Undersized Furnace?

[Gears]

Good day!

Through the colder weather the past few weeks, I have noticed our furnace seems to be on more frequently and longer than I would expect.

After checking the rating of the furnace and doing some basic research, I think the furnace installed by the builder may be undersized (and not meeting Ontario Building Code).

Details below:

+ New build, less than 1 year old.
+ 2 story
+ 1850 sqft
+ Location: Collingwood, Ontario

What rating (BTU) should our furnace be, +/-?

Not looking to hold anyone to it, just working on determining if I need to get a full calculation done by an accredited HVAC company.

[Hgye]

Does the furnace satisfy the thermostat?  What size furnace do you have?

[Gears]

Does the furnace satisfy the thermostat?  What size furnace do you have?

The furnace satisfy the thermostat, more or less. I have witnessed the temp drop (one increment) during one heating cycle.

BTU is 44,000.

I am finding consistent 'rule of thumb' being about 30 BTU per sqft...which would put me more in the 55,000 BTU range, but those seem to be general articles.

Thanks!

[samihabib]

Your R rating for a new build is so high ..that the furnace should be enough ..unless the builder cut corners on insulation of the envelope

[Hgye]

Does the furnace satisfy the thermostat?  What size furnace do you have?

The furnace satisfy the thermostat, more or less. I have witnessed the temp drop (one increment) during one heating cycle.

BTU is 44,000.

I am finding consistent 'rule of thumb' being about 30 BTU per sqft...which would put me more in the 55,000 BTU range, but those seem to be general articles.

Thanks!

Well, if the furnace is satisfying the thermostat, then it is sized correctly.  If the thermostat drops more than 2 degrees from set point, then you might be undersized. You might be over thinking it.

[Admin]

One thing to verify, if you have a two-stage furnace, is that it's set up correctly and not stuck running on low fire only.

It sounds like you might have a Lennox furnace which comes set for use with a two-stage thermostat.  If you have a single stage thermostat there may be a dip switch inside the furnace that needs to be adjusted.   A lot of times in new construction even if a two-stage thermostat is used it is only wired for single stage.

Without seeing the actual HVAC design it's hard to know.  A 44,000 BTU furnace likely has an output of around 42,000 BTUs.

My rule of thumb, for a newer home, is square footage x 25.5 = 47,175 btu's.  So your sizing is probably borderline but the F280 HVAC Designs tend to undersize equipment in an attempt to improve comfort.

[Gears]

Does the furnace satisfy the thermostat?  What size furnace do you have?

The furnace satisfy the thermostat, more or less. I have witnessed the temp drop (one increment) during one heating cycle.

BTU is 44,000.

I am finding consistent 'rule of thumb' being about 30 BTU per sqft...which would put me more in the 55,000 BTU range, but those seem to be general articles.

Thanks!

Well, if the furnace is satisfying the thermostat, then it is sized correctly.  If the thermostat drops more than 2 degrees from set point, then you might be undersized. You might be over thinking it.

Thanks for the help. You may be correct on the over think. I had a handful of challenges with the furnace in our last place...may be on the lookout for anything that might be wrong. 

[Gears]

One thing to verify, if you have a two-stage furnace, is that it's set up correctly and not stuck running on low fire only.

It sounds like you might have a Lennox furnace which comes set for use with a two-stage thermostat.  If you have a single stage thermostat there may be a dip switch inside the furnace that needs to be adjusted.   A lot of times in new construction even if a two-stage thermostat is used it is only wired for single stage.

Without seeing the actual HVAC design it's hard to know.  A 44,000 BTU furnace likely has an output of around 42,000 BTUs.

My rule of thumb, for a newer home, is square footage x 25.5 = 47,175 btu's.  So your sizing is probably borderline but the F280 HVAC Designs tend to undersize equipment in an attempt to improve comfort.

Lennox, single stage. The thermostat is setup for single stage.

Appreciate your feedback and concise reply!