Takes 2 hours to raise temp 5 degrees???? - Contractor Talk - Professional Construction and Remodeling Forum

rms8 · 02-20-2004, 04:54 PM

Hey,
I have a 3yr old ComfortMaker gas heater. I installed a digital thermostat when the home was finished. The temp drops to 64 degrees at bed time. At 6am (M-F) it should go up to 73deg (so it will be pleasent temp while getting ready for work). When I get up at 6:40am, the temp is only 68deg. The furnace is still running. The temp is correct, I have an indoor/outdoor temp gauge in the same room which says the same temp. By the time we walk out the door (~7:40am) the temp is only up to 69deg. It shouldn't take nearly 2 hours to raise the temp in the house 5deg, should it? The outside temp has been getting warmer around here (Chicago), so it is ussually ~35-40+ degrees outside during this morning warm-up period. The vents feel like they are blowing warm air, so what could be wrong? I did have a filter which is advertised as trapping the tiniest particles and reusable. So I replaced it with a cheapo "blue fiber mess" type filter.

Is this normal, or could something not be working correctly (limiter switch?)?

Steve Wiggins · 02-20-2004, 07:48 PM

hmmm do you know if your unit has a two stage gas valve? It might be only on low stage, just a guess. Can you take a temp meausrement of the differential between the supply and return air?

BTW thanks for filling out your profile. Being an engineer with Lucent I am going to assume you have more than one system on the home? If so you might be able to compare temps. Question, do you also have cooling with your new system(s)?

rms8 · 02-20-2004, 09:41 PM

Quote:

Originally Posted by Steve Wiggins

hmmm do you know if your unit has a two stage gas valve? It might be only on low stage, just a guess. Can you take a temp meausrement of the differential between the supply and return air?

BTW thanks for filling out your profile. Being an engineer with Lucent I am going to assume you have more than one system on the home? If so you might be able to compare temps. Question, do you also have cooling with your new system(s)?

Well, working for Lucent isn't what it used to be (in the last 3 years they have gone from 125,000 employees to ~33,000). I live in a 1700sq. ft. ranch. I finished ~ 1100 sqft of the basement myself too. But to answer your question, the house has only one system.

I used my indoor/outdoor temp gauge since it has a probe. I took two measurements of the supply : from the nearest vent (to the furnace) I got ~ 118deg & from the longest run I got ~ 98deg. On the return I measured 70deg. It seems that just the difference between the shortest run & longest is quite a lot????
And thanks for such a quick reply!!!!

Steve Wiggins · 02-20-2004, 11:04 PM

with those temps it is definately on full fire. I don't know about your area or your R-values for sure but I suspect with the square footage that your furnace might be a little on the small side. It is only 75,000 btu input and 20% of that goes up the flue so you are only getting 60,000 btu in the house. To verify this theory you could run a heat load calculation or ask the builder if one was done when the house was built three yrs. ago.

rms8 · 02-20-2004, 11:34 PM

Quote:

Originally Posted by Steve Wiggins

with those temps it is definately on full fire. I don't know about your area or your R-values for sure but I suspect with the square footage that your furnace might be a little on the small side. It is only 75,000 btu input and 20% of that goes up the flue so you are only getting 60,000 btu in the house. To verify this theory you could run a heat load calculation or ask the builder if one was done when the house was built three yrs. ago.

Again, thanks for the quick reply. I sprayed ~8-10" of cellulose insulation in our attic (on top of the R30 fiberglass). So the furnace is probably working normally, but is probably too small? It was probably fine for the original 1700sqft, but since I finished nearly 1100 more, I may be taxing the unit?

Thanks!
Are there any annual PMs u might suggest for maintaining a furnace?

Steve Wiggins · 02-21-2004, 03:46 AM

Keep plenty of good airflow by not closing off vents. Keep mother earth out by filter changing but never use an electrostatic air filter. That spark ignition comfortmaker's pilot orfice will get dirty and cause the pilot flame to be weak. I would say about every 3-5 years take out the orfice and blow it out with compressed air. Also blow out the air intake to the pilot at the base of the orfice holder. Keep a close eye on the vent pipe and make sure it doesn't drip any white milky substance down on the controls. I see in your pic a brown stain on the heat sheild right above the left burner. I can't tell but it might be from water dripping above? I think I see a cooling coil in your pic (take another pic further back) so don't let it overflow on your delicate furnace controls, circuit board etc. no one ever adds a secondary overflow drain to those upflow units even though there is a plug for one and the code requires it. Inspectors never enforce it.....what a shame for the consumer. That coil can produce up to 10 gallons of water on a hot summer day and will ruin a hardwood floor before you realize there is a problem. If the unit is upstairs it can rain down havoc on the building contents below.

If I were a rich guy like you I would jerk that comfortmaker out and install a 96% Amana gas furnace with a lifetime warranty stainless steel tubular heat exchanger. This way only 4% of your heat would go out the flue instead of 20%.

rms8 · 02-21-2004, 05:50 PM

Quote:

Originally Posted by Steve Wiggins

Keep plenty of good airflow by not closing off vents. Keep mother earth out by filter changing but never use an electrostatic air filter. That spark ignition comfortmaker's pilot orfice will get dirty and cause the pilot flame to be weak. I would say about every 3-5 years take out the orfice and blow it out with compressed air. Also blow out the air intake to the pilot at the base of the orfice holder. Keep a close eye on the vent pipe and make sure it doesn't drip any white milky substance down on the controls. I see in your pic a brown stain on the heat sheild right above the left burner. I can't tell but it might be from water dripping above? I think I see a cooling coil in your pic (take another pic further back) so don't let it overflow on your delicate furnace controls, circuit board etc. no one ever adds a secondary overflow drain to those upflow units even though there is a plug for one and the code requires it. Inspectors never enforce it.....what a shame for the consumer. That coil can produce up to 10 gallons of water on a hot summer day and will ruin a hardwood floor before you realize there is a problem. If the unit is upstairs it can rain down havoc on the building contents below.

If I were a rich guy like you I would jerk that comfortmaker out and install a 96% Amana gas furnace with a lifetime warranty stainless steel tubular heat exchanger. This way only 4% of your heat would go out the flue instead of 20%.

I see what u mean about the water stain. It's not a leak (at least I don't think??), but could it be from condensation during the summer months? The furnace is in the basement. As far as being rich, I hope that was a joke. My salary is still very, very much in the 5 figures. If I were upper management or executive status, then the sky is the limit. We (my wife & I) are modest people on a modest budget. I looked up some of those Amana furnaces you mentioned.... $$$$. They were well over $1500. Since this unit is only 3 years old, there is really no way to justify replacing it, unless it really breaks good.
I appreciate your time and advice. I will rpobably frequent this web site when I have a problem I have not run into b4! Thanks!