Originally Posted by leaholme
Hi and thanks for your replies.
I have a Grant burner, model "Minor one S" (and a Grant slimline boiler)
I have just been working on it and made some amazing (to me anyhow) discoveries:
1. IF the burner fires it runs with the plug going on to the solenoid on the pump disconnected!!! I presume this means the solenoid is stuck open?
2. In this situation (burner running but solenoid disconnected) one of the 3 terminals in the plug is continuously "live"
If the boiler fails to light the terminal never becomes "live" Does this mean there is an intermittent fault with the controller? The controller is a Danfoss BHO 12.1. The pump and solenoid are Suntec.
You might well have a problem with control box but its hard to know for sure, Danfoss are a reputable company their gear tends to be up to scratch so you could be confusing things, again hard to tell for sure.
Burners have different lives, some switched, some permanent, after a powered burner goes through ignition sequence and detects flame, its possible to disconnect a some leads / cables / wires while having burner still running.
One some jobs we used to manipulate a burner to come on while completely disconnecting burner from boiler, just to heat the room for a short burst as we worked, only giving this example to show how its possible for burners to run a number of different ways while burner firing.
It might not be your control box at all, then again it might, best have someone with experience have a look at it.