How old is your house?

What type of furnace did you replace and why?

Do you run the fan continously now at a lower speed?

Even though your bills are not crazy high for this size of house, it may be worthwhile to pay for a energy audit. It sounds like your main problems are insulation and air leaks.

herus

even for a moderate winter climate like Atlanta, an 80% eff furnace without a matching HP is really a dinosaur.

with that said, I would be disappointed with the gas usage and would keep bothering the installer until he responded by checking out the new system. what was eff on old furnace? you have two new furnaces? what size BTU output on low and high stage? any idea what the CPH is set at on your stats?

IMO

The house (and the old system) are about 15 years old. That system being in a junk pile somewhere I can't verify everything, but I know I replaced with something close. I believe it was a 70% furnace but *might* have been 80%.
Both systems (furnace, a/c everything but the ducting) are new. Upstairs is a G60UHV-36B and XC13-036 (so I guess this would be 3 ton AC, right?). Downstairs is G60UHV-60C also with XC13-036.
I have both blowers set to #2 speed (medium low). The downstairs was set to Low but I changed it (I was with the installer while he was setting them and learned how through him and the manuals). I changed it after the first instance of the high gas bill as I thought this would circulate air better and therefore be more efficient - maybe my thinking was upside down, please tell me. Upstairs was set to medium-low from the beginning.
The fan setting is auto, not 'on' continuously.

BTW- I would like to ask - should the vent pipe (flue?) get almost unbearably hot? This is the stack leading out of the furnace and going up through the first floor, then second, then attic. (lower unit is in the basement). When running I can barely touch this pipe, it is so hot. During the 'off' cycle I can maybe touch it for 2-3 seconds. I am particularly concerned about this as an issue separate (although possibly related to?) the high gas bills. Fire hazard, wastage, CO, you name it. I have placed a CO detector near it but the closest I could come (for electric outlet) is about 9 feet in the room adjacent to where the closet that houses the furnace is.

Any recommendations on whom to contact for an energy audit, the kind one pays for?

Thanks so much for responses so far. Please keep 'em coming. Am very bummed by this, not only because I dislike paying high bills of any kind, but also feel that I've thrown away over $10k for a system that might perform *worse* than the old one, and also for the fact that I am contributing to a wastage of natural resources. We are getting more conservative since the last few months of bad news in this country and world and yes, do feel regret that we bought this size of home to begin with. But at the moment I need to work on those things that are more possible.

www.resnet.us
it is not always in the best interest of the HO
to have a free audit from the company selling
you energy...
best of luck

Check your degree-day data for this year and last year.

I don't live in Atlanta, but in the DC area, HDDs are up about 5% above the average winter, whereas last winter was around 10-15% below average.

Translation: A colder winter means higher heating bills.

I will check the HDD again yesterday. I do recall talking to Gas South and they said it was higher, and sorta recall about a 20% jump. Let me check.

BTW I just noticed something that may or may not be interesting. The t-stat is programmed to go from 67 to 58 at 10 pm each day. It is now 11:20 pm and the room temp is 64 degrees. If I was having significant heat loss from leakage etc I'd have expected the room temp to be quite a bit lower, yes? I mean, given that it cycles at between 8-10 minutes during the day, in an 80 minute period that might be worth a bit more than just 3 degrees?

Looking for a reasonable answer to the above as I am not understanding why heat loss rate *seems to be* higher during the day, when outside temps are actually not as cold.

herus said:

"BTW I just noticed something that may or may not be interesting. The t-stat is programmed to go from 67 to 58 at 10 pm each day. It is now 11:20 pm and the room temp is 64 degrees. If I was having significant heat loss from leakage etc I'd have expected the room temp to be quite a bit lower, yes? I mean, given that it cycles at between 8-10 minutes during the day, in an 80 minute period that might be worth a bit more than just 3 degrees?"

One possibility is that if your furnace gets its combustion air from the house itself, when the furnace runs, it causes infiltration of outside (cold) air, which could prolong heating runs or cause the next run to start earlier.

This does not occur when the furnace is off (as in setback).

When looking at HDDs during periods of lower temps with smaller daily ranges, the totals will be greater, as well as gas usage.

V

Another thing on cycling is that your 'stat is probably set to keep it at the set point, not let it drop a full degree before coming on. So, if you lose a degree every 25 minutes, then your cycle likely would be every 8-10 (or 12) mins to keep it between (say) 66.5 and 67.5.

Also, your house has a lot of thermal mass. Air can cool a little bit easily, but cooling will slow down as the air absorbs the heat from the solid mass of the house as well, which isn't likely to happen to the same degree with

veesubotee: "One possibility is that if your furnace gets its combustion air from the house itself, when the furnace runs, it causes infiltration of outside (cold) air, which could prolong heating runs or cause the next run to start earlier.

This does not occur when the furnace is off (as in setback). "

Thanks. This makes sense to me. So, as a measure to reduce consumption, does it make sense to lower the fan speed back to Low? The logic being that a low running fan 'sucks' less vigorously (air from outside the home).

hiemert, not quite following the last para in your post, but the first one does make sense. I wonder if there is a setting on the t-stat that will adjust that cycle to 1 degree, and if so, is this a good idea to do?

The fan is not what's sucking air from outside, it's the combustion process. That takes air. It consumes air in your house, which means you need new air, which comes in through various cracks and holes.

As for t'stat--most can be adjusted re cycling.

The second paragraph was describing the fact that the walls, wood, metal, etc. of the house retain heat. That heat will radiate as the air cools. The whole house, not just the air, has to cool to 64 degrees overnight.