Correction the PVC pipes are 2" and the unit is 80,000 but
Tech guy is here, replace the ignitor with a OEM one and it actually made it worse... he is now taking apart the burner tubes and cleaning them.
Guess we will see what happens
PVC pipes are mostly either 2" or 3" inside diameter... Different manufacturers allow different pipe sizes for different furnaces... no rhyme or reason here. The number of elbows is a factor also.
Methinks there is a clog or restricted PVC pipe somewhere... and possible a clogged or bad pressure switch...
Get a tech out there who understands condensing furnaces... If you can find someone who has a combustion analyzer and knows how to use it... that would be a BIG plus. Fine-tuning the flame of a condensing furnace with a CA unit is well worth the cost!
Your comfort, Your way, Everyday!
Restricted secondary. Or pitted primary heat exchanger.
post model and serial number and maybe someone can access the manual to determine sensor/igniter position.
as beenthere said:
"May have only started for after they changed out the HSI/ignitor. But it was having problems before you bought the house. That's why the gas pressure was turned down to just over 2"."
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from an excerpt by Paul Jacob in Sun City, AZ
I will scan the diagrams in the manual and post them tomorrow.
As far as a update the OEM ignitor did not fix the problem. Tech took apart the burner tubes, and gas inlet thing that screw on the gas tube and cleaned them put everything back hooked the intake pipe up and still the eplosion. He replaced the ignitor with the universal he put in the 2nd time unhooked the intake pipe so it draws the air from the basement and it fires with minimal backfire.
Just fixed the same problem on the exact same furnace. Ignitor position was the whole problem, on an OEM replacement. Repositioned the ignitor and ignition was smooth as ever. After I checked the pressure, pressure switches, air intakes and exhaust, and secondary heat exchanger for blockages. The simplest fix of course was the last.
I had a closed combustion..,that when ignitor was replaced with universal this happened..,if intake pipe was disconnected it would not! The universal one did not cover the "hole" allowing air mixture to "swirrel". Taped off open area...,solved!