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.

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?

Any programmer would do. To be frank, most modern systems could work with a
couple of switches. A modern lagged cylinder can be heated 24 hours day. A
programmable thermostat will handle timing for the heating zones. I fitted a
programmer to mine, but only ever select "Off" or "24H". I have a cylinder
stat, heating the cylinder 24/7 and 3 (shortly to be 4) separate heating
zones with their own programmable thermostats.

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?

Yes. Programmable thermostats have advantages that can't be replicated by a
standalone programmer. The advantages include convenient access (i.e. living
room), ability to set a nighttime temperature (i.e. 10C, rather than -273C)
and anticipation of switch on time (i.e. coming on early if it is
particularly cold).

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).

You might as well. However, it is particularly important to lag the CH pipes
to the garage. Better still, replace any metal with plastic, as it is less
prone to freeze damage.

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....

Well, it is a simple upgrade. It isn't foolproof, but is a massive
improvement on a system without the stat.

Basically, with the CH On and the room thermostat activated, the hot water
will get heated anyway (and might get too hot). However, in the summer, with
the CH Off, the boiler will only fire when the hot water cylinder is cold.
This will MASSIVELY improve fuel efficiency and maintain the hot water at
the selected temp. Fitting the extra zone valve (or pump) will improve
efficiency further and prevent overheating of the water when the central
heating is on. It would improve efficiency still further to pump the
circuit, if possible.

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.

Yes you may normally. However, this may be dependent on the boiler. Some
boilers require an open gravity loop for heat dissipation, which precludes
using a valve. This isn't very common in gas fired boilers, though.

All open vented boilers require an open unvalved path from the boiler to the
vent. Most will also require an open unvalved path from the cistern outlet
to the boiler not shared with the vent path. What options are available to
you depend on your boiler and its safety features.

Christian.

In an earlier contribution to this discussion,
Alan Dempster wrote:


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?

Sorry, I've only used Honeywell.

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?

It depends on whether the Tempus 7 provides independent *timing* control
over HW and CH - and whether you want this. Many programmers only
essentially have one clock. If you have a programmable room stat, you can
set the Tempus 7 to provide "continuous" CH - and can actually control when
the CH comes on and off with your room stat. This can be at different times
from when the HW is on, and you can have different temperatures at different
times of the day. A programmable room stat also acts as a frost stat in its
"off" position.

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).

With the boiler being in the garage, this could possibly freeze up before
the frost stat in the house turns the system on. Maybe *just* a pipe stat -
wired to bring the boiler on when the pipe falls below (say) 5 degC - is all
you need to protect the boiler itself. Your programmable room stat will
protect the rest of the house.


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....

In a half-hearted way? Someone appears to have attempted to provide a boiler
interlock, but has only done half a job! In HW-only mode, the boiler will
turn off when the HW gets up to temperature. However, in CH mode, the HW
will get hotter than the cyl stat setting whenever the boiler is on.

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.

Presumably you have a vented system, with vent and fill pipes connected into
the HW circuit near to the cylinder? You should be ok if you can insert a
2-port zone valve in the the HW flow pipe very close to the cylinder,
*after* the vent pipe connection - thus continuing to provide an
unrestricted path from the boiler to the vent.

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.

You might be able to convert it to an S-Plan system if you can pump both
circuits and insert another zone valve in the CH circuit. Are there
currently 4 boiler connections - with separate circuits for HW (gravity) and
CH (pumped)? If so, you'll either need another pump (and the control logic
then gets a bit complex!) or you'll need to reduce the boiler connections to
3 - by tee-ing the CH flow pipe into the HW pipe a little way from the
boiler rather than leaving it directly connected. You can then put your
(single) pump in this common bit of pipe before the tee. You can keep the
separate return connections.

With 2 zones valves cutting off *all* flow, you *might* need a by-pass
circuit - but that is unlikely with a boiler which can survive with a
gravity system.

HTH.
--
Cheers,
Set Square
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In article , Alan
Dempster wrote:
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?

I put a Lifestyle in for my mum last month, and it seems fine - three
on/off times each day, (except on the cheapest model) run heating and
hw programs independently of each other.

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?

For myself I've got 2xHoneywell CM67's controlling my heating (2 zones)
- far more flexible if you take time to learn what the different
buttons do. You can do things like having a overnight setback
temperature for cold nights or kill the heating for five hours if
you're going out.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm