Central heating not working after summer lay off

[metaman]

Now that I’ve turned the central heating back on after the summer, none of the radiators are getting even warm, apart from one in the bathroom.

I should mention that we are getting converted from conventional to combi in three weeks, so if it’s not worth bothering with, then I shan’t worry about it. It just would be nice to have some heating for the next few weeks.

We are getting hot water fine, and the boiler is firing up (although not for any length of time, maybe five minutes before it turns off - and it is knocking/kettling).


The pump is running, although it doesn’t sound particularly healthy. Pipes on either side are hot, and the pump is hot. Took the bleed screw out and no air came out, and the pump appears to be spinning.

Feed/Expansion tank has water in it.

Three way motorised valve is working (i think). When heating is on, the lever has no resistance to it. When hot water is on, there is resistance on the lever to move it to Man Open. The A and B ports get hot.

All radiators have been bled and only have water coming out of them.

Things i’ve tried:
Had pump running at all three speeds, with no difference.

Drained and refilled the system completely, with no difference.

Left the pump running and opened the drain cock on the downstairs radiator. (A plumber friend tried this when we had an issue with downstairs rads not getting hot. A lot of air came out of the system and it fixed in then). This time, when several litres of cold water had come out, the radiator started heating up, but none of the others did. On closing the drain cock, the radiator gradually went cold again.

I’ve been round the rads bleeding them every couple of hours, but only water ever comes out.

If anyone has any suggestions, they would be most welcome. I just don’t really want to spend any money getting it working if it’s to be overhauled in a few weeks time anyway.

Thanks.

 

[Armo74]

Sounds like the synchron motors gone in the 3 port valve.
A temporary fix would be to put the valve in the mid-position by moving the lever put the hot water on,turn the cylinder stat up a bit,and turn the boiler stat down a bit so the cylinder stat never gets satisfied.
This should give you heating but only whilst you get a permanent fix sorted.
Also sounds like you have circulation issues which are probably down to system sludge.

 

[metaman]

Thanks for the suggestion. I'll give it a try. I might stick some cleaner chemical in the system as well, just to try and get it moving.

 

[metaman]

Update.

I've did as suggested a couple of days ago, but now we don't have heating or hot water.

Our plumber friend came for a look yesterday, and ended up having to admit defeat.

Again, considering that we are due for a combi being fitted in a few weeks, there wasn't much that was worth doing as we don't want to spend a load of money getting it working for just a few weeks.

Anyway, he disconnected the heating pipework into the cylinder and quite a bit of air was coming out, but no warm/hot water ever came out the other side. He checked the three way valve and thought it may be stunting flow into the cylinder, so took the head off the valve - strangely it seemed to be stuck in the hot water position, but the pipework going to the rads was still getting hot anyway.

He drained the system to have a look at the valve. The nuts on the three way valve wouldn't budge at all, so he took the top off the valve. The ball/lever was a bit gungy but was moving freely. He swapped the ball part for a new one and left it without the motor on the top, in the hot water position. Refilled the system but still no hot water coming out of the cylinder.

He then noticed that water was dripping from the bottom of the cylinder. Looks as if it is leaking from where the large nut/pipe comes out of the cylinder. After much debate, decided we would live without hot water for a while (we have electric shower), and drained the cylinder of water, and left the valve in the central heating position.

However, we still aren't getting hot radiators, except in the bathroom. All rads are bleeding water.

Now, question is, is it really worth me trying some sludge remover or is this more likely to be an air lock somewhere? I seriously can't get my head around how the rads are full of water, but no 'hot' water is getting to them, or why the bathroom rad is getting hot but none of the others. The system was cleaned out last autumn with x800 and was working wonderfully, but this year, absolutely nothing.

I'm also a bit concerned this will cause problems for the combi switchover if the system isn't working properly in the first place.

 

[twgas]

I think i would be looking at the pump, it may be blocked, if so it might be worth sticking a new one in, adding some cleaner and running it till near the swap over, then flushing out all the muck. This might seem hassle for an impending replacement but a dirty system will drastically reduce the reliability and life of a combi.

 

[metaman]

I'm thinking the same to be honest.

The engineers are going to clean out the system prior to installing the new boiler.

I might just live with it and let them deal with it during the installation.