Mid Position Valve Locked Problem.

[gibson8206]

Hi, still trying to sort my heating problems out re: wiring.
My mid positioner motorised valve seems permanently open or shut. When I operate the manual lever there is no resistance so I'm unable to open/close manually. The retaining spring is taught.
Even with the power off there is no change in the motor position and spring tension.
I believe the system is wired Y plan.
The boiler is a Potterton Prima F. The programmer is a Wicks basic rotary clock type, On/Off twice. No room stat , but connected to a cylinder stat.
Any advice welcome.

Best wishes from,

Gibson8206.

 

[kevplumb]

err the valve is stuck

 

[seco services]

with no power to the valve it should fall to the relaxed position heating closed hw open, giving you resistance on the lever.

 

[gibson8206]

Hi Mr kevplumb, is it easy to make it unstuck
It's not three months old.

Best wishes from,

Gibson.

 

[kevplumb]

take the head off and turn the shaft (ooh err missus)

if it wont turn with finger pressure its kerry packered and you system is about 3 mths behind it ie full of crud

short turm answer (and that is all it is ) spin the shaft with a spanner

 

[gibson8206]

Thanks for that kev. I've taken off the front and moved the tap by finger. Only travels about eigth of an inch either way. Is this the correct movement?

Best wishes from,

Gibson8206.

 

[kevplumb]

no

bit draining down req and see whats stopping it

 

[gibson8206]

Is it a full half turn either way?

Best wishes from,

Gibson8206

 

[gibson8206]

Does anybody know how far a normal mid positioning valve should move to manually turn it on and off? I assume the mid position is at 12 o'clock.

Beat wishes from,

Gibson8206.

 

[sooey]

1/8th inch either way sounds about right to me.

 

[Paul Barker]

the problem is that if it was stuck due to sludge then it needs taking out and cleaning properly or changing, at the same time as cleaning the whole system unles you enjoy repeating the job and watching the attrition of all other components in the dirty system one at a time.

The flat pin by moving a few millimeter moves a cheese wedge shaped rubber bung to one side or the other. It is geared in the wrong way so it takes a lot of effort to move the pin a small amount which converts to a large amount of movement by the paddle, which would be obstructed by sludge using very little effort.

To take the valve out you don't have to drain down, seal the system collect water from under one of the nuts, crack the nut when water flow stops remove valve, clean/change it.