'conventional' boiler. Basic timeswitch on h/w, wireless digistat on heating.

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Christian McArdle wrote:

Right. NOw you've lost me. Where can i find out what an 's' plan system is? Why do i need a cylinder stat if i dont have one at the moment?
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By the sounds of it there should be a cylinder stat, if there isn't one it would be required to modulate the hot water temp. If you don't have one at the mo you wont really see any benefits by having efficient heating controls if the rest of the system is innefficient. If you're thinking of entirely rewiring your heating system I would have thought you would be able to tell what sytem you have. If it is an S plan there should be the boiler flow coming into the airing cupboard, through the pump, then teeing into two valves. The outlet of the heating valve will go into the heating flow. The outlet of the water valve will go to the HW tank.
SJW A.C.S. Ltd.
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Lurch wrote:

The boiler, cylinder, pump and valves are all located in a large airing cupboard on the first floor. The piping and wiring are complicated by the addition of a large pump for a power shower in an en suite that takes a seperate feed off the tank - there are a lot of pipes and wires in one place!
Is there anywhere i can get good wiring/plumbing diagrams and an explanation of 's' plan for reference?
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wrote:

http://content.honeywell.com/uk/homes/systems.htm
There are more tech notes if you poke around on the site. .andy
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If you dont have a cylinder stat at the moment, my guess is that you have gravity H/W. i.e. Your pump only drives the Central Heating.
In this case you will always generate H/W when the C/H is on,
Typically the boiler is supplied with power whenever the time switch is on. The boiler starts whenever the water temperature falls below a certain point. The room thermostat controls the pump, i.e. the room thermostat supplies power to the pump whenever the room temp falls below a certain point.
If you just replace the room stat with a programmable one, you will have to leave the boiler on all the time and therefore generate hot water all the time.
You could avoid this by either:
a) Fitting a Danfoss Randall TP9 Programmer/Room thermostat to replace both your current programmer and room thermostat. Possibly very easy to install as you may well be able to use existing wiring. Less than 60 from plumbworld. The TP 9 allows six room temp changes and two on periods per day for H/W. Can be set to use a different program at weekends.
b) Fitting a H/W tank stat and zone valve with micro switch (Honeywell C plan). Requires plumbing work. Arguable a better solution but you need to be careful plumbing wise to be sure that you boiler wont mind having is ability to circulate water naturally restricted.
c) Using and additional relay to supply power to the boiler when the pump is on.
Option a) can be upgraded to option b). Nothing would be wasted.
Michael Chare
all the time the time
powered up all the time
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On Wed, 14 Jan 2004 23:12:44 +0000 (UTC), "Michael Chare"

If you would care to read previous posts you would note that;
a) there are 2 zone valves already installed, so that puts gravity out of the question.
b) there is a cylinder stat etc... (see a))

Already sorted that I think, wireless would guarantee no wiring would be needed in addition to the stat.

If it were me who asked the original question I would ignore all of this as irrelevant or incorrect.
SJW A.C.S. Ltd.
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it
valve
Maybe I have paid more attention to the O/P's statement that he does not have a Cylinder stat than to your argument that he ought to have one.
Michael Chare
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--

Regards

Michael Chare
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not
At which point I become confused again. I do have a cold water tank in the loft - i was under the impression this was a sign of a gravity fed system? I'm coming to the conclusion that it might be time to get a heating engineer in - having owned combi's for the last 10 years i'm rusty on everything else.
AJ
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Think a gravity system is where the hot water circuit isn't pumped. If you've got motorised valves etc, it probably is.
--
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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On Thu, 15 Jan 2004 23:44:44 +0000 (GMT), Dave Plowman

You can have a C plan set up where the boiler/DHW cylinder circuit is gravity (meaning convection) and a zone valve and thermostat are used to prevent the hot water from overheating.
.andy
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Hence my use of 'probably'. I'm sure it's possible, but I've never seen it.
More common was a sort of TRV to control the water temperature, rather than just the boiler stat.
--
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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