Folks,

Seeing as this is the right time of year to attempt DIY on our Central
Heating without freezing to death, I thought I'd delve into a little
project to upgrade our system.

The house that we bought towards the end of last year has a CH system
that could only be described as 'crude' at best! The boiler is in the
garage, and sports a gravity hot water system, with pumped central
heating. There was (until recently), a naff old Randall 102
timeswitch, which totally failed to either keep good time (typically
losing up to 1 hour per day) or to switch on/off at the defined times.

So, phase 1 of my upgrade project was to replace the CH programmer. I
chose an ACL Drayton unit, a Tempus 7. Good programmer, looks much
better, and with jumpers set correctly, behaves as I would expect -
i.e. allowing HW control on its own, or CH AND HW together (turning on
HW pulls up the CH also).

But here's the weird thing: our CH cylinder also has a tank 'stat, but
there are NO motorised zone valves anywhere in the system. Now this,
to me, is rather odd. I also stripped and rewired the 'wiring centre'
at the same time; as all the power to the boiler in the garage was old
and flaky, I have installed a double socket, a fused spur (with
appropriately rated 3A fuse) and a 'wiring centre' which in this case,
is a blanking plate over a ton of cabling in a flush-mount box,
suitably earthed!)

As far as I can tell, the mains from the fused spur feeds the timer.
The 'HW On' signal from the timer goes via the Cylinder stat and fires
the boiler if the Cylinder stat says 'Go!'

The 'CH On' signal from the timer goes via a Room stat in the living
room, and fires the water pump, if the room stat says 'Go!'.

To cap it all, there's a Honeywell Frost stat in the garage, which
connects the boiler directly to the mains, if the temperature drops to
+5 deg C. In this circumstance, this ensures that the boiler always
fires, if the Frost stat says 'Go!'....

So my questions are as follows:

1. The Drayton Tempus 7 seems like a good choice of programmer. But
there's also a similar model, a Lifestyle LP722, which seems similar
BUT it does have a fancy-looking backlit display, which might look
funky in the dark! Are there any differences between these two 7-day
programmers? Recommendations?

2. I'd like to replace the crusty old Honeywell room 'stat in the
lounge with a new Programmable Thermostat. But is there any point now
that I've installed the Tempus 7 programmer?

3. Should I install a pipe-stat as well as the Honeywell frost stat in
the garage, to protect the boiler? Or would this be unneccesary with a
properly installed Room stat in the living room (probably still
required for boiler protection, I guess).

4. How the hell does my HW system manage to regulate its temperature
without any zone valves? The Honeywell Cylinder stat certainly seems
to be doing something....

5. Can I bang a 2-port motorised valve into this system to upgrade it
to a C-plan? I understand that there are venting safety issues with
doing this.. FWIW, the Water Pump is sited directly beneath the boiler
in the garage.

The whole thing really does seem like an odd bodge, although I'm
guessing that I could upgrade it to a properly split CH/HW system,
with a bit of extra effort.

All advice would be welcomed, particuarly around the Programmer /
Digital Room stat issue.

Cheers all,

Big Al.