Central heating question.

knightstyle

DD has gas central heating and a valve keeps sticking, have tried WD40 and manually turning the valve a few times but it still sticks in the off position from time to time.
The actuator is SZM 1811 and I can see several with similar numbers for sale on Ebay etc. SZM1808 for example, will this do? Or do I have to have exactly the same number one?

Le_Kirk

I would suggest you need the exact number as the numbers are codes relating to 2-port, 3-port, 22 mm, 28 mm 3/4" etc.

knightstyle

All SZM look to be exactly the same, simple two port actuators, plumbing is identical it is just the connectors/voltage that may be different.
Sunvic say "SZ / SZM / SM actuators are all interchangeable, they will all fit the same valve, but wiring changes are required if changing from SZ / SZM to SM types and vice versa."
But they do not sat what the difference is between a SZM 1811 and an SZM 1808 is!

Le_Kirk

Use this link to go to the literature and you can see the difference. Depends if you want spring return or mid-position.

knightstyle

Yes, that is where I got the info quoted above from, but it is not clear what the different SZM numbers mean.