The "diverter valve" has gone bang on my mum's central heating system
and we are told that it is obsolete.
The system looks very much like a modern Y plan system - fully pumped, 3
port valve, separate timed control of heating and hot water, etc. The
only difference from a modern Y plan system is that the wiring box
contains a relay.
The plumber is being useless, so I may have to do the work myself, it
should be a straightforward task to replace the "diverter valve" with a
modern 3 position valve and replace the wiring centre with a modern one
without the relay.
The tedious bit will be identifying all the unlabelled wires coming into
the wiring centre - a task which would be made a lot simpler if I had a
Does anyone recognise the description of the system and have a wiring
diagram they could scan for me (or point me to one on the Internet). The
system is of mid 70's vintage (1976 or 1977 I think) and the diverter
valve and wiring centre are made by Satchwell. Unfortunately I am unable
to see any part number on the diverter valve.
Can't help with original wiring diagram, I'm afraid. But surely, there can't
be *that* many wires? There should be wires going to:
* Room stat
* Cylinder stat
* Diverter valve
Unless you're very unlucky, some of the cables will be different colours
and/or sizes or number of conductors from the others - so if you see what
they look like at the remote end, you can probably identify most of them at
the wiring centre end. Failing that, you'll have to disconnect them at both
ends, short live to neutral at the remote end of each one in turn, then use
a continuity checker at the wiring centre end.
What you're aiming at when you re-connect everything is a standard Y-Plan
setup as per
http://content.honeywell.com/uk/homes/systems.htm (scroll down to Y-Plan).
The only slight change to this would be if the boiler needs pump over-run -
which is unlikely if it's 30 years old!
Things to watch are that the programmer must have a HW OFF connection and
the cylinder stat must be the changeover type, with 2 connections. It's just
possible that the existing ones don't - and that the relay does what they
would otherwise have to do.
As a follow up to my previous post I have put a couple of pictures of
the diverter valve on a webpage in case it helps jog anyone's memory.
That is true and I have some idea of how it is all connected up because
I spent a very happy half term week at the age of 10 watching it all
being installed, however I do recall that the "professional" who
installed it wired everything up with multiple lengths of identical 3
Hence all the cables from the boiler, programmer and room stat look
identical at the point they enter the airing cupboard.
Working it out will be straightforward, however it would be much quicker
and much less tedious with a wiring diagram.
I'm pretty sure it does. There are certainly more than 3 wires going to
A good point, which hadn't occurred to me. Those are also things that a
wiring diagram would help with (I should point out that I don't live
particularly close to my mum so I can't just pop over there to have a
look). What I am hoping is that I can just turn up on Sunday with a 3
port valve and wiring centre and wire it up so that at the bare minimum
she has heat that she can manually switch on and off.
On Wed, 12 Oct 2005 21:55:44 +0100, Martin Wiseman wrote:
Quite a few of the wires will lead to nearby items. E.g. cylinder stat,
pump. The incoming mains should be easy to identify.
The boiler and pump may well be in parallel so easy to find.
The relay might simply be there because the programmer/timer does not
provide and HW off signal.
The remaining wire(s) will be to a room and/or frost thermostats.
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
This is an old Satchwell system - now 'Sunvic Controls Ltd'. Th
actuator is still made - part no DM5601, the valve body is an MK145
and you can still get a replacement circuit board and relay for th
junction box part no RJ2801. Phone the Sunvic helpline on 0169881094
for more info and a wiring diagram. If you fit a standard 3 port sprin
return valve you will need to replace the motor unit and the valve body
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