Rayburn 480K heating on even with timer set to off

[GrahamKSuff]

Hi - looking for some pointers. We have a Rayburn 480K with a Honeywell timer/control unit. Today the heating has been on non-stop - room stay is not calling for heat, and even with control unit setting to off the Rayburn is still firing up.

I’m assuming a wiring issue - but grateful for any ideas.

thanks

 

[oilhead]

Sounds like a stuck open motorised valve. What type of system do you have? Y plan (1 x 3 port valve) or S plan? (2 x 2 port valves).
With all power isolated, check the manual operating lever on the valve(s) . If you find is floppy, that is the culprit. Quite often it is only a failed synchron motor which can easily be replaced. Replacement for the common types like Honeywell are available from merchants such as Screwfix.
Do not be tempted with the cheap alternatives. Look for the genuine "Synchron" trade name.

 

[GrahamKSuff]

Thanks for the quick reply. My slightly panicked initial post probably not detailed enough. The Rayburn is behaving as it would if the stat was turned right up - ie. Firing up, running, shutting down (assume when temp threshold hit) and pump over run as normal. Then after a short period (minutes) firing up again. Not sure if that would be the symptom with a stuck open valve?

I wondered if the relay/switch on the interior circuit board for heating had got stuck closed (looking at wiring diagram, that looks like it would effectively ignore the clock and room stat setting).

Left it powered off over night and gave the front panel a tap this morning and we seem to be running as normal again.

if it re-occurs I’ll check out the valve situation ahead of any other checks. Thanks again!

 

[oilhead]

Rayburns are wired a little differently to the diagrams in control manufacturers diagrams. If it was operating "normally" except for the programmer switched off, then it may be a programmer problem. Certainly something that by passes the normal operation of the programmer. I presume you have the built in unit. If it does need replacing, make sure you get the Rayburn part. The standard Honeywell unit does not like the high temperatures it has to withstand.

 

[GrahamKSuff]

Hello - back again with the same fault. The Rayburn has a Honeywell controller - replaced a previous Honeywell unit four years ago. I’ve just put a brand new one in but fault remains - controller set to ‘off’, no call for heat from room stat, but boiler is on and running the CH. as before it behaves like we have the ch controller on and room stat turn up as high as it will go. Boiler cuts in and out as normal when running to heat the house up. Effectively I’m unable to turn off the central heating.

it’s a 2x2 port system, but as previous I don’t think the valve is the culprit as it can’t call for heat or override the controller?

checking for wiring issues on the control board to see if anything could effectively bypass the controller - I’m at a loss!

 

[GrahamKSuff]

Bit of a novice about these systems - going back to the motorised valve - was wondering if the CH valve got stuck, could it be that the Rayburn is effectively trying to heat the HW but instead CH is getting the heat. Symptom of that presumably would be that boiler would keep firing up as HW tank below temp, but rads boiling. That would explain all of the symptom except the fact that the boiler is still on even when programmer is off…?