In an earlier contribution to this discussion,
Phil Nettleton wrote:

"Jerry." wrote in message
...
Anyone know of any issues with Honeywell 3 port mid position
valves, i.e. installation, location or in service problems etc.,
I've had three or four go faulty in the last 4 years since the
system (and I hasten to add) was professionally installed and it
sounds like I might be approaching another !

It's either been problems with the valve it's self or the motor
drive not operating (opening the required port(s)) and thus causing
the boiler to overheat and cut out due to there being no flow - and
causing hot water and steam to be forced up into the boiler feed /
expansion tank :~(


this last part dosnt make sense as the valve will never shut both
ports no flow will be caused by a pump failure
if the valve is not powered the hw port is open if it is the ch port
will open or a blockage in the system
phil n


I agree entirely. Unlike using two 2-port valves - which can both be closed
at the same time - the 3-port valve doesn't have a position which shuts off
all the flow, and is unlikely to be the cause of your current problems. The
water always has somewhere to go unless all your radiators have TRVs on them
and they are all shut. If this *is* the case, you need to make some design
changes to the system!

It is far more likely that your lack of flow is due to problems with the
pump. How is this wired - is it simply wired in parallel with the boiler or
is it connected to the boiler's pump-over-run connection?
--
Cheers,
Set Square
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