Help: need forced hot air heater sizing

[vlocci]

I'm hoping members here can provide some real work experience.

I've had 3 contractors out, each of which has come up with a different size heater. Prices are all over he place.

I'm looking for a forced hot air gas heater like a modine hot dawg (or similar).

Shop is 60X30 shop, with 14 foot ceilings. It has R19 in the walls, and R30 in the ceiling. The front has two 12X12 doors.

I'm in Boston, and looking to get the shop to 60 on the coldest (0 degree) days.

My gut tells me 100,000 BTU's. Contractors have told me everything from 75K to 210K BTU's

Anyone have some real word experience?

Vin

 

[trbomax]

I think you are going to need an air handeler to distribute the heat along the 60' length,otherwise it will heat unevenly.A blower on one end with a cieling duct and at least 2 registers,you dont need to go the whole 60',maybe only 40.My old shop was 55' deep and untill I did this,the furnace end would be 20 degrees hotter. Best deal would be to put it on the side wall at 30' and duct it both ways.I wouldnt go less than 150k.If its too big,it will just not run as much,if its too small it will run all the time and never get warm.My new shop is 72' long with the furnace (forced air wood/coal) half way down the side,ducted 20' each way.It is rated to make 275k,and with the 13' ceilings and 2 ceiling fans will roast us out if its running hard.

 

[trbomax]

I think you are going to need an air handeler to distribute the heat along the 60' length,otherwise it will heat unevenly.A blower on one end with a cieling duct and at least 2 registers,you dont need to go the whole 60',maybe only 40.My old shop was 55' deep and untill I did this,the furnace end would be 20 degrees hotter. Best deal would be to put it on the side wall at 30' and duct it both ways.I wouldnt go less than 150k.If its too big,it will just not run as much,if its too small it will run all the time and never get warm.My new shop is 72' long with the furnace (forced air wood/coal) half way down the side,ducted 20' each way.It is rated to make 275k,and with the 13' ceilings and 2 ceiling fans will roast us out if its running hard.

I had this same furnace in the old shop and it would hold 70 degrees even with the exhaust fans running.

 

[vlocci]

Thanks for the advice. I'm stuck with a hotdawg style heater as it is being installed by the seller as part of the deal. Long story...

Looks like we will go with their 100K BTU/Hr output unit. Seller is installing 3 ceiling fans as well, which should help moving the air around, and pushing the heat down.

Still checking to see if they will simply give me a credit for the unit price and I can go with an air handler on my dime later.

Vin