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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7579
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I AM A LICENCED HEATING CONTRACTOR IN CONN AND NY I HAVE A

Customer Question

I AM A LICENCED HEATING CONTRACTOR IN CONN AND NY
I HAVE A DAUNTING PROBLEN WITH A PAIR OF STAGED BUDERUS GB 142
I SEEM TO HAVE NO CONTROL OF DOMESTIC HOT WATER PRODUCTION
EVEN ON THE LOWEST SETTING NEARLY OFF THE WATER TEMP IS OVER 140
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.
Welcome to 2 hours help.

Up to 48 hours trouble shooting and coaching on repairs $38 additional if you approve it at that time.

The manuals are here for future use, I am posting this so we can find them easier later.
http://www.supplyhouse.com/Buderus-GB142-30-GB142-83000-BTU-Output-Wall-Hung-Modulating-Condensing-Gas-Boiler-Nat-Gas-or-LP
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http://s3.supplyhouse.com/product_files/Buderus%20-%20GB142-30%20-%20Install%20Instructions.pdf
See page 17 and tell me please if you have a pump installed, item #3, or not and where its power comes from on the printed circuit card.
We can go from there.
Customer: replied 1 year ago.
THIS BOILER IS EXISTING I DID NOT INSTALL IT
HAS OPERATED FINE FOR MONTHS SINCE WE BECAME INVOLVED
I WAS THINKING THERMISTORS 2 SEEM TO HAVE FAILED
Expert:  Phil replied 1 year ago.
Thanks,
In that case, have you tried replacing the thermistors, those are not overly expensive.
Or you can test them for no resistance, or infinite resistance... in either case you know its bad.
If neither is the case you can test them for repeatable ohm/temperature tracking.
We can also look them in the service manual for ohm readings on the temperature curve chart.
If the thermistors check out OK, then the problem is with the printed circuit board or a relay built into the board with burnt contacts holding the pump on.
Let we know about all that, we can go from there in the morning.
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