In an earlier contribution to this discussion,
JH wrote:
Hi,
I'm preparing to add a room stat to an existing gas central heating
system and need some help with the installation.
The current system consists of
o Boiler: Ideal Elan 2, conventional fan assist gas boiler
o All radiators have TRV's
o Timer is a Horstmann 527 (electronic 7 day, 3events/day, for
independent heating and water control)
o Based upon the FAQ, I believe the system is a Type C or S-plan
installation
o There a two motorised valves
I've taken a couple of photos of the controls to help (which are
located with the hot water tank - a bit unusual, oh well)
timer.jpg - http://www.jjh1.demon.co.uk/timer.jpg showing the timer
rest.jpg - http://www.jjh1.demon.co.uk/rest.jpg with all the other
controls, including a wire box with its cover off.
I'm planning on adding the Danfoss TP7000-RF + RX1 7 day wireless
programmable room thermostat.
The main unknown is how to wire the unit into the existing system.
Logically it appears straightforward i.e. simple wire AC power to the
RX1 and then the boiler off/on/com wires in series with the timer and
that's it.
So to the questions
1. Any opinions, good or bad on the Danfoss TP7000-RF + RX1? I was
thinking of buying from
http://www.rkm-heating-controls.co.uk/danfoss.htm , any other places
worth a try?
2. What is the correct way of wiring the receiver to the mains.
Do I simply add the live and neutral terminals in the existing
wiring box in the picture above (rest.jpg)?
3. I have no installation manuals for the boiler or existing timer
unit so I don't know which three wires are on/off/con for the heating.
What's the best way of deducing this information (I've got a
Maplins multimeter to hand)?
BTW - I've had the timer unit off the wall and it has the following
legend for each terminal on its back
Off C ON OFF C ON L N
4. Once I know which wires are on/off/c for the heating, how do I
correctly wire the unit in series with the timer?
Many thanks in advance
Jules
If you have a conventional S-Plan system (and you appear to have the right
ingredients for this) it works as follows:
The motor in the HW zone valve is controlled by the HW demand from the
programmer and the cylinder stat, wired in series.
The motor in the CH zone valve is controlled by the CH demand from the
programmer and the room stat (if any), wired in series.
Additional "volt-free" contacts within each zone valve, which close when the
valve is open, are connected in parallel with each other between a live feed
and the boiler/pump demands. Thus the boiler and pump operate whenever
either or both zones valves are open.
In your case, there is no room stat at present, so the CH demand from the
programmer goes straight to the zone valve motor. You need to intercept this
wire, and connect the switching end of your room stat in series with it. You
should be able to do this all within the airing cupboard - provided this
will give you adequate radio contact with the programmable/display end of
the stat.
You should be able to trace the cables ok with your meter. In the programmer
there are 2 changeover switches - each with C, On and Off. There is very
likely a mains feed to each of the C terminals. The CH On terminal will
become live when the CH is turned on, and likewise the HW. Neither Off
terminal will be connected.
Incidentally, you should really replace the TRV on the rad in the room where
the roon stat will be with a conventional valve - otherwise you'll have two
independent control mechanisms which will fight with each other. For
example, if the TRV cuts that radiator before the room is up to the
temperature set on the stat, the stat will never operate and the system will
just run contnuously, as at present.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!