Water constantly heating up whenever central heating is on

[jwelch]

Hi,

i have a very old boiler system that is currently playing up. Initially the central heating would periodically not come on even though it was set to on the main control. Leaving for an hr or so then retrying it would normally bring it on. Typically when the engineer came out to it, it worked fine every time he tried it. When I explained the issue the only thing he could think it would be is a valve sometimes not switching across from hot water to central heating (the hot would always work if the central heating didn't).

More recently the hot water will heat up whenever the heating is switched on, even though the hot water is set to off. I have been wondering if it is the valve that is faulty and is now stuck open on both hot water and heating. I've tried switching between hot water and heating to see if I can reset something but no luck. Tried switching between, timed/once only and off for the hot water and is now set to off but still the water is heating up whenever the heating is on.

My main question is, could this be dangerous if the water is heating all the time? (for up to 6 hours non stop on an evening) I can keep running the hot water off so it's not too hot but this is a pain and a real waste. I will call the engineer out to it again but want to make sure I am ok to leave the hot water on in the mean time.

All help appreciated
James

 

[joni os]

Your valve is stuck in mid position. If output on boiler is controlled by knob 1 - 5 set knob at 2.
If you have a roomstat, set at 20 C and open rad valves to maximum. Your boiler should now cycle on and off without unduly overheating DHW cylinder.
An alternative is to remove head of 3 port valve and move spindle by hand. This involves live electrics and unless confident the 1st method is best until plumber can fix valve.

 

[jwelch]

Thank you loads for the reply. The only knob I can see on the boiler is the boiler temp knob (1-3) this is currently set at 1.5

I do have the thermostat at 20 with the rad valves at maximum. The boiler has always 'thumped' on and off if this is what you mean?

 

[joni os]

Being cold is also dangerous if there are young children or elderly in the home. If turning knob down to 1 gives sufficient heat do so, but don't be cold.