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[Sir Tigger KC]

My boiler has been kettling and the rads not getting very hot, so on Monday I drained the system, filled it/drained it again, then filled and added a bottle of Sentinel X800 cleaner and left it for 24 hours.  I had the heating and hot water on for several hours on Monday evening and then left it to do its thing as normal via the timer. 

Yesterday I drained it, filled/drained it again and then filled and added a bottle of Sentinel X100 inhibitor.  The water came out with an orange tint so I guess the X800 did its job.  The rads now get nice and hot and the boiler is running a bit quieter. 

However.    The boiler dosn't come on when I switch on the hot water, and if I switch on the hot water when the boiler is running the central heating it shuts down.    I can hear the motor in the 3 way valve whirring, but then the boiler shuts down. 

'dangle berries'! 

Any ideas chaps?    I'm wondering if some crud has lodged in the 3 way and it's jammed. 

TIA! 

[Kevin Wood]

3 way valves are pretty crude things at the best of times. Maybe it's got a bit of crud stuck in it, or the microswitch inside has died. There's also normally a resistor and a diode that applies DC to the motor to "stall" it in the central position when both heating and water are on which sometimes burns out (I told you they were crude!).

If it's not working in HW mode, I would say it's either jammed and not returning to the "HW" position or the microswitch is dead.

First thing to do is to find the position indicator on the side of the valve and see if it's moving to the correct positons when commanded by the heating programmer. If not, remove the motor and give it a good waggle by hand.

[STEMO]

When three way valves start going wrong, you can usually get away with giving them a whack to start them moving. Of course, this method only works for a short time, until they give up altogether.

[Sir Tigger KC]

The motor whirs, but the position switch dosn't move.  I can move it by hand though....

I gave it a whack, but it's still not behaving.
 
I guess I'll have to take the head unit off and manipulate the valve by hand?

[STEMO]

The motor whirs, but the position switch dosn't move.  I can move it by hand though....

I gave it a whack, but it's still not behaving.
 
I guess I'll have to take the head unit off and manipulate the valve by hand?

Why not just replace it? They're cheap enough and it's only a couple of compression joints and a bit of simple wiring. Just make sure you make a note of which wires go where.

[Kevin Wood]

Sounds like something has broken in the drivechain between the motor and valve, then.

The motor normally runs until the valve is open and then stalls, once the motor is de-energised, a spring returns the valve to the opriginal position.

Might be worth taking it apart and checking that the gear on the motor is meshing with the valve.

[STEMO]

https://youtu.be/T7UTDtrmcvM

[Sir Tigger KC]

Just watched the video that Uncle STEMO posted (I like that guy, he explains things very well.  ) and I have the same Honeywell 3 way valve as he does.

When I move the position switch, there is no resistance.  When he moved his in the video, you could hear the motor moving?   

Strange though that this has happened after running the system with a cleaner and draining/flushing a few times. 

[Allenm]

Hot Water is the standard position on a 3-way valve, so if it is ok when the programmer is only calling for central heating, then it is working, but it sounds like you have some crud blocking it from springing back to the default position.
If you are getting 240v through the orange wire to the 3-port valve when the hot water is calling for heat, then the electrics are ok.

I would drain down again (assuming you don't have isolators either side of the 3-way valve), take it apart and clean it through, if that doesn't work, just replace it, as Stemo says, they are not expensive.

[STEMO]

Just watched the video that Uncle STEMO posted (I like that guy, he explains things very well.  ) and I have the same Honeywell 3 way valve as he does.

When I move the position switch, there is no resistance.  When he moved his in the video, you could hear the motor moving?   

Strange though that this has happened after running the system with a cleaner and draining/flushing a few times. 

As Kevin said, the linkage between the motor and the valve has broken. You can fiddle about with it but I doubt it would last long, even if you got it to work.

[Kevin Wood]

I think on the Honeywell valves, you can just replace the motor, meaning you don't need to drain it.

Given that the failure seems to be between the motor and the valve, and that you've just filled it with inhibitor, I think that would be worth doing.

You can always buy the whole valve, swap the motor part and keep the plumbing half for when you next have the system drained.

As to why it failed, maybe the gears were getting weak, and some crud got into it as part of the flushing process and this was the last straw?

[Sir Tigger KC]

I've just removed the head off the valve and the valve moves freely, but not very far about 20 degrees or so? or in others words from 3.30/9.30 to 2.30/8.30 on a clockface.... If you see what I mean? 



Does that sound right?

[STEMO]

I've just removed the head off the valve and the valve moves freely, but not very far about 20 degrees or so? or in others words from 3.30/9.30 to 2.30/8.30 on a clockface.... If you see what I mean? 



Does that sound right?

I've no idea 

[Sir Tigger KC]

I've just removed the head off the valve and the valve moves freely, but not very far about 20 degrees or so? or in others words from 3.30/9.30 to 2.30/8.30 on a clockface.... If you see what I mean? 



Does that sound right?

I've no idea 

Thanks! 

[biggriffin]

It's about time sir Tig that you paid a professional to fix your heating, instead of continually bodgeing it....