Re: [OT] ishh central heating controls

["Mal Lansell" <mlansell@xxxxxxxxxxxxxx>]

--- In ukha_d@xxxxxxx, "Andrew Cooke" <acooke@e...> wrote:

> Question:
> I can't for the life of my figure out the electrical setup on the
heating
> and pump controls (I always like to know how things work incase
they go
> wrong and or allow me to check that everything is working as
expected).
>
> All I can see is that the pump, a T valve, hot water and heating
panel (ONE
> UNIT), and thermostat (Siemens far too complex) are all connected
together
> somehow.
>
> As for the boiler... well it looks like it has its own electical
source (not
> found where the wire runs to yet.. loft somewhere) so I can only
assume that
> it turns it's self on when it detects water flow ? Do boilers do
this..
> bearing in mind mine is quite old
>

The trick with CH/DHW wiring is in the motorised valves.  When power
is applied, the valve opens.  But this movement operates a
microswitch in the valve, which is used to turn on the boiler/pump

My system has two 2-port valves - one for hot water and one for
central heating.  Each has four wires going to it - two to provide
power to the motorised valve (which stays open as long as the power
is applied), and two for the microswitch (contacts closed when the
valve is open).  If you just have one 3-way valve, the wiring will be
different but I suspect the same principles apply.

Please take care with the wiring - there's no low level signal
voltages anywhere - it's all 240V!  I got a shock of mine that left
me gasping for breath on the floor (through carelessness on my part).

You could also try posting questions to the uk.d-i-y newsgroup on
Usenet (or just do a Google Groups search) - they are in the middle
of the annual central-heating-questions-fest at the moment ;-)

Mal