boiler/heating problem

good2talk

hi
i have a potterton boiler (not a combi one) it has a tank in bathroom and also tank in loft.
in the kitchen i have a control unit to turn heating/hot water on/off.
the problem i have is when i turn hot water switch to on and leave the heating water switch to off,the hot water comes on but the heating also comes on when it should not come on,as the heating switch is off.
in the living room theres a thermostat which is also in off position.
please can someone tell me a solution to this problem and let me know if i have to call out a corgi registered engineer and how much it could cost.
many thanks

silvercar

sounds like the (3 way) valve has gone. Only know that because I had a similar problem. According to the guys on here I was ripped off at a price of about £300, so expect a bit cheaper.

silvercar

In answer to who you call out, if that is your problem, you don't have to have a CORGI registered guy as they won't be touching the gas supply. But you will need someone who knows what they are doing and can diagnose the problem.

keith1950

Hi, check what make 3 way valve is fitted. Some have a removeable head unit so that you can replace the drive mechanism without replacing the valve itself. You should be able to find a replacement head unit on the internet for £25-£30, it only involves connecting 5 wires( with the supply switched off).If you need to replace the whole unit you should be able to find one for between £40-£70 however unless there are any isolating valves either side of the unit the system will need to be drained. Its an easy job for your average DIYer as long as you take your time and pay attention to connections etc. If you pay someone to replace it, it shouldn't take more than a couple of hours so total price for job should be max. £250 depending on make of valve and minor hiccups.

Lincoln_Imp

got the same problem with my system ,3 way valve H M W stuck on W
need to either take to bits or replace when i get a minute

if you locate the valve then look at the lever on top (H M W) and note whether it moves when you toggle between heating and water

been quoted 45 quid for a new unit and been told fairly easy to replace