On Fri, 06 Feb 2009 12:23:44 -0800, heeley wrote:

Hello Ed,

Thank you for your rapid response. I was hoping you'd read my post. I
have always noted how well informed you are boilers and gaswork.

I've actually got another 242 which was replaced though working , from
which I can cannibalise parts with a view to perhaps discovering what
the issue can be. Can you acquaint me with the sequence of operation
w.r.t the heating operation of a (grey front panel) 242?

I'd really like to be able to sort this one myself.

Regards

Heeley

1) There is a demand caused by applying 230V ac at terminal 4 (or by
joining terminals 3 & $ together which is the same difference).
2) The circulation pump starts.
3) The servo valve (the triangular one on top of the DHW flow detector)
is in the CH position (normal position).
4) The pump forces water through those tiny 4mm tubes to the diverter
valve.
5) The DV moves to the left from its normal neutral mid position.
6) One (or more?) micro switches are activated by the DV (in a box on the
RHS of the DV)
7) The boiler begins the ignition sequence. Which should be OK as DHW is
OK.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html