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servtech50
servtech50, HVAC Technician
Category: HVAC
Satisfied Customers: 322
Experience:  over 20 yrs. experience
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I have a Concord a95uh gas furnace the pressure switch drop

Customer Question

I have a Concord a95uh gas furnace the pressure switch drop out after 2minute of burn time. have check intake and exhaust
flue check hole on the pressure switch this is a new furnace just install less than 30 days, work find up untill now.I have check the pressure switch by manual runing the draft motor by it self, the switch dose not drop out
Lawson
Submitted: 5 years ago.
Category: HVAC
Expert:  servtech50 replied 5 years ago.

servtech50 :

Welcome to Just Answer. I am servtech50 and will assist you today.

servtech50 :

can you tell me how many btu this furnace is. the size of the vent pipes and approx. how long the vent pipes are?

servtech50 :

With the outdoor being as cold as it is and cold air being heavier than warm air, if th vent pipe is not the correct size and length that would cause your problem.

servtech50 :

or something could have been sucked into the intake pipe. or your condensation is backing up.

servtech50 :

did you check to see if you had any water in your pressure switch? and last these switches are man made, you could have a weak switch or a small tear in diaframe.

servtech50 and other HVAC Specialists are ready to help you
Customer: replied 5 years ago.

not at the furnace right now, will check out those things you have stated and get back with you. right now i will accept your answer, but may need a follow up on this problem.

Lawson

Expert:  servtech50 replied 5 years ago.
that is ok. thanks for the accept but in the future do not accept until you are satisfied with your answer. when do you think you will be home?
servtech50 and other HVAC Specialists are ready to help you
Customer: replied 5 years ago.

I have a follow up on the Question i ask about the furnace pressure switch droping out, after the furnace burn for about 3minute. I have check all of the thing you said could be the problem, stiil drops out.if i jump out the pressure switch the furnace run till the thermostat shut it off. i hear concord used different size pressure switch in there units

one .90 and .65 i have

a model no 95c1uh090dcp12-02 it has a .90 or is it possible to have a bad board

Expert:  servtech50 replied 5 years ago.

No you do not have a bad board. Though the board does look for the signal, the 24 volts, from the pressure switch it does not know if is jumped or working. So if you Jump it out and it runs a complete cycle it is switch not board. Does your pressure switch have two hoses to it? if so try this, take the hose that goes either to gas valve or burner box and disconnect. the other that goes to venter or collector box leave connected. Cycle your furnace and see if it runs a complete cycle. if it shuts off check other hose at the end where it connects to venter or collector box and see if water has built up or some sort of debris is in there.

Customer: replied 5 years ago.

i have done that no water come out that hoses

Lawson

Expert:  servtech50 replied 5 years ago.
What I meant was to just disconnect from burner box and fire furnace to see if it would stay running. and if not to check for water in collector box. I thought you probably checked for water in hose but the collector box may be filling up and not draining properly. The collector box is a cover that covers the secondary heat exchanger and the water from condensing flue gas collects there and then drains into trap then out to floor drain. And if the furnace does stay running then we have an air intake problem not getting enough air for combustion. and in both cases it also could be just a bad pressure switch. servtech50
Expert:  servtech50 replied 5 years ago.
it says we timed out, I hope we are still pursuing this. I just wanted to let you know I will be leaving for up north bow hunting but I will check mail later this evening. or 2622242517. I will continue to assist until this is resolved and we have a definitive answer. servtech50
Customer: replied 5 years ago.

Hi just found the problem the condensning trap that came with the unit was not used

after installing the proper trap. the furnace work fine, your answer put me on the right track. thanks,will be using your service in the future.

lawson

Expert:  servtech50 replied 5 years ago.

I am thankful you discovered the issue. any idea's on why the install company did not use proper trap? I was just wondering.

Thanks again for the accept earlier, it has been a pleasure assisting you. servtech50