Heating pump not turning off + weird noise/vibration

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Hi, I need some help!

Recently, I've been hearing an occasional loud vibrating noise coming from the radiators/pipework around the airing cupboard which lasts for just a second or so. It sounds almost like pipe hammer but doesn't last very long and makes the radiators in the house all vibrate a bit.

Now bear with me as I know very little about plumbing so I'm probably about to use all the wrong terminology! :)

After doing some research, I think what's happening is that the pump is not turning off. On days when I'm hearing the noises (which isn't every day) the pump seems to just stay on all the time, even if the heating and water are turned off at the programmer. The pump is running even when both the valves are in the A position, which I think means they're closed. The pump is audibly struggling with both valves the A position and if I manually push either lever to B the pump gets much quieter and water seems to flow around the system normally.

I have a system which has two 2-port valves near the pump. Pumps and valves are wired to a 5 inch square ACL Lifestyle electrical box in the airing cupboard and an Ideal Classic LX boiler downstairs (all about 11 years old). The valves are also ACL Lifestyle (part 779 H335 30L10).

On days when I don't hear the weird noises and the pump is stopping normally, both the valves appear to operate normally and go into their correct position. The pump comes on if I push either lever all the way across and stops as soon as I let go. I presume from this behaviour that the valves themselves actually turn the pump on using a micro-switch at the far extent of the throw and perhaps one of these switches is getting stuck in the closed position? I originally thought that perhaps there's a thermostat in the boiler that keeps the pump running when the water in the pipes is still hot, but after realising the pump is controlled by the servos/valves then I presume that's not the case?

If I turn the mains off for a few minutes, it makes no difference, but if I turn it off for at least an hour or two, when I turn it back on again everything goes back to normal for a few days. This is the bit that confuses me the most as it makes the problem seem a bit more complicated than a stuck microswitch!

I'm presuming that valves changing position when the pump is already running on full is what's causing the weird vibrating noises as it coincides with when I turn the water or heating on/off.

Should I look at replacing the valves, or could it be something else like the controller board/PCB in either the airing cub? Does anybody know what might be wrong or if there are any other tests I can do to narrow down the problem? I'm wary to call out a plumber at this stage, as the problem is intermittent and I think he could easily turn up when everything's working normally :(

Any help appreciated!

Thanks,
Nick
 
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I decided to give the valve manufacturer (ACL) a call and ask their advice. He's suggested I do the (obvious) test of measuring the continuity across each micro-switch after they've been unwired (with valve closed) to make sure that the switch isn't stuck closed. So I'll start with that I guess!
 
Thats the 1st place to start.What you describe is a common fault.I don't think you can replace those powerheads so it means a whole new valve.Some skinflints will say replace just the microswitch but I will not recommend that.Chose Honeywell as replacements.
 
I was about to ask for recommendations for replacement parts- thanks :)

Are Honeywell more reliable then? The only thing I'm worried about if changing brand is different spacing of the connectors. The pipework is VERY tight and what I think is the faulty valve has a 90 deg bend in the pipe within millimetres of either connector. If the replacement valve is any wider, it won't go in.

Which Honeywell part would be compatible with an ACL 28mm 2 port (ZA6 779H)? Sorry if that's a silly question but I have no idea if the wiring/dimensions are compatible with these things, or if I need to be very careful about what I buy. I think as I'm likely to have to drain down the system, that I'd rather change both to ones with changeable actuators at the same time, in case the other one goes too (it's 11 years old after all).
 
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In your case I'd stick with the same manufacturer.The latest version of your valves have a removable powerhead which makes future repairs a lot easier and dimensions and wiring are the same.
 
By what you describe, it seems that you have not got a bypass fitted in your system, what is happening is that when the last trv on the system closes the pump has no where to pump the water, hence the water hammer and vibration. In turn this will cause the boiler temp to rise and the pump will not switch off because it is kept going by the pump over run switch in the boiler. Have you got a trv on the bathroom radiator, if not open the lockshield more to let it act as a bypass. If the bathroom radiator has got a trv and you have got a bypass, then adjust the valve on this by opening it slightly at a time until the noise disappears.

Cheers

spraggo
 
I thought you only needed a bypass if you have a pump overrun thermistor (which mine doesn't)? From what I gathered on my phone call to ACL Drayton, if the valves are off, the pump should be off (on my system) and therefore a bypass wasn't necessary? Also wouldn't that be an installation error, so wouldn't this have been happening for the last 11 years? (It only started last week)
 
Exactly,no pump overrun on that Classic.In your system you would need a bypass if all rads have trv's.If no bypass fitted then use a rad with normal valves adjusted to provide a bypass.In your description of your system you don't mention anyTRV's.

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I have no thermostatic valves, no overrun stat and no bypass, so hopefully that's a valid install :)
 
I have no thermostatic valves, no overrun stat and no bypass, so hopefully that's a valid install :)

In that case one of the mv`s are playing up, the pump gets it`s power from a permanent live feed though the orange and grey wires connected to either of these valves when they are open. If they are both closed then then the pump should not continue to run.
It appears that the Ch MV is not closing correctly, the only way to test these valves are to check them each for continuity across the orange and grey wires, there should be no continuity when the valve is closed but continuity when it is open.
 

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