Why won't my 'warm' water heat up now that I've turned the heating off?!

[AndImFeelingSoBohemianLikeYou]

I know it sounds stupid, but I really can't figure it out! I've only lived in this house (rented) a year, and I'm sure there was hot water last summer.

The boiler is quite old, and has one of those timer dials with the 2 red and 2 blue clicky things that turn the boiler on and off. On the little box that the timer sits on there is a switch for 'On', 'Off' and 'Constant'. I had it on 'On' for having the heating on when it was cold, and then turned it to 'Off'.

On the boiler itself there is a switch labelled 'Thermostat' with the options

High
0
Low

It has been on low since I moved in.

There is a water tank with a thermostat which was recently replaced as it wasn't working and the water was too hot, it was fine after the replacement, but now turning that up to max won't make the water hot either. Everything was still fine when I had the heating on.

What's going on?! I can't find any more switches. In my old place there was a switch on the boiler with a choice between 'Off', 'Heating and water' and 'water', but I can't find anything like that here. Argh!!

Google the make and serial number of the boiler. You may find a trouble shooting page.

You could try switching the thermostat setting to 0 instead off turning everything off to see if the thermostat is just related to heating.

I once moved into a place (in the UK) where the only instructions to the boiler were written in Italian, so understand!

Have you got a Wall Thermostat?

If so, turn the boiler on and the wall stat down.

Most boiler programmers have separate setting for CH and HW. It sounds like yours doesn't.

Can you see one similar to yours here?

had one of these in a rented house and could only heat hot water with heating on. now have thermo which can just heat hot water without having heating on. i think like Piglet that if you want to heat your 'hot water', then you have to turn your 'heating' on too (but turn rads off so as not to bake in the heat)

is this it?

www.screwfix.com/p/horstmann-425-tiara-programmer/18470

Thanks for that advice. I'll put the thermostat on '0' to see what happens. If that doesn't work I'll try turning the radiators off but the heating on. Seems really silly to have the heating on in the summer, but I can't remember if it was off last summer. I think it was off, and the water was still heating up somehow. I think.

The timer is like
this one . In my previous place I had a nice room thermostat and everything was really logical and easy. sigh

If you didn't spot it, that link has a PDF for an instruction manual.

is there no room thermostat?

do the radiators have thermostatic valves?

No room thermostat, but the radiators do have them.

I checked the instructions, and it's a slightly different timer from the one I have, which is very old and does not have water/water&heating options.

no room stat is rather unsatisfactory, so the pump will be trying to push hot water round the rads even if they are turned off, and the boiler will be hot even when the HW cylinder is hot.

If it is a modern boiler and a modern cylinder (with a blue or green foam coating) the cylinder will be hot in about 20 mins, so I'd suggest that you set the timer for the boiler to come on no more than half an hgour before you get up, or come home, and to be off all the time you are in bed or out of the house.

You might find this reducs your gas usage in summer to less than a cubic metre per day, which will cost you something like 50p/day.

If the controls were better you could reduce it even more.

We had this problem this time last year. There was a problem with the motorised three way valve which controls whether hot water goes from the boiler to the heating system, the water system, or both. It is probably located near to the boiler.

It's a plumbing job to get it replaced.

if there is no room stat, and no HW/CH switch on the programmer, there will be nothing to signal a 3-port valve to turn off the CH flow

I'm not sure something stopped working properly as the water stopped heating up the day I turned the heating off. I think I'll have to set the timer so the boiler is only on for a little bit. It's just that I did not set the timer last summer and had hot water without problems, and then I set it for the winter and it was still fine. But now it's not.

I wonder if there is an electric immersion heater in the HW cylinder?

There is, but using that would be expensive.

Oh yes, but I mean, if it was on last year, that could explain why the hot water seemed to work.

You mentioned the cylinder stat was overheating. This can cause an immersion heater safety trip to cut out, or a sensible plumber might have turned off the immersion, thus you no longer have hot water unless the boiler is on.

Actually, you might be right. I think the plumber mentioned something about the immersion heater. Hmm. Perhaps that's it then and I've just got to keep the boiler running all year !

you could try a week of boiler, and a week of immersion heater, and see which is cheaper (in the summer). mine is cheaper on the (very modern) boiler, but I have tinkered with the controls to improve the efficiency and reduce heat loss.

It is very important to have the cylinder and hot pipes well-lagged. Are they? What with?

Not sure what 'lagged' is, does it mean insulation? If it does, the tank is covered in some greeny-yellow foamy stuff, pipes are not covered.

pipe insulation your pipes will be 22mm diameter near the cylinder and boiler, with some 15mm. If an old installation some may be 28mm. The pipes between the boiler and the cylinder will be the hottest, so will best repay the cost of insulation.

A cylinder jacket is not essential if you have a foamed cylinder, but the yellow is quite an old standard, and one of these, currently subsidised to only £3, will save even more. I have two red jackets on my foamed tank because I happened to have them handy.