S plan Pump overrun wiring help required

7 Sep 2011
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United Kingdom
Advise needed on Pump overrun wiring please!

System is fully pumped S plan 3 zone with Honeywell Auto-bypass valve following are the specification.

Boiler: British Gas 330
Pump: Grundfos Pump
Valve: 3 into Honeywell 22mm 2Port valve: 1>Heating Downstairs. 2>Heating Upstairs. 3>Heating Hot water.

Programmer: Drayton 742R Mitime programmer
Cylinder stat:Wired Drayton Cylinder stat
Room Stat: Drayton wired Room stat

I have managed to wire the system as per LWC1 wiring centre specification as below. Just need advise on how to wire pump overrun as per boiler specification? Could not find any information for British Gas boiler. Any help will be appreciated.

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You are using the wrong diagram. :) Here is the correct one:

Channel 1 = Heating
Channel 2 = Heating
Channel 3 = Hot Water
Channel 4 = Not used

Pump Overrun
Remove the link between 6 and 12 in the LWC1.

Wire Pump as follows:
Live to 12
Neutral to N
Earth to E

Connect boiler's Pump Live to 13

The boiler's Pump N and E are not used as they have been connected in the LWC1.
Just ignore the boiler instructions ;) how is the pump going to overrun if the op connects to 12?
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Thanks D_Hailsham: Do you mean Boiler switch Live to 13? Please advise.
Dont mention it mate, no really its no trouble :rolleyes:

and just incase you didint realise the "ignore the boiler instructions " was sarcasm.
Still in limbo help please!!!

From your MI's...
"Only feed the pump from the marked terminals in the connection
box on the boiler, not from a separate supply."

Unless of course you are using dedicated pumps for each zone which will terminate into 2/4/6 , obviously boiler/overun pump will terminate into boiler terminal strip marked pump live.

As Picasso says.
Thanks D_Hailsham: Do you mean Boiler switch Live to 13? Please advise.
Your quite right. I overlooked the fact that boiler's switched live is in no 12.

Ignore my previous instructions and wire as follows:

1. Leave link 6-12 in place
2. Remove link 12-13
3. Inset new link 13-16
4. Connect pump's live to 16
5. Connect boiler's pump live to 13.
Just to confirm that I have made wiring as per Hailsham instruction and everything working treat!!! So far no sound from boile I see pump is running after boiler stop supplying heat! Thank very much for your help guys!!!

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