Backboiler - Heating Thermostat Broken?

Aubs

...THIS IS PROBABLY MORE AN ELECTRICAL QUESTION...

Hi all,

Hoping someone will be able to help me with this one, and that I am posting in the right forum!

I've got a gas fired back boiler that heats the hot water and the radiators.

The hot water is working fine, and when you switch it on, the valve opens, the pump turns on and the boiler fires up.

The problem is the heating! At the right time, with all the cold weather (and lots of snow still outside!), it's decided to pack up. With the system set to constant and the thermostat on minimum you'd expect nothing to happen. When I turn the thermostat to maximum, nothing happens either!

I'm fairly sure the pump that sends water through the hot water cylinder also pumps water around the heating system. The pump works when hot water is turned on, so I'm guessing it's not that.

The control panel is set to constant as it always is so I'm discounting that (I have reset it and taken the backup battery out to clear it).

This, in my opinion only leaves the thermostat, which I disconnected a few days ago (with the main switch off on the -if you can call it one- consumer unit) while removing some hideous panelling that was behind it, but once put back worked fine, until now. The unit consists of 4 wires one Live, one Neutral, one earth and one "main system" I think. The diagram indicates that the live and "main system" are joined via a switch, which I guess is the relay(?) that is switched by the thermostatic sensor(?) - Turning the dial makes it click on and off. The Live is always live, but the "main system" is never live. I would have thought when the relay is switched, it would basically join the two wires, making a complete circuit and therefore making the "main system" live also as it goes back to the control panel.

I'm guessing I could fool the system by connecting the thermostat from the tank to the heating, but that's not really the safest option!

I may be completely off track, but I don't want to get an electrician/heating engineer out because we will be replacing the back boiler with a more efficient (50% compared with 91%!!) condenser combi boiler in the next month - That's spending money to save money!

I hope someone can help, it's getting so cold in here!

Thanks,

Aubs

amd

You may have gravity fed hot water, in which case the pump wouldn't need to fire up just for hot water, only for heating. Listen for the pump coming on. It could have packed in.

If it's a fully pumped system, and you can definitely hear the pump working, it's possible you have a motorised valve which should open when the heating system comes on, diverting water round the heating circuit. If you can find it, there's a little lever on top which you can push across manually where it clicks into place in the open position. We've had problems with ours in the past. It's quite small, near the pump usually - a little box with a little lever sticking out on one side. They often stick in one position or the other. It's electrically operated so would need checked properly.

Hope you get it sorted.

Aubs

Hi amd, thanks for your post.

When I say the pump works for hot water, what I meant was to heat the water in the tank, water from the boiler is pumped through pipes (calorifier) that are within the tank. I indeed have a gravity fed system so you are right that the tank would empty on it's own (under gravity), without a pump.

The pump does work when the hot water switch is turned on.

Thanks again,

Aubs

Aubs

Thanks for reading the thread.

I've just fitted a new thermostat from ScrewFix (£6.10) and it's working beautifully!! - Not quite, it's an expensive way to heat the house but at least it's warming up now!

Aubs