CH control question

[Syke]

I have a Siemens RWB9 programmer operating two Siemens motorised valves, on an oil-fired sealed system, one for DHW and one for CH. Recently, I've noticed that the CH doesn't always come on at the time set, although the red indicator on the programmer is on. When the program is swiched off and then on again on the programmer, it usually activates and then works normally. I'm wondering if the problem lies with the programmer, or with the motorised valve, (the actuator of which I've had to replace twice). I've also tried re-setting the programmer.

Regards and thanks in advance

Syke

[Dave Plowman (News)]

You need to check the programmer is actually sending an output when it says it is. They usually have relays to do this - and the telltale works on the switching circuit for the relay rather than from its output.

[Mathew Newton]

You've answered your own question really in terms of the necessary fault diagnosis - take the cover off the valve and get familiar with its operation if you're not already. Then, next time this issue occurs, see what state the valve is in.

With the valve open a microswitch should close thus triggering the boiler to fire. Hence even if the actuator is working, and the valve is opening, the call for heat may not occur if the microswitch/wiring is defunct.

Do note that with the Siemens valves the manual lever is not moved when opened by the actuator i.e. there is no obvious means to determine the valve position without taking the cover off.

Mathew

[Mike Barnes]

With the Honeywell valves we have here you can tell by attempting to move the lever and seeing whether there's any resistance or not.

A similar problem here was caused by the valve being a bit clogged and therefore unable to open fully. Sometimes it opened far enough to operate the switch and sometimes it didn't.

[geoff]

In message , Syke writes

Put a meter on and measure the volts when its meant to be switching

perhaps remove the programmer from the backplane and attach some flying leads (neutral and the switched live(s)) to a bit of connector block so you can make measurements more easily

[geoff]

In message , "Dave Plowman (News)" writes

Yes the RWB9 has

Yes, just the LCD display ... and the click of the relay

[Mathew Newton]

Good point - that'd work on the Siemens (amongst others I imagine) too.

Mathew