Should be very reliable though motor life varies dramatically with
temperature. Do you have unusually high ambient/flow temperatures or high
spec supply voltage?
Otherwise I have seen the rubber 'ball' which directs the flow to have
swollen for some reason, something in the system water assumedly. As you
describe a complete blocking of the flow which normally could not happen
with a three port valve, this could be the case. Perhaps you could do a
complete drain and flush next time, or maybe Honeywell would be interested
in examining your valve.
"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 :~(