Oversized boiler, gpm flow too fast, boiler bypass, not piped correctly?

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Old 03-20-12, 08:01 AM
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Oversized boiler, gpm flow too fast, boiler bypass, not piped correctly?

Oh wow. I wrote a long post and it got deleted somehow. Here it is again a little shorter....


Way too many things that can be wrong, but the most important is the return pipe that may not be in the right place. I don't seem to be able to post a pic yet because this is my first post. I drew a quick diagram of my boiler piping, so I'm sure I'll get it up here at some point.

Where to begin... Seriously, I've been reading this forum for 2 weeks, while not knowing which of the hundred questions to ask.

Here is my setup. 2 floors = 800 over 700 basement. I also have a top floor with a different heat source, which I won't include.

Weil Mclain 100btu gas boiler power vented. CGi 4 Gold. 4 zones total. 2 in the basement which I don't think I'll really use, and 2 up in the living space. One zone is radiant stapled up underneath the kitchen that is tiled. Kitchen is about 300 sf with 2 loops of 1/2 radiant totaling 450 feet or so tubes. They are stapled up with aluminum plates throughout the whole area and there is rigid foam board underneath for insulation. The other zone is baseboard slantfin type. Just under 50 ft. of bb in the living room/dining area for that zone. (basement has 40ft of BB)

My heat loss calculation for the living area is 17,900btu. I did not do one for the basement. (The top floor which we're not including, is <13,000 or so, loss).

I do have forced air heat throughout the house now, so this is just an extra thing I did years ago that I never finished. I would like to finally finish it before next winter season. lol. The boiler has less than 20 hours of use on it. Enough to feel the great warmth of the tile heated floors and know I want that.

So, the boiler cycles too many times. It reaches high temp of 180f in 2-3 minutes. I know NJTrooper's opinion on the IntelliconHW, but I think he may agree in my case it might work here. If I could somehow lengthen my cycle times, I would benefit a little.

My biggest concern is return temps being under 130 or so if I lowered my boiler temp range. As it is now, boiler kicks on at 140 and off at 180. That cycle goes for 10 minutes with the 2 zones being on. "ON" for 3 minutes and "OFF" for 7 minutes, then repeat, for an hour straight, if I let it go that long.

My next issue would be near boiler piping for "boiler bypass", although Weil Mclain manual says that should be second choice. Again, my concern is low water return temps.

I have a boiler circulator Taco 007 with 3 zone valves, then a seperate Grundfos pump on the radiant zone. Controlling everything is a 4 zone Argo controller and a single zone relay switch.

The return temps from the radiant is way too high. If 130 goes out, the return is max 4 degrees less. Mostly it's 0 or 1 degree less than the supply. I think this is where I need the boiler bypass to go from this return to the supply of the boiler. Or, do I need a 3 speed Grundfos pump on low(er) speed, because that is what was given to me by the people who sold me the pump, before it went bad and I replaced it with the single speed Grundfos.
 
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Old 03-20-12, 09:48 AM
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When you state:
Just under 50 ft. of bb in the living room/dining area for that zone. (basement has 40ft of BB)
Is that all finned tube or just the sheet-metal cabinets? If it is all finned tube then just like your oversized boiler you have way more baseboard than necessary. Having more heat emission than technically required is not necessarily bad, it will allow you to heat your home with a lower temperature in the circulating water and that, under some conditions, could save big time.

What you need is plain and simple in my opinion, more load. The easiest way to do this would be to install a "buffer tank" and repipe your system so that the boiler heats the buffer tank and the buffer tank supplies the heaters. You could then utilize three-way temperature regulating valves with variable speed circulators on the heating loops to supply just the required temperature to maintain desired temperatures in the living spaces. This would result in continuous water flow through the heating loops and an almost constant living space temperature.

The boiler would then be set up to start when the temperature of the buffer tank fell to within a few degrees of the higher heating loop supply temperature and raise the temperature of the buffer tank to some as yet undetermined setting. You will need a boiler bypass to allow the boiler to quickly come up to temperature to prevent condensation but the buffer tank would take a significant time to come back to setpoint thereby ensuring a long boiler/burner run time.

Downside is that it would require a fairly large buffer tank, several hundred gallons would be good in my off-hand estimation, and would be a high capital cost in addition to requiring the space for the tank. One other upside is that it could work quite well with a solar adjunct.
 
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Old 03-20-12, 10:03 AM
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Furd, thank you. I do see that a buffer tank would have been good for me, but I have zero room for one. As it is with my install, I do not have enough room for the boiler itself. It's a very tight space, that's why I have a drawing of the piping instead of an actual pic. For some reason, I'm having difficulty finding the pic on my pc to post, but that's another issue.

My friend, who is actually doing the repiping, suggested I should run BB heating to my second floor bedrooms. This would make use of the extra boiler capacity I have and IMO be more confortable. I do love the radiant heat under the tiles, even though they were only on for a day or so. The BB heat was a lot better than the forced air I have as well. But that is a higher price tag and may or not be in the future.

The first floor BB is all BB or fintube. Every foot of it is heating element, then it returns with the copper pipe on top of the elements, inside the enclosure to the boiler. 90 or so feet altogether between the basement (40ft) and first floor (50ft) is all actual heating fins or elements (sorry, don't know the terminology).

Would a 3 speed pump be a good application here since the flow rate seems way too high? Will the boiler bypass do anything to the flow? Can I adjust flow in any other way? My short term goals are installing Intellicon HW, boiler bypass and making sure the radiant zone return pipe is in the proper location, along with the high flow rate fix.

I just need to locate that drawing, which is a work of art btw. Thanks again for the reply.
 
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Old 03-20-12, 10:35 AM
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OK, here it is. Click on the link below... Yeah, it's funny, but I hope it can be seen. Can I do a boiler bypass from the return of the radiant on the bottom left, to the supply pipe of the boiler? Is that all I would need for that aspect of things?

Yes, the pump may be in the wrong place too. It should probably go on the right side of that expansion tank? If it's OK there, then I'll leave it because of the tight constraints.


drawing of boiler piping...

http://img13.imageshack.us/img13/770...awingforum.jpg
 
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Old 03-20-12, 10:36 AM
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First, if you want to post any pictures or drawings they first need to be uploaded to a photo hosting site such as photobucket.com and then post the public URLs here.

I would advise against the Intellicon and the boiler bypass. Neither will do you any good in your present situation. You simply have too much boiler for the load. My only other recommendation is that your present setup would work well with a small modulating / condensing (mod/con) boiler.

Others will have additional thoughts on using variable speed pumps. Residential systems are a bit out of area of expertise.

Ideally your 007 should be "pumping away" from the expansion tank but there are probably tens of thousands of installations piped as is yours. Unless there are air problems you can probably leave it as is.
 
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Old 03-20-12, 10:55 AM
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Thanks Furd, I would like to leave pump as is then. I did finally post a link to the drawing in my last post. We must have posted at the same time.

As it is, the boiler may be more efficient than my forced air heat, so tweaking it somewhat may help more. If all is well, I will just keep it like that if the fast gpm flow will not hurt anything. Again, I've only had it turned on for 10+ hours. It is now off for the season until next year. It's a "brand new" boiler that's over 5 years old. lol.
 
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Old 03-20-12, 03:12 PM
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Isn't the return from the radiant floor in the wrong place?

[I just started reading from the first post and see that is one of your first concerns... I looked at the beautiful diagram first!]
 

Last edited by NJT; 03-20-12 at 03:32 PM.
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Old 03-20-12, 03:50 PM
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As it is now, boiler kicks on at 140 and off at 180.
How so? I don't believe the controls on the WM have a 40 Diff.

"ON" for 3 minutes and "OFF" for 7 minutes, then repeat, for an hour straight, if I let it go that long.
And all this time it's not heating the home and satisfying the thermostats?

I doubt that you will need a bypass. A bypass may actually make a short cycling problem worse.

I don't think you should expect a 20 DT from the radiant floor, but the pump may well be too large. Scanning quickly I don't see that you've mentioned the pump model you are now using for that.
 
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Old 03-20-12, 03:52 PM
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Check out this article and see if there's something there to help:

A Little Floor Warming Please---John Siegenthaler - Column - Plumbing and Mechanical

If you tie that mixing valve in with a pair of close tees, and move the return from the radiant to the other side of the 007, you won't have to worry about the 130 water returning in large volume back to the boiler.

I believe this (the middle pic) is what you want to shoot for:


image courtesy pmmag.com

Unfortunately, none of this will help a short cycle problem of an oversize boiler and small-ish zones.
 
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Old 03-20-12, 05:05 PM
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Ha! You like that drawing, huh?

Thanks NJ, for the replies.

Yes, I think that return from radiant is in the wrong place. I'll have it move to above the pump. If I can move the pump as well, to the other side of the tank, I will. The other piping, I'm not so sure.

The boiler turns on and off like clockwork at 140/180 for an hour if I let it. I don't know if there's something wrong with the Aquastat? I turned the thermostats up just to test out the system. I had the rooms at 60's and raised them to 74 or so to test it. I didn't try and see if they shut off. Really had one day to figure this stuff out so far and now they're off for the season. The boiler was purchased at least 5 or 6 years ago. I forget, it's been so long. Does that make a difference in terms of the aquastast being like that? Either way, maybe I'd rather have that instead of 1 minute cycles! OMG

I may just get an additional Grundfos pump. The one I have is a 15-42f. I would replace it with the original one with 3 speeds as this is running too fast according to Delta T calculations. I know very little about all this, I just did the calc to find out gpm for the radiant pump. Then I would replace the taco with the Grundfos I am using now. I love the silent Grundfos compared to the buzzing of the Taco. The two pumps I have are a couple of weeks old.

I've read that article and will have to go over it again with my friend to see if he could actually repipe that other "close T" stuff. I do want to place the radiant return in the correct location though.


So..... I should NOT get the Intellicon? I thought it was OK for an oversized boiler like mine. IF it is, that is the main reason for my fear of low temps returning to the boiler. I'm not really worried about low temps at this stage.

One more question (for now. Ha ha) If I don't get something like the Intellicon, should I lower the aquastat on the boiler? Lower it just enough to keep temps above 130? Should I get an additonal aquastat that has a larger range? Mine seems to be 40 degrees. hmmm.

Thanks again. I'm just looking for that extra, or initial, efficiency with what I have to work with. I know it was done wrong to begin with. Long story...
 
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Old 03-20-12, 06:52 PM
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You have a jet engine (big boiler) strapped to a canary (low heat loss house). Or some other clever metaphor.

Trooper is correct that the middle Siggy diagram is the proper way to pipe your radiant zone. (As I was reading through this thread, I was already trying to remember the name of that article and pleased to see that Trooper beat me to it.)

And Trooper and furd are also correct that solving the cycling problem requires more than just what you are thinking. Throwing pumps and an Intellicon at this isn't the right way and IMHO a waste of time and money.

Any way you cut it, you are around 4-5x oversized. At design conditions, to say nothing of the other ~99% of the heating season when the heat loss is even lower. All revved up and no place to go. You need to add volume (buffer tank), downsize the boiler, or offer to heat a couple of your neighbor's houses, too.

If you could shoehorn in a 40 gal buffer tank, piped in a simple line, say on the return so it acted basically as a giant fat part of the pipe (a cheapie electric water heater might be adequate), that would bump up your firing time to ~8 minutes at a 25F deltaT and it would probably have many tens of minutes of off-time while those stored BTUs are distributed in the system.
 
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Old 03-21-12, 10:37 AM
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Thanks guys.

Looks like I'm back to square one. Maybe one day I will run BB heat to my upstairs bedrooms instead of using my forced air system up there as well. That would add a good amount of load for the boiler. (better than heating my neighbors' houses. ha!) I like the buffer tank idea, but absolutely no room for one. I wish I knew about this a few months ago before I bought a new HWH for $1000. I may have done something with a HE boiler and HWH in one or something. Anyway, that's history. I have 2 new units that I need to deal with.

Perhaps someday I will run the upstairs. For now, I will try and see how "efficient" this runs next winter. I love the heated floor and radiant heat of the baseboards compared to the forced air.

Thanks again. Lots of good reading here on the forum. Very informative posts.
 
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Old 03-21-12, 03:00 PM
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I don't know all the way back to square one... seems a little drastic!

A couple fairly simple piping changes will get you into the ballpark, and you might find that things aren't quite as bad as you fear!

Start by piping the radiant zone as shown and move the return line.

Note that the diagram I posted from the article shows a 'differential pressure valve'. This valve will tend to balance out the flows in the various parts of the system as the zone valves open and close. When all zones are calling for heat, that thing will be closed, when only one zone calls for heat it partially opens and relieves some of the head pressure from the pump. Google the term for more info. It's not absolutely necessary... but a good suggestion.
 
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Old 03-23-12, 06:10 AM
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OK, It took me a couple of days, but I finally figured out pdf... jpeg... etc... to post this image. I've been here but couldn't post it. Thanks for the reply.

Here is my dilemma. The radiant company gave me this diagram and it is exactly how my system looks. Even down to the radiant return in the current location. Tech support says do not put the return above the pump (which doesn't seem right to me when the boiler pump runs...but I'm a beginner). The radiant return water should not go "through" the boiler pump. So, if I *move* the boiler pump as planned to the suction side of the boiler/expansion tank, would anything change? If you see the diagram, my BaseBoard return piping is also where the diagram shows. Both returns (radiant and BB) come back to the boiler in two different locations. Can I still repipe like diagram #2 with my current setup? I'm certain my radiant zone will run far longer and by itself than the BB zones.

http://img607.imageshack.us/img607/3...ingdrawing.jpg
 
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Old 03-23-12, 02:16 PM
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Can I still repipe like diagram #2 with my current setup?
Yes... why not?

While obviously that diagram will work as evidenced by the fact that it did work, it's drawback is that it feeds cool water back to the boiler, and this is what we try to avoid. I'm not real sure why they would even suggest piping it in that fashion because there are better ways...

Piping per the diagram from Siggy's article, the cool return issue is mitigated by the fact that the cool water from the radiant is being mixed with some hot water around the loop and raising it's temperature.
 
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Old 03-23-12, 05:55 PM
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OK If I do that second diagram, I would have to change the way the pumps are controlled, right? Now, the radiant pump goes on by itself if the radiant Zone is the only zone calling for heat. Both only pump when the radiant ANND a baseboard zone is calling, or if the baseboard zone is calling for heat, then the boiler pump is the only one on.

It's not a problem, I just want to make sure if I have to change it so both pumps work while the radiant alone is running if I reconfigure the piping to that middle diagram?

Also a technical question about the "flow resstrictor valve". Is that just a normal valve that goes there that I need to adjust for flow and/or temp?

"Differential pressure bypass" I've seen many different types. Any suggestions to which one to use?

Weil Mclain manual says the boiler bypass needs two valves on supply and return and must be "adjusted" simultaneously one opening--- one closing... to get proper temp differential. Is this what I would be doing with this setup? Just want to cover all my bases before I present this to my friend for repiping. I want to buy all the proper stuff in advance.

Thanks again.
 
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Old 03-24-12, 07:10 AM
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Yes, some work on the wiring will be needed.

How is it currently being controlled? Do you have zone valves on the baseboard runs? What is the 007 pump connected to? What controls the Grundfos pump? etc...

I didn't re-read Siggy's entire article, but I think he explained the purpose of the restrictor valve... it should probably be a decent quality globe valve, but I'm not 100% sure that it's even necessary. I'll look again.

Forget about the bypass. You won't need it. Boiler bypass is only needed with systems that have a lot of water volume, i.e. cast iron radiators, converted gravity, etc. If the home were ALL radiant, you might be advised to use bypass but with only the kitchen as radiant, probably not. Also, if you do re-pipe to the diagram, there will be a 'built-in' bypass in the closely spaced tees. Also also, if you do install the diff bypass valve, that will act as a bypass as well.

As to which DBV to use... dunno... Honeywell, Taco, others... they all do the same job.

Honeywell costs more, but has a neat visual indicator that can help set the valve correctly.
 

Last edited by NJT; 03-24-12 at 07:51 AM.
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Old 03-24-12, 06:19 PM
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Hello CIH,

That cycle goes for 10 minutes with the 2 zones being on. "ON" for 3 minutes and "OFF" for 7 minutes, then repeat, for an hour straight, if I let it go that long.
On for 3 minutes, off for 7, is not the end of the world.
Make the simple changes NJT has suggested and run it. Let it rip and enjoy the warm floors.
When it is in the low single numbers F, my oil burner cyles like a clock 3 minutes on, 3 minutes off. Been doing this for 20 years. Still going strong.

Oh, and even if there is no room where the boiler is, the buufer tank may be able to be located somewhere else on the first floor, given that a couple of pipes can be run to it.


Peter
 
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Old 03-27-12, 10:14 AM
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Can't seem to reply on this site sometimes. Not sure what's going on...

I think I will revisit this thread at a later date when I have my friend look at it, because with every post, I seem to have more questions. I'm going the wrong way!!! lol

Thanks for the replies. I will come back when I have learned more of what's going on, I hope.

NJTrooper, I have 3 zone valves for the BB zones that the 007 pump is used for. The 007 is going right into the boiler's side where the return pipe goes into the boiler. IIRC The 007 is controller by the ARGO 4 zone controller when any the 3 BB zones call for heat. The Grundfos (radiant zone pump) is going on only when the radiant is calling for heat, and it is being controlled by itself with the single zone Azel switching relay.

The 2 pumps work independently. They do also work simultaneously if both the radiant and one or more of the other zones is calling for heat.

We seemed to have wired everything up correctly to work as instructed to us. If I do change over to this new piping, I would have to wire the 007 to run while the Grundfos is running, or in other words, when the radiant calls for heat, the 007 should be running as well, it seems.

One question before I go. One that I will ask, because I have more than one... WHERE is the return pipe from Baseboards on that middle diagram? Is it right under the pic of the flow valve? If you look again at my piping schematic I posted, it seems going from my current piping, to the one you posted is not as simple as it seems, but I need to do more homework first. That pic is way too small for me.

Thanks everyone for their help. I'll be back...
 
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Old 03-27-12, 11:16 AM
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Originally Posted by CIHomeowner View Post
.. WHERE is the return pipe from Baseboards on that middle diagram?
The red pipe at the bottom going into the boiler has 5 stub returns on it.

Peter.
 
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Old 03-27-12, 02:17 PM
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Thanks PeterNH.

Your previous post gives me a little reassurance. I am looking forward to the warmth of this system, finally after years of it sitting idle. It's so much better IMO than my forced air system. I almost turned it on today as the temperature dropped outside. thanks.
 
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Old 03-27-12, 04:28 PM
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Turn it on and be warm and happy.
Why not?
The few weeks of cold weather left won't kill it.

Peter
 
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