In an earlier contribution to this discussion,
mike ring wrote:

"Set Square" wrote in
:


The boiler input and output will be at virtually the same pressure.
The output of a pump will be at a higher pressure than the input -
and this pressure will be dissipated by the resistance of the
particular circuit. If only one pump is running, all points on the
other circuit are going to be at the same pressure (ignoring static
pressure differencers due to height differences) - so there's
nothing to induce any flow.

It's that "virtually" the same pressure that was worrying me - the
circuit looked so much like an electrical network I nearly started
using Kirchoff and Thevenin on it! I was certainly taken back to
backdoor circuits and steering diodes - and it _does_ have nonreturn
valves.

Seriously, do you have any thoughts about the system; It doesn't seem
all that dear at the moment, comes with the wiring centre, and in
priciple looks better to me.

But I'm extremely inexperienced, in faact, when iit comes to
upgradeing cylinders and CH - none at all

mike

You really don't need to worry about cross-talk between the circuits - it
ain't going to happen. If it really does have valves to prevent gravity
circulation, these will prevent anything moving in the circuit whose pump
isn't running, and it should do exactly the same job as an S-plan system.
Ignoring costs, I would see the pros and cons relative to S-Plan as:

PROS
* Less individual components to accommodate and install - since it doesn't
need zone valves or a by-pass loop - (but it *does* need the anti-gravity
valves)
* Failure of one half of the pump would still enable the other circuit to
operate (but there would be no pump-over-run if the HW pump failed)

CONS
* The pump and control centre are proprietary, and cannot be replaced by
generic components in the way that S-Plan components can
* You have to have precisely two circuits as opposed to S-Plan, which can
(in its S-Plan-Plus form) accommodate unlimited circuits by the addition of
more zone valves - enabling (for example) separate control of upstairs and
downstairs radiators

You pays your money . . .
--
Cheers,
Set Square
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