I've just moved into a house that has a "Glow worm - economy plus"
boiler (in the kitchen), it also has a controller (in the kitchen -
see below for more details) and a temperature control (in the lounge).
I'd like to replace the controller, currently a Honeywell ST699
controller, unit was not marked with a model but I have looked at
several honeywell units and this seems the most likely.
With this I can program 2 on / off times or manually control the
central heating and the hot water.
I'd like to be able to set:
CH - on at 7am off at 8:30 am on at 5pm off at 10 pm
Hot water - on at 7am off at 7:30am
If I switch the CH to TWICE and the hot water to ONCE, then the hot
water is on from ON1 (7am) until OFF2 (10pm)
not ON1 and OFF1 !
I don't like the way that the hot water and central heating can't be
controlled independantly. Surely if I can control the system manually
then I can replace the timer/controller and have the functionality I
Could you suggest a suitable alternative controller that will give
more flexiblilty ?
Can I use a Honeywell ST6400C controller instead ?
Yes, this is a very useful feature. It basically allows you to set morning
and evening times, but fill in the middle on weekends or when you take a
sickie. It is very standard for programmers to work this way.
Why do you want to control the hot water independently? I normally stick
mine on 24/7. Modern insulation standards mean that you won't waste much
energy doing so. Also, if you have a gravity hot water heating circuit,
you'll be unable to turn off the hot water when there is a call for heat
from the heating circuit anyway. (You'll also get pitiful reheat performance
by modern standards).
P.S. the model you have looks identical to the one I've got on my old system
(shortly to be RIP, hooray!) However, mine seems to have a mind of its own
and doesn't seem to come on when instructed. Horrible thing. It is
particularly annoying setting the clock. It will only advance the minutes at
a grotestquely slow rate. I think it needs about five minutes to advance by
12 hours. Life is simply too short to bother.
If you are still convinced you want independent control, consider other
manufacturers too. I quite like the Horstman stuff, for example.
P.S. the link you gave had prices on the high side. Unless you get some sort
of discount, try (amongst many others) www.discountedheating.co.uk.
I'm not sure whether your system is fully pumped or not. As others have
said, if hot water is by gravity circulation, you're stuffed and cannot have
heating without hot water.
Lets assume that it's fully pumped in which case you will have a 3-port
valve (or 2 x 2-port valves) and a cylinder stat. I assume that the
temperature control in the lounge is just a room stat?
One possible solution to your requirement is to replace the room stat with a
programmable stat. You can than set your existing timer to switch the hot
water on and off at the times you wish - and switch the heating to
continuous (manual). The heating will then actually be controlled by the
programmable stat - which enables you to have different temperatures at
different times should you so wish, as well as being OFF when required.
Thanks for the replies.
After a bit of an experiment it seems I may have got this wrong :(
I thought that I could control the hot water independantly, but it
seems that I can switch it ON indepedantly, but if I switch the
central heating on then the hot water is on anyway...
It just seemed a bit of a waste leaving the hot water "reheating" all
day... and the water gets VERY hot... after climbing around in the
airing cupboard and ripping up a floorboard it seems my system is
setup a little differently than I thought... I thought I had one of
these Y designs that had a valve somewhere between the boiler and the
hot water tank, but the only thing I can find is the pump (above the
boiler).. no valves anywhere (unless it is under the floorboards in
Anyway, the hot water is very hot and I found the temperature setting
on the hot water tank, it's set to 70 deg C so I might lower that to
60 deg C.
Doesn't seem worthwhile ripping out the pipes and connecting a valve
and a new programmable timer.
Seems I have 3 options
1. live with it and see how much the gas bill is after winter.
2. get a combi boiler installed (can't really afford this at the
3. get a programmable stat (thanks for the suggestion, didn't know
Would this mean that the hot water would be on whenever the
programmable stat called for heat ???
Any ideas which stat I could use, the current one is an old brown
honeywell thing with no model number on (or in) it. I could take a
photo of it and the small wiring diagram that is on the inside of it,
and upload it on the web somewhere ??
P.S please excuse any typos, in a bit of a rush !
You may have gravity circulation. Could you describe the number and sizes of
the pipes coming from the boiler. You should have a gas supply pipe and two
pipes for the central heating. If you have two more pipes (possibly larger
than the others), you have gravity circulation. This is bad.
I'm still not quite sure whether your system is gravity or fully pumped. It
was beginning to sound like gravity - in which case you *can't* have heating
without hot water - except that you mentioned being able to set the hot
What sort of control is it which enables you to do this? Is is a thermostat
strapped to the side of the tank, with wires going to it? If so, it must be
controlling something - such as a 3-port valve or zone valve. Where do the
Alternatively, you could have a Cyltrol valve or similar in the return water
flow. This is purely mechanical, and works like the thermostat inside a car
engine - with an expanding bellows which cuts off the gravity flow when a
certain temperature is reached.
[Just a long shot - I presume you're not referring to a thermostat
incorporated into an immersion heater which, of course, would only have any
effect when heating the water electrically rather than with the boiler?]
If you can clarify this, we can determine what is or is not possible.
Join the club ;)
I've checked and I don't have an electrical immersion heater. Guess
you could have both... ?
Don't know why you would, but I haven't.
The boiler has 3 pipes:
1. thin (approx 10mm) pipe - marked "gas"
2. thick (approx 22mm) pipe - goes to the water pump then up into the
3. thick (approx 22mm) pipe - goes up into the airing cupboard
pipe 3 appears to have a drain tap on the end of it - is that for
draining the central heating ?
OK - I think we're getting somewhere!
The fact that there are only 2 water pipes going to the boiler - one of
which is in-line with the pump means that you have a fully pumped system.
The fact that the tank stat is electrical, and has a cable which disappears
under the floor almost certainly means that there is a zone valve (or
possibly a 3-port valve) hidden somewhere under the floorboards.
At some point between the boiler/pump and airing cupboard both your flow and
return pipes MUST split into two circuits - one for hot water and the other
for heating. On the return side, this is probably just a T-piece. On the
flow side, it is either a T-piece with a separate zone valve on each output
or a 3-port valve which incorporates the T and the zone control in one unit.
You have almost certainly got either an S-plan system (2 zone valves) or a
Y-plan (3-port valve). See http://content.honeywell.com/uk/homes/systems.htm
Either way, you appear to have the capability of controlling hot wat and
heating separately *including* having heating without hot water - provided
that it is wired correctly.
BUT, if you want them both to be timed but at different times from each
other, you need two independent timers - and the ST699 only has ONE timer.
This was why, in an earlier post, I suggested that you should consider a
programmable thermostat. This is a replacement room stat which switches on
and off with rise and fall of temperature but ONLY within the times
programmed into it. [Have a look at the CM31 or CM37 in the Honeywell
catalogue which you referenced in your message].
You can thus set the clock on the ST699 to switch on and off at the times
when you want hot water. You can set its heating control to continuous -
which means that the heating will be on whenever (but only WHEN) the room
stat says it should be. If this is a programmable stat, you can thus use it
to control both the temperature AND the timing of the heating. As I said
before, you will then be able to have heating *without* hot water - if that
is what you want.
Yet more info...
Operation "rip-up-the-floor-boards-n-have-a-butchers" complete ;)
Found a valve under my hall (upstairs) floor boards.
I have a Honeywell V4073A1039
The V4073A is a motorised Mid-Position valve...
is it 3 port ? ie 1 input and 2 outputs ?
pipe goes from boiler to pump to valve (port AB):
port B seems to go to the airing cupboard (HW tank) and then back
(with feed to bathroom & back bedroom radiators ???)
port A seems to go to the other rads.
Anyway, the (5 core) cable from the valve goes into a small junction
box and then down do the main junction box in the kitchen (next to the
But the cabling and plumbing (radiators connected to the HW return
flow - HW tank to boiler ???) seems very different from the pdf I have
from the Honeywell site, didn't have much time - I'll check it again
Can the V4073A give CH without hot water ?
The short answer is YES, as long as it's installed properly.
It is now clear that you have got a Y-plan (more or less).
The V4073 is indeed a mid position 3-port valve capable of providing hot
water only, heating only, or both together.
For this to work properly, there *must* be a Hot Water OFF feed from your
programmer, and your cylinder stat must be the change-over type - with one
input and two outputs. One of these outputs is live when hot water is
required, and the other becomes live instead when the demand is satisfied.
[You'll see what I mean if you look at the Y-plan wiring diagram at
The reason I said it was "more or less" Y-plan is that a couple of radiators
seem to be doing something different!
It is not uncommon for the feed for the bathroom radiator to be taken off
*before* the mid-position valve - so that the rad will get hot whenever
either or both of the hot water and the heating are on. In this way, your
towells get aired in the summer when the water is being heated even when the
heating is off. Is this what you've got?
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