Honeywell Power Head very hot

[MysticMartin]

I have a Honeywell "Power Head For Motorized Valve" 240V which operates fine. But the motor inside gets very hot - too hot to touch even when the boiler is not in use. It's in the off position (i.e. hot water only) so I'm surprised it would be taking power. The connecting water pipes are nearly cold.
Is this normal?

The model is 40003916-003

Thanks
Martin

 

[MysticMartin]

Upon further investigation, the Power Head remains in its last state when no longer needed. So if heating is on and the motor is therefore powered up, when the heating turns off the boiler goes off but leaves the motor in its heating position thus taking power and heating itself up.

In the off state the grey (hot water off) wire has power.

The get-around is to set the timer so the water heater goes off after the central heating.
I can't believe it was designed like this so maybe it does have a fault.

 

[45yearsagasman]

Look in the sticky and you will see a good explanation as to how a mid position valve works internally. It would be good if you could re design Honeywells age old proven equipment. Let us know the results.

 

[D_Hailsham]

Mid-position valve operation and fault finding

 

[Whitespirit66]

Saw something online a while back where someone had 'pimped' their motorised valve by drilling lots of holes in the valve's cover and the cap that covers the internals of the synchon motor. I suppose anything that helps them run cooler and disperse heat has to be good for the longevity of the unit.

Or maybe the bloke just needed to get out more.

 

[Whitespirit66]

Found it.

http://www.handyantman.webspace.virginmedia.com/V4073.html

 

[D_Hailsham]

Saw something online a while back where someone had 'pimped' their motorised valve by drilling lots of holes in the valve's cover and the cap that covers the internals of the synchon motor. I suppose anything that helps them run cooler and disperse heat has to be good for the longevity of the unit.

All that to cool a 6W motor.

 

[MysticMartin]

Thanks for the info. It's surprising how such a simple circuit can be so complex. It's also surprising how hot a 6W motor can get; I don't think I'll start drilling holes in it.

I'm wondering if my programmer is not working as expected. When the hot water and CH turn off the programmer leaves the grey (HW satisfied) wire at 240v and this is holding the motor at full position. If it took away power from all the wires then the motor would rest.

Do other people find their programmer leaves the grey wire powered up when it's all turned off?

Thanks
Martin

 

[D_Hailsham]

Nothing wrong with your programmer or the valve.

It is a quirk of the mid-position valve that the grey wire stays live,holding the valve open to CH, when CH only has been satisfied. If you read the explanation in the link I posted you will learn why it happens.

Sunvic produce a "motor on/motor off" valve which overcomes this "problem"; but it has never caught on and has a reputation for failing. If it was any good, I would have expected Honeywell to have bought them out by now, so they could get their hands on the patent.

 

[Dan Robinson]

It's actually deceptively simple. Not to mention reliable and versatile.

Sunvic's efforts are laughable.

The Honeywell VC range are also good but only oem here

 

[stem]

The get-around is to set the timer so the water heater goes off after the central heating.

That isn't bound to work, because if the hot water is 'on' at the programmer, but the cylinder is hot and not calling for heat, the cylinder thermostat would have already turned the hot water 'off' by making the grey wire live (hot water not required)

If you are worried about it, convert it from a 'Y-Plan' to an 'S-Plan'. An S-Plan uses 2 x two port valves instead. They would only be energised as and when required. However, depending upon your system / boiler, you may have to add a by-pass loop. Because with two port valves, the hot water and central heating circuits could both be closed at the same time.

 

[Agile]

I do have to say that if it really is only 6w they do seem to get very hot.

Normally with system off much of the heat is conducted away through the cold pipework.

But for anyone who is concerned by the valve being so hot then spray painting it with matt black paint will enable much of that heat to be radiated away.

Tony

 

[MysticMartin]

That isn't bound to work, because if the hot water is 'on' at the programmer, but the cylinder is hot and not calling for heat, the cylinder thermostat would have already turned the hot water 'off' by making the grey wire live (hot water not required)

You're right it doesn't work

I'm just surprised the programmer doesn't make all the wires 0v when both heating and hot water are turned off. Surely that would do the trick.

It's tempting to put a push-to-break switch inline with the grey wire so I can press it before going to bed to reset it back to resting.

 

[stem]

Sometimes it may be advantageous for the valve to stay where it is when the water and heating go off. Many boilers operate the pump for a while when everything goes off to dissipate 'residual heat'. In this case the valve remaining where it is, is useful.

If every-time the central heating thermostat or programmer switched off, the valve returned to the 'at rest' position (hot water only) the regular supply of 'residual heat' to the cylinder may cause it to become overheated.

Anyway, summer is coming soon, so once the central heating isn't being used, the valve will sit in the 'at rest' position permanently.

 

[MysticMartin]

Anyway, summer is coming soon, so once the central heating isn't being used, the valve will sit in the 'at rest' position permanently.

Very true, it won't be a problem in the Summer!