Diagnosing boiler/timer/heating fault

[EN]

A couple of years ago our central heating timer developed an independent streak and started stopping and starting when it felt like. Very annoying when you come home from work on a cold day expecting that the heating had been on for an hour or so only to find it all off. So we gave up with it and switched the heating on and off at the mains switch which at least you can rely on although obviously not as convenient. However we actually got round to deciding to replace the timer and today a lovely new one was fitted. However, it is still no better. At the moment I can hear the boiler roaring away yet the timer is showing off, no lights or anything. It's due to come on at 4.30. I'll have to switch it off at its main power switch again in a moment.

Can anyone suggest what the problem could be? The electrician said that two extra wires came into the box, probably from the open fire thermostat which has a back boiler but just heats water not rads. I'm wondering if the problem is something to do with that, in which case I haven't a clue where that actually is or how it is replaced if faulty.

Not sure what info anyone might need to help diagnose this - it's oil central heating, the timer controls the boiler, ie everything, no separate controls for water and heating, there is no room thermostat, we just have to go round turning the radiators on and off to control things.

Help please!! Thank you

Liz

[Set Square]

It's hardly rocket science! After all, a timer is simply a switch which switches on automatically when programmed to do so. It has to be wired in series with the boiler controls. If the boiler comes on when the timer is off, it quite obviously hasn't been wired in correctly.

Sounds like you need a decent electrician who knows what he's doing.

But longer term, you really ought to put some decent controls on the whole thing - with motorised valves and room/cylinder thermostats, and TRVs on the radiators - so that heat is directed where you want it when you want it without wasting energy.

[EN]

However we actually got round to

Thanks for such a speedy response. I'm not sure it is the electrician who is at fault as the problem with this timer is exactly the same as with the original one, which did use to work fine and no-ne has messed with it. It just stopped behaving.

And although you're absolutely right about what we need to do long term, this is actually a rented house and I don't want to spend that sort of money on it.

Thanks again.

>

[Set Square]

In that case, you need to provide details of boiler make/model in the hope that someone here may be familiar with its potential quirks.

So shouldn't you then be getting the landlord to sort it - including the timer problem?

[Richard Faulkner]

In message , EN writes

Did the electrician fit the timer? Did he know about your previous problems? Have you got a C/H boiler separate from the fires' back boiler?

If so, I wouldnt be too impressed with the electrician. There will be a terminal in the C/H boiler from which two wires need to be taken to the timer. If the wires from the fire are connected, they wont control the heating.

Perhaps you should replace the timer again, with a programmable thermostat - only about £30-£40 or so.

[Ed Sirett]

Without knowing the setup it's hard to guess accurately.

This could be.

1) faulty frost thermostat. 2) zone valves faulty / stuck open. 3) boiler electrical/ electronic fault. 4) bad new timer. 5) faulty wiring (unlikely as it used to work OK).

[John]

There are a VERY limited number of options for an oil boiler to be a back boiler. Does the OP mean his heating is powered by an oil back boiler or is this something seperate entirely, possibly no longer in use? The fact that it "used" to work helps but does not preclude a wiring fault from long ago perhaps a broken or even a rodent damaged conductor with an intermittent break. However it would have helped enormously if we had been told what make/model of lovely new timer we had to reckon on. I'd take a shot in the dark that thee "back boiler" might be an old solid fuel one with a "stat" to run the pump before it got to boiling hence the two unknown wires. A boiler running without a call from the programmer and thermostats does indeed suggest a problem with a frost stat set too high or a motorised valve limit switch which is a good place to start looking but more details are needed