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Central Heating

Re: central heating only works when hot water is switched on

I have a Megaflow system with potterton profile boiler and Honeywell 9400 programmer.Up to now it was working fine .After draining the system to add fresh inhibitor , the central heating now only works when I turn on the hot water switch.The system was plumbed with separate motorised valve for hot water and separate for central heating,If I switch on the central heating switch the central heating does not work but if I switch on hot water switch the central heating works until the water reaches the required temperature then the heating goes off also.Any idea of what to do ,any advice will be highly appreciated. Once the water temperature goes lower from required temperature, the heating comes back on from hot water switch.

Any other answers for the above problem. New answers will be highly appreciated

4 Answers from MyBuilder Heating Engineers

Best Answer

could be 3 port valve not working if y plan system or 2 port valve if s plan system may need new valve or just new sycron motor to be fitted


Answered 19th Dec 2012

Your central heating wiring is either incorrect or it has been piped up incorrectly at the valves, you have what is called an S-plan. Please note, if the wiring is wrong, then you will need to push central heating button for Hot Water, seeing as you have not mentioned this, I would suggest that it is piped wrong.


Answered 23rd Jan 2013

as above your motorised valve is faulty or the signal is being fed is incorrect. GET a gas safe experienced engineer to solve the issue.


Answered 23rd Dec 2014

I'm a gas safe engineer and as the two answers above its the 3 port or 2 port value it may just be the sincrone value instead of whole value


Answered 17th Jan 2019

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