MOTORISED VALVES - so many faults/diagnostics/remedies!

[stuarthall]

from what I have learned and gathered (from this forum and from previous knowledge, etc), motorised valves have quite a few things that can go wrong with them for eg, motor burnt out, shaft seized, valve not closing properley allowing hot water to pass through it, etc

and there are also many ways you can disgnose a faulty valve eg, manual lever loose means valve is always open, certain wires having no voltage means motor not motoring across and switching power to orange wire, etc.

basically is there a simple way to summarise all the problems/diagnostics/remedies of motorised valves up? as it seems very confusing there being so many things/remedies.....

 

[Corgigrouch]

By and large, the simple motorised valve is a pretty reliable piece of kit but it is a machine and machines do fail... The tests that you have learned about are what we have to do to prove or disprove the failure of a motorised valve, they are as simple as you can get, how much more simple does it need to be? I suppose that the manufacturer could fit a diagnostic panel with LCD readout but then we would have to test the diagnostics to prove that what they are telling us is accurate.... and the price would double.

 

[poolebybirth]

am i right in thinking that the MANUAL lever on a MV only OPENS the valve and does not actually puts power on to the pump and boiler?

so in an emergency with a 3 port mid position valve you can have HTG also on with HW?

On a 2 port valve which has a permanent live feed you can actually have the pump and boiler on and firing when the valve is CLOSED but this is not possible on a 3 port mid position valve is it as it does not have a permanent live feed and auxiliary switches?

 

[EliteHeat]

am i right in thinking that the MANUAL lever on a MV only OPENS the valve and does not actually puts power on to the pump and boiler?

No

so in an emergency with a 3 port mid position valve you can have HTG also on with HW?

Emergency?

On a 2 port valve which has a permanent live feed you can actually have the pump and boiler on and firing when the valve is CLOSED but this is not possible on a 3 port mid position valve is it as it does not have a permanent live feed and auxiliary switches?

That's why a bypass is always required on "S" plan systems. It is also possible on a 3PV but the valve can never close.

 

[poolebybirth]

if the manual lever being pushed across DOESN'T open the valve fully then what does it do?

By emergency I mean if you have no Heating but Hot Water as the motor has failed then pushing the lever across when Hot Water is on gives you Heating also...

Yes I agree about the bypass - it is also used where TRVs are installed and when they close down. SOme boilers do not require a bypass though or even have one built inside the boiler casing.

 

[nickso]

if the manual lever being pushed across DOESN'T open the valve fully then what does it do?

.

opens it for draining down the system.

 

[poolebybirth]

if the manual lever being pushed across DOESN'T open the valve fully then what does it do?

.

opens it for draining down the system.

yep i know it also helps to drain down system (on 3 port it will drain anyway if not even pushed across though)

but my point was - on a 3 port mid position: it does allow whole circuit to be open (so heating to be on when hot water is calling if valve motor fails but once hot water is satisfied it will not keep the pump and boiler on.

basically the manual lever then opens the circuit fully up but on its on cannot make the switch contacts start up/put power to pump and boiler..??

 

[EliteHeat]

basically the manual lever then opens the circuit fully up but on its on cannot make the switch contacts start up/put power to pump and boiler..??

The action of manually opening the valve and securing it in position should also operate the microswitch which in turn should power the pump / boiler / whatever.

 

[poolebybirth]

I was told that the lever opened the valve but didn't actually operate the switch that puts power on to the pump/boiler.

Unless this is onlt the case for the 2 port valve?

 

[ChrisR]

No no and no.

yep i know it also helps to drain down system (on 3 port it will drain anyway if not even pushed across though)

You'd still have a coil and more, full of water. Systems never drain completely though

The action of manually opening the valve and securing it in position should also operate the microswitch which in turn should power the pump / boiler / whatever.

WRONG

The manual lever doesn't open the valve far enough to "make" the auxiliary switch when it's on the latch.
The lever's really there to enable the system to fill (and drain) though yes it can be useful if the motor fails (see FAQs).
Valves do vary though, I have seen a 3 port operate an internal switch, though not the Honeywell which is the most common.. If you push the lever hard, the momentum of the motor will usually close a switch (you typically hear the pump start up for a second or so) and if you jam the lever inpositionat the end of its travel, it will sometimes hold the switch closed.

There's more that can go wrong, such as
Soggy ball - the Honeywell rubber ball goes big and soft and doesn't seal properly (inhibitors used to do this, cheap ones probably still do)
Hard ball - the rubber again doesn't deform to seal properly
Worn seat - the brass aperture wears so the ball can't seal
Broken arm - the ball becomes loose in the chamber
Stuck shaft - as you said
Blocked chamber - recently took out a 28mm one where the hole n the middle of the clag was about 10mm, and the arm couldn't move.
WOrn shoes - the D shaped ones which rotate around, get scored and let-by
etc etc

 

[poolebybirth]

the system will drain fully surely? otherwise you'd never be able to change it!

 

[ChrisR]

the system will drain fully surely? otherwise you'd never be able to change it!

Depends on the plumbing. There's no limit to what diy plumbers will do! Forgetting a drain cock altogether is very common "pro"'s way of saving money..

 

[poolebybirth]

no drain valve is very bad.

without one how would you drain a system?!!

i guess if the spindle/shaft is seized a new vale is needed (not just actuator) is needed - obviously!

 

[ChrisR]

You would drain by removing a rad, usually, but there are other ways.

If the spindle's seized you can dismantle, etc, if you have the right sort of abilities...

 

[poolebybirth]

if the spindle (shaft) is seized it may be best to change the whole valve anyway as in the long run you'd be best off surely?