Honeywell Programmer No Hot Water/Central Heating

I was called to look at a system because the customer was complaining that they had no hot water but that their heating was working. For a system with a three-port valve this is unusual but not impossible. Looking in the airing cupboard I remembered that I had fitted a new Honeywell motorised valve last year so thought it unusual that it should fail. Their was an old Potterton PTT2 cylinder thermostat so thought that this may be the issue.

I put the hot water on at the programmer and returned to the airing cupboard. The cylinder thermostat was lit to say it was demanding heat and I could feel that their was circulation around the hot water circuit. I turned the cylinder thermostat up and down and it was responding to my demands. All working with no problems.

I put the heating on and waited for the radiators to get hot. I waited and nothing happened. Strange, I've come to look at why there is no hot water which is working and now I have no central heating. Returning to the airing cupboard I checked the electrics in the junction box. There was no power on the white, and there was also no power to the room thermostat from the programmer.

I went back to the programmer, Honeywell ST9400, which I had fitted five months ago and turned the heating and hot water off. I then turned the heating back on, five seconds later the boiler fires up and the radiators have started warming. I turn the hot water back on, and now this isn't working. Usually when either the heating or hot water is switched on their is a click and the related green light illuminates. However, in this case both the lights would come on but their would be no click from either the heating or the hot water depending upon which you switch on second.

I fitted a new Danfoss FP715 programmer and set the dipswitches to the 7-day mode and everything was working as it should be.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.