boiler/central heating timer problems

[gillm]

Hi,

having some problems with our boiler and really hoping someone might have a clue why:

We have just tried to replace our central heating timer: The old one was a Randall 103 which switched the central heating and hot water on and off together. It broke this week so we have just replaced it with a homexpert by Honeywell THR850SUK single channel timeswitch which uses the same wiring as a honeywell ST6100.

The heating is Y-plan I think with a 3 way diverter motorised valve and there is a 7 port junction box with the thermostat and valve wiring and I think one cable linking this to the timeswitch.

We have substituted port 1 (on) on the randall to port 4 (on) on the Honeywell and port 3 (common) on the randall to port 1 (mains input) on the Honeywell. There was a link between live and common on the randall so we have put that into the new one aswell (live to mains input, which the instruction manual suggested was right)

Whilst doing this we have taken the covers off the junctionbox and the motorised valve but have put them back without doing more than look at any of the wiring.

When we turned the power back on the boiler came back on and is continuously firing up and down for a few seconds of each. This happens whether the power to the clock is on or not and regardless of whether the room thermostat is turned up or down.

I'm really confused about how this could have happened as even when the mains supply to the clock is off it's still doing it, but we haven't touched any of the wiring other than that which goes through the clock.

The boiler is a british gas 330

If anyone has any ideas then I'd be really grateful
Thanks in advance

Gill

 

[TCCHeating]

Try without the link? (I have a feeling the live link wire isnt necessary on the honeywells) Orherwise you need to check your wiring. Honeywell have a good wiring/faultfinding guide. Have a google for it

 

[gillm]

Tried it without the link already, doesn't make any difference.

Will have a look for that guide thanks.

I just can't get my head around why the boiler is doing strange things even with the whole clock completely switched off?

Thanks
Gill x

 

[TCCHeating]

Because the boiler is getting a switch live supply from somewhere. Check your wiring

 

[gillm]

Switched the 2 cables that look the same in case we had them the wrong way round all that happens is the clock doesn't work at all that way round the boiler still does the same thing.

Very sure that I've substituted the wires as I said in the original post and every website/ manual I look at suggests that's right

Very confused now.

Don't know what other wiring to look at as we haven't changed anything else

Gill x

 

[twgas]

You need a 2 channel programmer, A single channel will never work properly on a standard, non-combi system.