"Christian McArdle" wrote in message
. net...
The best is what I explained. Individual
control in all rooms and a flow switch to
act the "interlock". The regs state "or other
device such as a flow switch". "Any other
device" are the key words.
Reasonable, but not best, surely.
Not the best of course, but cheap and effective individual control in each
room. The best will be complicated and expensive.
Although you get individual temperature
control in each room using that method,
it is better to have individual time
control in each room as well, as rooms
in a house have very different usage
profiles.
This is true, but expensive and more complexity.
This could be done with seperate
programmer thermostats in each
room, which could drive conventional
2 port valves with microswitch boiler
interlock,
A CM67 and zone valve for each room? Nice but expensive.
or modified TRVs that take a control
signal, with boiler interlock provided by
flow switches,
Very expensive as a controller will be required to mosulate the TVR valve,
and then a timer for that room too. Ouch!
or the logically ORed
outputs from the programmers.
The second approach (i.e. logically
ORed outputs) gets past the problems
associated with flow switch interlocks,
which although good at stopping the
flow, aren't so good at noticing that
TRVs have opened again without pulsing
the pump regularly.
That is why you use an Alpha pump.
(Obviously an automatic bypass valve
is essential if the interlock has the
possibility of not corresponding directly with TRV
position).
I suppose you could combine the two
methods and pulse the pump when the
logical signal indicates the valves should
be open (given a minute's delay
for the TRV to respond). That way, the
interlock operation might be more
reliable in the event of a TRV's failure to
respond to its signal, but will
prevent pump pulsing when the system
"knows" that no heat is required
already.
You are delving into the realms of commercial systems, where say a large
conference room would have its own controls. In a domestic house? Not
likely.
The cheapest and more practical is what is suggested: Alpha pump, by-pass,
flowswitch and TRVs all around. Then split the system into two zones,
probably up and down, using a stat/programmer in each zone and one zone
valve. Cheap, easy, simple, economical to run and will satisfy most peoples
needs.
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