[Dr Alli]

Hello.

I posted once before about the same furnace (Carrier 58PAV135-20 upflow, single stage, 80% efficiency, manufactured in 2001). On top of the LED flashing 33 periodically, the service guy (from a Carrier distributing company) showed me that the heat exchanger is cracked. He thinks it cracked because the house builders got too big of a furnace for the size of the house.

We have gotten three quotes for furnaces and we are thoroughly confused about the load calculations and whom we want to purchase a new furnace from. We are looking at 2-stage, high efficiency (95%) furnaces.

"Bruce" (I'm making up names) from Trane figured that we need 105K BTUs. He wants to sell us the same size unit (120K BTU) we currently have (Trane XV95). So, he said he is not sure why the heat exchanger cracked... possibly a flaw in the design.

"Jack" from American Standard figured we need 80K BTUs. He wants to sell us a (Freedom) 95 BTU. He agreed with the service guy that the heat exchanger cracked because the current furnace is too big. He said we have ductwork to support a 4 ton blower, and a 120K BTU furnace would have a 5 ton blower.

"Phil" from Carrier also said the house needs around 80K BTUs. He thinks the heat exchanger cracked because the current furnace is too big. We are not going with Phil for other reasons.


We would go with Bruce, because he was recommended from someone we know who bought a furnace from him and is happy, but we are concerned that 3 people told us the 120 is too big. What questions should we ask to resolve this dilemma? Any suggestions?

[hvac1000]

ASK them for a copy of the manual J they did for your home since it is the ONLY way to size the furnace correctly.

[csavage1]

ASK them for a copy of the manual J they did for your home since it is the ONLY way to size the furnace correctly.

That's the best way to size for sure. The BTU sizing is based on heat loss,sq footage ,walls,insulation,windows doors,etc...

If they can show you one they did for you that's who I would hire.

When a lot of chambers crack it can be from damp,wet moisture areas.
Another culprit would be lack of cold air return to cool down the system properly.

Properly balanced supply and return is as important as BTU size of furnace.
If the bigger one runs less and is more efficient that what I would use.

Good luck

Hvac1000 will be able to help better than I.
If all 3 said the 120 was too big they may be right