Problems with Goodman Gms8 60k btu/ Possible Sizing Issues?

[grant087]

Not too sure if the problem with my furnace is it being undersized or an issue with furnace. The furnace is a brand new Goodman GMS8 80% 60000 btu in a 926 bungalow 9ft walls, ceilings are insulated, walls are not insulated, and 4 inch rectangle high supply duct(house was build in 20s). The problem that i am finding is that it is producing luke warm air and the furnace continues to run and run. I tried to adjust blower speed but even with setting set on high it will not even heat above 50. The supply duct on top of the furnace seems to be warm but not hot. Any ideas on why the furnace is only producing luke warm air and not hot air? And will this furnace even be enough to satisfy this size house requirements? I know ive seen some newer construction houses larger with a 60k looking for some imput.

Thanks,
Grant

[hvacvegas]

Not too sure if the problem with my furnace is it being undersized or an issue with furnace. The furnace is a brand new Goodman GMS8 80% 60000 btu in a 926 bungalow 9ft walls, ceilings are insulated, walls are not insulated, and 4 inch rectangle high supply duct(house was build in 20s). The problem that i am finding is that it is producing luke warm air and the furnace continues to run and run. I tried to adjust blower speed but even with setting set on high it will not even heat above 50. The supply duct on top of the furnace seems to be warm but not hot. Any ideas on why the furnace is only producing luke warm air and not hot air? And will this furnace even be enough to satisfy this size house requirements? I know ive seen some newer construction houses larger with a 60k looking for some imput.

Thanks,
Grant

You messed with the blower speeds?
Wrong call.

Call a professional about this one. Messing with blower speeds without knowing what your doing can cause you to crack your heat exchanger, or cause condensation in the flue, ruining your chimney.

Either way, you could need a new furnace if you continue. Bumping up the speed could cause you to need a new furnace AND chimney.

[beenthere]

Call the installing contractor back, its under warranty if it was just installed.

[dan sw fl]

Not too sure if the problem with my furnace is it being undersized or an issue with furnace.
The furnace is a brand new Goodman GMS8 80% 60000 btu in a 926 bungalow 9ft walls,
ceilings are insulated, walls are not insulated, and 4 inch rectangle high supply duct
(house was build in 20s).
The problem that i am finding is that it is producing luke warm air and the furnace continues to run and run.

I tried to adjust blower speed but even with setting set on high it will not even heat above 50. The supply duct on top of the furnace seems to be warm but not hot.

Any ideas on why the furnace is only producing luke warm air and not hot air?
And will this furnace even be enough to satisfy this size house requirements?
I know ive seen some newer construction houses larger with a 60k looking for some input.

Thanks,
Grant

Unless your house is as leaky as leaving he windows open, 60,000 BTU/Hr is likely adequate.

4" high duct does not seem to be a good situation
IF you are referring to the main duct (header).

_ 4" x 20" = 80 sq. inch = ~ 0.6 sq feet
which might handle 600 CFM / 1,000 FPM

50,000 BTU/Hr = ~ 70'F temperature rise.
------------------------------------------------

Simplified Heat Load will be calculated based on
following Parameters
Ceiling R-20 926 Sq. Feet
Floors R-6 926 Sq. Feet
Walls R-3 900 Sq. Feet
Windows U-1 100 Sq. Feet
Infiltration 1 ACH ( 0.2 Tight, 0.6 Typical )
No basement

as a Worst Case ( W.A.G.)
You will need to adjust values to match your actual situation.
....................... ___________ ..................... _____.................

[dan sw fl]

926 Sq. Foot / 1920's Residence

Ceiling______ 2,800 BTU/HR
Wall _______ 18,000
Window_____ 6,000
Floor _______ 9,300
Infiltration___ 10,700
_______
Total _______ 46,800 at 10'F
dT _______ 60 dT
Loss per degree __ 780 BTU per Hour / 'F
50' - 10'F _______ 40 dT
_______ 31,200 BTU/Hr

1,400 Therms per year in 6,000 Heating Degree Day climate
____
Location was NOT provided by OP.