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Aquastat fails to trigger circulator

Antonios Member Posts: 1
I have a Buderus G215/3 Boiler. It was originally fired by oil, has recently (2 yrs) been converted to a Riello 40 N200S gas burner. The aquastat that was originally installed ~15 years ago is Honeywell L8148A 1124. This version as a fixed 15F differential. There is a singular circulating pump and two zone valves.

I know the problem is power to the circulator. I get zero volts when testing the circulator terminals with thermostats and burner on. I currently have the circulator directly wired to 120VAC so that it is running constantly, even when the thermostats are off. The heat seems to work normally with this mod. I assume it's not good to have the circulator running with the zone valves closed.

my question is, what is the best replacement part for the aquastat? I'm assuming there may be upgrade options here since it was originally installed 15 years ago. Perhaps an electronic model. I found electronic L7224U model but that specifies it is for oil heat. I'm looking for a control designed for gas.

I saw on another thread that the problem may be cracked solder on the circuit board. I have not taken it apart to investigate.


  • rick in Alaska
    rick in Alaska Member Posts: 1,420
    You can use the L224U on that boiler. It doesn't matter that it has a conversion burner on it.
    And yes, I can almost guarantee it has a cracked solder joint on the relay. They can be resoldered, but there is liability issues by doing it, so you are best off replacing it.