Honeywell motorised valve not working correctly?

[doitmyself]

Oh, so it appears its all working correctly then?

So if i ask for CH its normal for the motor not to move at all, as the default position of the valve is for the CH and so doesn't need to send power to the motor to move the valve as its already in the default open position for CH?

But why if i ask for HW the motor activates but when i turn the HW off the motor doesn't move the valve back to the default position which is for CH?, surely the motor should activate (be it to open or close the valve) again once i turn the HW off??

The default position, when there is no voltage to any valve wire is for port B to be open. This is the connection to the HW cylinder. Port A is the CH connection.

If CH was the last call, the valve is held in the CH only position. So there is no need for the valve to move if there is a subsequent call for CH.

If the valve is held in CH only and you now call for HW, the motor does nothing. Turning HW on removes voltage from the grey wire, so the valve can return to the default HW only position under the power of the spring.

Look carefully at the second set of diagrams I posted and all will be clear.

 

[fezster]

From the FAQ sheet: https://heatingcontrols.honeywellhome.com/documents/All/pdf/975.pdf

"When this Heating demand is satisfied, during a Heating ON period, 50V to 150V (voltage can vary according to the supply) will remain on the orange wire and the valve will continue to be energised and warm to the touch. Switching Hot Water ON or turning OFF at the mains will de-energise the valve and it will spring return back to the Hot Water only position until the next demand"

The default position is port B to be open (HW only). Which means if there's no power to the valve, that's where the spring will have it rest.

Where you are getting confused is at 1 min 5 in your video. When you turn the HW off, you are expecting the valve to move - it will not. At this point, the valve has 240V on the grey wire (from the HW off terminal of the programmer) - so from the quoted text above, the valve will maintain it's current position (which happens to be port B open / HW only). You then proceed to move the valve manually, which means you've now moved it to CH only (port A open / CH only), and the valve maintains that position because it has power on grey.

At 1 min 26, you turn the heating on, expecting the valve to move, but it is already in the correct position.

 

[John.g]

Only last position it can't remain in is Mid-position??.

 

[SJB060685]

It holds the last port of call, thats how any mid position valve works!

 

[John.g]

I always find it difficult to understand how it stays in mid position when the HW & CH are switched off, I thought it might motor to CH only as there is now no power on the white wire (only), probably misinterpreting what last port of call really means.

 

[SJB060685]

It never stays in mid position after a call. If HW was last call then its returned to HW. If CH was last port of call its held in CH position. Theres a resistor and diode involved. I will upload an image, although its been shared before.

 

[John.g]

So it doesn't stay in mid position so as this is really not the "last port of call",

 

[SJB060685]

It holds the last point of call

 

[John.g]

I have no problem in understanding the last port of call if it has been in either CH only or HW only, on CH only the valve is (240V) kept energised by the grey wire via SW1 only (HW off) to keep it it in this position, on HW only the valve is in its unpowered state anyway so remains there.

If its in mid position, it is kept there by feeding 240V via the white wire through a diode and a resistor which reduces it to ~ 60/70 DC volts, SW1 is now also closed to the grey wire but no problem as no voltage from this wire. If you then switch off the CH first then the valve will return to its unpowered state which is HW, if you then switch off the HW there will be 240V on the grey wire but because SW1 is now opened from the grey wire then the valve will stay unpowered. But if you switch the HW off first then you will have 240V on the grey wire which will power the valve to CH only and it will remain there if you then switch off the CH, is this how it might work?.

 

[SJB060685]

Yes mate. That's not the best image but one I quickly found for you. Try these two.
If in mid position and you swith CH off. You will lose power to the white wire, which is what's holding the valve in mid position with pulses of DC. The valve will spring return to HW and close switch 1. If you turn off HW first then grey wire will supply 230 volts and fully motor over to CH position and switch switch 2 over supplying 230 volts to orange.
Whatever is the last port of call is held in either case. One of the problems with this design though is if CH was the last port of call the valve remains energised and motored over to CH, which is why they frequently burn out.