Central Heating Zoning controls (was Are room thermostats out of fashion?) longish question

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Co-location is impossible. They are programmable room thermostats. They won't sense the right temperature if they are in the wrong room. I suppose you could use a multi-channel programmer and straight room stats. However, this would cause many disadvantages. Firstly, this system doesn't allow different temperatures at different times of day. Secondly, manual override (i.e. boost/advance) buttons will be in a dark cupboard under the sink with bottles of bleach in the way, rather than on a convenient well lit nearby wall.
Christian.
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On Wed, 17 Dec 2003 13:00:05 -0000, "Christian McArdle"

Oh do shut up ;-) I thought the OP had mentioned RF devices, so was presuming he was putting the sensors in suitable rooms, with the actual programmers nearer the (um, let's see) zone valves, I guess. They don't *have* to be next to one another, but it would be simpler if they were.
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On Wed, 17 Dec 2003 13:00:05 +0000, Christian McArdle wrote:

I agree the idea of a master switch is well useful for maintenance if nothing else.
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Ed Sirett wrote:

I am pretty sure its mandatory - my whole heatng system is run off a big switched fused spur with its own neon and switch bang next door to the controller and very near the boiler. I thought you had to do this with all boilers extractor fans etc etc.

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In an earlier contribution to this discussion,

Yes, you need an isolating switch for the *whole* system - but that's not the point! This discussion is about turning off a multi-zoned heating system *without* also turning off the hot water.
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On Thu, 18 Dec 2003 01:12:12 +0000, The Natural Philosopher wrote:

I am not suggesting that the programmer replaces proper DP isolation. I'm talking about, say, you want to diagnose the boiler, you are testing it out live but want to be sure you don't have a CH demand only a HW one.
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But then, that would be entirely different. The propsed switch only turns off the central heating side and certainly doesn't isolate anything. The boiler should remain powered.
Obviously, some sort of DP isolation should be provided to the entire system, too. I've ended up with two DP isolators on mine. The boiler and cylinder are in the loft. The heating zone valves and programmer are in the understairs cupboard. I have a DP isolator in both locations, both of which isolate the entire system.
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On Wed, 17 Dec 2003 12:36:21 +0000, John Laird wrote:

I over-hauled a large heating system last year. 4 Heating Zones and DHW. All this used a Keston C40 which has seperate temperature control for heating and HW. It is true that for a short while the boiler output is at a higher temperature whilst the tank is being reheated.
However the extra heat in the radiators is not a particularly big problem and is further minimized by the fact that the water circuit for the DHW coil is very much lower than for the radiator zones. (Short run of 22mm pipe right off the 28mm main manifold). This means that very little water is inclined to go through the radiator for the 10 minutes (typically) whilst the tank is reheating.
Another way would have been to use a large 28mm 3 port diverter valve with DHW priority which would kill the heating during DHW reheat. However experience shows that some people like to turn the heating & HW off if the go on away in winter and resent waiting the _entire_ cylinder reheat time say 25mins (170 litre, nominal 14kW coil) before the radiators _start_ to heat up.
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Christian McArdle wrote:

Have I missed somethinhg here?
My three way time controller has buttons that switch off any of its three zones?
Completely. No thermostats or valves are energized.
So no pump and no boiler.

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The proposal is for programmable room thermostats and no overall programmer, just a switch to turn off the entire heating system (except HWC).
Obviously, a 3 channel programmer with non-programmable stats is a different system, also with an easy way to totally turn off the heating. However, it doesn't allow a local button for override/boost and doesn't allow different temperatures at different times of day.
Christian.
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P.S. I don't see the point of not having a programmer instead of a switch. You probably need one anyway for the hot water side, and a twin channel isn't much more than a single channel. I suppose some people would find it simpler to operate a switch, given that the timing function is unlikely to prove useful.
Christian.
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Christian McArdle wrote:

Fairy nuff. Sounds amusing enough.
I am going to radically side with a single IMM comment, that circulation hot water through fan convectors does a fair job of heating without the fans on.
If you are really picky, fit a motorized valve.
I can;t answer for teh Kickspace, but my 'vectors had no balancing valves. These are manadatory to stop them hogging CH flow. If you have a motorsized valve per convector that may not be such a problem - since hey will hog till the romm warms up only.

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Well I was always going to install at least one valve, shared between the two. However, I'm leaning towards installing two now. The main objection to having two was aesthetic anyway.

Well, I'd prefer a proper balanced system anyway even if fully valved. I was intending to install balancing valves if none were fitted. The technical specs don't mention it, but do say what flow rate you need through them to get full power, with the obvious implication that you should throttle them down to that if you want anything else on the system to work.
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On Wed, 17 Dec 2003 09:56:38 -0000, "Christian McArdle"

I see what you're saying....
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wrote:

I installed a Honeywell CM67NG RF recently. It has an 'off' setting on the programmable thermostat part - which is not really off but a user-selectable frost-free setting which is 5 deg C out of the box, IIRC.
Neil
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In an earlier contribution to this discussion,

Sure - but the earlier discussion related to a system with 2 or more heating zones, each controlled by a programmable stat. So you would have to turn each of these off rather than doing it in just one place. Also, I'm not sure that with some programmable stats you can effectively turn it permanently off with disturbing the other settings. Maybe you can?
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You can, because the programmable stat part is battery powered, whereas the receiver/controller part is wired into the boiler control system. If you power of the boiler it removes power from the receiver/controller (which actually decides to turn the boiler on/off) but the thermostat itself is still on.
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