Need help confirming Modine btu for garage

[jzinckgra]

We built our house 6 yrs ago with radiant heat running off a baxi ht380 propane boiler. The builder ran pex to the garage for future addition of hydronic heater. Our garage is insulated with spray foam with sheetrock 10' ceiling. Sqft is 800.

In looking at heat load calculators it says if we want to heat up to 60f we'd need a 46,000btu Modine. Does this sound right? I'm not sure if we should get copper or aluminum version heater.

Local plummer will do work and it looks pretty straight forward. Anything else to consider? Thanks

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[2011laramie]

Will this be a hydronic unit heater? Glycol Supply temp plays a big role is btu output for these heaters.

 

[jzinckgra]

Yes, hydronic. No glycol

Will this be a hydronic unit heater? Glycol Supply temp plays a big role is btu output for these heaters.

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[jzinckgra]

I'm getting different results using two different calculators. One says I need 30kbtu while another says 63k.

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[klassenl]

One quick and dirty calculation we use is 10 watts/square foot. So in your case that would give you about 30000btu.

A few "buts" on that: 10 foot ceilings may need a little more and my suggestion is based on a well insulated and sealed space.

 

[jzinckgra]

Garage is pretty tight. Spray foam walls, but a little leaky around garage doors. Any issue going with Modine 45kbtu over the 33? I'd rather be over than under and pretty certain our boiler can handle it

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[2011laramie]

What size boiler and what is you boiler water temp?

 

[jzinckgra]

Baxi HT 380. 183F.

What size boiler and what is you boiler water temp?

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[jzinckgra]

I've asked our plumber to go with the 47K BTU unit. I do see Modine's specs say that the 47K BTU is if you're using steam. with hot water, it'll only put out ~34k BTU. Still should be ok.

Our boiler is only ~15' away from where heater would be. Would it still be advised to use an aquastat? I don't really care if the fan blows cold air for a few minutes.

 

[jzinckgra]

Anyone else have any comments, thanks

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[R.Beans]

I was advised by my HVAC company to do a 45,000 btu for a 30x40x10.. went with a Reznor UDAS. Time will tell.