fuse keeps blowing in wiring centre

[bhm1712]

if the pump comes on for HW its not a gravity hot water system.

does the fuse blow straight away when you select HW?

sounds to me like something is pulling loads of current when it starts up.

there must be a short circuit somewhere, or something is breaking down somewhere in the circuit. can you photograph the wiring centre inside and post it?

 

[27oak]

if the pump comes on for HW its not a gravity hot water system.

does the fuse blow straight away when you select HW?

sounds to me like something is pulling loads of current when it starts up.

there must be a short circuit somewhere, or something is breaking down somewhere in the circuit. can you photograph the wiring centre inside and post it?

Hi thanks for your post

The pump does work on HW, and the fuse is blowing when switching on HW, but only under certain circumstances, ie when CH and HW are up to temp and some HW is used when the stat calls this will blow the fuse?

Hope I am making sense?

Regards

 

[27oak]

your wiring centre , does it have " honeywell smartfit " written on the front cover?

Hi

The cover has a serial no 42005748-001, nothing else of front, but just noticed some instructions inside, including an instruction saying that the white wire on the MV should not be used on fully pumped systems??? do i have a fully pumped system?? now I am confused!!

 

[bhm1712]

well,

when the cylinder stat calls, the switch inside closes, the pump will turn on and the MV will move to the required position for HW heating, and finally the boiler will fire. with this in mind i would suggest , like somebody else already has, checking the wiring of the MV, and also checking the pump.

the white wire is usually AFAIK for c plan systems and is not used on fully pumped.

you say that the problem occured when turning the heating back on for the winter. when exactly did this fault start? as if your HW was on for summer then i cant see why HW is causing the fault now. you changed the pump for what reason? and why did you change the MV?

I suggest putting a 3 amp fuse in for a start.

take a pic of the inside of the wiring centre and put it on here......

 

[D_Hailsham]

The cover has a serial no 42005748-001,

That's the Honeywell Sundial wiring centre with the terminals on three sides of a square and pre-labelled.

but just noticed some instructions inside, including an instruction saying that the white wire on the MV should not be used on fully pumped systems

If you read carefully, those instructions apply to the V4043H valve. You said you have the V4073A valve; can you confirm you are correct.

The V4073A is the one on the left; the V4043H is the one on the right.

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