Worcester 28i RSF Boiler + Honeywell CM907 Thermostat, Help!

Hi all

I'm new here and looking to pick someones brains over my boiler.

I have a Worcester 28i RSF boiler which currently only has a mechanical timer on the front. I gave Worcester a call and they told me I could fit a programmable thermostat onto it instead and suggested Honeywell

Armed with this useful information I went onto Ebay and picked up a brand new Honeywell CM907 Thermostat.

So far so good...

Now I come to fit it I disconnect the Blue, Grey and Brown wires from the mechanical timer and look at the Honeywells installer 'instructions'

Straight away I see an issue, the suggested setup for a Combi Boiler only uses two wires... So I go and buy a 2 wire cable and look at the boiler for a while trying to figure out what wires it means.

The problems I have is the symbols on the boiler and thermostat don't remotely match up infact the honeywell instruction don't even appear to explain what their terminals do...
I decided since the Honeywell manual says only 2 wires for combi boilers that I will wire in the negative cable and the switched live cable to ports A and B. I figure its run on batteries and probably doesn't use the live like the mechanical switch

Wired in I turn it on, lights come on but when I set the CM907 to turn on the heating theres a click but nothing happens on the boiler. I decided then to take the only other configuration which was wire in the live and the netural instead and that just blew a fuse on the boiler the moment I turned on the mains.

Help!!

What am I doing wrong, do I need to use a 3 wire cable instead? Does the CM907 even work with the 28i RSF? The only thing I know for certain is that the mechanical switch can be unplugged, Worcester told me that but couldn't help me with anything else so perhaps someone here knows what I need to do to wire in my thermostat, a guide with terminal to terminal would be great

Chris

discon existing integral timer wires.
use boiler terminals r1 & rl wire these 2 wires to A & B.in cm907.
rl=A.....r1=B.
use cable suitable for 230v.ensure 3amp fuse in spur/plug.
cm907 has no neutral wire,it is just a switch.
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DO NOT connect any wire to boiler terminals rn or cn.these are neutrals.an incorrect wire here will give you grief.
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boiler terminals link ci & cl.

My friend you are a genius!

Thank you, that worked perfectly

Chris

you are very welcome,i just pulled wiring info from worcester and potterton sites and married them together.
curry time now.just found a really decent curry house in ealing,5 plumbs/gas a brain surgeon and a fireman going on the lash now.
your worcester will need some tlc in the future so get back here and ask.
cobra and curry now.or something like that.