Conservatory heating - how to 'zone' extended CH radiator?

Hi Set Square, Lurch et all,

OP here, many thanks for all your helpful posts!

Set Square, your post at 17:16 on Oct-01 was very helpful thank you, in particular your reference to the honeywell site was really usefull. I've studied the wiring diagrams and that side of things is fairly clear now. In order to further my education, a couple of questions spring to mind if I may be so bold...

(1) Why is S-plan favoured over y-plan? Y Plan seems to be considerably cheaper to implement (assuming a changeover stat is not overly expensive) and neater (ie less clutter under the boiler and disruption to pipework). Also, regarding failures, the Y plan is never 'closed' so no chance of the pump being activated when both circuits are off. (Clearly the boiler has a bypass if the above were to occur on the s-plan). I guess I must be missing something here.

(2) What is a changeover stat?

(3) Why can the motorised valve(s) not be installed on the return rather than the flow?

BTW, I don't have TRVs on any of the rads. We have lived in this house for a year now and the system seems to hang together quite nicely without them. In addition, most of the rads have microbore into 'same-end' rad valves and I don't think I've seen TRVs in that configuration before.

Thanks all

Mike

Reply to
Army
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The actuator used used on a 3-port mid-position valve is quite complicated in terms of internal components and micro-switches and is prone to failure. [A high percentage of central heating problems discussed in this NG can be laid at the door of the 3-port valve!]

By comparison, a 2-port valve is simpler, and less prone to fail - and also doesn't represent a single point of failure for the whole system in the way which the 3-port valve does. In addition - maybe not of interest to you - it's easy to extend an S-Plan system for multiple zones - whereas a Y-Plan system can only handle 2 zones, one of which is *usually* hot water.

Sure, an S-Plan system may require a by-pass - but that's easy enough to implement with an automatic by-pass valve. You may, in fact, also need one on a Y-Plan system if you have TRVs on all (or virtually) all rads because - although the valve always provides a path, this may be closed off by TRVs.

Its a stat whose switch has 3 contacts - common (COM), normally closed (NC) and normally open (NO). At temperatures below the stat setting, COM is connected to NC. When the set temperature is reached, the contacts 'change over' so that COM is then connected to NO. So, instead of simply switching off when the demand is satisfied, it directs the input voltage somewhere else instead. In a Y-Plan system, the cylinder stat - in one position - switches the boiler directly. In the other position, it supplies power to the 3-port valve - enabling that to switch the boiler via one of its internal micro-switches when the conditions are right.

As far as I know it can. Did someone say it couldn't?

Good luck with your conservatory!

Reply to
Set Square

Isn't it because the flow is supposed to go into the centre port. So if you join two returns back into one the valve is working backwards. Doesn't this make them liable to stick as the flow is working against the springs/actuators?

Maybe the OP didn't mean joining two returns into one?

If you going to use valves use 2 port ones with end switches. Then the whole thing is much easier to wire. You just parallel up the end switches, connect one side to a live feed (not the output from the stat!) and the other to boiler on. Then you connect the thermostats for each zone to the motor on the valves. You can put a timer in series with each stat if you want (that's all a combined timer+stat is).

There are two types of 2 port valves.

The most common are spring return.. these open when you power the motor and close when you stop powering it.

The other type needs power to close and uses a changeover stat to provide power to open or close as required, this looks complicated but it isn't. (It can save electricity but not a lot and it needs two live feeds from the stat.)

BTW the plans are there because most *plumbers* wouldn't be able to do it without the plan but its all basic logic really.

Reply to
dennis

OK, S-Plan it is then. The only downside to me is that, as both valves will be living in the space between the (wall mounted) boiler and the kitchen worktop, I may have to redo my nice neat boxing in to create some more space. The boiler has an automatic bypass within the casing and in any case, there are no TRVs on the system at all. I suppose that the cost difference between 2 2-port valves and 1 3-port valve is pretty insignificant in the grander scheme of things.

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2, on the right, about half way down. I just noticed that this is refering to the Y-Plan. The S-Plan makes no mention of this limitation so perhaps S-Plan is OK to fit on the return.

Thanks!

Mike

Reply to
Army

In article , Army writes

If you get honeywells (2port valves) then they are quite slim and fit well together, my system is multizone & I separated them by just 65mm (pipe centres) but staggered them lengthways by 150mm to make servicing easier. As the third pipe on the 3 port comes out at right angles I think it is just as tidy to have 2 x 2 ports. Buying honeywell means that spares will be available for longer than you have the house and buying 22mm will be cheapest due to sales volumes with prices usually cheapest on-line.

A well set up system can often get by happily without them and you're right, same end valves would need a conversion to opposite end for TRVs.

Reply to
fred

formatting link
> Page 2, on the right, about half way down. I just noticed that this

Well, that's pretty definite! It is certainly *usual* to install the valve in the flow pipework. However, I can't see any obvious reason why it wouldn't work on the return - but it's clearly best to stick with Honeywell's directive.

I don't think it matters where you put the 2-port valves in an S-Plan system as long as they don't block any vent path from the boiler to the F&E tank in a vented system - unless anyone knows otherwise, of course!

Reply to
Set Square

Thanks all,

I think thats all pretty clear now. Just that small matter of building the conservatory and I'll be able to put this into practice!

Cheers!

Mike

Reply to
Army

The inside temparature is very unlikely to be as low as the outside temperature. It is only so here when the aircon is running.

Reply to
<me9

You're right to have doubts. Just read back through a few of his previous ramblings.

MBQ

Reply to
manatbandq

Which one is causing you concern?

Reply to
dennis

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