Polaris PG50-130-2NV. intermittent code1 "press switch closed"

cheerios2

Hey guys!
Got a real head scratcher for myself here.

Have a Polaris pg50-130-2NV that's responsible for domestic hot water and radiant heat.

Came into this after a few family members had a go at it, but from what I understand they woak up and found the house cold. I gave the air pressure switch some light CPR and the thing fired back and was fine until it cycled off again.
I'm busy the next day so an HVAC guy gets called up. Puts yhe tester on the air lines and says bad switch, Replaces the switch, and its working again. He mentions "Green water in the condensate drain" but I can't tell you more because I was not there to talk to him.

The next morning after the HVAC guy worked on it, the ignition control module is flashing code 1, press switch closed.
I remove and clean the pressure lines, clean the little negative pressure venturi in the intake, shop vac out the intake and exhaust to make sure they are not clogged and button it up.

Working great, I leave. Morning its not working again. The blowers running constantly, error code 1 press switch closed. Over the phone i take a stab in the dark and I just suggest rapping on the side of the access panel with a wrench.

Amazingly, it Fires right up and works all day!

Next morning its still working but about mid morning ..... Sure enough.... Blower running error code 1.
Another light tap on an access panel and it fires right up.

Seems every 15 or so hours it requires a magic tap (although I'm going to escalate it to a kick if I can't get this solved.)

The HVAC guy can't come out for a few more days, and ideas?

Thanks in advance!

Ironman

Did he put the correct pressure switch back on it? Check the part number with the manufacturer. They are not all the same.

The switch being closed before the inducer starts is telling the board that there's already a draft and therefore a fire when there shouldn't be.

The only way to confirm the proper function of the pressure switch is with a manometer attached and checking it as the heater goes through each step in its sequence of operation. In other words, was the switch closed because it's bad or was there actually a draft causing it to close?

On another note:
Though this type of system (radiant on an open domestic loop) was a popular install 15+ years ago, Americans have begun to wake up to what the Europeans were tellings us all along: namely, that this is a breeding machine for Legionella bacteria and it should be replaced with the radiant on its own closed loop! It's been outlawed in a lot of places already and should be in all.

I'd highly recommend that this be replaced with the proper appliance: an ASME rated boiler with an "H" stamp.