On 01/05/2019 09:36, T i m wrote:
Hi,

A while back I asked about a motorised 3 way ch/hw valve that was
giving the symptoms of allowing ch when hw was called for.

I got the chance to test the valve from cold yesterday.

Removed the valve head
Rotated the valve to the hw position
Powered up the system.

I kept my hands on the pipe work either side of the valve (as far as I
could from the valve itself) and felt both sides heating up nearly
equally? ;-(

So, this suggests to me that the valve itself is faulty (damaged ball
etc) and whilst I'm more than happy to change the entire valve body
(it's on fairly short pipes that may need some 'persuading') it looks
like the valve itself is secured to the face of the valve body with 4
screws and sealed with an 'O' ring and so, might be swappable with
another / new / good unit?

http://www.freeheatingadvice.com/wp-...valve_ball.jpg

I have seen just the bodies available new for around 20 quid so this
would just cost the elderly lady that plus fresh inhibitor etc?

Worth a go ... or what are the chances the valve seats are worn etc?

I would think it more likely that they will need cleaning up. The ball
is often some sort of "rubber" and the seats can end up with a rough
ring of rubber stuck to them as the ball deteriorates. The ball also
moves only a few millimetres and arrives at the seat flat on, so there
is little chance of seat wear.

SteveW