Oversized Hot Air (?)

neilc

Picture a 1000 sq ft ranch, 1 floor over basement, built 1963, south west Ct.

12" insulation ceiling, 1 1/2+/- walls, double pane windows, fairly airtite @ the sheetrock.

60k input HA @ 56k output, 93% I think, installed 1997.



Woke up this morning about 4:30 and decided to time furnace run times.

At 4:30am, and 5 degrees, I time 8 minutes run time, 19 minutes off time.

Now at noon and 20*, I time 7 min On, 25 Off,

See attached,



I figure Fairfield Ct, 06824, for a 0 degree design temp, and my furnace nearly twice as big as I need.

I did 2 different free heat losses and came up with 33 - 36k loss calcs, meaning a 40k input being about right, right ?

Not really looking to replace it yet, but an interesting exercise just the same.



So, what do ya think ? comments ? Am I missing anything big here ?

neil

Tim McElwain

The first thing I

would ask you is the house comfortable? If yes then it is doing its job.



Concerning input/output. Your heat loss at 36,000 assuming it is accurate should be matched to the output of the equipment not the input so 56,000 is not a problem.



I would also ask you this is the furnace going off on high limit during the long run time? The blower would still be running but the burner would have shut off. If the burner stays on during the entire on cycle then it is working okay. By the way keep the filter clean. I change mine once a month as they are very cheap.

Steamhead

What I'd do in your case

is insulate the heck out of the house. Then, when your furnasty dies, you can get an even smaller one. The 12" in the ceiling is a good start, but the walls obviously need more.



Insulation is much cheaper than buying extra fuel!

neilc

cool calm cucumbers

Oh, yeah,

we are comfortable, keep the heat at a steady 62*, by choice, and the filter is clean, change our's monthly also, pleated,,,.

The furnace runs fine, it's not bouncing off the limits.



And by run times, I meant and should have specified the fan.

I hear the burner start first as it should, then the fan, then the burner shuts off about 30 seconds before the fan does, with the thermostat satisfied.



It's actually the short run time, and the longer off time which I was noting, as it relates to the furnace sizing.

I was really more commenting on oversizing, and looking to confirm my heat loss and output needs, 40K, based on today's run times, at or near design.

No immediate plan to replace, but feeling out the waters, and I knew this was the place to ask,,,,



.

neilc

insulation

Yup,

was thinking this too,

family does sheetrock, and I'm the carpenter, jack of all,,,

considering stripping SR and foaming the 2x4 walls, then blowing more up top, cellulose over existing fiberglass batts,

gotta do a roof too, but that's another story.