CH on only when HW on!!!!(merged threads)

tollanarama

Hello There... I'm very new to this board, I only found it today!

I hope someone can help me with my problem.(I've searched the site, but cannot find a solution)

My house has a boiler that serves both HW and CH via a fully pumped system (or at least the timer switch is wired for such!), so I can have HW only, CH only or HW+CH on at same time.

The HW has been running throughout summer with no probs, and a couple of days ago I thought about testing the CH as it was getting cold (it has been turned off for about 5 months).

Now, the CH won't work on it's own - the boiler does not come on and the radiators stay cold!
It does work if I swich on the HW as well, but the CH turns off once the HW has reached desired temp (I've got it set on the water tank for 60C). This is inconvenient to say the least!!!

(If I switch on just HW the radiators stay cold)

I've turned all radiator thermostats and the room thermostat up to full with no joy; I've also checked the wiring to the timer but it seems OK - I haven't delved any further!

Anyone have any ideas what the problem can be?

Many thanks for your time

glosman555

Sounds like the diverta valve is stuck: if its a motorised valve you can take the motor off the valve and turn the valve so that the central heating will come on,but it may be needed to be replaced. I replaced mine some years ago, the complete valve cost £60 but you can buy the valve and the motor separatley. It depends how good you are at DIY as it entails draining the C/H system, it took me four hours in total to do the job.

tollanarama

Sounds like the diverta valve is stuck: if its a motorised valve you can take the motor off the valve and turn the valve so that the central heating will come on,but it may be needed to be replaced.

Many thanks for the quick reply!
I've no idea what a diverta valve is!!!
Can you please tell me what I'm looking for and what I have to do?

Thanks again!

glosman555

Have a look at the screwfix website and look for item number 53314
https://www.screwfix.com
If it's similar to the picture unscrew the two screws and take off the motor. Underneath is a spindle turn it a quarter turn left or right and turn on your C/H if the radiators stay cold turn the spindle in the opposite direction.

tollanarama

Thank you for your quick help!

I'm currently at work, so I'll take a peek when I'm home!

Just one more question (a la Columbo!)... Do I replace the motor once I've twiddled? And, I take it that if this does not work, I'll have to replace the valve? (sorry that was 2 questions!!)

RACHIE77

I have a very similar sort of problem, my CH comes on when HW is switched on and/or when both are switched on but not on its own. I'm rubbish at DIY so have just been switching off both switches at the same time and switching both on which is a bit of a pain but a lot easier than following the instruction above for my non-DIY brain! lol!

does this mean I need to call a plumber, or my dad or someone similar??

Thanks in advance

R

ka7e

There are 2 types of 3-way valves. One type sits on the pipe (as described by glosman555) and is quite simple to exchange. The older type actually bisects the pipe and the whole system has to be drained to take the faulty unit off, as I know to my cost!!

glosman555

Yes replace the motor after trying my suggestion.
Moving the spindle back and forward may free it but there could be corrosion inside the valve, but it could also be the motor that is defective.In the summer months it's a good idea to turn on the C/H for a few minutes each week so that the valve moves back and forward.

djohn2002uk

About 10 or 15 years ago there was a very common system which was as you describe. The only choices on the programmer were :- HW&CH or HW Only. The theory being that you need HW all the year round so only need a means of switching the CH off in summer. Of course the programmer has the same on/off functions as any other.

tollanarama

glosman555 wrote:

Yes replace the motor after trying my suggestion.
Moving the spindle back and forward may free it but there could be corrosion inside the valve, but it could also be the motor that is defective.In the summer months it's a good idea to turn on the C/H for a few minutes each week so that the valve moves back and forward.

Glosman555,

You are a genius!

I did as you suggested - the only difference was that I did not need to remove the motor - after I removed the cover I found a small "rocker/pump" switch. I pumped this a few (and more!) times: this seemed to free the valve. Job done - CH now working.

Thanks for your time and effort.

I am moving house in a couple of weeks and so did not wish to spend a fortune on the HW/CH system; also I did wish to leave the system in working order!

You help on this has been invaluble!

oldagetraveller

I've always found it a good idea to switch the CH on for 15 minutes once a fortnight in the summer or during any prolonged period when it is not used. It keeps everything "free" including the 3 way diverter valve. Plus you know it still works rather than switching on the CH at the first cold spell and finding it doesn't!!