motorized valve- jammed open microswitch

[johnnyplumb]

motorized valve- jammed on microswitch

went to a call today where customer complained about pump running constantly even when programmer in off position & room stat / cylinder stat turned down. s plan system & both zone valve motors where turning ok. orange wire to pump & boiler was permanently live due to htg zone valve microswitch jammed in on position. i dont do a great deal of fault finding work, mainly new installs. just wondered how common a fault this is as most zone valve problems ive seen are usually burnt out motors.

 

[diamondgas]

It's a common one that throws a lot of guys/galls into thinking the programmer or room stat is faulty! It can be any of the zone valves that give this fault. Process of elimination gets you to the one at fault though

 

[johnnyplumb]

yeah, nearly fooled me till i got the thinking cap on.

 

[Best]

Always happening, even on motorised valves only a year or two old. Seems the actual mechanical bits of the valves don't get a chance to wear out!

 

[armourer]

Easiest way of tracking this is to just disconnect the (zone valve) orange wires one at a time from the 10 way, when it stops you know which valve is causing the problem.

And yes it is quite common as well as jammed motors.

 

[Jonwells]

Motorised valves are a pain, my advice is to replace the complete valve ( head and body) if faulty, been fitting a type of motorised valve ( I think seimens) that has a plug into the valve head, a lot easier to change than 6 poxy wires. Jon

 

[Fred Bloggs]

I have a system with a three way Drayton motorised valve, every three to four years the actuator packs in (I think the heat in the airing cupboard slowly toasts the micro switches). I now keep a spare ready to fit. The actuator can be changed in about 5 minutes as it just clips onto the valve body. Very common fault I think, but can be confusing to diagnose unless you've seen it before!