no hot water or heating

[blister72]

I've had the programmer set to hot water only since it's been warm and since yesterday morning, we've had no hot water. When I say no hot water, it's very lukewarm.

So I thought I wonder if the motorised valve is faulty?? I set the programmer to both heating & water and it had not made any difference. The radiators is just luke warm too.

The pump is working ok (I only replaced this less than 2 years ago) The motorised valve must be ok (Again I only replaced this less than 2 years ago).

The boiler does fire up and heats but only for 10 mins maximum before it shuts down again.

I replaced the thermocouple was replaced approx. 6 months ago, when the pilot light would not stay lit.

I then wondered if there is 'air' in the system or some leak? I've bled all the radiators and thats was all ok. Checked the header tank and plenty of water in there.

I am guessing that it could be either the boiler thermostat that is faulty or could it be a more serious problem, like the heat exhanger?? It's a Thorn Apollo 30/50B - an older boiler that needs replacing but it will have to wait until it's a must.

Anyway - any ideas what it could be before I call the heating engineer out??

Look forward to your replies

blister72

[Christian McArdle]

Could you explain these statements. Why must the pump and motorised valve be OK?

Christian.

[Bob Mannix]

Quite. Many years ago I thought I had identified an intermittent ignition fault in the capacitor in my car distributor. Bought a new capacitor, tried it, fault still there. Bugger. about a day later, having removed bits of wiring loom, dashboards etc., I tried another capacitor out of someone else's car. Problem went. Replacement I had bought was faulty. Grrr. I was unable to take it back to the shop as I had reduced it to a two-dimensional object with a 2lb lump hammer.

Bob Mannix

[blister72]

The motorised valve works ok as

1) I can see the lever move automatically when I select water & heating, from water. 2) both rads and water are lukewarm.

Motorised valve is fairly new - it was replaced not so long ago because I could not have hot water without the heating being on!

The pump is working ok as

1) When I select different speeds, I can hear and feel the pump running at different speeds. I can also feel the water gushing up the pipes, particulary when I change from low speed to fast.

Perhaps I could be wrong, I accept that new (or fairly new parts) can go faulty at any time. Is there a better way of checking??

blister72

Christian McArdle wrote:

[Christian McArdle]

I was just checking that you weren't eliminating the components on the basis of installed time...

Christian.

[Richard Polhill]

"blister72" wrote in news:1122044859.947705.142380 @g49g2000cwa.googlegroups.com:

Have you bled the air from the system bleed valve too? usually it'll be near the pump, valve, etc (in the airing cupboard) and will be a length of copper pipe sticking up out of the system with a bleed valve on top. It'll be higher than the pump, valve and coil.

Rich

[blister72]

Yep, I did that too - there was no air in the heating system whatsoever.

blister72

Richard Polhill wrote:

[blister72]

I've done a bit more investigating this morning.....

The boiler fires up when I switch the heating and water on. The cold entry pipe into the boiler is cold, as it should be. The hot water pipe from the boiler is lukewarm. The boiler itself is hot but not very hot as it usually is.

After about 5 minutes, the boiler then shuts down.

I am now wondering if there is an airlock in the boiler itself????

The cold entry pipe has a drain c*ck but there isn't one on the hot pipe. I wouldn't be able to get rid of the airlock by draining water out of the cold drain c*ck.

I wonder if it will be worth draining the whole system completely??

Any other ideas?????

Cheers

blister72

blister72 wrote:

[Set Square]

Is it a vented system with a small fill & expansion tank in the attic? (Not to be confused with the large header tank for the domestic hot water).

If so, is there any water in it? It's not uncommon for the water to leak and/or evaporate and for the ball valve to stick shut. This can deprive the primary circuit of water - and may possibly explain your symptoms.

[blister72]

It's a vented system and there is plenty of water in the header tank. ball valve is ok.

[Set Square]

You're definitely looking at the *small* tank, and not the big one, aren't you?

In that case, is there a tap or gate valve in the pipe which feeds the primary circuit from the bottom of this small tank? If so, could it inadvertently have got turned off? It needs to be fully open.

[blister72]

Yes, I looked at the **small** tank - it is def. working ok, hasn't been turned off. ballcock valve is working fine - releases water when I push the ballcock valve down.

I have a **big** tank up in the loft which is the cold water store.

I will be draining the system today - nothing to lose by doing this. I can then re-fill it and then balance all the rads again. If that doesn't work, it's def. a problem with the boiler.

Set Square wrote: