Worcester 24CDi - timer

[boris_karloff]

Hi All

I've got a Worcester 24CDi combi boiler with a rotary mechanical timer. The timer is on its way out (making a clunky ticking noise all the time) so after checking the Worcester site I bought a replacement digital timer (part 7-716-192-003-0).

Today I removed the fascia to fit the timer. Everything looks fine - just as described in the instructions there is a plug on the right side of the main boiler circuit board with a "timer" symbol on it and the label ST5. The plug fitted to the timer fitted perfectly. With the fascia back on everything looked fine - but the timer doesn't switch the heating on. When it turns on a red light on its panel lights up, but the boiler itself doesn't fire.

I noticed that the old timer was wired into a completely different location, under the circuit board next to where the mains power goes in. It was screwed into three connectors - Ns, Ls and LR, so I'm assuming neutral, switched live and live. This connector is marked ST8.

If anyone's got any ideas as to what could be wrong I'd appreciate it. Is there some way of selecting which connectors (ST5 / ST8 actually controls the boiler, for example?

Cheers

Boris

 

[CorgiIOW]

As far as i can remember, no there is no way of switching STs you plug the
digital timer to the board.
Just make sure its connected properly, failing that you may have a rogue timer, it does happen.

 

[boris_karloff]

Thanks for your message - I suppose it could be a duff timer, although I don't know how I'd prove that to the vendor. The package had a big sticker saying that it wasn't returnable once the plastic bag containing the timer was opened, but I suppose if it isn't fit for purpose etc..

It occurred to me later last night that the connectors where the old timer were connected looked a lot like they were designed for wiring in a simple "on/off" switch for the heating, so maybe that setting is overriding the new timer.

I think it might be worth trying to close that connection with a short link of wire - maybe the new timer would then be able to turn the boiler off as needed. I'm a little concerned about damaging the main board, though. Any ideas?

Thanks again

Boris

 

[boris_karloff]

Right - got it working.

Spoke to Worcester who confirmed that the LS and LR terminals on ST8 should be linked unless a room thermostat is fitted. With a small link of wire fitted between them the digital timer controls the boiler fire-up perfectly.

Apparently the rotary switch had been fitted wrong when the boiler was installed.

Thanks again for your help

Boris.

 

[wendywoo]

Brilliant, exactly what I was looking for!