I noticed that it was taking hours to get from 58 to 68 and not making it. I raised the system temperature to 170 and speeded up the pump. All went back to normal. Think what I could have done if I went to 180 or 190,

If you have a variable or multispeed pump, turn it up to high. More flow might help.  I'm assuming (I hate that word) that you had one of those old fashiioned systems that some now hate that worked so well for years and now are so passe'. If there is a way to make it run on high limit, do it. Forget about the outside temperature. The onboard computer can't comprehend what the actual outside tempersture is because it can't get wind speed in the input. And it doesn't know that the room is cold so it can't comprehend a wider variation in temperature differential.

What aree your supply outlet and return temperatures? In the zone that doesn't heat well enough? 

CMadatMe

The Boiler Can

The boiler can comprehend if the room is cold provided your using Vitotrol 200 or 300 control with the boiler. You could also utilize the external demand feature for a particular zone if you wanted and set the temp to what ever you want for as long as you want.



It's reduced room temp (setback) feature also gives you the ability to boost the heatng circuit if need be. I think just to flat scrap what the boiler can do because somone may or may not have coded it correctly or they don't understand what the control is capable of is not the right anwser.



Max water temp is 176 on the new Vitodens 100 and 200 up from the 165 of the previous version.

 

icesailor

Vito coding question:

Chris,

I have no problem with the ability of these high tech mod-coms doing what they do. My problem is how few there are who can manage them and the bad name they will get. The complexities of setting these up are overwhelming. The problems that someone can run into when they are problematic can send the best installer into fits. The above post is a perfect example of what I am talking about.

Most who work on these learn it all by rote. Someone told them what to do. They may have no idea of what the problem is and how to resolve it.

I used to sell a lot of Honeywell analog clock thermostats. I always gave customers a choice. But I quantified that by suggesting that if they had a problem with programming their TV remote, they might be happier with the analog over the digital. They always picked the analog. I have a digital in one room and digital in another. I can flip the program with a push of a button on the bottom in the dark. The digital, I have to go and push the up or down button, how many degrees I want to change it.

Try explaining to a customer over the phone, how to do what you just described in your post. You can't. If they called me and had an old fashioned system, I would tell them to take the grey cover off the control on the front of the boiler. Look at the red knobs.See the one that says "Hi"? What does it say? 160? Turn it up to 180. Give it a few hours and if still cold, call me back, Either way, I'll drop by tomorrow.

And when this Hydronic High Tech is all done, everyone will be switching to scorched air. You can't run 110 degree air because the ducting systems are so screwed up that the house will never heat up. I think all this stuff is way cool. I love it. I just can't fins anyone willing to pay for all this excessive stuff and a lot of installers are installing this stuff and not making any money. When the price is in the clouds, they go to scorched air. Catch 22.

JED_5

thanks all!

Ok, first to make all of you cringe.  This was a DIY job with a friend whose been commercial/residential plumber for ~15 yrs.  I went this route after getting overly priced quotes from folks I just did not trust.  He had no experience with this sort of system but we consulted with an experienced installer and the vitodens helpdesk (great support!) on design (retrofit into a system with 3 zones, each on a Taco 007), learned about hydronic separation, etc.  I think the install is solid, but I now realize I was 100% ignorant about the finer points that make a mod-con install work.   So things like heat loss calculations, don't exist.  





I got confused about maximum setpoint as p. 27 of the manual I have says "The maximum adjustable high limit of the boiler is 180F/82C."  and p48 when describing address C6:74 discusses it going all the way up to 261F but does say (limited by the boiler coding card).  I figured it was factory set at 165, and I needed to do some adjustments to reach the 180 mark.  Based on what everyone has said, i assume it can get to 180 by adjustments to the heating curve.  It gets to 176 now when its really cold.   I just checked address 06 and its set at 82, which is 179.6F. So, I'm pretty sure I'm coding card set at 180 and can't go higher.  

I think my set back issues were caused by the Honeywell "smart response" technology on the thermostats, which figures out when to start heating so the house is warm at the desired time.  If it had been warm a few days, then suddenly got cold, the timing used by the thermostat brain did not work well with the modulation of the boiler.  



I've considered a Vitotrol but don't have enough know-how to understand if this is a better option than others. 

The zone in question has 4 huge, original windows (huge amounts of heat loss), a high ceiling, no insulation in the walls, and a bunch of recessed lighting that are not sealed with the attic. Yes, should have started with energy conservation prior to the install!  A home energy audit indicated an above average leaky house.  

The system is set so when a thermostat makes a call, the Taco's pull from the primary loop.  Like Icesailors example, I'm not sure if the flow is not fast enough to keep up with heat loss.  The boiler temp will be at 176 during this time.  I've considering trying to calculate inputs vs outputs as I can estimate room volume, heat loss, and input based on length of fin tube, but have not found much info on the net to assist with these calculations.



While using setbacks I found I had to really push the heating curve to get reasonable fast recovery times (2.6).  I stopped the setbacks last month (slight increase in therms, but a decline in kilowatts) and was going to reduce the curve back to factory settings and then adjust based on comfort after this cold snap.   I know I'm not getting optimal efficiencies at these temps, but I'm still using ~50% less gas than the old boiler.  

thanks again!

 

CMadatMe

Ice

I agree and here what your saying. I can say though that you can do the same thing with this boiler as the aqustat on the traditional boiler. The boilers curve is calculated by room set point and outdoor temp. The dial on the front which you could say acts no different then a thermostat. You simply can change room set point by turning it to the right to raise and left to lower. The boiler will boost or decrease the curve on its own. The homeowner doesn't need to go into the coding.

CMadatMe

Jed

I have a quick question for you. Did you tie the end switch from your zone control to the 123 plug (External Demand) thinking you needed the zones to tell the boiler to come on? Did you use a low loss header and low loss header sensor? If you did indeed use the 123 plug then there are coding issues that need to be done. When using the 123 plug you are  not letting the boiler do it's thing. It's no longer the mother just a child and you have to input what you want the boiler to do..



If you used the llh sensor which you should have, then you do not bring anything back to the boiler  from the zone control. You just wire your therms and circs to the zone control and that's it. The llh sensor will fire the boiler when it senses temp change in the LLH.



Your problems sound to be coding issues. Did you adjust any of the factory settings such as reduced room temp which is defaulted to 37 degrees?



The Vitotrol is basically and extension of the boiler control that can mounted remotely in a centralized area. It provides you indoor temp feedback, dhw control, limited boiler control and boiler fault codes. You can program it basically like a thermostat. The boiler will use that indoor feedback with the outdoor and low loss header sensor feedback in the calculation of the heating curve.



Attached is the basic Quick Start Programming Guide. It will give you the basics for a system with one heating circuit and  DHW.

JED_5

llh and 123 plug

Hi Chris



Nothing to the 123 plug. Each thermostat simply goes to an individual Taco007 that pulls hot water when needed. This was the original set up and we did not want to mess with it.



Low Loss header. If you download the following



http://www.caleffi.us/en_US/caleffi/Details/News/files/HydSep102508.pdf



and check out slide 11 "some systems begin and end individual load circuits in the mechanical room:" you'll see what we did to get Hyd. Sep. It was the best solution for the retrofit. I currently do not have the small green square "supply temp sensor for boiler reset controller". So NO, I do not have a LLH sensor. If I need this, I assume I'll have to get an external sensor that mounts on the pipe. Vitodens help desk indicated this would help me get 'better control' but did not indicate it was critical.



I'm only using the external temp sensor (which was tough to locate away from afternoon sun!).



The only coding changes I've done are on the heating curve. That said, you are probably right about poor coding. I just went through all my records and the one page where I kept track of coding changes Vitodens help desk suggested (back of P.1 of the trouble shooting guide) is missing...just my luck!



Thanks for the quickstart guide...that is one PDf I had not found!



Jay

CMadatMe

Oh Boy to Slide 11

The sensor won't do you any good piped pri/sec. This boiler really needs a low loss header. It's pasted all over the manual that a low loss header is highly recommended. Can you post some pics of the install?





What system type did you code the boiler as? 



Did you purchase this boiler from your buddies supply house or the internet? Just curious...Also where are you located?

JED_5

follow up

We considered an LLH but figured all the discussion in the manuals was about hydronic sep, not because the added sensor was critical for optimal operation. We must have missed this in the manual but Vito helpdesk did not stress this when talking to them. That was when they mentioend that and external sensor might be useful. Doh!



The system is coded as type 1. 1 heating circuit, without mixing valve, without DHW.



We live just outside of Denver and I bought it from an online vendor.



Waiting on pic's from my buddy. I've since added some very, VERY ugly insulation.

CMadatMe

I'm Torn

I really want you to know that I'm torn. Let's me guess Pex Supply..I'm only trying to help because you had a friend who was in the trade install the boiler. The reason...Internet companies have  no concept in selling these types of boilers other than to swipe your credit card.



There is no way in hell I would ever sell this boiler without the LLH and sensor. I don't think any true Viessmann supplier would either. The problem with these interenet companies is that they don't buy from Viessmann nor will Viessmann sell direct to them. They purchase this product from a local wholesaler and then push it off on dyi's that have no clue as to the real nuts and bolts of the boiler.



With that said, I really want to help you out with the best advice I can. The boiler needs to re-piped with a LLH and the appropriate sensor. Then, A HEAT LOSS and measurement of existing emitters per zone and room to set the proper heating curve. Then, the correct coding.



In your case it's not the arrow but the indian that seems to be responsible for your problems.



If you don't want to re-pipe then atleat install a copper x female tee into the primary loop and insert a well and then the sensor. This way the boiler will atleast attempt to make supply side water temp that is needed.

scott markle_2

more vito talk

Not having the low loss header sensor means you are measuring boiler supply as opposed to system temp. Since you are hydraulically decoupled and have multiple zones boiler supply and what the system actually sees is a moving target so to speak.



Doing setback with thermostats is not as efficient as using the boiler to do this. Using the (boiler which has full 7-day clock features )You loose the ability to have individual schedules at each zone but you have the advantage of a lower global reset curve.



The bottom line is that a poorly balanced multi zone fin tube distribution system is not a great match for this boiler. If your zones have wildly different requirements your forced to use a reset curve that matches the zone of highest demand. When you graft conventional on off circulator zoning to a boiler like this your kind of missing the point of what it can do.



Yes ODR misses wind and solar influences, but the reality is that when the sun goes down and the wind picks up your house may get a little bit cooler, Conversely When the sun is shining bright on a january afternoon it gets a bit warmer, which feels nice. This idea that we need to maintain such a narrow comfort-range is very cultural. I think the end user would do well to ask how important this kind of comfort really is. Another thing I've noticed is that many people will see a temperature deviation between the setting and the room and become uncomfortable when they were fine, It's a control issue more than a comfort one. Psychological as much as physiological. I kind of like the simple wall feedback temp adjuster that mates with the 200 vito because it has only a simple analog setting dial (in Celsius) no display of the actual temperature, I think people are actually more comfortable(and less neurotic) when they gauge comfort by the way they feel as opposed to what they see on a thermostat display.



What I'm trying to say is that I'v designed residential systems that used absolutely no indoor feedback using Viessmann boilers with no mixing valves (no primary secondary either) and my clients were very pleased with the results.



I believe your job would have been better served with a new vito 100 (assuming the load is under 94k) and a tekmar house control 401. It gives you four circulator relays, and DHW, uses indoor and outdoor feedback combined to set the water temperature, it also synchronizes the operation of the zones to maximizes the amount of time they are running simultaneously.



Just did one like this and it seems to be working like a charm, Condensing a lot too.

CMadatMe

Scott Has It

Scott your writing comes as clean as our phone conversations. Your top spot on unfortunatley those of us that deal with this understand your lingo but I don't think this homeowner can feel the concept you bring.



Scott is a Viessmann customer of mine and someone that knows the boiler inside and out. Take his information and run with it. He is spot on with how to gain better control of the Vitodens 100. He is one of none that has taken advantage of the ability to access 0-10vc and OT on the 100 and make a simple boiler into a monster....

JED_5

going for the monster!

Thanks for the feedback Scott and Mark,



I greatly appreciate the time for someone not in the business! The unit came from Radiant heat products, not PEX. Despite all the issue's you've raised I guess alot of what Scott mentioned rings true. I'm quite happy with the product! I'm using ~50% less gas than I was before, I'm 4K lower than the lowest bid, and my house is 100% comfortable 90-95% of the time. At this rate, the system will pay for itsself and start making me money (relative to the old beast) in 8-10 years, perhaps earlier depending on price of gas and the tax rebate.   This assumes the current settings don't reduce its life span or break it!



I don't think it would be hard to repipe to a LLH. Definitely waiting until spring though!



Do either of you know a Denver area professional I could consult with (i.e hire) on this? After all the details I've heard here, I'm convinced the person I did consult with, isn't experienced enough with these systems.



That said, I'll start reading about the tekmar. Why the new vito 100 instead of the WB2B? I ask as I initially thought a 100 would do the trick, but the Radiant heat folks said I needed a 200 after I told them I eventually wanted to do DHW. Funny as they actually sent me a 100 and my friend installed it while i was out of town. Upon return I saw a 100 up there though I ordered a 200...back it went!



I like the monster analogy.  I think I can get there if I find a local who knows these systems!



Thanks again! Jay

icesailor

Heat Loss:

I agree with everything you all are saying on how to correct this thing. But, when you are all done, you are still going to have a problem. This all started with this one room. Trust me when I say that this room will NEVER work properly with the rest of the system. Uninsulated walls are one thing but the recessed ceiling lights put the whole thing out the window. Unless you have had to figure out why something you did, wasn't working in certain situations (like I have had to do many times), and you found the solution and it was the ONLY thing that caused the problem, you will never develop a respect for how bad recessed ceiling lights are above the first floor, in a slanted ceiling or an attic. They make lights that are supposed to be tight. Tight like having protected sex with a wool sock.

If all the zones in the house are tight and well insulated, and this zone isn't, like I think it is, no amount of fiddling will fix it. If it is 5 degrees out and no wind, and the boiler is cycling and the room is 70, all is well and good. On another day, it is 25 degrees out, the wind is blowing 35 and the temperature in the room won't go over 60 but the boiler is on high limit and cycling, you have a severe infiltration problem. The boiler won't work unless you fix the heat loss problem. Go up in the attic and lay another foot of insulation over what's there and cover those ceiling lights. Blow the walls with insulation and your problems are solved. Or at least made better. Been there too many times, Done that.

CMadatMe

Sorry Ice but You are Wrong

We can eliminate the problem with this boiler for a particular zone. If it becomes a nuisnace I can simply pu this zone on external demand. I can then tell the boiler what I want this zone to do when it calls. The rest of the house can go on reset and I can tell the boiler what water temp I want when this zone calls. I can also gain control of the pumps from the boiler for it too....

CMadatMe

Mark Eatherton

Get a hold of ME he is here on the WALL all the time. I know he is in the Denver area but you would have to contact him to see if he services your area.



Generally with a system that requires less than 120,000 btus and only requires one water temp the 100 fits the bill and that includes using an indirect. The Vitodens 100 has the same heat exchanger as the 200 although the gas valve and control are different. For a baseboard job I never go to the 200. It's overkill. The 200 is more meant for multiple temp applications of where you need more that 120,000 btu's. Viessmann only makes 2 Vitodens 100's and the 120K is the biggest.

scott markle_2

the monster

Thanks for the encouraging words chris..



To spite my own fascination with the interface of algorithmic electronics and pipes and valves I will admit that implementing this stuff is not with out it's struggles. The monster bites both ways.



The good news is that once these systems are fully dialed and debugged they seem to hum very well.



I'm actually having some kind of issue with the tekmar and the open therm interface. boiler is not going to high fire even though the control has not reached it's target.



I'm sure the good folks at tekmar and viessmann will come to my aid, but yes problems do effect moral and profits.



Another way of viewing a problem (before the multi meter goes flying across the room)

is as an opportunity to learn. Some of the best leaning experiences are not the slam dunk jobs but the ones that gave us a problem.



Hard to frame it this way with all of the pressures facing the self employed



My advice to the OP. Can you add some radiation to this zone. If you have the required flow I might consider a mon-flow T to a panel radiator. Or just swap out for high output base.



Another thought. Get rid of the the bing/bank stat that you have in this high heat loss room/zone. Replace it with either of the Vissmann room controls that Chris mentioned. Put this zones circulator and the main boiler pump (and ideally the DHW pump too) all on the appropriate relays that the 200 provides.



This room/zone will now set the reset curve for the whole heating circuit based on a combination of indoor and outdoor feedback. Because this zone is clearly the zone of greatest demand the remaining zones will generally be receiving warmer than necessary water, and will be regulated by the bing bang stats. Because the curve will be higher than necessary you will loose some efficiency but you will gain a bit of headroom, I say forget using the individual stats for setback and use the boilers clock to set your (single) setback schedule, keep it fairly tame maybe 3 or 4 degrees. Time your recovery to reflect the responsiveness (lack of) of your system.



I wouldn't pull the hydo seperator for a low loss header before you improve your insulation/infiltration or up your radiation. While I'm sure there is good reason to get feedback from this sensor location it may not be the make or break issue for you.

Paul Pollets

tekmar??

why use a tekmar with a Vitodens 200 W2B??

CMadatMe

Not On a 200

Paul,



The Tekmar was incorporated into a Vitodens 100 not a 200.

JED_5

-9 today and the monster

Scott,

Your suggestions (and others) are all extremely helpful and I wish you luck on your issue (as if I can give you any useful ideas!).  I'm fully enamored by this new technology, and figured it would take me time to dial things in, just didn't know the learning curve would be steeper than the heating curve so to speak!   Sounds like I need to: 

1.  Make sure system design is functional and coding matches.  This means A.  heat loss eval for each room.  B.  Likely a LLH+sensor. C.  Mating the system to a better control system (tekmark, vitotronic).  While I'm at this I should probably do the DHW so it's fully integrated. That said, I'm curious about Scotts comments regarding installs with no pri/sec and only external control.  

2. If not enough, consider physical changes to the house.  Step 1 would be better insulation.  Step 2, up the BTU's getting to the rooms with more fins and reset coding.  Knowing if this is necessary should come from the Heat loss eval. 

The cold has hit and the boiler temp is not going above 165.  I'll track down the infamous ME or one other contact I have and start the process!

Thanks again!  Jay

CMadatMe

More Fins

Jed,



Instead of adding more board consider changing out the existing board to a high capacity board that will fit in the same profile as the existing board. If you have simple residential board going with high capacity will give you more btu's per sqft yet you won't have to really do any re-piping other than sweating in the high cap to the footprint of the existing.



As an example Suntemp 700 Series Residential puts out 560 btu's a foot with a 1gpm flow rate and 180 degree water. Suntemp 800 Series puts out the same btu's with 160 degree water.



Attached is a de-rating chart that could be of use as you continue on your project.

Viess

Coding.

Sounds like we have pretty much the same setup. I have a WB-2B with finn heat.

The High Temp setting is to protect the boiler. Set it and forget it.

You need to go to Coding Level 1 d3:14 and change the slope. The factory setting is Slope 1.4 Shift 0 You only need to change the slope according to what your average lowest temp is for the winter or what works to keep the place warm. A higher slope value will allow the burner to raise the boiler operation temp. In the summer you may need to turn it back down if you can't control the room temp by just turning the temp dial down on the boiler.

PS the slope is adjustable from .2 to 3.5 or as it is seen on the screen 2 to 35. So if the boiler is factory set the slope will read Slope 14 and Shift 0

JED_5

coding

Hi Viess,







Thanks for the possible solution.  Slope and shift have already been bumped up quite a bit.  Can't get the boiler temp beyond 165, and it should be based on the curves.  External temp on return pipe hover's very close to the 14.4 F (address 9F on Coding 2) degree differential (165-14.4  = 150) discussed in my manual (p. 30..describing the heating curves).   That said, I won't mess with the 9F address (differential setting) as I assume making the boiler increase water temps beyond factory settings is asking for trouble. 

I'm clueless about how the control unit truly works beyond what the manual says.  I wonder if it won't pump out more BTU's because it does not have any info on the room temp vs. the thermostat set point (about a 2 degree difference right now).  

Address 06 is set at 82C  ~ 180F.  

Address C6 is defaulted to 165F (the current, seemingly max the boiler is putting out).  It's described as the "electronic maximum supply temperature limit".  I've changed it, observed, then set it back to the default with no apparent change in boiler output.   I wonder if C6 only functions if a temp. sensor is attached in the LLH.  Again, just a hypothesis. 

Jay

scott markle_2

Direct connect

Direct connect systems have very specific flow requirements.



One of my favorite systems was all home run TRV'd pannel rads to a old style Vito 200

Which had a built in variable speed pump and differential presure bypass, a really simple and elegant system.



You really need to understand flow rates to do this successfully.

scott markle_2

Direct connect

Direct connect systems have very specific flow requirements.



One of my favorite systems was all home run TRV'd pannel rads to a old style Vito 200

Which had a built in variable speed pump and differential presure bypass, a really simple and elegant system.



You really need to understand flow rates to do this successfully.



Sorry for the double post, darn I phone... BTW I got the monster

"dialed in" and she it working like a charm, problem was simple, the guys

at Tekmar are great.



Jed, your interest is keen but just remember "a little knowledge is

dangerous thing"

JED_5

tomorrow

Thanks for all the help folks. ME is coming over tomorrow.  Should be humbling.

Jay

CMadatMe

What's the Result

So how did you make out with ME?

Viess

Hey Jay

Hey Jay what did Me have to say?

Mark Eatherton

Not happening yet...

JED was told by the factory that the boiler couldn't and shouldn't be raised above the 165 limit. They recommended an increase in EDR to accommodate the lower water temperatures. The best I could do at this point is to confirm proper fuel pressures, code settings, flue gas analysis etc, and it doesn't sound as if he's short fuel because if he were, he wouldn't have been able to hit the 165 temperatures he is achieving.



Am on standby for the time being whilst he consults with his better half regarding his next move. He has a bunch of other "issues" that need worked out prior to my showing up, and he is aware of those thanks to all the comments on this post.



ME

JED_5

exactly

Mark got it right.  We need to discuss the potential for DHW and a radiant floor in a currently unheated sunroom-like add on the previous owners built.  Unfortunately, I'm out of town all next week and most of the next.   I hope everyone can handle the suspense!    Thanks again, to all!





jay

Viess

Sizing?

So the heat loss of the house is greater than the output of the boiler? Or you just don't have enough baseboard finn tubes to extract all the heat the boiler is putting out?

croydoncorgi

But this is a CONDENSING boiler!

Whew - LOTS of replies here - maybe I missed what I was looking for, but I only found ONE use of the word 'condensing'.



Point is that this boiler WANTS to condense to be efficient but CAN'T unless the heat exchanger is cooler than around 130 degrees.  That's basic physics.



If you wind the temperature up to 176, yes - the boiler will do it but it will also protect itself by not allowing the temperature difference across Flow and Return to exceed 35 degrees or so.  Therefore, if it gets to 176, the minimum the Return COULD be is 141 degrees.  So no condensing is possible!  (and up to 7% of your potential fuel-efficiency is lost)



Also, as I've found to my own cost, getting the design wrong with large-water-volume systems and low-water-content, high-resistance boilers is very easy and potentially expensive to fix.  Problem is that WHATEVER pump you put on the system, it's phsically impossible to get enough water around the system to RAISE the Return temperature fast enough.  The system then 'gets stuck', with the burner at low power, the Flow nowhere near the setpoint and the Delta-T at max for the boiler.

I guess that's why Viessmann is so keen onfitting headers on converted systems in the US.



PS Sorry if I sound like I'm teaching egg-sucking, to use a British phrase.

CMadatMe

Condensing

Sorry but water temp alone isn't the only driving factor of efficiency. Rate of modulation plays just as important of a role.  See attached graph.



One of the benefits I believe with this particular boiler over most is not only the recommended use of low loss headers but the use of the sensor in it. The boiler is more concerned with keeping system side required water temp then boiler water temp.

croydoncorgi

Not showing its best curves!

But those graphs are not modulation rate!

They show part-load and full-load efficiencies at different delta-Ts.  Surprising thing is that in UK that graph doesn't appear anywhere, as far as I can see.  The boiler specs here quote just 2 figures: 1 for part-load, 1 for full-load.  The thing that kicks up the tail of the efficiency graph is higher flue temperatures as the gas flow through the boiler approaches max.



Which temperatures do tghese curves represent? Boiler? or the sensors on the header?  To be honest, if they're the boiler delta-Ts, there's something wrong somewhere....the stack loss for this type is not going to be THAT bad at (say) 80% load on trhe middle curve.  Or is it showing other losses too...?



Another question: why choose (specifically) the 140F and 120F temperatures?  The boiler can work with a bigger difference, so if 140F happens to be the desired Supply temperature, why not use 110F as the Return.  Then the curve (with much more condensation possible) would be much flatter.  Or maybe not.....

Viess

Condensing.

I think most of us get the condensing part but the further north you go at times depending on your setup the boiler may have to operate at a little higher supply temp than what's ideal for condensing. That's why I asked if adding additional registers or maybe  some radiant floor heating would allow more heat into the room there by reducing the return water temps. Voilà back in condensing mode. My setup has the low loss header with sensor, outdoor temperature sensor, all baseboard finn tube heat. The system is around 25 gallons and the boiler holds less than one gallon. Small tube high resistance that requires one pump strictly for overcoming the header loss and one pump for constant circulation of the system. When it gets really cold say 20 below the  boiler runs a little out of the condensing mode range. If I had radiant in floor heat it would probably run in fully condensing mode all the time.  Still getting 50+ percent savings over the old boiler. 

croydoncorgi

'Slight Pregnancy!

The awkward thing about condensing inside a boiler is that it's like pregenancy: the temperature of the heat-exchanger surfaces is either below the Dew Point, or it's not.  If not, NO condensation takes place at all.  Then there's also a necessary question about how far BELOW the Dew Point the temperature needs to be for condensation to deliver  useful benefit.  The Dew Point figure is usually taken to be 56C / 133F.  Obviously, the back end of the HX is going to be cooler than the end nearest the burner.  I usually work on the assumption that Return temperatures in the 40s Celsius will give a good rate of condensation.  The detailed performance depends on multiple other factors: actual gas flow through the HX, and temperatures at different locations, and other variables depending on the design.  If you REALLY want a boiler to condense a LOT and achieve maximum efficiency, then set the SUPPLY temperature BELOW 133F!  Believe it or not, with many designs of underfloor heating, that's perfectly practical - but the boiler is then not very useful for other applications.



I was suspicious about what the graphs in the posting above were actually showing because there are no 'knees' in the curves where condensation might be expected to start to have an effect.



Sizing of the radiators (of whatever type) with respect to the heat losses of the rooms is clearly critical.  It's the heat-transfer that matters, so surface temperature (relative to the air temperature in the room) times effective surface area is what counts However, there are also user expectations and assumptions to consider.  Users expect radiators to be HOT.  If they're not (by design), then users will tend to judge the room comfort subjectively and complain that 'they're cold'.  Re-education, that high-efficiency heating means cool radiators but warm rooms, often needs to be a priority at the start of a new system.  Hiding radiators under covers is also more damaging to system performance if the surface temperature is low.  They reduce air-flow and therefore effective surface area - but interior designers just LOVE fancy covers!

croydoncorgi

Another useful Viessmann document

IF you can handle the math - I struggle with it!

Viess

Comfort.

One other initial assumption/mistake my installer made was he tried to set the system up just like the old one. On or off zone heat with zone valves. These boiler are meant for continuous circulation. Only when the outside temp is within 2 degrees of the indoor temp will the circulating pumps and boiler shut completely off. Nice even heat with no over cycling. The nice thing about these boilers if your wondering about weather or not your boiler is condensing and at what temp is ideal. All you have to do is place the condensate tube into a 5 gallon bucket and watch it. It won't take long and you'll get a good feel for what's ideal.

Jean-David Beyer

Good feel?

I only have a 2-gallon bucket; of course, I could buy a bigger one. In warm weather, I get about 2 gallons a day. When it is cold, though, the water freezes on the top of the bucket, and the rest spills out. But to be useful, I have to know not only how much water condenses, but how much gas I used at the time, so I can calculate how much of the possible condensing I am actually getting. The fastest needle on my gas meter goes all the way around when 1/2 cubic foot goes through it, so I could record those measurements.