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Author Topic: Plate size for in floor heat  (Read 734 times)

E Yoder

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Re: Plate size for in floor heat
« Reply #15 on: December 23, 2017, 01:07:00 PM »

Some rambles here-
Do you mean the boiler makes both heat and domestic water? My father-in-law has a System 2000 that does that. I have one 3X8" 30 plate transferring to it. Does two zones of copper baseboard and domestic water (using another 14 plate off the oil boiler).
Interestingly, the site Honda sent me a link to will say "insufficient flow" if the flat plate is grossly oversized, I guess it has to do with losing turbulence. Not usually going to happen in the real world.
« Last Edit: December 23, 2017, 01:49:23 PM by E Yoder »
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justinb

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Re: Plate size for in floor heat
« Reply #16 on: December 28, 2017, 05:46:53 PM »

Ive been out of town with limited access to internet.  I spoke with the installer and he said the manufacturer recommended the heat exchanger that he installed.  I didnt want to argue with him so I let him do his job.  Everything has worked fine until this recent cold snap.  Temp in the garage wont get above 45F. 

I had him T into my return line (after DHW, furnace hx).  Its a closed circuit with its own pump.  Im not sure of the return flow nor return temp.  I dont know how to measure either.  He had the water temp after mixing valve set to 110.  I just bumped it up to 125F.  Hopefully that will help.
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E Yoder

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Re: Plate size for in floor heat
« Reply #17 on: December 28, 2017, 07:47:37 PM »

A lot of digital electrical testers have probes you can tape to the lines with foil tape and insulate. In a few minutes you'll have a fairly close measurement The surface of an uninsulated pipe will read low.
The higher temp water will help if the flat plate is big enough to get that hot, but that's plenty hot for mild weather, it can overshoot on warm days.
So I think you're saying there are two tees and a pump on the stove line that pumps over to the flat plate for the floor, and another pump for the floor side of the flat plate?
Keep us posted.
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wreckit87

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Re: Plate size for in floor heat
« Reply #18 on: December 28, 2017, 08:07:21 PM »

Sounds to me like he just teed off the main line to serve the plate and is using the primary circ to feed that, and the secondary pump is on the radiant side. Correct? There needs to be flow across the plate to work properly which cannot be achieved with a pair of tees both in the return line- there needs to be one in both the supply and return line to gather enough pressure drop to force circulation. Not being able to maintain temp in the garage is a sign of either not enough exchanger (which I would say is the case), not enough tubing in the floor, or a poorly insulated building. Adjusting the mixing valve will help nothing if the plate is undersized and can't make enough hot water to put into the mixing valve. Just grab ahold of the supply line before it enters the manifold to the floor. If it's almost too hot to hold on to, you're getting enough hot water and have an issue with the building. If it's easy to hang on to, you need more hot water and need to either upsize the exchanger or pipe it differently to maximize flow through it
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mlappin

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Re: Plate size for in floor heat
« Reply #19 on: December 28, 2017, 10:22:43 PM »

Some rambles here-
Do you mean the boiler makes both heat and domestic water? My father-in-law has a System 2000 that does that. I have one 3X8" 30 plate transferring to it. Does two zones of copper baseboard and domestic water (using another 14 plate off the oil boiler).

SOP procedure in the UK, except if I understand correctly heating and drinking are the same water as the whole heating system is copper as well. Least thats what I think the service guy said that was working on aunties boiler. I was a wee bit hungover so maybe that ain't what he said.
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E Yoder

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Re: Plate size for in floor heat
« Reply #20 on: December 29, 2017, 05:08:03 AM »

Sounds to me like he just teed off the main line to serve the plate and is using the primary circ to feed that, and the secondary pump is on the radiant side. Correct? There needs to be flow across the plate to work properly which cannot be achieved with a pair of tees both in the return line- there needs to be one in both the supply and return line to gather enough pressure drop to force circulation. Not being able to maintain temp in the garage is a sign of either not enough exchanger (which I would say is the case), not enough tubing in the floor, or a poorly insulated building. Adjusting the mixing valve will help nothing if the plate is undersized and can't make enough hot water to put into the mixing valve. Just grab ahold of the supply line before it enters the manifold to the floor. If it's almost too hot to hold on to, you're getting enough hot water and have an issue with the building. If it's easy to hang on to, you need more hot water and need to either upsize the exchanger or pipe it differently to maximize flow through it
I thought about that laying in bed last night, turning up the temp would indicate not enough flow or not enough piping in the floor. If the plate is too small it won't get hotter regardless of where it's set.
Anyway, I' d love to see pics.
Justinb, keep us posted.
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wreckit87

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Re: Plate size for in floor heat
« Reply #21 on: December 29, 2017, 07:29:33 AM »

Sounds to me like he just teed off the main line to serve the plate and is using the primary circ to feed that, and the secondary pump is on the radiant side. Correct? There needs to be flow across the plate to work properly which cannot be achieved with a pair of tees both in the return line- there needs to be one in both the supply and return line to gather enough pressure drop to force circulation. Not being able to maintain temp in the garage is a sign of either not enough exchanger (which I would say is the case), not enough tubing in the floor, or a poorly insulated building. Adjusting the mixing valve will help nothing if the plate is undersized and can't make enough hot water to put into the mixing valve. Just grab ahold of the supply line before it enters the manifold to the floor. If it's almost too hot to hold on to, you're getting enough hot water and have an issue with the building. If it's easy to hang on to, you need more hot water and need to either upsize the exchanger or pipe it differently to maximize flow through it
I thought about that laying in bed last night, turning up the temp would indicate not enough flow or not enough piping in the floor. If the plate is too small it won't get hotter regardless of where it's set.
Anyway, I' d love to see pics.
Justinb, keep us posted.

Yeah I get that, but I guess what I was thinking was that since it doesn't sound like he has a temp gauge, the supply water temp is unknown. Therefore if the plate is only making 100 degree water, turning the mixer from 110 to 125 isn't going to help because there's not even 110 available to use. Just thinking out loud I guess. 110 ought to be great plenty to keep a reasonably insulated building at 70 with the right tubing layout, so the fact that it can only hold 45 tells me there's not enough heat available in the water. I've seen some pretty janky systems with only half the tubing they should have that still keep up more than 45 degrees. This is interesting
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Re: Plate size for in floor heat
« Reply #22 on: December 29, 2017, 08:23:55 AM »

Wreckit87...yes that is how its plumbed.

Here are some recent observations:
-i was able to adjust the mixing valve to 125 with no problem.  However, when my house furnace kicks on, it drops down to 105 and remains there until the furnace shuts down.

-The supply line to the garage plate hx is very hot to the touch, except when the house furnace is on.

- The garage is around 1000sqft, is 2x6 construction and well insulated.  I dont know if foam boards were placed outside of the footings.  I do know that foam boards were placed under the pex tubing in the floor.

-My uneducated mind is thinking that either my pump that is on the wood burner is now undersized, or the heat exchanger is restricting flow??  Im going to hardware store today and buy something that will allow me to take a temp.
-Im going through an unbelievable amount of wood.
-pics to follow
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justinb

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Re: Plate size for in floor heat
« Reply #23 on: December 29, 2017, 08:47:41 AM »

Pic1
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Re: Plate size for in floor heat
« Reply #24 on: December 29, 2017, 08:49:27 AM »

Pic2 of the T in return line
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Jon_E

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Re: Plate size for in floor heat
« Reply #25 on: December 29, 2017, 09:09:35 AM »

There is no such thing as "too big" on a plate exchanger. That 40 or 50 plate would do ya more favors than the little 14 plate even for a price, but can't beat free! I certainly wouldn't waste my time with the little guy if that was an option, but I would be interested to hear how it goes if you decide to use the little one.

Am I seeing correctly that you're using the same exchanger to serve you domestic water as well as your radiant floors in the house??? Good luck with that Legionaire's disease

I was wrong on the plate exchanger size - it's a 16-plate, not a 10.  Still small, but I think it will do OK.  Not looking for a huge amount of heat.  Website says it will do 110k BTU.   I'm going to plumb it in with unions anyway, just in case.  You guys are making me have second thoughts. 

In my house, the loop from the OWF comes into the HX and heads back out.  There is a 'main' loop which has several zones, one for DHW which goes to an indirect tank and the rest are radiant heating loops.  There is no contact between the DHW and the water in either the main loop or the circulation loop from the boiler.  So, no worries about legionella or anything else.  I have a special concern for legionella because it is part of my job to have a program in place for testing and preventing it in our workplace water system. 

I am following this thread with interest as my plumbing layout and conditions for my garage is almost identical to Jason's.  I don't think I will have the same issues as I have a dedicated pump and loop from the OWF which will only feed this garage.  If I run out of hot water then it means the whole boiler is either shut down or failing to keep up.
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wreckit87

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Re: Plate size for in floor heat
« Reply #26 on: December 29, 2017, 09:50:52 AM »

Justin- The reason your loop temp is dropping when the furnace runs is because you are trying to force 100% of your boiler water through that little 3/4" plate. The restriction there is HUGE and severely hinders the flow through your main loop. That's what we'd call being piped "in series" which is what was being discussed above by Yoder and RSI. You are now limiting you main loop flow to 2-3 GPM instead of 6-7 like it should be. What pump do you have at the boiler for that loop? Looking at the WM specs on that plate, you're only able to transfer 30,000 BTU at 3 GPM on the boiler loop at 180 degrees. This would allow 100 degree return temps to raise to 120 across the plate at 2.5 GPM on the radiant side (which is about par for 3 loops). With 1000ft of floor space, you also have a tubing shortage in the floor with only 3 loops, but that's small potatoes here. I didn't realize you had thermometers on the manifolds so that is good to know. What do the return temps from the floor look like without the furnace running? Say 125 supply, where is the return at? Looks to be a fairly considerable difference from the little I can see of the thermometers. The perimeter insulation has a very large bearing on radiant slab performance; and if you don't have any may very well be a large portion of the issue here. Return temps will tell some of that story

Jon- I hadn't considered an indirect tank, it sounded to me like you were running your heated domestic through the floor for space heating as well. Some people do that, it's actually recommended by some big name radiant companies (cough, cough, BlueRidge, cough) and a very crappy idea. Glad you weren't suckered into that!
« Last Edit: December 29, 2017, 10:03:11 AM by wreckit87 »
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E Yoder

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Re: Plate size for in floor heat
« Reply #27 on: December 29, 2017, 02:02:25 PM »

Justinb, the valve between the two tees on the main line should not be completely closed. That would be just to purge. Opening it partially should eliminate the restriction on the main loop, getting your flow rate up, giving you hotter water. Should have it's own pump going over to the flat plate to move more water through it.  Without it you'll have to play around with how far open the valve between the tees should be. Not ideal but maybe you can get it to do better.
As wreckit said, restriction on the main loop is a big issue here.
« Last Edit: December 29, 2017, 02:26:17 PM by E Yoder »
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Re: Plate size for in floor heat
« Reply #28 on: December 29, 2017, 03:13:16 PM »

Thanks for all the help guys.  The pump on the stove is a Badger gpd25, which is equivalent to a grundfos 26-96(3 speed).  The return temp on the manifold hovers between 50-60.  I will partially open the valve on the T and see what happens.  I havent made it to the store yet for a temp measuring device.  The pump on the closed circuit is a Grundfos 15-58 and its on the 2nd speed.

As an experiment, I shut off the supply to the furnace today.  So Im only running dhw and the garage.  I want to see what happens.
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Re: Plate size for in floor heat
« Reply #29 on: December 29, 2017, 03:41:43 PM »

Thanks for all the help guys.  The pump on the stove is a Badger gpd25, which is equivalent to a grundfos 26-96(3 speed).  The return temp on the manifold hovers between 50-60.  I will partially open the valve on the T and see what happens.  I havent made it to the store yet for a temp measuring device.  The pump on the closed circuit is a Grundfos 15-58 and its on the 2nd speed.

As an experiment, I shut off the supply to the furnace today.  So Im only running dhw and the garage.  I want to see what happens.

Good to know. Being able to raise the return temp 65-75 degrees through that tiny plate is more than impressive, I must say. The fact that your return temps are that low, however, say there's a lack of insulation either underneath or outside the slab. Do you have green grass against the outside wall or is there snow right up against the foundation? I assume this slab has been running for days since you said you can't get it above 45, so with return temps of 50 or 60, your slab will never be warmer than 60 degrees. You might try turning that 15-58 up to 3 to push some more water through the floor and get the return temps up. 65-75 degree delta through the floor is astronomical at best- you want to keep that closer to 20 or 30. That would potentially allow you to have 100 degree supply water and 80 degree return water, keeping an 80 degree slab and 70 degree air temp. There's a restriction somewhere and/or very poor insulation. Being able to pick up 75 degrees across that plate says you have pretty low flow on your radiant side as well. Speeding up the Grundfos may help remedy that part of it a bit, but insulation is going to be the key factor here I'm afraid. I've never used those manifolds before, but they appear to have flowmeters on each loop. Make sure those flow valves on each loop are screwed wide open; remember lefty loosey! There is no reason a 15-58 shouldn't be able to keep a 30 degree delta in 3 loops on speed 2 unless you're heating the lawn
« Last Edit: December 29, 2017, 03:47:10 PM by wreckit87 »
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