BoilerMate or Boiler at fault?

I have an old Boilermate II (approx 20 years old) and after draining the CH system down to fit a gate valve and fixing a resulting cold feed blockage, I noticed that the green light is on constantly and the boiler pump runs constantly. In addition, the boiler (Valiant EcoTec 438) fires up every 2 min and runs for 7 s reaching its max temperature of 80 degrees C before shutting down again. My feeling is that this is a Boilermate fault rather than an inability of the boiler to supply heat or a blockage in the pump but I would be grateful for any advice on this before attempting/commissioning any repairs.

GM
Manchester

Is the BM II hot?
If you had a blocked cold feed, on the BM II I presume.
Then you could have a blockage / sludge at the boiler pump to.
If the unit is not getting hot enough, then it will keep asking the boiler to fire.
But if the unit is hot then you could have PCB trouble hence the boiler pump running.
Mike
MGC/H2O
Norfolk

Thanks Mike.

The BoilerMate heats up very quickly (10-20 min) once I turn on the mains power supply to the CH system to provide hot water. I am only doing doing this twice a day to save wear on the pump and the boiler pending finding a fix for the problem. As we don't need room heat at the moment the thermostat is effictively switched off (antifrost mode).

I thought of draining the system down again via the boilermate to check for sludge in the bottom. Do you think this is a good idea? I got lots of black stuff out of the FE tank when I cleared it and the feed pipe after the radiator drain down. I take your point about the pump PCB but What could be causing the boiler to fire continuously given that the BoilerMate heats up appropriately?

GM

Well if using the BM II heating pump heats the unit up.
Which in some ways would move water.
I would be looking at the Boiler pump.
Has it a supply?
Does it turn freely?
Does it goes round with a supply?
It would not to drain the unit down.
You could have some sort of sludge problem.
It is a BM II ?
Mike
MGC/H2O
Norfolk

Hi Mike,

Yes it is a Boilermate II and, just to clarify, I am not turning on the heating pump when I switch on the mains because the room thermostat is set very low so doesn't demand any room heat. What comes on, and stays on continuously, is the boiler pump (the lower of the two on the outside of the boilermate II).

You seem to be saying that it wouldn't hurt to drain the boilermate down so I will do this and see what comes out.

Any other tips would be greatly appreciated.

GM

In that case PCB then.
Or BM II stat.
Mike

Thanks again Mike.
GM

sounds like a valve is still shut causing no flow around the system or you have not filled the system up properly and there is an air block if the boiler is getting up to temp quickly it means there is no or reduced flow around the system, go back over what you have done, bleed the rads, bleed the boilermate from any bleed points make sure water is coming out of them, check pumps have been put back on the right way , check pumps are spinning, check gate valves have been opened fully, these can sometimes have a lot of backlash so you think they have opened and they are still shut should turn 4-5 times. hope this helps and sorry if you have tried all this.

I don't think there is any doubt that the boiler pump is working: a) I can hear it; b) it brings heat into the heat store very rapidly when I turn on the power and the pump and boiler kick in together. The problem is it doesn't switch off and the green light is on continuously. The one thing I don't understand fully is why the boiler fires up every two minutes. This is possibly due to the BoilerMate demanding heat when the heat store is up to temperature or possibly higher: e.g. if the thermostat is not functioning and the thermal store could reach the boiler's limit of 80 degrees at which stage it could be firing every couple of minutes just to maintain this temperature?

Hi - did you ever resolve this issue as it sounds very similar to my issue - sorry can't add link for a few days, but in the Boilermate II Iforum (Odd behavior after SAC replacement)

The morning store demands are fine, boilermate shuts up when all lights are lit.  But later it runs all the time, occasionally triggering the Potterton, otherwise just wasting electricity and heat!

Seems like de-sludging may be a good idea - our local engineer recommended this as he has seen some very sludge up units on my estate.

Cheers

Eserim