Thanks for that desktop. Yes a circulation issue does seem to be the consensus and will investigate with my plumber. The only thing is, I thought the boiler temperature would need to be much higher say 80 or so for it to short cycle. Can I be sure the boiler is working ok?
Not Getting Hot Enough!
- Thread starter Nelly B
- Start date
Is the system sealed or open vent?
If the flow is only reaching 64degC on max then it's not an overheat causing it to cycle, if that was the case then it wouldn't normally run for ages, usually an overheat occurs relatively quickly on a boiler that can't get rid of it's heat. With this one it seems the boiler is reaching set temp and that's when it short cycles.
How is the new pump set up?
If the flow is only reaching 64degC on max then it's not an overheat causing it to cycle, if that was the case then it wouldn't normally run for ages, usually an overheat occurs relatively quickly on a boiler that can't get rid of it's heat. With this one it seems the boiler is reaching set temp and that's when it short cycles.
How is the new pump set up?
Tank feed / open vent id be checking pipework with a magnet around open vent/ cold feed area.
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@desktop987456 has a point, I tend to forget not everyone uses electronic TRV heads which give a code if jammed etc. My wall thermostat and two out of 10 TRV heads produce graphs
so I can see how they have preformed.
If one radiator valves are stuck wide open, the returning hot water can cause the boiler to modulate, same with a by-pass valve. We tend to look for blockages, rather than the reverse. Only takes someone to have opened a lock shield valve as they were cold, to upset the whole system.
so I can see how they have preformed.If one radiator valves are stuck wide open, the returning hot water can cause the boiler to modulate, same with a by-pass valve. We tend to look for blockages, rather than the reverse. Only takes someone to have opened a lock shield valve as they were cold, to upset the whole system.
Thank you for all your help guys.
Exedon: Bearing in mind I have a chalet bungalow, the feed and return pipes from the boiler go into the loft first, which is the same height as the upstairs as it is on top of a lounge/kitchen extension. Two pipes go off to the header tank on the far wall of the loft (feed and vent) then along and down into the airing cupboard. All of the feed pipe I could get to in the loft is magnetic (not the pipes to the tank). Also magnetic near the pump in the airing cupboard. Not magnetic on the pipe to the hot water tank from the valve or anywhere on the return to the boiler that I could get to. I assume this indicates sludge build up and maybe my problem? There is a 'Magnaclean' on the return pipe in the airing cupboard but was only fitted 7 years ago with the new bolier. House had new plumbing completely around 1994 when the bungalow was converted/extended.
Ericmark: All the radiators have TRVs but I don't generally use them so are left open. Of the 12 radiators, 7 TRVs are at the feed end of the radiator and 5 at the lockshield end. My understanding is this is OK as the TRVs are bidirectional but can make balancing more tricky?. I have balanced the radiators using the lockshield valves, i.e. closing them all but one and then opening a little as required starting with nearest the boiler. The radiators seem to warm up together but some a bit better than others.
Exedon: Bearing in mind I have a chalet bungalow, the feed and return pipes from the boiler go into the loft first, which is the same height as the upstairs as it is on top of a lounge/kitchen extension. Two pipes go off to the header tank on the far wall of the loft (feed and vent) then along and down into the airing cupboard. All of the feed pipe I could get to in the loft is magnetic (not the pipes to the tank). Also magnetic near the pump in the airing cupboard. Not magnetic on the pipe to the hot water tank from the valve or anywhere on the return to the boiler that I could get to. I assume this indicates sludge build up and maybe my problem? There is a 'Magnaclean' on the return pipe in the airing cupboard but was only fitted 7 years ago with the new bolier. House had new plumbing completely around 1994 when the bungalow was converted/extended.
Ericmark: All the radiators have TRVs but I don't generally use them so are left open. Of the 12 radiators, 7 TRVs are at the feed end of the radiator and 5 at the lockshield end. My understanding is this is OK as the TRVs are bidirectional but can make balancing more tricky?. I have balanced the radiators using the lockshield valves, i.e. closing them all but one and then opening a little as required starting with nearest the boiler. The radiators seem to warm up together but some a bit better than others.
I'll have a bet that the pipework is restricted with crap.
Pic of one we sorted.
Pic of one we sorted.
As there seems to be insufficient flow to carry away the heat being produced by the boiler have you tried setting the pump to the maximum speed?
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So did I, worked A1 in mother's house but did not work here. I did the fine-tuning by reading the TRV display,
the current should not exceed target, it can easily do this while warming up, overshooting, and harder to get spot on if the TRV is on the return, but it did work, the anti-hysteresis software seemed OTT, so would set to 22°C at 7 am and 20°C at 8 am to get around the software, took some time to get right, but it did work spot on, only when sun shining through windows would it over shoot. I was rather proud how well I had set it.Then I moved here, and the TRV head does not work with an on/off oil boiler with micro bore, as well as they did with a gas modulating boiler, with 15 mm pipework. Main problem is the hall cools too slowly, so having the main thermostat in the hall did not work, and the Nest Gen 3 thermostat needs a 12 volt power supply from the hub, so not really an option to reposition it.
So fitted a Wiser hub in parallel, and Wiser wall thermostat in the living room, and TRV in the wife's bedroom. Living room now at the temperature I want, but a bit slow re-heating, but think that's simply down to the size of the radiators.
Of the four homes I have lived in, every one was different, home one hot air worked very well but expensive to run (1970s) Next water open plan, up-stairs got too hot, TRV heads upstairs only cured that, open-plan house, added extra radiator downstairs, but thermostat in arch between both rooms, and it worked well. (1980-2018) So mothers was a problem, cured by fitting a TRV on hall radiator with the hall thermostat. And this home sorted by fitting multi-thermostats. Seems no one system suits all.
Anywhere 'magnetic', i.e. your Magnet is attracted, will indicate Sludge and Crud build up, restricting the flow through the pipework, which is rather likely to be a big part, if not all, of your issue.
Depending on how much Pipework you think is affected, a Powerflush would probably be a good start to give the entire system a thorough clean, and see if there's any improvement, before condemning the pipework and replacing the most affected areas.
Depending on how much Pipework you think is affected, a Powerflush would probably be a good start to give the entire system a thorough clean, and see if there's any improvement, before condemning the pipework and replacing the most affected areas.
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