UKC

Was hoping a heating engineer/plumber could give some advice...

I've just come home to a cold house despite the heating being on, checked the thermostat, and it seems to think temp is about 12 degrees (I have it set to 18 normally)yet the boiler isn't firing (Pilot light is on) On further investigation the boiler still has some residual warmth, and the hot water tank is full of hot water.

If I turn the hot water on, the boiler fires up ok, but after a minute or so shuts down (presumably because the HW tank is full) I did notice that the HW system seems to be making more noise than normal (as if bubbles are in the system?) and when I run a hot tap it splutters to some degree (along with more noise).

I'm wondering if the problem is likely to be:

a) Room Thermostat not sending signal for more heat
b) Hot Water tank Stat not sending the signal for too much heat (thus making the boiler shut down due to overheating)
c) Some kind of leak in the system (checked round the house and can't see any signs)
d) Hot water pump not working (with the heating on I can't feel it vibrating)
e) some other problem?

Any ideas would be great

Thanks

In reply to balmybaldwin:

Diverter valve? So not hot water being allowed into the central heating.

In reply to ebygomm:

Hmm, certainly a possible culprit, but all three pipes around the valve are hot to the touch (but I guess this could just be heat conducting along the pipes?)

In reply to balmybaldwin:

Most likely to be the three-port valve. It's possible that the cylinder stat has packed up so is not sending a "satisfied" signal to the boiler/3-port valve, so hot water retains priority, but the 3-port is the more likely to fail.

In reply to balmybaldwin:

You should be able to try and manually override it to see if that gets heat to your radiators.

In reply to Cthulhu:

Thank you, my next question then:

Is the system safe to leave on for HW until I have time to get this sorted? (as it's warmed up I can live without heating for a few days)

Also, how do I test that it's the valve rather than the HW tank stat (so I don't buy one unnecessarily?)

In reply to balmybaldwin:

What make and model of boiler is it?

Should have someway of telling you what type of fault it is

In reply to balmybaldwin:

Yes. Or, there's a little lever on the 3-port valve that you can move across to the heating position. That'll keep the valve in the mid position, so water and heating have equal priority.

You can bridge the wires on the stat, which'll complete the circuit and send the satisfied signal.

In reply to Cthulhu:

Thank you, I've found that little lever, and I'm now getting some heat in the radiators

Will go shopping tomorrow for a new valve head (or motor if I can get one)

Many thanks

(The wonders of UKC!)

In reply to xplorer:

It is a Prima F potterton i think (at least those are the only markings on it. It has no way of communicating (lcd screen etc) and is pretty ancient. It's definitely working though.

In reply to balmybaldwin:

You can buy synchron motors in most boiler spares shops. However - you're getting heat because you manually put the valve in the mid position. You haven't (as far as I know!) determined WHY the valve is not actuating...

Check the stat before buying the motor...

In reply to Cthulhu:

Ah, I know the Stat is working by turning it down which gave the satisfied signal and shut off the pump and boiler

In reply to balmybaldwin:

Good stuff!