Home electric furnace troubleshooting

[dkjwall]

Hey guys,

My small 900 sq. ft. home is heated with a BROAN 10KW electric furnace that was put in around the year 2008. It's very basic with no electronic circuit board or 2 stage blower like modern electric furnaces have.

I've had a trouble with heat output for the longest time, and I'm really starting to notice it with the temperatures we've been experiencing for the last couple of days (-35C). I've had trouble keeping my home, which is insulated to R19.5, even 19C.

I believe my return air duct is undersized. The reason I think this is because when I've removed the front panel to inspect the furnace (while it's running), giving the blower maximum air, the temperature at the register jumps from approximately 22C to 30C according to my temp gun... I know it's not an accurate way to read temperature in this case, but it gives me a baseline for improvement.

My return air duct is tin and measures 6x14, and then necks down to 4x12 as it runs along the underside of my floor joists. Seems awful small.

What do you guys think?

Thanks,

Derek

 

[oledude1952]

Does sound small.... and the RA duct being downsized from 84 sq. in. to 48 sq. in. is NOT helping.

What is the opening size of the furnace filter, and is the filter in good condition as far as it not being restricted with dirt ?

The units filter RA opening size in square inches, will give you an indication of what the RA duct size should be in square inches... generally speaking.

 

[dkjwall]

That would make sense. Filter is in good shape. I replace them every month roughly, as I use filters that are 3 for $5... Haha. The furnace filter opening is 20x20. To temporarily improve my situation I've removed the return air ducting after the elbow where it upsweeps to the ceiling... I'm drawing cool basement air which isn't great, but it's still much better.

 

[oledude1952]

That would make sense. Filter is in good shape. I replace them every month roughly, as I use filters that are 3 for $5... Haha. The furnace filter opening is 20x20. To temporarily improve my situation I've removed the return air ducting after the elbow where it upsweeps to the ceiling... I'm drawing cool basement air which isn't great, but it's still much better.

So the furnace manufacturer designed the unit to breathe well, on around 400 sq. inches of RA. So IMO, you would do well to work on getting those RA duct sizes increased somehow to get at least 300 sq. in. of RA duct.

And remember, installing larger RA ducts will not help if the combined total combined sq. inch openings of the RA grilles be them floor, wall or ceiling mount, do not add up to close to 300 sq. inches. And every elbow is equal to 5 linear ft. more of duct run, meaning more static resistance to air flow.

The RA ducts will only have the amount of RA going through them, the combined RA registers sq. in. openings, will allow to be sucked in. JMO and Good Luck.