RE: Re: [OT] ishh central heating controls

["LeeUKHA" <mailinglists@xxxxxxxxxxx>]

Mal is quite right, it's all down to the motorised valves.
The programmer just tells the valve(s) to open, these tell
the boiler to fire and the thermostats can cut the boiler
off when they get too warm.

A two x two way valve system (called an 'S plan' system) is
very simple to follow, the one x three way valve system (called
the 'Y plan' system) is just really stupid imho...

As well as a 'heat the house' wire and a 'heat the water' wire,
there is a 'DONT heat the water' wire coming from the controller.

Here are the sites I found (no connection etc) that explained
what was going on...

http://www.gas-news.co.uk/feature12.htm
print this one put & make notes
http://www.gasman.fsbusiness.co.uk/wiring.htm
scroll right down...
http://www.tlc-direct.co.uk/Technical/DataSheets/Horstmann/Pics.pdf
http://content.honeywell.com/uk/homes/FAQ/v4073aop.pdf

Using Ians idea, I'm now going to install the HA kit into the airing
cupboard where the central wiring box is. However due to the
'DONT heat the water' wire and the need to have SWMBO manual control
of the one hour boost, I haven't yet figured out how to wire the
HA into the existing wiring and still have manual control.

Anyone have any ideas?  As I see it, the 'DONT heat the water' wire
from the controller would override the 'heat the water' from the HA,
so I think I'm going to have to install a bunch more stuff to sort
it out...

Lee



>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.


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