No heating since boiler move but hot water fine

[DavidR52]

Hi,

We had our approximately 7 year old logic combi 30 boiler moved earlier this week. It was only along the wall about 6 foot so no major pipe changes and this was done by a registered gas safe engineer.

The following night we tried to turn our central heating on. The first two in the chain got semi warm but stayed mostly cold at the bottom and the return pipes remained cold. No other radiators heated up at all. We bled the radiators, this did nothing. We tried balancing them. Nothing.

The engineer came back and suggested its a blockage as the boiler fires up for about 50 seconds then powers off. After a few minutes it fires up again then this repeats itself. He said to empty the radiators, run the system through using the filling loop then refill. This did nothing.

We have tried closing the valves to each radiator. This does nothing.

Today we put some sludge removal in the system. This also did nothing except make the boiler make some horrible gurgling noises. We bled the radiators (not that much air came out at all) and tried again. Again, it still keeps just firing up for 50 seconds or so then resetting.

We think it's unlikely that it's a blockage because although the boiler itself is around 7 years old, the radiators and 90% of the pipework are only 2 years old. We haven't had them on since March (ish) but they worked perfectly then.

The pressure is absolutely fine and doesn't budge. The pump sounds like its working and is hot when the CH is being called for.

Interestingly, whenever we've drained the system down relatively close to trying them, the return pipe feels warm. This suggests there's no blockage right?

No error codes come up on the boiler either.

Absolutely no idea what to try next - is it a new boiler job?

Sorry for the long post but its been a very cold, frustrating few days!
Thanks in advance.

 

[terryplumb]

Sounds like a lack of circulation. Check the circulator .

 

[ianmcd]

get the installer that moved the boiler back

 

[DavidR52]

get the installer that moved the boiler back

We did - he's the one who said it's a blockage. We messaged him today and he said to try the sludge remover and if that fails then it's most likely a boiler issue. To be fair, we did only put the sludge remover in an hour ago so maybe I'm just being impatient. Stupid question but can we actually hold him liable to this? He left a certificate saying it was all visually fine but doesn't seem keen on coming and fixing it.

 

[DavidR52]

Sounds like a lack of circulation. Check the circulator .

How would we go about checking it? It sounds like it's working but I guess it could just not be running properly.

 

[DavidR52]

How would we go about checking it? It sounds like it's working but I guess it could just not be running properly.

Also the engineer felt it when he came the other day and said 'it feels like it's working' whatever that means.

 

[denso13]

'it feels like it's working'

You can't tell by simply feeling it. I'd be getting the fitter back to carry out some basic checks, first one being the pump.

 

[ianmcd]

We did - he's the one who said it's a blockage. We messaged him today and he said to try the sludge remover and if that fails then it's most likely a boiler issue. To be fair, we did only put the sludge remover in an hour ago so maybe I'm just being impatient. Stupid question but can we actually hold him liable to this? He left a certificate saying it was all visually fine but doesn't seem keen on coming and fixing it.

sludge remover as you call it will not clear a blockage, all chemical cleansers need circulation to work

 

[DavidR52]

sludge remover as you call it will not clear a blockage, all chemical cleansers need circulation to work

That's what the engineer called it we emptied the system, put the cleaner in then topped it up again, will this not have circulated it enough?

 

[terryplumb]

If there is no circulation ,the chemical will do nowt.

 

[Alec_t]

Perhaps the pump impeller has seized, even if the pump sounds as though it's working. Have you tried running the pump at its maximum speed?

 

[oldbuffer]

1. It certainly sounds like a circulation issue. The boiler fires, heats the water, tries to send it round the circuit. It doesn't lose enough temperature (because it isn't going anywhere), the boiler detects there is too big a difference between flow and return temperatures, so shuts down. Water cools, differential falls within limits, boiler fires and off it all goes again.
2. Because its a combi, all the usual suspects (pump, zone valves) are within the boiler. So it must be one of two things:
2a. A genuine blockage within the heating circuit.
2b. A problem within the boiler.
3. Things to check on the heating circuit:
3a. That the flow and return valves, under the boiler, are both fully open.
3b. That any magnetic filter, usually on the return to the boiler, has both its valves open.
3c. Beyond that you'd be looking for a pipework blockage. You could:
3ci. Try flushing through as your plumber suggested. The filling loop is most likely attached to the return pipe, so you will be flushing in the reverse direction to normal flow. Ideally you would disconnect the flow pipe from the boiler and direct it to a drain, to avoid flushing through the boiler. However, not necessarily a DIY activity, so you would need to drain through a radiator drain point.
3cii. While flushing, do the whole system, then shut down all but one radiator, flush that one on its own, then move on to the next in turn. If doing that close both valves on each radiator but the one you are doing, making a note of the number of 1/8ths of a turn required to close the lock shield valve. When finished make sure you open all the lock shields to their original settings.
4. Things to check on the boiler (by a gas safe engineer only).
4a. That the diverter valve is working properly.
4b. That the pump is working.

 

[DavidR52]

Perhaps the pump impeller has seized, even if the pump sounds as though it's working. Have you tried running the pump at its maximum speed?

Not sure how to do this but after running the CH for an hour or so the pump is too hot to much, I assume this is a cause for concern and it could be/is overheating? Thanks

 

[DavidR52]

1. It certainly sounds like a circulation issue. The boiler fires, heats the water, tries to send it round the circuit. It doesn't lose enough temperature (because it isn't going anywhere), the boiler detects there is too big a difference between flow and return temperatures, so shuts down. Water cools, differential falls within limits, boiler fires and off it all goes again.
2. Because its a combi, all the usual suspects (pump, zone valves) are within the boiler. So it must be one of two things:
2a. A genuine blockage within the heating circuit.
2b. A problem within the boiler.
3. Things to check on the heating circuit:
3a. That the flow and return valves, under the boiler, are both fully open.
3b. That any magnetic filter, usually on the return to the boiler, has both its valves open.
3c. Beyond that you'd be looking for a pipework blockage. You could:
3ci. Try flushing through as your plumber suggested. The filling loop is most likely attached to the return pipe, so you will be flushing in the reverse direction to normal flow. Ideally you would disconnect the flow pipe from the boiler and direct it to a drain, to avoid flushing through the boiler. However, not necessarily a DIY activity, so you would need to drain through a radiator drain point.
3cii. While flushing, do the whole system, then shut down all but one radiator, flush that one on its own, then move on to the next in turn. If doing that close both valves on each radiator but the one you are doing, making a note of the number of 1/8ths of a turn required to close the lock shield valve. When finished make sure you open all the lock shields to their original settings.
4. Things to check on the boiler (by a gas safe engineer only).
4a. That the diverter valve is working properly.
4b. That the pump is working.

Thanks for such an in depth reply. All valves are open. We've tried draining each radiator individually as suggested and that didn't work. The pump is too hot to touch after running for an hour or so, so an uneducated guess would be that the pump (or something in it) is overheating. Whether as a result of a faulty pump or a block in the boiler system I'm not sure. I've put forward to the engineer that it could either be the diverter or the pump - hopefully he comes back but he seems more unwilling to come and fix it each time I message him.

 

[terryplumb]

Is the pump a grunfoss ? Show us a pic .