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60,000 BTU for 2,000 sq ft?

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jjack100

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I have a Carrier Weathermaker 9300TS 58MTA (93% eff.) 60,000 btu input furnace. The house is in MN and is 2,000 sq. ft.

I recently bought this house. For some reason, the previous owner did not put any vents in the downstairs family room (there is a baseboard electric heater in there instead...wow, is that expensive to run). I am wondering if this furnace is just too small to handle that space or not, because I want to add vents down there.

I realize there are many factors in sizing a furnace, but on the face of it this furnace seems much too small for this house in this climate. The house was built in the 70s and is not tight.

So, I'm trying to figure out if it is worth trying to add vents/improve insulation with this furnace or if I really just need a larger furnace. Any advice?

Thanks
 
#3 ·
jjack100 said:
I have a Carrier Weathermaker 9300TS 58MTA (93% eff.) 60,000 btu input furnace. The house is in MN and is 2,000 sq. ft.

I recently bought this house. For some reason, the previous owner did not put any vents in the downstairs family room (there is a baseboard electric heater in there instead...wow, is that expensive to run). I am wondering if this furnace is just too small to handle that space or not, because I want to add vents down there.

I realize there are many factors in sizing a furnace, but on the face of it this furnace seems much too small for this house in this climate. The house was built in the 70s and is not tight.

So, I'm trying to figure out if it is worth trying to add vents/improve insulation with this furnace or if I really just need a larger furnace. Any advice?

Thanks
Click to expand...
I always tell my customers to add the ductwork as needed for the addition or basement and "see" how it goes. Remember that you'll have the back-up heat (elec.) when it really gets cold.

If a larger furnace is needed, you can do that at a later time or zone as B. T. said. At least let the contractor know your intentions. If room allows, he can run a seperate ductline to manually or auto zoning in the future.
 
#4 ·
60k is not out of line at all.

If it can't keep up, do everything you can to reduce heat loss.

A room by room load calc may be required to fix the duct system - adding a couple of vents won't cut it.
 
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#5 ·
60k is a LOT of heat. Think qty 12 of those 115V plug in heaters..
 
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#6 ·
Over-sizing gas furnaces never ceases to amaze me.
I've seen 125K/80% units on 800 sq ft homes.
I truly enjoy it when I see 40K units keeping customers warm, and comfy.
And we're in a cold climate.
After having enjoyed the comfort of a properly sized furnace, I could not imagine the agony of getting blasted by an over sized unit.
Don't over size if your guy says 60K will do it.
Get it in writing, and hold him to it if it doesn't work.
Keep in mind, on the coldest days, it will run constantly to maintain, and may not be able to recover from a set back for hours.
 
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#7 ·
2old2rock said:
Over-sizing gas furnaces never ceases to amaze me.
I've seen 125K/80% units on 800 sq ft homes.
I truly enjoy it when I see 40K units keeping customers warm, and comfy.
And we're in a cold climate.
After having enjoyed the comfort of a properly sized furnace, I could not imagine the agony of getting blasted by an over sized unit.
Don't over size if your guy says 60K will do it.
Get it in writing, and hold him to it if it doesn't work.
Keep in mind, on the coldest days, it will run constantly to maintain, and may not be able to recover from a set back for hours.
Click to expand...
Come to think of it I've never lived in a house where a gas furnace WASN'T oversized... I guess high BTU furnaces don't cost much more to buy than correctly sized.
 
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#8 · (Edited by Moderator)
60,000 BTU for 2,000 sq ft

I have a Carrier Weathermaker 9300TS 58MTA (93% eff.) 60,000 btu input furnace. The house is in MN and is 2,000 sq. ft.
_________________

I'm a novice looking the same problem with the exact same 9300TS Carrier furnace in southern MI, considering whether the 60K BTUs will support an addition that will bring total to ~1900 sq. ft.

These guys sayLinks to direct purchase sites are not permitted.
45 BTUs per square foot (zone 4=S. MI) 50 BTUs per square foot (zone 5=MN)

2000 sq ft * 50/sq ft = 100,000 BTU

Are they just trying to sell a bigger furnace or is 60,000 BTU really enough for 2000 sq ft in MN/MI? From previous posts sounds like you can definitely get by with less -- are these BTU/sq ft recommendations blowing hot air?

Thanks
 
#9 ·
You would need to do a heat load calculation to determine what size furnace you would need. Because every house is different, sizing by square footage is a very easy way to get a furnace that is either too big or too small.
 
#10 ·
Considering the cost of ductwork, it might be worthwhile to compare that with the cost of a minisplit heat pump for that room, if it's a large room. At least it's something to check into.
 
#11 ·
You have enough heat for that home. I have a1968 1,500 sq ft home in MN, and with our cold -20Ëš cold snap, it had no issue keeping the house warm.

Also basement don't need much to keep warm since it's in the ground.
 
#13 ·
REALLY ?

johnny_five said:
45 BTUs per square foot (zone 4=S. MI) 50 BTUs per square foot (zone 5=MN)

Are they just trying to sell a bigger furnace or is 60,000 BTU really enough for 2000 sq ft in MN/MI? From previous posts sounds like you can definitely get by with less -- are these BTU/sq ft recommendations blowing hot air?
Click to expand...
That the rule from year 1891.

.. Two centuries have passed. So divide by 2.
 
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#14 ·
60,000 BTU might be on the low side but, remember, heat rises and whatever you put into that room will mostly find its way upstairs, eventually (a sort of "auto-zoning"). ;)
 
#15 ·
When you talk about over sizing, they do it big time down here. This house has a 90,000 btu Lennox gas furnace for 1800 sq ft. It's way to much heat for Houston.
 
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#16 ·
Texas-Tech said:
When you talk about over sizing, they do it big time down here. This house has a 90,000 btu Lennox gas furnace for 1800 sq ft. It's way to much heat for Houston.
Click to expand...

You guys probably don't have much choice, since yo need to have a blower big enough for the A/c you need.
 
#17 ·
beenthere said:
You guys probably don't have much choice, since yo need to have a blower big enough for the A/c you need.
Click to expand...
You may be right, but I think you could get a little less heat with the same blower package but maybe the temp rise would suffer. Hell, a majority of the heaters here only run for maybe 30 to 40 days out of the year.
 
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