"Phil" wrote in message ...
In message , Harry
Bloomfield writes
It happens that spamlet formulated :
"Harry Bloomfield" wrote in message
. uk...
wrote :
On 21 May, "spamlet" wrote:

Are there any good ones out there?

IME no. I've ended up changing to two port valves. They seem much more
reliable (10+years rather than 6 months)

Nothing at all wrong with the actual valve, just the actuator design
which lets it so badly down. It simply needs someone to design
something more robust, which has the motor move the valve to the
correct position then stop - rather than the motor constantly
oscillating on the microswitches against the spring. Surprisingly, I
have not seen a DIY replacement actuator yet, but it doesn't look at
all difficult to do.

-- Regards,
Harry (M1BYT) (L)

There's a job for you Harry: sign me up for one when you've sussed it!
I would imagine that while they have us over a barrel knowing we have to
buy new every other year, there is not much incentive to come up with a
different design.

S

There is a rather good web site somewhere which explains their principle
of operation and how to repair them.

It needs something like a tiny DC motor (to provide forward and reverse
motion), geared down to provide the torque, a two lobe cam to trigger the
two micro-switches - then a timer circuit to run it back to the default
position.

Even an electrically operated brake, which held the position and turned
off the motor - would be a major improvement on the existing botch of a
continual rocking motion.


I'm somewhat confused about some of the comments so far. I have a
Honeywell 3 Port which I had to replace recently after 10 years of
service. It was itself a replacement for one that was 15 years old when it
died.

Anyway, the motor head had worn out its gears and research revealed the
downside of the system when used in my CH/HW setup. My CH timer is on 24/7
and the control is via a programmable thermostat in the living room. I was
shocked to learn that this invariably left the motor sitting in the CH
position with the full 240 volts applied to the motor so, I devised a
simple fix using a relay which returns the motor to the rest position when
the HW and CH thermostats are no longer calling for the boiler.

My main confusion is with the "hunting" or "rocking motion" mentioned and
presumably this refers to the centre position i.e. HW and CH on, as I have
no such motion on my control head.

The motor moves to the central position, hunts once to find the second
microswitch and then sits there with no further movement.

--
Phil

I'm no expert on the electronics: just the faults. Possibly with your mod
the contacts last longer, but when they get burnt the motor can be heard
hunting and the pop pop pop each time it hits the contact can be picked up
on any radio you have near the device. Mine has just gone again: which will
be about three actuators and two sets of replacement contacts now. As yet I
haven't decided on what to buy this time. The 'momo' type has been
suggested, but no one has enlightened me yet as to whether a momo actuator
can be bought separately and directly replace the current spring type.

S