Using 6 gal per minute coil to heat barn?? Will it work?

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Frank F
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Post by Frank F » Mon. Feb. 20, 2023 8:21 am

Good morning all! It’s been a while since I posted. For a little background I have an AA220 liesureline boiler installed in my barn with underground pipes to the house.

Up to this point I’ve just used the residual heat off the boiler to keep the building 48-65 degrees depending on outdoor temp.

Building is 27x40x10, with 4” rigid foam all the way around except concrete floor. All joints are spray foamed. It has one window roughly 2’x4’, a man door, and an 10x8 insulated garage door.

I’d like to utilize the 6gal per min coil and run a small system to heat the barn with coolant, in the event I have to shut down. So I don’t have to worry about frozen pipes. The main system does not have coolant so I don’t want to tap off of that.

I have 2ea 24 plate tubular cast iron radiators and on 16 plate(roughly). I also have a modine heater (think 25k).

What are your thoughts, will it work??

 
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Rob R.
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Post by Rob R. » Mon. Feb. 20, 2023 8:41 am

Frank, if the boiler is in the barn and won’t have antifreeze, what is the point of using it in the barn zone? Maybe I misunderstood.

 
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Post by franpipeman » Mon. Feb. 20, 2023 8:43 am

For instance, propylene glycol at a 40% concentrated mix with water produces a specific heat of 0.895. That drop ultimately reduces the total amount of heat transfer we are able to achieve with identical flow rates and temperature deltas as compared to 100% water.

this means coolant will have a lower heat capacity than water . you need to do some heat loss calc to assure success. or if your just tying to take the chill out do the best you can with what you have .

 
Frank F
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Post by Frank F » Mon. Feb. 20, 2023 9:05 am

Rob R. wrote:
Mon. Feb. 20, 2023 8:41 am
Frank, if the boiler is in the barn and won’t have antifreeze, what is the point of using it in the barn zone? Maybe I misunderstood.

Hi rob, sorry I should have explained better. I have a boiler room in the barn. That I can heat with an alternate source if the boiler goes down. The whole of the barn I’d prefer to not have to do that. There are many times I have boiler room closed and garage door open all day working on equipment that doesn’t fit. I’d like to minimize that risk.

I’d also like to not steal the hot water from the house, I want the house to be the priority.

And I feel like that coil is being wasted!


 
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Rob R.
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Post by Rob R. » Mon. Feb. 20, 2023 9:15 am

okay now I got it. Your coil should be adequate to do this. With a 6 gpm rating I assume it has 3/4" connections?

How warm do you want to keep the barn and at what outdoor temperature?

 
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Post by Frank F » Mon. Feb. 20, 2023 10:19 am

Rob R. wrote:
Mon. Feb. 20, 2023 9:15 am
okay now I got it. Your coil should be adequate to do this. With a 6 gpm rating I assume it has 3/4" connections?

How warm do you want to keep the barn and at what outdoor temperature?
I’m going to add another level here. The barn temps are fine for me except I occasionally do some painting. So I need to raise the temp to 70-75 at any point during the winter. I’m not painting cars but I make metal signs and have to clear coat them. So I may section off 1/3 of the barn to be my “paint shop” that’s where I plan to put the radiators. The other 2/3 I plan to use the sterling modine heater which is a 34,800 btu now that I’m looking at it.

 
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Post by exwoodburner » Mon. Feb. 20, 2023 11:07 am

You should do a thorough heat loss analysis and then determine your flow rate from a 10-20 degree design supply/return delta. Do you have insulation in the ceiling? 4" of rigid foam is approximately R20. My "barn" is very similar to yours. Its 24' x 40' with 12' ceiling. I have R19 batt insulation in the walls, R38 batts in the attic, 2" rigid foam under my floor slab and 6" rigid foam around the perimeter of the slab. One man door and one 11'x14' insulated overhead door. I heat the slab with a 23,000 BTU electric boiler at about 3.2 gpm. Water is 14 degrees cooler coming back to the boiler. I don't use any glycol. Even on the coldest -10 degree and windy days around Christmas time it had no problem maintaining 60 degree slab temperature. I get my system is totally different than what you are proposing but the principles are the same. You just need to figure out your heat loss first at your worst case scenario (75 degrees inside - coldest outside temperature you would expect to have). All you are doing is replacing those BTUs. Your GPM will be dictated by your heat loss. Does the boiler manufacturer specify a return water temperature threshold?

 
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Post by Frank F » Mon. Feb. 20, 2023 12:25 pm

exwoodburner wrote:
Mon. Feb. 20, 2023 11:07 am
You should do a thorough heat loss analysis and then determine your flow rate from a 10-20 degree design supply/return delta. Do you have insulation in the ceiling? 4" of rigid foam is approximately R20. My "barn" is very similar to yours. Its 24' x 40' with 12' ceiling. I have R19 batt insulation in the walls, R38 batts in the attic, 2" rigid foam under my floor slab and 6" rigid foam around the perimeter of the slab. One man door and one 11'x14' insulated overhead door. I heat the slab with a 23,000 BTU electric boiler at about 3.2 gpm. Water is 14 degrees cooler coming back to the boiler. I don't use any glycol. Even on the coldest -10 degree and windy days around Christmas time it had no problem maintaining 60 degree slab temperature. I get my system is totally different than what you are proposing but the principles are the same. You just need to figure out your heat loss first at your worst case scenario (75 degrees inside - coldest outside temperature you would expect to have). All you are doing is replacing those BTUs. Your GPM will be dictated by your heat loss. Does the boiler manufacturer specify a return water temperature threshold?
Gotcha!

My thoughts on the glycol are for when the system is off. When we go on vaca or we are gone for a while and temperatures are below zero outside. I’d assume Eventually with the system off things may start to freeze. I have a small space heater in the “boiler room” but I won’t have that for the lines and radiators in the barn.


 
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Post by Rob R. » Mon. Feb. 20, 2023 12:37 pm

Frank F wrote:
Mon. Feb. 20, 2023 10:19 am
I’m going to add another level here. The barn temps are fine for me except I occasionally do some painting. So I need to raise the temp to 70-75 at any point during the winter. I’m not painting cars but I make metal signs and have to clear coat them. So I may section off 1/3 of the barn to be my “paint shop” that’s where I plan to put the radiators. The other 2/3 I plan to use the sterling modine heater which is a 34,800 btu now that I’m looking at it.
You only answered 1 of my 3 questions. 8-)

 
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Post by Frank F » Mon. Feb. 20, 2023 3:36 pm

Rob R. wrote:
Mon. Feb. 20, 2023 9:15 am
okay now I got it. Your coil should be adequate to do this. With a 6 gpm rating I assume it has 3/4" connections?

How warm do you want to keep the barn and at what outdoor temperature?
Sorry had a “squirrel moment”.

Yes the coil has 3/4 connections.
I’m upstate NY so it could get below zero but most of the time 20 deg outside I guess. Except for this year, it’s been extremely warm.

On the average day 60 deg is perfect working temperature. But I need mid 70’s for painting.

 
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Post by Rob R. » Mon. Feb. 20, 2023 4:20 pm

Is there any insulation around or under the concrete floor?

 
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Post by Frank F » Mon. Feb. 20, 2023 6:02 pm

Rob R. wrote:
Mon. Feb. 20, 2023 4:20 pm
Is there any insulation around or under the concrete floor?
Only under the boiler room 12x12. The rest doesn’t have it under. There is on the sides of concrete.

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