No heating when water hot

[penno]

My heating system is 6 years old and comprises a Potterton Suprima 50 Boiler, EP2002 Programmer and a Tribune Premier TP210B Hot water cylinder. The problem is that everything works ok until the water is hot then the heating shuts off. If you then run off hot water the heating will fire up again. The PCB was changed in the boiler but made no difference. Any suggestions gratefully received or recommendation for a reliable heating engineer in the Runcorn Area.[/u]

 

[ChrisR]

It's a bit obvious that the problem wasn't with the PCB - who changed that??

ANyway its the bits you don't mention which are giving you bother - control valve(s). Have you got 1x 3 port or 2 x 2 port, or some other combination?

 

[penno]

I've got 2x2 port valves and the motors have been changed

 

[chrishutt]

You should have mentioned that in the first place . Did the problem start after the motors were replaced, or did it already exist? And what else has been done?

 

[penno]

The problem started before the motors where replaced, changing the motors didn't change the symptoms. Going back to square ione the system was in a new house and when we moved in the upstairs radiators worked and downstairs didn't. We got the cowboys back who installed it and they went through changing the boiler, pump and installing more pipework than Cape Kennedy until they actually found a blocked pipe under the bedroom floor. However, the system has worked as advertised until earlier this year.

 

[ChrisR]

SOunds like it could be just about anything doing it, with that history!

Normally we'd say it sounds like a basic wiring error, but it could also be plumbing!
If you aren't handy with a wiring diagram and a volt meter, it's heating bloke time.

 

[gstens baxi]

has your programmer been changed?

 

[penno]

No the programmer has not been changed although I have theorised that this may be part of the problem.

 

[penno]

Anybody got any further views on the possibility that the Programmer is u/s?

 

[ollski]

probably taken a live feed to the heating from a switched live to the water somewhere....time to get tracing those wires.

 

[penno]

If I understand the logic of the system, it worked correctly for 5 years and then stopped working correctly. If the wiring has not been disturbed can it be a wiring fault?. At the point when the HW reaches temperature the call to the CH switches off, so what component in the system is not allowing the demand to get through?

As already suggested could it be the programmer?

 

[penno]

Any more advice Please guys?

Just tried running through the Potterton Fault Finding Guide for the boiler (Suprima 50).

Everything works as advertised apart from the final step; If I turn the Boiler temp control from Max to 0 the flame goes out but if I turn it back to Max it doesn't re-light.

Is this relevant to the original problem of no CH when HW reaches temperature?

 

[ChrisR]

No it doesn't. You have a wiring error. Have you checked it? Sounds like the CH is connected through the cylinder stat or something.

Wiring diagram is here: http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.2 S Plan.pdf

 

[penno]

Thanks Chris

Only thing I can't get my head round in terms of wiring problems is why did it work ok for 5 years then stop working if the wiring has not been disturbed.

Could it be a dodgy connection?

 

[penno]

I've chased a few wires and the feed from the HW side seems to work fine. However, when the CH is switched on it is reading about 180volts at the orange wire from the 2 way, this is the same reading at the boiler but there is nothing at the pump. Any suggestions lads?