Control system mystery

[Peter Slawson]

I have an oil fired pumped CH system that has worked fine for years. Recently the system has stopped reacting to boost or advance requests on the Grasslin Towerchron QE2 controller but still is fine in normal timed mode. I say stopped but sometimes after a very variable time the system does react when on boost or advance albeit seemingly having a mind of its own!

I've tried what I think are the obvious, tap stuck pump with hammer, similar to various valves, waggle wires etc. Sometimes this starts the boiler but not usually- nothing is consistent!!!

This morning I removed the control box and sprayed with contact cleaner to no avail. Set on boost nothing happened then maybe 20 minutes into a one hour boost (indeed as I write) suddenly the system fires up.

Once this has happened it will go back to normal timed mode and be OK.

Any ideas anyone???

Cheers Pete Slawson

 

[Elkato531]

If the system works fine when in normal timed mode but the boost function doesn't work as it should, I would expect the programmer to be at fault. If you are competent with a multimeter you should be able to check the output from the programmer. Does it give a consistent live feed into the system when the boost button is pressed?

 

[Peter Slawson]

Thanks for that. I'm away at a funeral but will check tomorrow. Cheers Pete S

Am home now, heating is on on timer. Just a thought:

When I press boost on the warning light comes on. Is that sufficient or do I need to check for voltage at the boiler?

grateful for your thoughts

Pete S

 

[Peter Slawson]

Hi. There is no live feed at the boiler when boost is pressed nor advance nor constant. However I ran the hot tap for a while when on constant and at first no joy then 5 minutes later boiler fired up. Once this happened boiler would fire on boost and advance. Could it be a sensor in the hot water system hold off the boiler feed even when CH set to constant. BTW my QE2 is set to gravity as there is no link to the HW when set to pumped - but it has always been that way.

 

[Peter Slawson]

The QE2 is only two or three years old a replacement for an old mechanical one. Do they develop faults like this could be? Cheers P

 

[Peter Slawson]

The QE2 is only two or three years old a replacement for an old mechanical one. Do they develop faults like this could be? Cheers P

 

[Peter Slawson]

Thanks for your guidance I've checked the output and the controller is duff. Ordered a new one. Cheers Pete S.

Just in case anybody is following this it wasn't the controller but the CH control valve.
I bought a new head but that made no difference BUT EXERCISING THE VALVE ITSELF DID!!!
Got a nice new modern controller and a new valve head but just a screw driver in the valve itself solved the problem.

cheers P