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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7914
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I'm working on a lochinvar knight. The low voltage circuit

Customer Question

I'm working on a lochinvar knight. The low voltage circuit board shorted out between the low water cut off terminal and the gas pressure switch. This caused a gas pressure switch lockout. I installed a new low voltage circuit board with no change. I contacted lochinvar tech support and went through diagnostics with them. Once we confirmed that I was recieving 24v from the transformer to the main control module, they advised me that the control module needed to be replaced. I replaced the control module and the boiler is still locked out with a gas pressure switch problem. The gas pressure is fine but I'm thinking the problem may lie in the switch itself. I've reset the switch several times and am getting to my wits end. Any thoughts would be greatly appreciated. Thanks.
Submitted: 1 year ago.
Category: HVAC
Expert:  Rick replied 1 year ago.
Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue.
What is the model of the boiler?
Customer: replied 1 year ago.
210 floor mounted. Lochinvar knight. Natural.
Expert:  Rick replied 1 year ago.
Have you tried jumping out the gas pressure switch (terminals 9 & 10 in the terminal board)?
Customer: replied 1 year ago.
Expert:  Rick replied 1 year ago.
If you jumped 9 & 10 and you're still getting a gas pressure switch error with a new board then I don't have an answer for you from here. Maybe one of my colleagues has an idea what's going on here. I'm going to open this backup to my colleagues so one of them can help. Please don't respond (even to acknowledge this post)until you get a response from us. If you respond first it will only delay your answer.
Expert:  Phil replied 1 year ago.
Hello, page 32 see the gas pressure switches mentioned here but do not see them shown on any of the diagrams Lockinvar provides (typical of my experience with the company) If you can take a well focused, well lit photo of the wiring diagram, from straight on, the one glued to the inside of the boiler service panel, I will see what is actually installed in that unit and mark it up with trouble shooting notes and arrows etc. Use the paper clip icon at the top right to attach the photo. We can go from there.
Customer: replied 1 year ago.
I figured it out. The problem was a manufacturing defect in the low voltage circuit board.
Expert:  Phil replied 1 year ago.
Good work! I have seen this before with Lochinvar equipment. A while back the pins on the gang connector that plugged into the back of the display module were too short to make a stable connection, the 20 pin connector kept falling out. If you care to rate my efforts so far I will appreciate it, it will not affect your charges but is how I earn a living. Thanks!