In an earlier contribution to this discussion,
Clive wrote:

Hi,

My immediate problem is no DHW.

I have searched this group and I think I have the following CH/HW
setup

1.“Conventional” gas boiler i.e. Feeds a (poorly) lagged copper
cylinder via an indirect coil from the boiler
2.Supplementary electric immersion heater in HW cylinder
3.Two 2-port ACL Lifestyle valves controlled by the Honeywell
controller
4.Various water tanks in the loft

Now, various pipes connected to the HW cylinder are scalding hot
but the HW delivered at the taps is tepid.

I am thinking the 2-port valve on the HW side has failed. I haven't
yet traced the various water pipes and I need to study more about how
such a system is connected and should operate (and fail) but I need
help on the following.

I am guessing I can determine if the problem is a failed motor /
valve by “forcing” the valve open while the HW setting on the
controller is on. Now, the problem is, I can't find any online
information about the ACL Lifestyle valve. Does anyone know these
devices? There is a little black “switch” on top of each valve – I
would have thought this was a manual override to open or close the
valve but the bit of plastic just “waggles about” when I fiddle with
it – certainly there is no feeling that a switch is being operated
that might cause a motor to open or close a valve.

If I can force the valve open and satisfy myself the motor is the
problem does anyone know of a supplier for the “actuator” part of the
valve? I can't find online a reference and I guess it is an obsolete
device.

If I can't override the motor, can I detach it from the valve and
use a screwdriver to force the valve open?

If by trying to override the valve I determine the HW problem
(probably) isn't due to the valve, what else might be worth looking
at?

Naive question. Are the 2-port valves on the boiler / supply side
of the circuit or the “demand” side of the circuit? I am thinking they
should be on the demand side to enable either circuit to be switched
independently – giving independent HW and CH. I can understand the
operation of a 2-port valve on the sealed loop that goes around the
radiators but I can't understand how such a valve would work on the HW
side. Surely the DHW just comes off the top of the HW cylinder – and
the water removed is replaced by cold water supplied from the tank in
the loft. So what flow is the second 2-port valve controlling?

Have you still got the problem, or have you fixed it?

What you have is a fairly conventional S-Plan system. See the S-Plan section
of http://content.honeywell.com/uk/homes/systems.htm for a schematic and
circuit diagram - which help to explain how it's supposed to work.

The bit you're missing in your question is that the HW cylinder is actaully
a heat exchanger. It has a coil of pipe inside it through which water from
the boiler flows, and indirectly heats the actual domestic hot water without
any mixing of the primary and secondary circuits.

The primary circuit works as follows: Water heated by the boiler flows
through the pump and then splits into two sub-circuits - each controlled by
a zone valve. The CH sub-circuit goes through the radiators, and back to the
boiler. The HW sub-circuit goes through the indirect coil in the HW cylinder
and then back to the boiler. [The two returns may well combine into a single
pipe before they get to the boiler].

As far as controls are concerned, the CH zone valve is controlled by the
programmer and room stat, and opens when there is an unsatisifed demand for
heating. Likewise the HW zone valve is controlled by the programmer and
cylinder stat, and opens when there is an unsatisifed demand for HW. Each
zone valve has a secondary micro-switch - not connected to the motor
circuit - which closes when the valve is fully open, switching on the boiler
and pump. [So the boiler and pump run when there is a demand from either or
both circuit, and switch off when both demands are satisfied].

If you're not getting any hot water, it almost certainly means that the HW
zone valve isn't opening, and isn't turning on the boiler and pump . This
might be for any of a number of reasons:
* Faulty wiring from the HW output of the programmer to the cylinder stat
and zone valve
* Duff cylinder stat
* Zone valve failing to open because of a duff motor in its actuator
* Zone valve opening but not turning on the boiler and pump due to a duff
microswitch [Not very likely because the HW would still be heated whenever
the CH is on]
* Zone valve failing to open because the mechanical part of it is seized.

Armed with a mains voltmeter, you should be able to find out whether the
valve motor circuit is powered - and check back through the cylstat etc. if
it isn't. If it is powered, but still doesn't open, remove the actuator -
whilst leaving it connected electrically - and see whether that moves when
it's not on the valve. If it does, it's a seized valve. If it doesn't, it's
a duff motor.

To answer your question about over-riding the valve, the manual lever on
some valves opens the valve but doesn't move it far enough to operate the
microswitch - so the boiler still doesn't come on. I don't know whether
yours is like that. If you open the valve by rotating its spindle with the
actuator removed, that won't turn on the boiler unless the microswitch in
the actuator also closes.

HTH!
--
Cheers,
Roger
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