On Wed, 10 Dec 2003 09:04:59 GMT, Moonshine
wrote:




OK this might be an interesting one,could be on to something. I've removed the
operating head off the only motorised value in the past now when it has been
making a bit of a noise to find the valve below stuck. With some gentle
persuasion with pliers I've managed to free the valve.

Hmm.. That's concerning. It can sometimes happen after the summer
if the heating has not been on. It shouldn't otherwise. You can
avoid the summer issue by turning the heating on briefly evey week or
so.

How much should this
turn? It only moves probably less than 1/8 of a turn.

I haven't looked at one for a few months, but I think it should move a
bit more than that. There are two main designs. One type has a
kind of cylindrical rotating paddle inside and is generally able to
rotate continuously. The other, which seems to be more common, has a
roughly spherical rubber component inside which is mounted
eccentrically. As this rotates it opens and closes against one port
or the other with a 3way valve and just against the port in a two way
valve. These tend to have restricted travel.


What is the correct
proceedure for putting the head back on? Does the motor/spring need to be under
tension? Is there a right and wrong way to turn the head when mating up to the
spindle?

There is basically a motor and gear train in the head and a big
spring. With power off the spring moves the actuator position to
one end of its travel. With power on, the motor runs the actuator to
the other end and then stalls (it's designed to do this). Basically
with the power off, you manually move the cam on the valve base so
that it will line up with the head as you locate it into place. It
should only go one way.



It does not appear possible to just run the CH with the head removed as the
motor continues to turn and the cams cut the pump off on each revolution and
then come back on again, thinking out loud perhaps with the HW switch on it
won't do this.

As it is now the manual overide lever doesn't go under tension in either
direction.


It sounds like the spring might have gone or possibly part of the gear
train has stripped because the valve base was stuck.

Normally, with the power off you should be able to slide the lever and
operate the valve, then latch the lever at the far end of the travel
in a notch in the case of the head. If you release it then it should
return under spring tension.

You probably would be able to fool the system by having the valve head
off of the base and creating a hot water demand, as you say, Then
operate the cam on the valve base to the CH position.

If it then works OK, I think that pretty much you will have diagnosed
a faulty head. They are easy to change, but note the wiring
connections.

Since you have been having valve sticking problems, I would replace
the valve base as well. You can buy the complete thing pretty
cheaply.




..andy

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