Central heating Y-Valve

[sotal]

I seem to have constant problems with the Y-valve on the central heating

I replaced the head last year which improved things but we still had some issues.

Then I've forgotten about it all year as we haven't had the heating on, now we're back to colder weather we have started to use the heating and we are having problems!

The other day I put the heating on for an hour, all worked perfectly well the radiators heated up nicely and the house became warm - then when bath time came we realised the water was scalding hot even though it hadn't been on since earlier (before the heating was on).

Tonight I put the heating on (the water was already on for heating at this time) but half an hour later the radiators were still cold. Pulling the lever on the side of the valve has made the radiators start to w?arm up but it doesn't seem right.

Any ideas what I should check?

It's a conventional system. The boiler is only a couple of years old, the y-valve is about 6 years old although the head was replaced last year.

I think the valve is a danfoss valve.

 

[45yearsagasman]

If you remove the head you should be able to rotate the exposed spindle by hand. It does sound like yours may be seizing up. If this is the case, then it is possible to renew the valve internals, but renewing the complete valve is a better option. Do the check first and come back.

 

[MANDATE]

looks like you'll have to replace the valve head again unless it's just the motor thats faulty
Sounds like the valve moves to mid position but no further or you're moving it to mid position with the lever.
The problem with mid position is that its only temporary position. Both HW and CH get a equal share of heated water until either HW becomes satisfied or CH becomes satisfied then one of the ports gets closed leaving the other one fully open.
The boiler gets its power through the HW cylinder stat at HW position and HW/ch position.
When HW becomes satisfied there are two actions required.
(1) The valve has to be driven by the motor to CH position
(2) A micro switch has to be triggered to allow power from the valve heads 'orange' wire to light the boiler.
Regarding (1)
programmer provides power to room stat.
room stat provides power to valves 'white wire'
power has to go through micro switch contacts to drive motor to mid point.
power has to go through different contacts on same micro switch to drive motor from mid point onwards.
Regarding (2)
Dirty/burnt contacts on second micro switch prevents power leaving the valve head to light boiler.
The lever is provided for the purpose of latching the valve in mid position when filling the system. Using it to wind the motor forward it will only take it to mid position.
So you can not get CH on its own.
With a replacement head you do start afresh with new motor and micro switches, but best to check power to the valves 'white' wire before spending

 

[sotal]

Thank you both for the answers - much appreciated.

I have removed the head and found that I could not move the spindle by hand at all and there was visible corrosion around the base of the spindle.

I have sprayed penetrating oil and used mole grips to free it off, it now turns by hand although there is a tight spot at the same point. It does just keep turning in either direction is that correct?

I've put the head back on, I tested HW first nothing happened but the water is probably much hotter than the stat wants from the heating. I then tried heating and I can't hear the valve doing anything but the heating kicked in and the pump started whirring.


Thinks I noticed but am not sure about...

As I wasn't disconnecting any electrics I left the power on, the control panel was set to off on both so neither were calling for heat. The head felt quite warm which I put down to the heat from pipes etc but it still felt very warm half an hour later when I came to put it back - it also feels like it is buzzing a little - is this normal?

The lever on the side is now in Auto (had gone back by itself before I started taking things apart) When I slide the lever there is no resistance - is that right - I remembered it feeling like you were pulling a spring (but that might just be a memory of an old Honeywell one from the last house?!)

Looking from underneath I expected it to turn the plastic bit that goes round the spindle when I moved the lever but nothing appears to move - is that correct?


My guess is that the spindle seized and now the head has broken inside - something works to energise the system but the spindle doesn't get moved?

What I don't understand is...

For the last 6 months we've only used HW, the rads have never warmed up while using the HW so I wouldn't expect the spindle to be in the mid position. Yet when we use CH both are heating.

Am I right in thinking I need a whole new valve really? Is there a more reliable one to buy?

I think when I replaced the head last year I turned the spindle with molegrips which probably made it work for a bit (and sporadically) with the new head but has now ruined the new head.

 

[45yearsagasman]

Replace it with a Honeywell v4073 mid position valve.

 

[sotal]

Thanks - is there any difference between a 4073 and a 4073a?

Thanks

 

[D_Hailsham]

Thanks - is there any difference between a 4073 and a 4073a?

The correct number is V4073A, but it's often referred to as a V4073.