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I just moved to a new house and the furnace is a 100,000 btu…

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Hi, I just moved...

Hi, I just moved to a new house and the furnace is a 100,000 btu Payne model PG9YAB. The furnace has problems firing up. Several contractors have looked at the installation and the consensus is that the exhaust pipe installed is too small for the distance it has to travel and that the furnace is oversized. In short, condensation builds up and the furnace stops working. One contractor suggested reducing the gas pressure, derating the furnace. He thinks that that might reduce the btus and reduce condensation. Does that make sense? Is it worth trying? It's a 7 year old furnace, down the road I would like to replace it but maybe I can avoid it for now. Thanks

Contractor's Assistant: Did you check the furnace's filters?

Yes

Contractor's Assistant: Do you plan on doing the work yourself?

No

Submitted: 4 months ago.Category: HVAC
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Answered in 2 hours by:
3/23/2018
HVAC Technician: Machinc, General Contractor replied 4 months ago
Machinc
Machinc, General Contractor
Category: HVAC
Satisfied Customers: 1,032
Experience: Has written home improvement articles since 2008. Earned South Carolina Residential Builders License in 1991.
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The contractors evaluations do not sound professional.
There are several things to consider.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
The unit is seven years old so did the previous owner put up with seven years of inefficient heat.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
If it is a design defect as suggested then wouldn’t that be the case.
It is not logical that they went through seven years of that kind of problem.
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Customer reply replied 4 months ago
They told me they spent the coldest months of the winter somewhere else. The furnace seems to work when it’s not very cold
HVAC Technician: Machinc, General Contractor replied 4 months ago
I am just going on the assumption that the contractors you have called are depending on each others findings.
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Customer reply replied 4 months ago
I got independent opinions and they all conclude it has to do with the size of the exhaust pipe. I’m actually hoping it is something else
HVAC Technician: Machinc, General Contractor replied 4 months ago
The furnace problem should also have been mentioned in your disclosure information when you bought the house and it’s repair covered by that contract if you have one .
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HVAC Technician: Machinc, General Contractor replied 4 months ago
A licensed insured HVAC contractor should be able to diagnose the problem which is possibly the pipe size which would have to be replaced.
If that is the true problem then you have no choice.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
I would have one more experienced HVAC company come out . Let them start from scratch . Do not tell them anything about the pipe . If they come up with the same conclusion then you should have the vent replaced with the right size.
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Customer reply replied 4 months ago
I think I'm coming to terms with that conclusions. The main problem is that the apartment is on the 4th floor and reaching the terminations outside is almost impossible. One contractor suggested just enlarging the pipes up to the terminations and keeping the 2" termination going out. Would that work? I'm not sure we can fix the pipe if we have to go outside.
HVAC Technician: Machinc, General Contractor replied 4 months ago
Trying to downsize the existing unit and reusing the same vent is not a likely or good solution .
Proper venting and exhaust can be a safety as well as a service hazard.
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Customer reply replied 4 months ago
What about enlarging the pipe all the way up to the end? That's their suggestion
HVAC Technician: Machinc, General Contractor replied 4 months ago
Two inches is too small if those numbers are correct.
While hard to do someone got up there before and a professional will do what is needed to do the job correctly.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
It has to be enlarged all the way to the outside.
You need a contractor who is qualified and equipped to do the job completely.
The pipe should meet code all the way
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HVAC Technician: Machinc, General Contractor replied 4 months ago
I’m sorry but you need to find a more qualified contractor
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HVAC Technician: Machinc, General Contractor replied 4 months ago
I know it is hard to get to but that is what needs to be done . You can’t leave
the end of the vent too small just because the contractor is unable or unwilling to get on the top of a four story structure.
There are contractors who can get up there and will complete the replace ment properly as that is what is needed.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
This area can be reached by a “bucket truck” . Larger companies will already own one . Smaller companies rent them as needed.
This should not be a problem.
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Customer reply replied 4 months ago
It's the back of the apartment building, no room for a truck or a lift, i think. It might have to be hanging from the top, I guess. Is that possible?
HVAC Technician: Machinc, General Contractor replied 4 months ago
The smaller vents are too small and will cause fumes to back up in the larger pipe.
With the right equipment this is no problem to repair.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
We rent lifts that fit through a gate . They are electric and rolled in place by hand.
It is also possible to complete this job with a ladder.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
I’m sorry but being hard to do is no excuse . A professional will get it done. Scaffolds are also an option.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
You just need to get in touch with a more experienced and better equipped repair /service company.
I don’t mean to sound hard but this needs to be done right.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
In response to your previous guestion a hanging scaffold like window washers use is also an option.
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HVAC Technician: Machinc, General Contractor replied 4 months ago
I’m sorry you are going through this but it is best to go ahead and get it done right . This will eliminate any future problems with the venting system.
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