Testing 3 way valve

[GB]

It's that time of year again when the central heating goes on again. Only the central heating is not coming on. I took the top off the three way valce, and the mechanical part seems to be working fine. Pushed in, it serves the hot water, and when I let go the plunger comes up and the central heating comes on.

So, it's the electrical part that's wrong, and I am not clear how to test it. There's a lever on the outside, and this seems to be locked in the fully down position, and I can't lift it up at all. The thing is that I can't see whether this is because the unit is faulty or because the central heating controller is keeping it pushed down because it doesn't think we need any heating? Should I be able to push this lever up and down regardless of what the central heating system wants to do? Or do I need to disconnect it electrically first?

The electrical bit looks just like this:

for any help.

[John Rumm]

Right good start. It needs to move relatively freely - if you can push / twist (as appropriate for the type) by hand then its usually a fair bet it will be ok when driven by the actuator.

If you make sure that the programmer (if you have one) is set so that it is demanding heating, do you hear the valve move when you turn the room stat up and down?

Do you have basic test tools like a multimeter handy?

[Dave Liquorice]

Wha'd'ya mean "goes on again"? It's never been off and with such a bad summer I'm struggling to think of times when the (programable) stat hasn't demanded heat at least first thing in the morning or early evening.

In a "normal" summer there is a period around late June to July into early August when the heating probably won't come on but not this year.

[GB]

Hmm, I've since found that it is stuck in the hot water position. In the past when I have hit it with a hammer it has freed itself, but it's stuck fast now. It's worse than before, because having hit it a few times with a hammer to free it, the circlip and washer holding the spring on flew off somewhere. In any case, as it's seized up a few times, it's time for a new valve, and I'm not sure that I am competent to fit it, as it's a really big one with 1" fittings. Am I being a wimp?

The white lever on the actuator is now moving freely up and down, but it doesn't seem to respond to the central heating controls.

Yes, I do have a multimeter.

[John Rumm]

Rather than clomping it, You may find lubricating the shaft / plunger and working it back and forth works quite well to free it off. (had to do this with one of my two port valves last year - it was moving, but not the full travel, and hence preventing the microswitch from closing when in the full open position)

If you can get a like for like swap, then it ought to be relatively painless to swap. A bit depends on where it is, how easy to work on, how easy to isolate or drain down enough etc to do it.

ok so its really just a case of looking at the wiring diagrams I linked to before, and working you way through the connections from input to output to find where it stops behaving. Say you have a classic Y play setup like:

with the system powered, and obviously taking great care not to go poking fingers into electrical connections, set the multimeter to read AC volts on a range high enough to read 250V. Clip the black lead to a handy neutral, and then probe with the red to check you have a 230V supply:

1) going in to the programmer (it may well appear "dead" if not anyway) 2) Coming out of it when CH is "on" at the programmer. 3) To the room stat, and then out of the room stat when its "calling for heat" (turn it up to 30 - you should heat it click at some point if its an old mechanical type) 4) at the CH input to the valve 5) at the Heating Only call from the valve (usually connected to the microswitch on the valve that closes when its in the heating position) 6) at the call for heat to the boiler and/or pump

This should then let you isolate where the problem is. So if there is main going too the room stat, but you never get it out regardless of the position, then the stat is probably dead.

If you get mains out that goes to the valve but it never moves or eve tries to, then it might be the valve motor. If it moves but you never get a output from the microswitch on the valve, it might be the switch, or the wet bit of the valve is not letting it move far enough to close the switch.

[Andrew Gabriel]

Ah, the pingfuckit...

[Dave Liquorice]

somewhere.

Or for polite company the wherdigo.