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help with moderately complex system
Harold
Member Posts: 249
I have a real problem with the heating system for my new home. I would appreciate some help on this.
First the conditions and history. I am building my retirement house. For various reasons involving getting subs to schedule my project we started before we should have. I had set limits on the overall cost and we had a foundation poured before my general contractor provided a cost. It was double what we had targeted with him and much more than we could really afford. In general I am using subs recommended by the builder. Identifying the experience and knowledge of local subs was the primary reason I did not fill the general contractor slot myself.
The recommended HVAC sub specified the major system components but failed to provide a meaningful system diagram. They simply copied one from someone's manual and it did not particularly resemble anything I had specified. He was unable to really discuss how things were going to work. He ignored my requirements that I presented to him prior to the bid and how the house would be built. He specified a system with constant circulator operation. While I believe the constant circulation has some merit and is popular in Europe, the energy consumption and wear and tear did not seem reasonable to me. Without any discussion he switched to non-constant circulation after I asked for the rational of constant circulation.
I sought another bid from the plumbing sub who is also a radiant heating contractor. I waited too long and the vendor took way longer than they said they would to provide a bid. I got their bid on a Friday and literally had to decide which vendor would start putting tubing down that weekend. The second bid was twice as much as the first bid and both were using name brand equipment (Wirsbo and Roth). I preferred Wirsbo, and it was a more professional proposal, but they were the 2X price. So I went with the original sub.
I once again asked for a system diagram, the manual for the controllers, and an explanation of the design. I got another diagram copied from somewhere with the comment "it is not what we will use but we can fix it". That brings us to today.
Tubing is going down. I am going to have a Munchkin TM 80 boiler, which I specified. I am using the boiler to feed indirect DHW, a higher temperature air exchanger for make-up air for the range hood, and 18 radiant zones. The max heat load for the house is about 47KBTU. The fairly mild local climate and building use is such that I could easily have minimum demands of only a couple of KBTU for heating with just one or two zones active. R8 glass everywhere. Two large rooms have most of the wall in glass and they face due South. Overhangs are designed to provide winter solar gain and shade during the non-heating season. All of the floors are exposed concrete with a 4" slab thickness. The tubing is at the bottom of the slab. I did not want the tubing that low but everyone insisted on that because we will have to do a lot of decorative/crack controlling cuts.
I believe the two rooms with all the South facing glass will have a problem with overheating. I also think the boiler will short cycle in any of the contractor proposed systems.
I have a system drawing form Modern Hydronic Heating that John Siegenthaler kindly sent me that mostly validates the implementation of what I have been asking for. A tank that works as a buffer for heating and as a DHW source. My intent was to allow only boiler water in the tank and use exchanger coils in the tank to provide DHW and radiant. The drawing I have has the boiler on a secondary loop using closely spaced Ts to get water into the primary loop. The storage tank is then in series with the primary loop and zones are taken off the primary as secondary loops. The boiler loop is after the tank bottom connection and before the primary circulator. This design means that both the boiler circulator and the primary loop circulator will have to run for DHW. This also heats up all of the piping associated with the primary loop. I am not completely happy with this. I would think there would be merit in using the storage tank as the only load for the boiler and then using coils to feed everything else. This still has the same number of circulator pumps for heating but keeps the amount of pipe involved when heating only DHW somewhat smaller and runs only one circulator when heat is needed in the tank. The drawing I am talking about shows the primary loop return water entering the top of the storage tank and the boiler return from the bottom of the tank. It seems to me that this scenario will mix the tank water quite a bit and potentially lower the DHW performance. It would also feed the primary loop from the bottom of the storage tank which would, it seems to me, not provide the hottest water to the primary loop when the boiler is off. I would think swapping these tank connections would make more sense by maintaining some stratification and higher exit temperatures for DHW. If I keep the boiler out of the primary loop and just feed the tank, then the boiler could feed the top of the tank and draw from the bottom. This may also make it easier to keep the Munchkin condensing.
The two problem rooms with the South facing glass I believe need slab sensors and smart thermostats if they are going to have even a chance of being comfortable. The control environment of all this is moderately complex. I have read the proposed controller manual (Roth 1050) and have the distinct feeling that it is not up to controlling this environment. I believe that this is a rebadged Tekmar unit. The contractor did not know for sure but he thinks it is a 362 or 363. The contractor's current approach to feeding the heating loops is with a common circulator and zone valves. Rather than use a pressure controlled variable speed circulator, he is proposing a fixed speed unit and bypassing the flow as valves close. I am not real fond of this either. The Munchkin also has a Vision 1 update to their internal controller which may not play nice with everything else.
What I am trying to learn about is the proper boiler, controller, system configuration, and the overall strategy. In other words, how should I do this. I have to get this resolved with the contractor before it is too late.
First the conditions and history. I am building my retirement house. For various reasons involving getting subs to schedule my project we started before we should have. I had set limits on the overall cost and we had a foundation poured before my general contractor provided a cost. It was double what we had targeted with him and much more than we could really afford. In general I am using subs recommended by the builder. Identifying the experience and knowledge of local subs was the primary reason I did not fill the general contractor slot myself.
The recommended HVAC sub specified the major system components but failed to provide a meaningful system diagram. They simply copied one from someone's manual and it did not particularly resemble anything I had specified. He was unable to really discuss how things were going to work. He ignored my requirements that I presented to him prior to the bid and how the house would be built. He specified a system with constant circulator operation. While I believe the constant circulation has some merit and is popular in Europe, the energy consumption and wear and tear did not seem reasonable to me. Without any discussion he switched to non-constant circulation after I asked for the rational of constant circulation.
I sought another bid from the plumbing sub who is also a radiant heating contractor. I waited too long and the vendor took way longer than they said they would to provide a bid. I got their bid on a Friday and literally had to decide which vendor would start putting tubing down that weekend. The second bid was twice as much as the first bid and both were using name brand equipment (Wirsbo and Roth). I preferred Wirsbo, and it was a more professional proposal, but they were the 2X price. So I went with the original sub.
I once again asked for a system diagram, the manual for the controllers, and an explanation of the design. I got another diagram copied from somewhere with the comment "it is not what we will use but we can fix it". That brings us to today.
Tubing is going down. I am going to have a Munchkin TM 80 boiler, which I specified. I am using the boiler to feed indirect DHW, a higher temperature air exchanger for make-up air for the range hood, and 18 radiant zones. The max heat load for the house is about 47KBTU. The fairly mild local climate and building use is such that I could easily have minimum demands of only a couple of KBTU for heating with just one or two zones active. R8 glass everywhere. Two large rooms have most of the wall in glass and they face due South. Overhangs are designed to provide winter solar gain and shade during the non-heating season. All of the floors are exposed concrete with a 4" slab thickness. The tubing is at the bottom of the slab. I did not want the tubing that low but everyone insisted on that because we will have to do a lot of decorative/crack controlling cuts.
I believe the two rooms with all the South facing glass will have a problem with overheating. I also think the boiler will short cycle in any of the contractor proposed systems.
I have a system drawing form Modern Hydronic Heating that John Siegenthaler kindly sent me that mostly validates the implementation of what I have been asking for. A tank that works as a buffer for heating and as a DHW source. My intent was to allow only boiler water in the tank and use exchanger coils in the tank to provide DHW and radiant. The drawing I have has the boiler on a secondary loop using closely spaced Ts to get water into the primary loop. The storage tank is then in series with the primary loop and zones are taken off the primary as secondary loops. The boiler loop is after the tank bottom connection and before the primary circulator. This design means that both the boiler circulator and the primary loop circulator will have to run for DHW. This also heats up all of the piping associated with the primary loop. I am not completely happy with this. I would think there would be merit in using the storage tank as the only load for the boiler and then using coils to feed everything else. This still has the same number of circulator pumps for heating but keeps the amount of pipe involved when heating only DHW somewhat smaller and runs only one circulator when heat is needed in the tank. The drawing I am talking about shows the primary loop return water entering the top of the storage tank and the boiler return from the bottom of the tank. It seems to me that this scenario will mix the tank water quite a bit and potentially lower the DHW performance. It would also feed the primary loop from the bottom of the storage tank which would, it seems to me, not provide the hottest water to the primary loop when the boiler is off. I would think swapping these tank connections would make more sense by maintaining some stratification and higher exit temperatures for DHW. If I keep the boiler out of the primary loop and just feed the tank, then the boiler could feed the top of the tank and draw from the bottom. This may also make it easier to keep the Munchkin condensing.
The two problem rooms with the South facing glass I believe need slab sensors and smart thermostats if they are going to have even a chance of being comfortable. The control environment of all this is moderately complex. I have read the proposed controller manual (Roth 1050) and have the distinct feeling that it is not up to controlling this environment. I believe that this is a rebadged Tekmar unit. The contractor did not know for sure but he thinks it is a 362 or 363. The contractor's current approach to feeding the heating loops is with a common circulator and zone valves. Rather than use a pressure controlled variable speed circulator, he is proposing a fixed speed unit and bypassing the flow as valves close. I am not real fond of this either. The Munchkin also has a Vision 1 update to their internal controller which may not play nice with everything else.
What I am trying to learn about is the proper boiler, controller, system configuration, and the overall strategy. In other words, how should I do this. I have to get this resolved with the contractor before it is too late.
0
Comments
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No disrespect
Sir,but it sure sounds like you have a bmw taste on a shoestring budget.
I think,being you'll the boss,you should put your project on hold and get all your issue address.
Called a couple of more contractor if you have to.But make
sure that you dont put in a system that you will not be happy with the rest of your life.The time to get it right is now.
If the first contractor can not show you the math,then moved
on to the next one.
I'm sure there a reason that # 2 is higher then the other one,Have you ask?
It sound like to me you have alot of great issue to be address,heck you could proberly talk all day on how to control high mass and solar gain and get many opinion.
If I recall Mr Siegenthaler does consultant for a living.
I sure he be more then happy to design a system that will
address all your issue,at his price.
For us contractor it so hard to get some of our customer to compare apple to oranges,because they are focus on price alone.
Please,what ever you do dont rush in,and squeez some more out of the buget and get someone who and can address all your issue,you only have one chance to get it right.
Good luck!
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what page in ziggi's book
fyi about connection swapping -
cooler water is denser - thus heavier, and will displace warmer water even in a single pipe, so if you are not pumping DOWN at least 18" vertically from hot to cold, then you better use spring flow-checks liberally or cooler water will just drop right into your holding tank or DMH tank - so dont pipe anything in the boiler or system piping that will promote natural convection enforce the rule that only a pump is allowed to move any water from point a to b in you system
you wont have a problem with overheating if you use tekmar 500 series thermostats with slab sensors, In fact, besides the internal air sensor it can take two others, and you can add even more for temperature averaging, as long the sensor loops mean resistance is 10kohms, you can series/parallel wire the sensors with 2 rows of 2 sensors, or 3 rows of 3, 4 rows of 4 and so on and have it average out the temps in the space
also, focus on comfort and control, not efficiency, it is an elusive goal that is usually not finely, achievable outside the lab, I am not saying economy is not important just that its secondary
that cost of ziggis software is nothing compared to what mistakes can cost you get it
I also hate radiant in a slab if there is a choice, I prefer the above the floor composite aluminized panels with the slots for pex, The R values are lowest and its easy to fix later eg thermal track from zurn --- http://www.zurn.com/pages/catalog.asp?ProductGroupID=137&OperationID=17
You might also consider http://www.warmfloor-solutions.com/index.html
ps tekmar themselves have great application diagrams - the A-brochures at http://www.tekmarcontrols.com/literature.html0 -
Are you in Colorado???
This project sounds painfully extremely familiar...
Probably happens every day...
ME0 -
why
tie the radiant AND potable water together?
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
Responses to posts
Don - I do not believe I am focusing on cost. Cost is always a factor. Both vendors proposed very similar (mostly identical) equipment but one was $20,000 more. I beleive at least some of this was because of number two being a bigger contractor with higher rates/margins. The project being delayed will also cost an appreciable amount of money on a daily basis as well as possibly losing some subs to scheduling conflicts. Both of these contractors appear reputable. I have no reason to believe I will randomly (or any other way) find someone who does understand or pays sufficient attention. This customer was focusing only on properly doing your fruit comparison until they showed up with banannas and peaches, and hit me up side the head with price differences.
Kal - I believe I understand the convection issues and one of the things that puzzels me is that the buffer tank is configured on the return side of the loop with the cold return water going in the top and the cooler bottom water entering the loop past the boiler secondary loop. That is why I was talking about a loop with just the boiler and tank and then the tank feeding the high temp side of the primary loop from the top. Regarding the thermostats - yes I agree. I have seen discussions of these before and that is my target. The contractors both proposed only regular thermostats for these spaces. Comfort is indeed my number one priority. But "needless" energy uses will be minimized. The floors are already half poured. We chose colored concrete as our finished surface to avoid carpets over the radiant, provide an easy to maintain surface, and keep costs down. And we like the look. If we were doing something else for a surface I would have probably used a thin slab. Particualrly in the South side I need the mass.
Dave Yates - I am not sure what you mean here. The DHW and heating water are not "tied together" any more than any other indirect DHW system.
Mark - I am in the Pacific NW north of Seattle.
Please keep the ideas comming.
Harold0 -
to resound the question...
connect the radiant into the domestic.... ? if you are the engineer of choise maybe a second opinion is in order.heres a what if.....you are away on vacation your houssitter calls joes plumbing and heating repair...joe arrives oh wow! this thing needs Anti Freeze! pumps a 30 70 mix into the Radiant...after fixing a blown out 3/4 " 90.maybe joe left his divining ex ray glasses home that day.had no idea some one would even Consider plumbing these two waters together,...0 -
the return water may be cooler but still warm
and would also still be warmer the the buffer's outlet, so we pump down, as for it going downstream, it seams that the buffer is being used as a mix buffer, and when the system comes to full temp, will have plenty of energy left to mix down - pls post the diag0 -
Clean and treat
When you get the system completely installed, you should then consider cleaning and treating the radiant side of the system. This will prevent all kinds of future chemical problems within the system. Check out our web site at www.rhomarwater.com. You can also call me at 800-543-5975
This final step is missed by many, much to the regret of the homeowner when the problems begin to appear.
This pre-ventive maintenance will keep the system working at peak efficiency.0 -
well
"My intent was to allow only boiler water in the tank and use exchanger coils in the tank to provide DHW and radiant."
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
If you are near Seattle.......
call Paul Pollets at Advanced Radiant Technology. www.advancedradiant.com Listen to Paul. No one better in your area.
hb
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"There was an error rendering this rich post.
0 -
Is this the diagram you're working off of?
http://www.pmmag.com/pm/cda/articleinformation/features/bnp__features__item/0,,78589,00+en-uss_01dbc.html
Here there's one, but with your 18 zones, there might be a need for two, utility secondary zones to parallel feed the low temp radiant zones. Remember the indirect is on the primamry loop with a large water mass with most of the hot water flow moving to the indirect. The low temps off the other secondary cannot drop the buffer tank's temp that quickly unless all the zones come on at the same time from a setback condition (REAL COLD RETURN). The down side is you need many circs running at the same time, but the priority here is to optimize the boiler run time not electrical costs.0 -
This doesn't Sound
like it'a all that complicated. You have 1 application type tubing in slab. 18 Zones are worthless unless there are thermal breaks in the slab in between zones. Remember hot goes to cold.
Basically you have a high temp zone and a low temp zone. The high temp zone should be taken off the same supply and return that the indirect is on. Let the boiler's curve control the radiant. No mixing valve. Use a high limit aquastat that breaks on temp rise. As for the solar gain issue. Wether you have a slab sensor or not it won't help unless you have that thermal break. If that room with the solar gain is not calling but an ajoining room is calling it's going to migrate to that portion of the slab. Your problem could be repspone time when that big heat tab in the sky goes down and you need that heat now.
You say you have 18 zones. How many manifolds? I bet it's all telestated. Not a very good design. The tubing is in a slab, water temps should have been close enough where it possibly should have been zoned via manifolds.
Did you ever get a RADIANT HEAT LOSS/DESGIN. That alone should tell the story. Like others have said I would get someone in there that knows what they are doing. Doesn't sound like the people you are dealing with do.0 -
More responses
Joe - that indeed is the diagram John sent me. I have attached a rough sketch of an alternative that I would like to have feedback on. I have no details like reverse limiting, valves etc. in my drawing.
I have done full heat loss analysis. I am trying here to get thoughts on appropriate controllers and archtecture. The environment is known.
Isolation of slabs between zones is an interesting point. I will look into that. All zones, with one exception, are separated by doors. If anyone has experience with inter-zone interference please share your results. For large zones particularly, I would think that the effect of edge gain/loss from adjacent zones would be a fairly minor influance, but I have no data.
I do not know how many manifolds are configured. Remember part of the problem here is no system diagram. There are 3 so far in the basement.
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Your diagram
is only partial without the details of the primary loop, correct? I don't see the difference of having a second heat exchanger for the primary loop. You've only complicated it by now requiring water feed/air elimination and expansion tank requirements for both boiler and the heating side of the system. Without the boiler being an isolated secondary, you've made it easier for the boiler to suck heat back out of the tank as it cools due to stand by loss. You have 18 zones, indirect and a high temp air makeup fancoil and you're worried about an extra circulator! I don't know were you would even find a stock double coil tank like that, possibly from solar heating manufacturers,0 -
May I ask
why you have 18 zones in a home that has a 47k heat loss?
Mark H
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Buffer tank suggestion;
Gregg Gibbs got me an Amtrol tank that has the DHW coil in the TOP of the tank. I need a maximum of 140 degree F water in the tank to provide copious amounts of DHW. Their intent with this tank is to provide dual use, a buffer tank as well as a low temp (as opposed to 180 deg F) DhW tank.
I can't seem to locate the schematic they provided me with, and I didn't hook it up the way they wanted me to anyway because of the little condensing boiler I have on line. THey also make a dual coil tank, one on the bottom and one on the top.
Call Gregg Gibbs at Shamrock Sales at 303-399-9181 and I'm sure he'd be glad to line you up.
PS, I found the drawing..
ME0 -
Amtrol Buffer Tank
Harold, you are welcome to give me a call 303.399.9181...
The Amtrol Rep. in your area is Mechanical Solutions (Jim Cooke) 509.448.12000 -
For the same reason a dog licks himself...
because he can!
Sounds like short cycle city without a buffer tank to me....
ME0 -
20 zones.
went to visit a house a buddy is tweeking,20 zones not counting the water maker.and 3 car garage. lotsa square footage..2 buderas..garage slab and basement two radiant Zones:) 18 other assorted panels towel warmers base board toe kickers:)) work of art:)dialed in
his buddy worked for a year and a half on the plumbing and heating:) just way Large building. 0 -
zones
Thre are two ways to get 47 KBTU load. Small house with not-so-good insulation or pretty big house with real good insulation. I have the latter.0 -
MOre concise questions
I have not quite gotten the responses I was hoping for from my rambling questions. Let me present some explicit questions whose answer would help my progress.
1 - Is a Munchkin with Vision one the correct boiler or is there a better choice?
2 - What controller do I need to run this system? Preferably a Roth model number but Tekmar model is OK.
3 - Is the system diagram from John the best way to accomplish what I need. Is there merit to running the boiler ONLY to the tank as I have described?
4 - How important is slab insulation between zones?
0 -
Your questions???
The Munckin is a decent boiler, but not the best ...in my opinion. Have you considered Veissmann? Or Buderus?
If using the Vision 1 control on the munchkin, then you are being somewhat redundant, by thinking you need Tekmar or other. Yes they do more than the vision 1, but how much more do you need than the oudoor reset, dhw sensor, high temp. zone and the radiant control in vision 1?
We use a lot of tekmar and love it, but not on Munchkin.
Boiler systems are just that, "systems". You will find that most better companies have thought out the control process, for their boiler, a lot more than you have. I would advise sticking to designs that match the boiler you choose. Try to combine the best of all worlds, and you may end up with a mess, and spend way more than needed to do a great system.
Their may also be real good reasons the contractor has chosen to do things a certain way, but I agree, he should be able to tell you why. Could it be he wants to install soemthing he can stand behind 100%? I have had customers who wanted me to do things certain ways, and I sometimes have refused. After all who are you going to call if it doesn't work right? Are you hiring someone to apply their knowledge, or just yours? If so, are you taking the warranty responsability for the job?
Steve0 -
This Siegenthaler's design
is realy not for a modulating/condensing boiler, just low mass. Since you have to keep the buffer/indirect tank above 140 to insure hot water availablity, when would it get a chance to modulate or condense? During the summer, the boiler could be cold started when DHW calls lower the tank temp but is would have to run for at least 10-15 minutes to bring the 26 gl of boiler water up to temp. No need for outdoor reset and I don't think that DHW priority is possible since you dont know if DHW is flowing through the coil, reducing the tank temp.
You might want to look at his older diagram in which the indirect is in parallel with the primamry loop piping.
Now you can use all the features of the Tekmar or Vision controls. I think having the reverse indirect there adds some buffering and the boiler can run full tilt on a DHW call, or modulate down when servicing the radiant side.
On a munchkin, I think it makes more sense to go with their electronics since they'll optimize the boiler modulation better.
http://www.pmmag.com/pm/cda/articleinformation/features/bnp__features__item/0,,66806,00+en-uss_01dbc.html0
This discussion has been closed.
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