3 Port valve wiring advice

[ianmcd]

Sorry I don't understand most of that.

There shouldn't be any feedback. Where is power being fed back from? Everything associated with the heating system should get its power in one way or another from the 'load' side of the same 3A fused spur, in a 'chain' of supply. So, the fused spur supplies power to the programmer, the programmer supplies power to the thermostat, the thermostat supplies power to the motorised valve, and finally at the end of the chain the motorised valve supplies power to the boiler and pump. So that only when the link is completed is power transferred down the chain programmer....thermostat....motorised valve....boiler / pump. There shouldn't be any thing connected that could cause feedback.

I would also be seriously worried that if I understand you correctly, you now have a heating system without a 3A fuse to protect its wiring and internal circuitry. If it's being supplied from the 32A MCB for the socket supply in the consumer unit, and as most of the heating system wiring / components will only be rated at a few amps what do you think might happen if a fault occurred?

Also, why a 3-Pole isolator? There's only one Live and Neutral supply for the whole heating system. Earth wires are permanent connections and not fed via switches. Below is how it should be connected. N L E from the load side of a 3A fused spur. You can have multiple wires in the FCU load terminals, but there shouldn't be any other mains supply into the heating components to cause any feedback.

View attachment 214543

@stem the way I read it was he had 3 core plus earth going to the fused spur and he had conneced two wires to the perm live and at the other end one of the wires was connected to the oranges from the zone valves, but as you say totally baffeling

 

[GQ1]

@stem the way I read it was he had 3 core plus earth going to the fused spur and he had connected two wires to the perm live and at the other end one of the wires was connected to the oranges from the zone valves, but as you say totally baffeling

Yes, sorry what Ian said was spot on. Apologies for not being clear. The system is turned off now fully, and wont be coming back on again. The only supply to the old junction box consisted of a 3 core, plus earth - from what I could determine, 1 of the wires was the switched live from the boiler. This tracks with the manufacturers handbook. Am concerned now of course though, so am going to admit defeat and contact a professional. Thanks for the advice and help.

 

[ianmcd]

Yes, sorry what Ian said was spot on. Apologies for not being clear. The system is turned off now fully, and wont be coming back on again. The only supply to the old junction box consisted of a 3 core, plus earth - from what I could determine, 1 of the wires was the switched live from the boiler. This tracks with the manufacturers handbook. Am concerned now of course though, so am going to admit defeat and contact a professional. Thanks for the advice and help.

All you have to do is find which wire that you connected to the live went to the orange wires in the junction box and disconnect and isolate it, or even better disconnect it at both ends, it isnt required for anything, not hard to work out which one it is there are only two, you only need L,N & E from the spur nothing else

 

[GQ1]

Update - after Ian's advice, re-visited. Double checked the boiler manual to confirm that the power supply to the junction box originates from the boiler, with the addition of a switched L.

Got my hands on a 3 pole, 3amp fused isolator switch and wired it all up, ensuring that both the Permanent L and Switched L are fused. Tested it and when isolator switch is switched off, no current to the junction box. When on, all working perfectly - Hive, 3-port, pump, boiler firing and all working as/when they should.

Still going to get a sparky in to check the lot and the fixed wiring in the property as wiring all pre-2006 and don't know when last assessed. Thanks again for all the advice.

 

[MangoBoy]

I had exactly the same problem and this thread helped me solve it.
I had the same faulty Sunvic Duoval (DM5651) mid position valve and had replaced it with the same Drayton (MA1/679-3) mid position valve - but couldn't get the new valve to work correctly until I read this thread.
I replaced the wiring unit with the Drayton LWC1 mentioned in this thread (incidentally, the instructions for the wiring unit made it REALLY easy) and when I connected it all up it worked perfectly.
Thank you all!