Valves

[Roger Mills]

No, because the two zones are still independently controlled by timers and stats - even if one zone combines this in the form of a programmable stat. [In fact, one of Honeywell's application notes describes just that - "S-Plan with programmable room stat".]

It may be splitting hairs but I see a distinction between that and a system which suppresses the feed to one zone until the demand of another unrelated zone is satisfied.

Surely, it's implicit in the word "independent".

I think perhaps it's time to call it a day. The OP - if he's still watching! - must be thoroughly confused by all this!

[Andy Hall]

There is a distinction of course, but it isn't excluded from Honeywell's spec.

The controls remain independent. The timer(s) control the operational times and the thermostats control the demand for heat,

The additional part is that if there is demand for CH *and* HW because of the time range and the temperature, then the valve for the HW will open and the CH one will remain shut until the either the HW thermostat is satisfied or the HW on time expires.

Even before this, controller logic has been improved. For example, optimised start is increasingly commonplace. Thus if I set the controller to 21 degrees and a start time of 0700, it computes approximately how long it will take before the house is up to the setpoint temperature and start the boiler earlier to achieve that. Now the boiler is starting at a time earlier than that set.

It's simple enough. With the controls integrated in the boiler, wiring and operation is very easy.

[Ed Sirett]

When a motorized valve cost was about the same a say a half day's labour. It made some sort of economic sense to fit one valve which took a bit longer to fit.

Now the valves have come down in price (there under £20 in the BES catalogue - Honeywell compatible), and the labour for 1/2a day has gone up a lot. The whole balance is in favour of using 2 or more valves.

[Si]

Do their new SmartFit plans have any real advantages?

[John Rumm]

This is true for three port diversion valves. A three port mid position valve will also allow both to run at once. This is a better proposal for slow recovery cylinders since it does not divert the heating for too long.

[Rumble]

Well, it's an aide-memoir for installers...

Y is an "icon" for a 3-way mid-position valve.

W is an "icon" for a 3-way diverter valve.

S stands for "separate" HW and CH valves.

C stands for "convection" (i.e. gravity) hot water.

HTH

[John Rumm]

Yup, makes sense to me... I had worked out that Y and W were pictographic, but was struggling with S and C!