3 port valve, valve head or something else?

System appears to be a 'Y' plan, with a Potty Flamingo RS keeping things warm. Everything appears to have been running as it should for years.

A couple of years ago the room stat was changed for a more sophisticated one. The original timer was left in place to control the hot water only.

Recently, a change in hot water use has resulted in the heating running despite the room stat showing satisfied.

When the room stat is satisfied the pump stops, the 3 port valve moves from'H' to 'M', and the pump re-starts, under control of the cylinder stat, and the heating continues to run until the cylinder stat is satisfied. The valve then returns to 'H' and the pump shuts down. By this time the house is much too hot.

The lever on the valve head moves easily by hand to all three positions, and I can hear the switches operating in the head, but it never moves to 'W' of it's own accord.

I suspect the 3 port valve, but cannot rule out pre-existing problems just highlighted by the change in hot water use.

The valve head is blue plastic, marked 'BGMVSP-23'

Before I get the multimeter out, and start prodding around, Where would you start? What electrical conditions need to be met for the valve to move to 'W'?

TicklyT said:

The valve then returns to 'H' and the pump shuts down. By this time the house is much too hot.

Click to expand...

if the hw was last port of call and its then satisfied it should stay in that position W held by the live on the grey wire from the cyl stat.

The lever on the valve head moves easily by hand to all three positions, and I can hear the switches operating in the head, but it never moves to 'W' of it's own accord.

Click to expand...

switch off the power to the heating system this will reset the valve to its relaxed position W.

Before I get the multimeter out, and start prodding around, Where would you start? What electrical conditions need to be met for the valve to move to 'W'?

Click to expand...

only power on the grey from the cyl stat satisfied or hw off.
if hw was last port of call it will stay in W position if everything satisfied.
if heating last port of call it will stay in H position.

W is valves relaxed position.


if you isolate all the power to the system and the valve still stays in M position sounds like somthings blocking it in the valvefrom returning to W.

What you have is a British Gas labeled Drayton 3 port valve.

I would think that the valve head needs changing. Your local Plumb Center may b a British Gas stockist and have the exact same head (colour) if not a drayton head is the same.

Thanks for the info G4U and Seco.

I finally got round to dismantling the airing cupboard shelves to look for the release catch for the valve head (It's easy once you know where to look for it, and I didn't actually have to touch the shelves )

When I took the lid off, the reason became clear - The return spring mountings had both broken off the plastic case, so the valve was left flapping in the breeze unless there was a call for heat, when the motor drove it across to 'H'. The rest of the time the valve just settled wherever it wanted to, usually halfway between heating and the mid position.

Putting a couple of 4mm screws through the bottom of the case to hang the springs on has set everything copacetic again.

Now all I've got to do is put the airing cupboard shelves back together.

And thank you Tricky T, I had the same problem this morning, but I just
adjusted the springs a little, and hooked them through the base plate, job done for now but it just goes to show what a load of crap BG put there name on
once again thank you for coming back with a solution!!!