Central Heating only works if Hot Water set to ON

by **dalisidhu** » Tue Feb 03, 2009 11:03 am

Hi

New to this forum.

I have a problem whereby the central heating (radiators) do not work when the CH option on the programmer is manually turned to ON or is turned ON via the timer (ONCE/TWICE settings etc)

THE CH ONLY WORKS IF THE HOT WATER IS SET TO ON AT THE SAME TIME AS THE CH

Set up is as follows:

ACL DRAYTON LP241 Programmer
POTTERTON PRIMA 30B Boiler

Does anyone have any pointers please?

Many thanks

by **rosebery** » Tue Feb 03, 2009 11:02 pm

Do you have a fully pumped system or gravity hot water. The unit has a link on the back which is set according to which you have.

If you are fully pumped you may have heating and hot water separately controlled with the link set to P.

If its a gravity DHW then you cannot have heating without DHW but you can have DHW on it's own. In this case the link is set to G.

Your installer would have set the link according to your system configuration.

It's in the MIs.

Cheers

by **Steve the gas** » Wed Feb 04, 2009 7:05 am

Hi,

Not megga familiar with the prima, but, its a diverter problem if a combi, or motorised valve knackered if a conventional boiler. If the latter change the head as a starter.

Hth

by **dalisidhu** » Wed Feb 04, 2009 9:03 am

Thankyou for the replies. Really appreciate it.

Rosebery - The system is a fully pumped one. This problem has only started occur. Before there wasnt a problem when we just wanted the CH on, on its own.

Steve the gas - I've been informed by BAXI that the Prima 30B is a conventional gas boiler. In the airing cupboard upstairs (where the tank is) i've noticed that there is a small unit attatched to the pipe work near the Grundfos pump. I think this is the diverter unit.

What puzzles me is that this problem has only started to occur. As I have said, before we were able to turm the CH on without having to turn the HW on. However now, when we turn the CH on via the programmer there is no response from the boiler (pilot light burns as normal) BUT as soon as we turn the HW on via the programmer (while CH is still on via programmer) the pilot light in the boiler roars to a brighter flame (and the radiators start heating up as expected)

Thanks for your time.

by **teeny** » Fri Jan 29, 2016 10:49 am

Can I ask if you got this fixed in the end and if so how? It's just started in our house and our plumber doesn't seem to have a clue. Many thanks.

by **pundabuyer** » Sat Dec 23, 2017 7:54 am

Hi guys,

Did anyone get a fix for this? Just bought a new house with a Potterton Prima F and the same happens, it has a pump so I’m guessing it’s a pumped system.

If jumper on the controls is set to pumped the heating only works when you switch the HW on... if the jumper is set to Gravity when you switch the CH on the HW automatically comes on.

Is this by design or should they work independently?

HELP!