I only get heating when hot water on

[chris71]

I have a Potterton Suprima 50 and my heating only works if the hot water is on.
If I switch off the hot water the heating wont fire up at all. What would be causing the heating to not work independently from the hot water?

Any help much appreciated

 

[ollski]

the synchron motor in the 3 way valve.

 

[ChrisR]

Do you have 1 x 3 port valve or 2 x 2 port ones?
One I need to mull over, but my first thought is that you have a 3 port valve , which isn't opening/switching properly. (Assuming it's wired correctly )

If it was just a synchron motor dead, the heating wouldn't work at all.

 

[chris71]

Do you have 1 x 3 port valve or 2 x 2 port ones?
One I need to mull over, but my first thought is that you have a 3 port valve , which isn't opening/switching properly. (Assuming it's wired correctly )

If it was just a synchron motor dead, the heating wouldn't work at all.

Yes its a 3 port valve. It should be wired correctly as its been working ok but now doesnt and no one has touched the wiring since installed.

Thanks for the help so far

Can I fix it myself?

 

[namsag]

You may have a heat store cylinder , which means the heating gets it heat from within the hot water cylinder as opposed to straight from the boiler so if you turn the hot water off the heating does not have a heat source. Way of telling this is if yor 3 port valve only has 3 wires within it`s supply cable...

 

[ChrisR]

Have you got, and can you use, a voltmeter on live mains circuits? It would be appropriate to test things first, like the wires from the programmer, which could conceivably cause your problem.
Then go to the Honeywell domestic controls web page, sundial Y plan system, for the circuit diagram.

CHanging the head is easy enough, if you have to.

 

[ChrisR]

Previous post crossed with namsag.

I always forget those heat store things .

 

[chris71]

You may have a heat store cylinder , which means the heating gets it heat from within the hot water cylinder as opposed to straight from the boiler so if you turn the hot water off the heating does not have a heat source. Way of telling this is if yor 3 port valve only has 3 wires within it`s supply cable...

But before this problem appeared I could run the heating without the hot water having to be switched on.

The boiler used to fire up all the time when the thermostat clicked in (even when just on heating alone) but now will only fire up when hot water on.

ChrisR, I have a meter so will try your advice.

Again many thanks and no doubt will be back for more help

 

[chris71]

Finally got chance to test things with a meter.

When the heating switched on the grey wire shows around 240Vac but nothing on the white or orange. Only supply to orange when water switches on then heating comes on but still nothing on the white.

 

[ChrisR]

Grey should go live when HW is NOT wanted.

White should go live when CH IS wanted. It comes from the programmer, through the room thermostat. It seems there's a fault in that line. By convention the live from CH ON inthe programmer goes to terminal 4 in the junction box and the return from the thermostat goes to terminal 5. But sometimes all you get is a spiders web of wires - good luck!

The orange wire goes live to turn the boiler on.

Honeywell Y plan is here: half a megabyte so will 4 take mins or so on dial-up:
http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.4 Y Plan.pdf