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shop floor heat help please

I'm new here but hopefully someone can help me. I have a 60 X 40 farm shop. It has one large single zone of floor heat. There is 1800 ft of 3/4 inch pex split up into 6 runs. I have a 100,000 btu corn burning boiler with a primary/secondary loop system. I'm in Minnesota so it can get pretty cold.
Here is my problem. When it gets down in the teens or single digits especially over night, my boiler can't keep up. I absolutely cannot get my return temperature over about 73 degrees which leaves my floor at about 62 and my air at only 54. My water going into my floor is about 82. The boiler is running 170 degrees but I have to mix it down to keep the stove warm. If I run any more than 82 the stove will cool off quickly and the aquastat will shut the pump off until it warms back up.
Here's my question. My boiler holds 18 gallons of water but the rest of my system holds more than that. Would it help to have a storage tank so I have enough hot water stored up to run through the whole system?
Or any other suggestions? Any help is appreciated. Thanks
Here is my problem. When it gets down in the teens or single digits especially over night, my boiler can't keep up. I absolutely cannot get my return temperature over about 73 degrees which leaves my floor at about 62 and my air at only 54. My water going into my floor is about 82. The boiler is running 170 degrees but I have to mix it down to keep the stove warm. If I run any more than 82 the stove will cool off quickly and the aquastat will shut the pump off until it warms back up.
Here's my question. My boiler holds 18 gallons of water but the rest of my system holds more than that. Would it help to have a storage tank so I have enough hot water stored up to run through the whole system?
Or any other suggestions? Any help is appreciated. Thanks
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Comments
What are you using for Circulator pumps?
How long are the loops? 300'?
What are the centers?
How thick is the slab?
Got pictures?
BTU's are btu's..the storage will not help you too much. Somehow the load is too big OR the BTU are as ME says thermally constipated in the boiler.
It also helps to run the slab on and ODR (outdoor reset curve)
In some cases it may be necessary to hang a Modine from the ceiling to supplement the load during rapid outdoor temperature declines.
Harvey
ramermechanical.com
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To answer some of the questions above:
The slab is somewhat insulated. It has insulation underneath around the outside but none in the middle. Its kind of a unique situation. The building had a previous floor in it that was un even. Below my slab is 3 inches of gravel. below that gravel is another 6 inches of cement.
I have a small taco pump on the primary loop which is 1-1/4. The primary loop has a larger Bell & Gosset pump on it and is 1 inch. (im not sure of the exact pump specs)
My loops are 300' on 16" centers.
The slab is 7 inches thick in the middle and thins to 4 inches at the wall.
I realize BTU are BTU. My thoughts were that the mass of my boiler was too small in relation to my floor.
Keep in mind, I am no expert on hydronics. Here was my thought process:
(this is just an example)Say I had a boiler that only held 1 gallon of water and a system that holds 20. During they day (average day) my water sits in the floor because I don't require much heat and goes down to the floor temp of 62 degrees. Once I require heat, the pump kicks in and that 1 gallon boiler has to heat 20 gallons of water up from 64 degrees. Would it not have trouble at any btu due to the large amount of water being returned to a small amount of heat area?
It just seems to me that the amount of cool water coming back to my boiler is too large of a volume compared to the volume of my boiler. I thought if I had enough BTU stored up during the day that I could pump a bunch through all at once to actually get my return temps to rise. Which in turn would allow me to run higher input temps.
Also keep in mind that with the corn boiler, even with no call for heat, the boiler is always burning on low fire. It needs to burn for 3 minutes every 10 minutes to keep itself burning. On days in the 20s with minimal wind, if my thermostat is at 56, it will be close to 60 by the end of the day due to extra heat being made. That was also part of my storage tank theory.
Im sure my thought process is not how it actually works so please correct me where needed. Thanks!
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The main reason I started thinking of this is because a friend of mine has a storage tank that he is no longer using. It would be free but Im trying to determine if its worth my time to install it.
ramermechanical.com
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EcoSteam ES-20 Advanced Boiler Control
Boiler pictures updated 2/21/15
https://www.facebook.com/media/set/?set=a.10202744301871904.1073741828.1330391881&type=1&l=c34ad6ee78
As far as the way its plumbed or the way it operates?
EcoSteam ES-20 Advanced Boiler Control
Boiler pictures updated 2/21/15
https://www.facebook.com/media/set/?set=a.10202744301871904.1073741828.1330391881&type=1&l=c34ad6ee78
First, with a little change you can get slightly more heat out of the boiler and help to improve indoor temp swings to some degree. Install a 2-way I-series ODR mixing valve and replace your manual valve with a real balancing valve . Follow the Taco manual to a T on the setup. And yes, a 3/4" 2-way Mix valve will give you up to 400,000 BTU capacity, going from a high temp boiler to low temp radiant. Say 180° to 120°. It won't have the flow restriction of a 3-way valve.
Every little thing you can do to tighten up the shop will help a lot.
As far as the boiler running all night, I don't see why you couldn't put in a 24hr timer that would shut off the call for heat at intervals of your choosing.
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Can someone explain to me what the 2 way mixing valve and real balancing valve actually do?
If someone could draw me a diagram of how these valves would be plumbed in I would really appreciate it. (its easier for me to picture it that way) Thanks again everyone.
ramermechanical.com
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I do agree with you though. With most conventional boilers, I have no qualms deleting the boiler circ and closely spaced tees.
I this man's situation, with the uninsulated slab, the measures we have suggested will be an improvement but not a complete fix. I have dealt with uninsulated slabs before and there is only so much you can do to maintain temp control. The heat sink under the slab just becomes to massive. They all operate in the same fashion. They run all night and stay shut off all day.
With that in mind, I would maintain the boiler loop for the purpose of adding in a Modine to buffer the cold spells.
ramermechanical.com
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ramermechanical.com
To learn more about this professional, click here to visit their ad in Find A Contractor.
ramermechanical.com
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ramermechanical.com
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Could I use a night setback with this setup?
Night setback is never a viable option with radiant floor in a concrete slab.
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Couple last questions.
1, Do I need any sort of mixing valve to run the modine? And where would I hook it in the system.
2, If in the future I install a larger boiler, will my floor heat work any better or am I still going to need the modine?
By the way, what is the btu load on the boiler? And what temp does it keep the shop say when you have 0° weather for a week?
You need to establish a baseline to get an idea of the size for the Modine.
Harvey
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http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_10.pdf
A ton of info in that publication
For what it worth, I also have a high temp heat source connected to low temp radiant, I was advised to use the ESBE Thermic (there are other brands of the same style device, Hot Rod & SWEI have 2 that come to mind) to protect the boiler, It works like a charm to protect the boiler on the 2 systems I have then installed on.
Tim