Munchkin 140 lock out problem

b young

I have a customer that has a Munchkin 140M with the anolog board not the 925 controller. I am having trouble with it locking out on 8 flashes or vent pressure switch open. As soon as I reset the power and start it, it will run for a week or two. When it runs i have no mean of trouble shooting it. The chimney is open and with in specs. The drain is working and it producing condensate. Any ideas? I called HTP yesterday and they did not return my call. Any help would be appreciated.

radiantyeti

140 lock out on pressure switch

I am assuming you mean the air pressure switch and not the flue switch. Having said that, things that I have found that affect the air pressure switch are condensate not draining properly, condensation acumilation inside the exhust flue, and fan speed not being made at start-up. the last is a little harder to find with the anolog board because just before they came out with the 925 boards the had a very small batch of blower fans that did not meet HTP norms in turn I have had two boilers one a 199 and the othe a 140 that from time to time out of the blue the fan blade would slip just a little bit on the shaft. This was obvious once I opened up the fan housing and you can see clearly where it had been slipping, the trouble was it only happend every now and then (which usually was at critiacal time, when the airport depended on their snowmelt)It was only out of frustration did I change out the blower then take apart the old one, and made the discovery. But Check your the iside of your heat exchange first, what does it look like? is there a white powder inside, or a damp thermal board in the back of the heat exchanger.

Guy_6

8 flash

That switch is merely to prove that the blower is working. IF the flue were blocked, even more pressure would be put onto the switch to close it.
At this point, that switch is several years old, and may be getting stiff and finicky. It would be worthwhile replacing the switch.