Problems with Honeywell motorised 3 way valve

[djuhl]

Apologies in advance for very, very long message but figured you would need all the facts.

Original problem. Heating not coming on when called. Hot water coming on when called but some of the upstairs radiators coming on. Called engineer who said he fitted a new replacement powerhead. This appeared to solve the problem, I paid him and off he went. However the next day same problem as before. He came back, fiddled around a bit, said he wasn't sure exactly what problem was and was going to replace "powerhead and valve". I specifically asked him if this meant the brass T shaped piece of pipework below powerhead. He said no and implied it was not that but the powerhead with something else (but not the T shaped brassware) which would cost another £100. Left me confused as I thought you replaced either whole powerhead +/- valve below unless you replace one of the components like the motor or microswitch individually inside powerhead. Not sure he really changed powerhead as doesn't look new.

I took cover off powerhead and had a little investigate myself and this is what I have found:

When no power to valve: lever has resistance and springs back. Can't hear clunking gears.
When power to valve: lever loose.
When neither HW or CH calling valve is open.
When just hot water called: nothing moves and boiler and pump fire up.
When just CH called I can see motor turn valve towards microswitch but boiler and pump do not fire. If I then use my little finger to push microswitch the boiler and pump fire up.

I also took powerhead off completely to check valve - using my finger I can move spindle but not very far.

So my lay-person's conclusions:

Programmer to valve signalling working as motor does do something.
Electrics to microswitch working because when I manually close it circuit is completed.
Motor working to some degree because it does travel when CH firedValve seems okay as I can move spindle.

Questions:
1. Could it be that the motor not got enough oomph to turn all the way to close microswitch?
2. Could 1. be caused by a stiff valve. As I said it did move but I don't know how far it should move and how stiff it should be.
3. If it was 1. surely that would have been solved if he had replaced powerhead as he claimed he did.

Any help gratefully received. I am a single mum and don't mind paying for genuine work but just have a feeling I may being taken advantage of. Thanks, Diane

 

[Echo the husky]

You are missing the hot water off signal to the grey wire on the valve. To get the valve to CH only, both grey and white wires need 240V.

It is also possible the new valve is faulty but this is unlikely, most of the faulty valves the gears make horrid grinding and clicking sounds as the teeth jump.

 

[djuhl]

Hi there,

Thanks for taking time to reply. The HW comes on and off successfully via programmer on auto-setting so didn't think (as a total layperson) there was anything wrong with hot water signalling. When CH called the motor does move around an the little brass-coloured metal thingy pushes microswitch a bit but it is as if it does not push it quite enough and when I do this with my finger the boiler and pump fire up and radiators get hot. Assuming wiring is correct if the whole actuator (powerhead) was replaced with new is it fairly safe to assume that this would fix problem (again assuming valve spindle which I have tested moves and it does)

Thanks again.

 

[Echo the husky]

The valve requires no power to make HW work, when CH and HW are needed power is applied to the white wire and the valve moves to the mid position. If only CH required, hot water off signal is applied to the grey wired to push the valve from mid position to CH only.

 

[djuhl]

Hi

Thanks again for your reply.

Me again! I can see the valve moving (as you have described) to 3 diff positions. If I depower and reset everything it starts at left position for HW only and stays there when hot water called, moves to mid-position when HW and CH both called and then moves to right when CH only called but when in that right (CH) position it does not fire boiler unless I "manually" depress microswitch which makes me think that there is a signal to grey wire to push valve but does not seem to be moving far enough to trigger microswitch.

Thanks.

 

[Echo the husky]

I see you took powerhead off of valve with same results, in that case, the new powerhead is faulty and needs to be replaced. Honeywell had problems with the mechanisms in their powerheads a while back after a design change, (presumably a cost cutting design change) but I've only experienced that problem with their 2 port valves. It was easy to check for the faulty valves before installing them, gently operate the manual lever, if the gears jump it is one of the faulty ones.