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I was at my customers today to swap a venturi and igniter on a Prestige solo 110 I put in 9 years ago. This unit has been trouble free. I got a call about the floors being cold saturday and found a bad pump. As I was standing there I noticed it fired a little loud, so I looked at the venturi and it was super sooty but not broken, but I figured better get it done.
So today I went back and swapped the venturi, and igniter, I grabbed my test 320 to tune it up and the Co2 will not come up on high fire, on low fire its fine. Called TT, they say must be wrong venturi, its not. Then they said its gas pressure, its not. Then he had me test the outlet on the gas valve to see the negative it pulls when the fan comes on, its only pulling a -1.0 inwc.
He tells me fire side of the Hx is plugged. That answers my question as to why my numbers on high fire are whacky but then opens the door to a new one, why is it plugged and how to clean it?
Any thoughts? My thought was to use fernox ds40, pull off the top of the HX and hook up my transfer pump, put a bucket under condensate line minus the trap, and catch in the bucket what I pump into the top, do that for a half hour or so?