Very old boiler/thermostat advice

moreofthegoodstuff

We have an old Potterton Netaheat boiler, it's very old but hanging in there. We also have an old Honeywell thermostat, the same one shown on this old post. https://forums.moneysavingexpert.com/discussion/2449587

We have to have the heating on for half an hour each day to warm the water as the immersion heater died a couple of years ago, this hasn't really been an issue. What is confusing me is that when the heating is on, upstairs is very hot and all the radiators are on full, but downstairs either goes on for a little bit and turns off, or stays on if we set thermostat to 23degrees (23 is the only point on the thermostat that 'clicks') I was just wondering how this all works? How come downstairs is controlled by the thermostat but upstairs is boiling? And is there a thermometer downstairs and that's why it turns off unless set to 23?

It's very old and I know it will need replacing but we are hoping it lasts the rest of this year and then we can replace it, just trying to fully understand it and check it's still working as it should? I thought it stayed on downstairs regardless of the temperature in previous years but never monitored it.

maninthestreet

Surely you have switched your central heating off for the summer by now?

TheCyclingProgrammer

maninthestreet wrote: »

Surely you have switched your central heating off for the summer by now?

Never really understood this. I have my thermostat set to 20. I want it to be 20 as its a comfortable temperature, whatever the season. It still occasionally gets cold in late Spring. If it's cold enough to drop below 20 indoors (as it has been the last few weeks) then I want my heating to come on. That's the purpose of a thermostat, so why turn the whole system off?

moreofthegoodstuff

I wish we could turn it off! It has to go on for half an hour every day to heat the water otherwise I wouldn't touch it. I'm just trying to understand the upstairs/downstairs programming.

jk0

It sounds like your pump is kaput also. In its absence, the system will work as a thermo-syphon.

(Boiler heats water, which rises, and then cools in upstairs radiators, so flows back down again.)

Le_Kirk

Have a look for a diverter valve, it could be stuck open or partially open allowing water to pass to radiators. On your control system do you have a selector switch for DHW/CH/Both? (DHW = water, CH = central heating). Is it set to Both perhaps?

Biggles

Why do poor boilers always get the blame? Though your subject heading starts 'very old boiler', none of your problems seem to be related to the boiler itself. I also have a Potterton Netaheat, now over 33 years old. If a new CH engineer comes to service it, they start by sucking their teeth dubiously but, when they leave, they say, 'They knew how to make boilers then, that's good for years yet'.

Part of the setup will be an item you haven't mentioned, which will be the timer (now usually a programmer, but yours may well be the old electro-mechanical sort). It should have a CH and a Water setting, even back then domestic CH systems would enable you to set them so that you could have the water on (say, half an hour a day) and the heating off. This would operate the pump (if still working) and the 3-way valve (if still working).