3 port Y value failure diagnosis - do you agree?

Hi all

I think our 3 port value is defunct - just want to check I'm not missing anything.

I've been thinking that the heating is taking longer to warm the house up in the mornings, also SWMBO commented that the water was very hot. Made me suspicious that the valve was not going all the way to the CH/A position.

Electrically all measures correct 230V on the White wire from the room thermostat and 230V on the Grey from the cylinder stat (when water tank is hot - and I have turned the stat down to 50). Also last night I moved the Grey wire to the room stat with the White - so the valve should now be operating in CH only/HW only and no mid position (like a W plan but with priority to CH).

Not sure how well feeling the pipes works (as copper conducts so well) but I can't detect any temp difference on A and B sides of the valve - both very hot. More telling perhaps is the return pipes - the pipe coming out the bottom of the tank is very hot (you want to remove your hand after a couple of seconds), whereas the return feed from the heating is noticeably cooler (can hold for ages).

The manual lever moves the value to the same position it ends up in when driven by CH only. So I'm concluding that the value itself has failed an it letting water through to the HW circuit when in the motor is in CH position.

Any thoughts before I splash out £100.

Steve

What make of valve is it? Some have detachable heads.

If it moves correctly detached from the body then the heads ok and just the body is seized.

The pipework does conduct heat well so it can be difficult to tell by checking the pipes close to the motorised valve. So, set the programmer to hot water 'off' and leave it for an hour or two. Then feel the return pipe from the hot water cylinder (This is the one directly below where the pipe from the motorised valve enters the cylinder) if it's warm, that's OK. If it's hot, water is flowing through the valve.

If it is hot, it doesn't necessarily mean the motorised valve has failed though, the cylinder thermostat could be stuck 'on'

petit_pablo said:

What make of valve is it? Some have detachable heads.

If it moves correctly detached from the body then the heads ok and just the body is seized.

Click to expand...

Honeywell Sundial - has 4 screws that look they hold the head to the valve body will check and try it with the head off.

Hmm - loosened two of the screws that hold the valve head - water started dripping out, screwed back up quickly. I guess that suggests the seals have gone on the body?

P.S. Didn't say earlier we are talking a 30 year old valve here.

A Honeywell valve will have a dimple in the outer silver metal box if the head is changeable.
If no dimple needs complete valve.
Doesn't need to be a Honeywell again though.

A valve that old may be a 1" or3/4" valve with internal threads so the nuts won't match the new one if that's the case

No dimple on the cover - just a label that give differential pressures for 1"/28mm and 3/4"/22mm.

Head seems to be doing all the right things - so must come down to the body. Off to screwfix it is then.

Question now is - genuine Honeywell @£112 or Drayton @ £75 - or take punt on a Hortsman at £45!!

Or I see online places at £65-80 for the Honeywell - any recommendations?