Central heating control unit blowing fuse

[Chris]

Hi, I have a Drayton Central Heating control unit ( i.e. controlling the times the heating and water come on ) which keeps blowing the 3 amp fuse protecting it.

Is it a case of getting a new unit ( and how complicated is that to fit) or is there any likely chance of repair.

As far as I know the unit is about 8-10 years old as it was in the house before we moved in.

Many Thanks for any guidance

Chris

[Owain]

I suspect there is poor insulation caused by dampness somewhere, pump or motorised valves would be my guess.

Owain

[John Rumm]

How do you know it is the controller that is blowing the fuse? Its more likely to be something on the output of the controller. If you disconnect everything from the switched output of the controller, power it up and have it switch on the heating etc, does the fuse still blow?

[geoff]

In message , Chris writes

Is it the controller or what the controller is switching ?

i.e the boiler or associated bits, the pump for example

If you were the sort that could repair it, I would have thought you would have got inside and tried without asking

but you're asking a how long is a piece of string question

Since you haven't actually said what model it is, its hard to say as different ones have different backplates which you may or may not have to change, depending on age

My feeling is that its probably the further down the line where your problem lies, programmers don't tend to blow fuses

[Chris]

Thanks for the replies ... Have since found out that the unit is a Drayton Tempus 7 and on replacing the fuse again - the unit displays the time etc. OK which you can programme but blows the fuse when the hot water is turned on by "advancing" or by timing. ( No central heating turned on)

[Dave Plowman (News)]

You need to be certain it is that and not something it feeds or the wiring to those. My guess is it's far more likely to be the latter options. If it were a fault in the unit itself it would likely have stopped working by now. Basically it's just two switches operated by its electronics.

If it were the controller at fault, given the lowish price, a pro repair is unlikely to be viable.

[Dave Plowman (News)]

Trouble is this action could be operating a variety of things - could be moving a 3 port valve or operating a single one. So more information on the system needed. Does it work ok on heating only?

[Roger Mills]

Assuming it's a fully pumped system, I'd put my money on the pump. This is the point in the system where water and electricity are at their closest - and if a fault causes them to get *too* close, blown fuses (or tripped RCDs) are likely to result.

[Chris]

Fixed - Leaking gland nut was dripping water onto the pump circuit and blew the circuitry.

Thanks for all teh help

Chris