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I noticed our Triangle Tube Prestige Solo 110 boiler is on constantly. This is so even if there is no call for heat from any zone, and even if the DHW tank temperature is okay.
I can disconnect the thermostats, the aquastat sensor, even the ambient air temp sensor, and the boiler keeps heating. And none of the circulation pumps are active, so the only warm pipes are those adjacent to the boiler.
The main circuit board is identified as a PTRKIT509. Could it be defective?

Does the display say "Standby" or "No Demand," with no flame icon and the burner is still firing?