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Shop heat sizing?


brewcrew
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It’s finally time to get a heat source in my shop. I have in floor loops, and a mini split to make the office area an appropriate working temp above or below shop temp. Building dimensions are 44’ by 60’, 18’ height. Plans for down the road include provisions to expand to 100’ long, but no timeline on that. I see ND state university says well insulated shops need just 20 btu/hour per square foot, which puts me under 100k including expansion abilities. How does that sound to those of you with such a building? I figure it will likely be kept around 45° unless working in there, then likely bump it to 50-55°. This will not be a continuous use building going in and out constantly, but it’s main function is storing and washing my semi on weekends. I have a pair of 16x24 doors on either end. I’m planning to fire the boiler on propane unless someone tells me a better idea (not wood!) and it will also do hot water for the bathroom. I’d love to hear some testimony from those who have already been there! Thanks.

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I have 50x70, 14’ walls 

80,000 navien lp

works well.

you won’t see much savings between 45-50, unless totally against it just keep one temp

use outdoor sensor to have water temp on curve, just trust me on that.

I would personally get an indirect water tank and have a boiler instead of “combi “ unit but that’s just me!

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60x96x18 shop with 12x30x8 office, and Mech/bathroom in east central MN, 3 trucks and hoppers are parked in it year around, doors are opened twice a day most days, and cold trucks backing in at night in the winter. We have in floor heat, on a lp tankless boiler, set at 55 degrees.  I can’t recall the size of the boiler at the moment, but it does the job on 2 fills of lp a winter, 1000 gallon tank, so roughly 1500 gallons of lp a winter.  Start the boiler in Oct, shut it down in late March or April depending on the spring warm up. 

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I just finished the last end of my main shop last fall and and it is 42x38 x16 sidewalls and  heat it with a 50 gallon LP hot water heater  . I have two tube heaters up in the rest of the shop and they work really well but that hot water heat in the floor is they way to go 👍 

Danny

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16 hours ago, DirtBoyz07 said:

I just finished the last end of my main shop last fall and and it is 42x38 x16 sidewalls and  heat it with a 50 gallon LP hot water heater  . I have two tube heaters up in the rest of the shop and they work really well but that hot water heat in the floor is they way to go 👍 

Danny

I had considered using the water heater from my milk house, I believe it’s 105 gallon electric. But I was told it will run constantly and not keep up, plus suck electricity. Currently I don’t use any propane on the farm except to dry corn. I need to check with my coop if they even have a tank!

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16 minutes ago, brewcrew said:

I had considered using the water heater from my milk house, I believe it’s 105 gallon electric. But I was told it will run constantly and not keep up, plus suck electricity. Currently I don’t use any propane on the farm except to dry corn. I need to check with my coop if they even have a tank!

If you run it on generator power it won’t run the electricity bill up so much 😉

i had a Hot Dawg that came out of a very poorly insulated 40x80 ish machine shop in there it was always as warm as you wanted it to-be. I didn’t use it myself as we ended up with a wood furnace instead. 
https://www.homedepot.com/p/Modine-Hot-Dawg-75-000-BTU-Propane-Gas-Garage-Ceiling-Heater-HD75LP/205964276

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28X42, 12' ceilings. Heating with Miller mobile home furnace 60f all winter on just over 300 gallons of oil. Shop is well insulated with 2 9X9 doors and 1 11X11 for the lift bay.

Floor heat was not in the budget at build time but I've had good experience with the Miller furnaces on cottage bases before. 

Furnace is rated 80,000 BTU in; 64,000 out so that pencils out to more per square foot than your numbers. My climate near the coast is milder as well and I'm keeping the shop warmer than your plan. 100,000 BTU sounds light for such a big building but the radiant heat is probably much more efficient than hot air.

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7 hours ago, brewcrew said:

I had considered using the water heater from my milk house, I believe it’s 105 gallon electric. But I was told it will run constantly and not keep up, plus suck electricity. Currently I don’t use any propane on the farm except to dry corn. I need to check with my coop if they even have a tank!

My electric company guy told me to use gas exactly for the reasons you mention.  

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On 9/7/2022 at 6:52 PM, zleinenbach said:

I have 50x70, 14’ walls 

80,000 navien lp

works well.

you won’t see much savings between 45-50, unless totally against it just keep one temp

use outdoor sensor to have water temp on curve, just trust me on that.

I would personally get an indirect water tank and have a boiler instead of “combi “ unit but that’s just me!

Well spoken sir

 

^^^This is good information, from someone in the trade.

 

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On 9/8/2022 at 11:46 PM, brewcrew said:

I had considered using the water heater from my milk house, I believe it’s 105 gallon electric. But I was told it will run constantly and not keep up, plus suck electricity. Currently I don’t use any propane on the farm except to dry corn. I need to check with my coop if they even have a tank!

Is the dryer tank that far away?  Sometimes drying propane is cheaper than heating. 
 

John

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11 hours ago, Weapon said:

Is the dryer tank that far away?  Sometimes drying propane is cheaper than heating. 
 

John

I get a portable tank in every year to dry corn. There is probably 100 yards between the two uses.

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On 9/8/2022 at 11:07 PM, vtfireman85 said:

If you run it on generator power it won’t run the electricity bill up so much 😉

i had a Hot Dawg that came out of a very poorly insulated 40x80 ish machine shop in there it was always as warm as you wanted it to-be. I didn’t use it myself as we ended up with a wood furnace instead. 
https://www.homedepot.com/p/Modine-Hot-Dawg-75-000-BTU-Propane-Gas-Garage-Ceiling-Heater-HD75LP/205964276

man, have those ever went up in price, i bought the 50,000btu model 3 years ago and it was just somewhere around $400....its in newly built 24x24x10 garage with cathedral type ceiling. keep it about 40 degrees all winter and pump it up to 60-65 when i work in there

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On 9/9/2022 at 3:39 PM, AKwelder said:

Well spoken sir

 

^^^This is good information, from someone in the trade.

 

 

On 9/7/2022 at 10:52 PM, zleinenbach said:

I have 50x70, 14’ walls 

80,000 navien lp

works well.

you won’t see much savings between 45-50, unless totally against it just keep one temp

use outdoor sensor to have water temp on curve, just trust me on that.

I would personally get an indirect water tank and have a boiler instead of “combi “ unit but that’s just me!

I am planning and building a 40x40 with in floor can you expand on the outdoor sensor?  This I think this makes sense when the outside temp is close or warmer to inside?

And "combi" your suggestion is a to have a dedicated boiler for in floor and a separate water heater for water.

Thanks,

Scott

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20 minutes ago, 460 said:

 

I am planning and building a 40x40 with in floor can you expand on the outdoor sensor?  This I think this makes sense when the outside temp is close or warmer to inside?

And "combi" your suggestion is a to have a dedicated boiler for in floor and a separate water heater for water.

Thanks,

Scott

Z may have a better take on this, we have extreme heating needs and it has a lot of an effect on my heating systems

If you use a boiler that allows it, An out door sensor adjusts the target heating temperature the boiler is trying to reach, so when it is 20* outside it might be making for 80* water for your floor.  But when it’s -35* it might be making 100* water for your floor.  

If your boiler is only making 80* water, and is a high efficiency modulating boiler, it make have exhaust that may only be  120* ( or some such, this varies). This means you waste a lot less BTU’s going out the stack.  More efficient, less cost

 

a combi is a combination boiler and hot water heater. In my opinion they make lots of compromises to do both.  I do not install them, others swear by them.  
 

If you buy a modulating boiler I recommend you buy a fire tube model of a common brand in your area, something that all the supply houses carry.  Here we see Lochnivar, NTI, and IBC.  They all make some very small boilers like the 85k btu models, which turn down to less than 10k btu when the heating load requires it. 

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Agree with everything stated above 

move always understood the outdoor reset to be a sort of “restrictor plate”,

so you say “hey boiler, at 0 degrees outside (insert whatever number you want here) I want my water temp to be 105. Any outside temp above 0 will have a curve of where it’s at. So at 60* it may have 70 degree water or whatever the smarty pants engineer says it needs to be 😁

mill grab a picture at home of how I did mine, we butcher a lot and use a greater than average amount of hot water. 
so my water tank has a coil in it that when it calls for hot water, it energizes boiler to run full tilt basically to satisfy that call. 
 

im not a fan of combi units either. Robbing Peter to pay Paul comes to mind with them, 

of course certain instances they make sense. But I try real hard to limit them lol

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For the heating guys: How about a high efficiency condensing gas boiler? I know nothing about them but my hot air backup at 94-96% seems to sip the propane.

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6 minutes ago, New Englander said:

For the heating guys: How about a high efficiency condensing gas boiler? I know nothing about them but my hot air backup at 94-96% seems to sip the propane.

The boilers I’ve mentioned are condensing.

something to keep in mind is condensing means it will have condensate water when it runs. So make sure there’s provisions for that! 

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36x40, 14ft walls, r25+ walls, r35 ceiling, 150,000 reznor lp ceiling mount. Keep at 55, crank up to 65-70 when working, 400 gallons a year. Insulated overhead doors, low e windows. Generally 5-6 months in use.

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60’x96’x16.5’ with one 30’ overhead door, 3” thick. 600 gallons of LP thru a tube heater keeps it at 55 degrees all winter in NW Iowa.  Most days the door opens twice to run my truck out & then back in later in the day

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