Failed central heating valve?

Let me start by saying that central heating systems are a black art to me. Ours is a conventional oil fired boiler supplying DHW and three traditional wet radiator zones. Two zones are working, but the third is not, and has not been used for two or possibly three years.
The zone valves are Honeywell, with a silver box on top, and having read that the protruding lever should have resistance when the heating is off, and no resistance when on, I have found the offending valve. There are three valves in total, presumably one for each zone. Just one pump, too.
I've taken the top off the silver box (one screw) and can see the actuator, but beyond that? Will tapping the actuator or the valve or anything else release it? I guess it is stuck because it hasn't been used. Can the actuator be changed without water pouring out?
--
Graeme

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If you select "images" after typing honeywell 3 port actuator into Yahoo, it should make things fairly clear.
I believe the synchronous motor holds the valve position against the stop by means of a constant "stall current" which affects the reliability of the motor. The motor is available as a seperate item.
AB
On Sun, 11 Sep 2016 13:43:49 +0100, Graeme

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My valves are 2 port not 3 port, but I see what you mean. Thank you.
Thinking about it, just changing the actuator is not going to help if the valve itself has stuck. Bugger.
--
Graeme

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writes

Well if you cannot open it manually then it is buggered. I assume that the programmer and stat are calling for heat.
--
Adam


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But which part? The actuator or the valve?

Yes.
--
Graeme

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Well the simple test is to try the actuator whilst it is removed from the valve and see what happens.
TBH if after removing the actuator, the valve spindle will not turn with the help of a pair of pliers then that is your answer.
--
Adam


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On Sun, 11 Sep 2016 14:02:31 +0100

Let's go back to basics.
You say that you have identified the offending valve. Do you mean that it should be powered, therefore open, and so should have no resistance on the manual lever, but that it does have resistance, indicating that it is still closed?
If so, can you move the lever against the resistance, thereby opening the valve? There should be a little catch so that you can lock it in the open position. Does doing this allow hot water through the zone?
If not, why do you think this is the defective valve?
Approaching this logically should give us the answer.
Do you have a voltmeter, and the ability to use it safely? I am not being funny, I don't want you to electrocute yourself.
--
Davey.


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writes

Excellent.

It does have resistance whether or not the system is calling for heat.

Yes! Why didn't I realise that? Anyway, yes, little catch locked, and rads heating. I could live with that, at least for a while. This zone heats four rads in what was our shop, attached to the side of our house. The shop is closed and the space will be my 'hobby room', so remembering to use that little catch to heat the place is acceptable if not perfect.

<grin> I'm no electrician but yes, I have a small multimeter, and can use it for fairly straightforward stuff.
--
Graeme

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On Sun, 11 Sep 2016 14:53:23 +0100

Which indicates that the actuator is not functioning, for whatever reason, but the valve should be ok.

Good so far! Now we need to find out why the actuator is not working.

You will really need a wiring diagram at this point. I expect that the valve and wiring look something like the one shown in the 'S' Plan: http://www.honeywelluk.com/documents/All/pdf/974.pdf
This shows that the Brown and Blue wires are the power for the valve, so IF you can get the probes for the meter to these terminals, you should see 240 V AC across them. If they are unreachable, then find where the wires go to, there will most likely be a junction box of some kind within a few feet. Try there for the same thing, and report back.
http://www.honeywelluk.com/documents/All/pdf/Wiring%20Guide%20Issue%2016.pdf
shows various Plans.
--
Davey.


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wrote:

Exactly right. If the lever moves back very slowly when released then the wet part of the valve is OK
If there is 240vAC across the motor when the system is calling for heat on that zone then the motor is shagged.
Does your valve have a removable head? The early ones didn't. In either case I wouldn't buy a replacement head or valve, as the synchronous motor is obtainable by itself. Generic ones should be under £10 delivered, I think I got my last ones from BES.
If there isn't 240vAC across the motor then you need to look at the thermostat and switches that are dedicated to that zone only.
--

Graham.

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On Sun, 11 Sep 2016 16:17:54 +0100

And that's where a correct wiring diagram will make all the difference. Remember that not all setups are wired correctly, though, as I found out earlier this year.
Good luck.
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Davey.

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writes

Thanks for all the advice guys. I'm not ignoring you, just waiting for the weather to turn. Seems a pity to be doing indoor stuff on days like today.
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Graeme

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Normally the sort of job you can do in August:-)
We hit 30 deg today Linconshire
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Even up here in Aberdeenshire we hit 26 which is good for mid summer!
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Graeme

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On Tue, 13 Sep 2016 09:39:06 +0100

Coincidentally, my boiler started to run yesterday, but stopped after a few seconds. It did not run again all evening or night. Today, I started by checking that it did indeed run of the CH was turned on, which it did, so the boiler is ok. Proceeded to do electrical checks, and eventually found that the cylinder 'stat was stuck Off, I had to turn it all the way to max. to make it work. It's now working, but I'll get a replacement. It's now working, but I'll get a replacement, it's clearly not happy any more.
It's not always the valve!
--
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writes

Right. Removed the whole actuator assembly from the valve, and the valve spindle turns easily. Held the actuator and applied power - I'm assuming the actuator should actuate, but it didn't so either the actuator is dead or there is a wiring problem.
There is indeed a nearby junction box and, within, the four wires from the actuator are connected to a four wire cable which runs to the programmer. The wires within the junction box are all neatly connected and insulated, so cannot get probes in, to test. Would it be OK to cut the wires, remove the four connectors and replace with a chocolate block, which will fit within the junction box?
--
Graeme

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On Sun, 18 Sep 2016 11:36:59 +0100

Personally, I see no problem, but I'm not a qualified electrician! What you describe is how mine is done.
Can you find the other ends of the wires that feed the junction box, at the programmer end, and check the wires for power there? That might find a problem, closer to its actual location. Or maybe test the wires at the actuator?
I reckon at this point that the actuator is probably dead, but it's worth checking as far as possible first, just in case it's not that.
--
Davey.

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writes

I went ahead without waiting for a reply. Five wires, not four, one being earth. Anyway, now joined via a choc block and 240v indeed across the brown and blue wires.
Tried applying power whilst the actuator was off the valve, and nothing, so looks like a new actuator. Oh well, at least the wiring connections will be easy, now.
Will report back when actuator purchased and fitted.
--
Graeme

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On 18/09/2016 13:20, Graeme wrote:

If you fancy taking it apart you may find that you only need to replace the motor - obtainable from the likes of Screwfix for about 16 quid. http://www.screwfix.com/p/drayton-synchronous-motor/28670?_requestid )0766 [Read the reviews for further info.]
--
Cheers,
Roger
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Yes, I had thought about that, but the area just below the motor itself seems stuffed full of little parts ready to ping around the room, never to be seen again. I'll have another look, though. Having got this far ...
--
Graeme

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