Internal fuse keeps blowing when i connect HW zone i to my wiring centre!

[John Smiley]

I have wired an s plan plus system. Consists of 2 hot water 2 port valves and one central heating 2 port valve. The boiler is a worcester bosch cd classic.

Problem began when i turned the boiler on first time and nothing happened! Found that the internal 2.5A slow blow fuse had blown. Disconected the Ls and Lr terminals to my wiring centre and replaced the link between them.

After this boiler turned on and fuse was fine with 230V coming out of the Ls. So i isolated the fused spur and wired the room stat and the heating valve and turned boiler back on. Everything was ok.Room stat working and valve operating.So i knew that wasnt the problem. Isolated supply again and connected one heating valve and programmer i to my wiring centr and turned power on.

Boiler didnt react. Internal fuse blown again. Ive only extended the motorized valve cable about 2 meters to my wiring centre so cant see that there will be a short on the extended cable.The 4 core flex i used had blue..green and yellow..brown..grey and black i connected all cables to match exept the orange from the motor went with black from my 4 core flex.

Any ideas please. I only have so many fuses and patience

 

[ShaunCorbs]

need a 5 core for zone valves

only thing i can suggest is to get a heating engy out as your not allowed to remove the cover of the boiler

 

[garygvl]

so your 4 core has actually got 5 cores. blue, earth, brown, grey, black

 

[Harvest Fields]

Why has it been extended?

 

[John Smiley]

sorry i meant 5 core they had to be extended because the valves were not close together or close to where my wiring centre was going to be in the cupboard.

 

[Harvest Fields]

sorry i meant 5 core they had to be extended because the valves were not close together or close to where my wiring centre was going to be in the cupboard.

Check the wires.

 

[John Smiley]

thanks....going to go through it with a fine toothcomb again.

 

[firemant]

thanks....going to go through it with a fine toothcomb again.

Have you not got a multi meter?

 

[Harvest Fields]

Have you not got a multi meter?

Most sensible thing you’ve ever said mate

 

[Murdoch]

thanks....going to go through it with a fine tooth
comb again.

Sounds like you need to check continuity AND insulation resistance ....

How did you make the connections between the 2 cables?