central heating timer malfunction

[graham72]

i have a danfoss fp715 timer which will no longer bring on the central heating, when heating is selected the timer clicks and flashes continuously.
when water heating is selected it works perfectly.
as a work around i have used a pipe thermostat attached to the hot water pipe to bring in the central heating pump, which works fine.
i should also point out that the system utilizes a neutralizer.
what i would like to know is if the timer can be fixed or does it require a replacement ?
my thoughts are there could be a problem with the electronics in the unit.

 

[SJB060685]

If you're competent enough to wire in a pipe stat why not just replace the programmer. Cant tell you if it can be fixed or not but it would probably cost as much as a new if it could.

 

[graham72]

If you're competent enough to wire in a pipe stat why not just replace the programmer. Cant tell you if it can be fixed or not but it would probably cost as much as a new if it could.

thank you ..I'm retired now but used to be an electrician ...not on central heating i would add

 

[SJB060685]

I've never installed a neutralizer but I'm looking at system layout and trying to find a wiring diagram of a particular valve I believe you have (no such luck yet). How far have you tested? Do you have a feed to and from the room thermostat?

 

[Murdoch]

Just replace it. They are not expensive

 

[graham72]

actually i don't have a room thermostat i just turn the boiler up or down depending on the weather, but also the boiler is not used that often, the boiler feeds the neutralizer, i also have a back boiler in one room in a fireplace, which also feeds the neutralizer to give hot water and a pipe thermostat brings in the ch pump if the water gets too hot. I also have a wood burning stove in another room which is my main source of heat in the winter, it also has a pipe thermostat on the flow and a pump on the return which pumps water to the neutralizer ...that's it

 

[SJB060685]

Ow wow, sounds very primitive. So from programmer is CH on supposed to activate pump direct without the roomstat you say you don't have? Is the programmer set to gravity as I suspect?

 

[graham72]

Ow wow, sounds very primitive. So from programmer is CH on supposed to activate pump direct without the roomstat you say you don't have? Is the programmer set to gravity as I suspect?

not primitive ... simple ...when ch is selected on the timer, both the ch pump and the pump next to the boiler come on simultaneously, but when hw is selected only the boiler pump comes on, sending hw to the neutralizer and I use the pipe thermostat to bring in the ch ...most of the time i just use the wood burning stove which heats the hot water and brings in the ch via the pipe thermostat

 

[SJB060685]

not primitive . simple ...when ch is selected on the timer, both the ch pump and the pump next to the boiler come on simultaneously, but when hw is selected only the boiler pump comes on, sending hw to the neutralizer and I use the pipe thermostat to bring in the ch ...most of the time i just use the wood burning stove which heats the hot water and brings in the ch via the pipe thermostat

I believe I understand how its wired, Im assuming the programmer is set to gravity from what you said, I'd like to see a wiring diagram though just for my own curiosity. Yes everything you said suggests it is the programmer but a quick Google suggests they're about £70 new so its probably best to just replace it.

 

[graham72]

i have no idea if the programmer is set to gravity or not, it has worked ok for 20 years ( i am not at home to check that at the moment) but if i was to guess I would say no ...the water is pumped from the boiler to the neutralizer, it is also pumped from the wood burning stove to the neutralizer and obviously pumped round the radiators ...so i would say it is a fully pumped system ....with 2 tanks in the loft, one for the hw and one to top up the ch if needed...

 

[SJB060685]

Yes it is technically a fully pumped system. If you take programmer off and look in the back theres often a switch or lug to go from fully pumped or gravity, this just affects how the programmer works and I'm assuming its gravity based on what you've said and no mention of motorized valves.