My dealer is replacing my 60,000 btu Carrier 58MVP furnace to a 80,000 btu Carrier 58MVP furnace. This is due to the furnace not heating the house efficiently.
My question is does anything else need replaced for the new furnace or existing 3 ton Carrier 38TDB air conditioner to work correctly?
Thanks in advance for the help!
I would verify that a load calculation was done to confirm that the 80K is needed.
They did a load calc and stand by the fact that a 60k furnace is what the house needs but the problem is with the fact that I keep the thermostat set on 71 but the furnace runs constantly on low speed and the low speed does not keep the house warm. High speed is great and does a great job heating the house. There is about 1600 sqft of space to heat.
At the install they wanted to put in a 2 ton air and I asked for the 3 ton which does a great job of cooling the house.
As teddybear is fond of pointing out, the problem is frequently more to do with caulking, sealing and insulation than sizing. Most go the easier but more expensive route of replacing the equipment than doing the painstaking labor to deal with the real issue. One creates a higher bill, the other permanently lowers it.
Have they tried something as simple as raising the fan speed for the heating mode? Are you trying to close off rooms to save/waste money?
First thanks for all the insight..
My windows are also brand new and were installed right before the new furnace and air conditioner. I have checked the seal and perimeter of the windows with a lighter on windy nights and there seems to be no leaks what so ever. I also just blew 6 additional inches of insulation in the attic.
I had 5 estimates and all were for 75 to 80k units. This guy assured me this was correct and gave me a swap out warranty.
One last thing.. Most of the vents in my house are closed so the heat only goes to rooms that I use. He has adjusted the fan twice now.
[Edited by jim15102 on 01-31-2005 at 07:53 PM]
Good luck with your mold problems in the future...
Why would I have mold? There was only 3 inches of insulation in the attic in the first place.
Oversized air conditioner does not remove humidity.
Sounds like you hired some hacks if they tell you that you need a 2 ton A/C then you tell them you want a 3 ton and they do it.
Are you saying the 60,000 btu unit heated properly, ran constantly and cycled between high and low fire when under design conditions?
If this is what you are saying i think you have the correct furnace installed already. The low fire should run all the time and go to high fire as neeeded to maintain temp. Maybe all you needed was a thermostat with a closer differential setting!
I would never put in an oversized heating system in your home due to lack of customer understanding.
You cant close off vents in your home. A heating system designed to heat a home cant be used to heat just selected rooms unless designed with a zone controll system. You will see higher bills after you change the unit. You will also crack the heat exchanger unless you OPEN the damn vents!
My guess is the guy wouldn't accept that this is how his new 2 stage furnace works and they put in one that would "cycle" more frequently to shut him up.
A two stage system will run longer on first stage, and the temp is a little cooler too..
Ideal thing is have the furnace run longer..
Also agree with the guys, over sizing the A/C is not going to help..
I have browsed this site for a while now (great information) never had a question and the one time I do these are the reponses I get??? No one even attempted to answer my question!!!
Just for the heck of it I will respond so hopefully everyone does not think I am an idiot...
The house called for a 2 1/2 ton ac the 38TDB came in only 2 and 3 ton units. Since I had other estimates for 2 1/2 and 3 ton units I asked for the 3 ton.
I did not close the vents the installer did to force air to the rooms I was complaining about! I did not know this would cause a problem.
I also understand the two stage furnances, the problem like I said before its that on the first stage (which is most of the time) the house is cold even with the thermostat set at 71. On high fire the house is very comfortable.
The reason I do not think this furnace is correct for my house is that I used 16 MCF's (bills are always actual) to heat my house last month. That is more than my 32 year old 130,00 btu furnace ever used in a single month. And the fact that most other estimates were between 70k and 80k furnaces.