On 2007-12-26 12:12:07 +0000, "Roger Mills" said:

In an earlier contribution to this discussion,
Andy Hall wrote:


According to Honeywell's specs. the requirements are listed above.

What if the controller is a PID type with automatic learning and
prediction of heat requirement? Does that mean that it's not S-plan
any longer because it's not the T6360B1028 Room Thermostat listed on
the web site.


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.

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




Honeywell's description of S-plan says:

"The Sundial 'S' Plan is designed to provide independent temperature
control of both heating and hot water circuits in fully pumped
heating installations. Time control may be provided by a time switch
or programmer."

It says nothing about whether or not one can be given priority over
the other.

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

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.





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!

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