Central Heating: Replacing Drayton 3 Way Mid Position Valve

MikeHayward1 · 9 Feb 2009

Hi,

New here so be gentle with me. I'm OK with most DIY tasks but just want to check this out with you guys.

We developed a problem with our central heating yesterday. We get hot water but once that has reached the required temperature the boiler will cut out and not fire for the central heating.

I've narrowed down the problem to the mid postion valve (a central heating enigneer has also confirmed that this is the likley cause).

The valve is a old ACL Drayton Lifestyle 679H340-30L0, I've searched the net and found that Drayton do a direct replacement which is a 'press fit'. The old unit which is fitted is not a press fit.

Advice has been offerred on the forum that indicates that the head of the old unit can be dismantled.

Before I go any further can I confirm that after disconnecting the electricity all I have to do is dismantle the unit (the head??) without touching the pipework. The replacement can the just be fitted direct.

Sorry to sound a bit thick on this but I just need to check before going any further.

Thanks in advance

Mike

seco services · 9 Feb 2009

does the heating come on if you push the lever on the end of valve across ?

MikeHayward1 · 9 Feb 2009

Thanks for the reply.

No, nothing happpens if you push the lever across. The only way to get any heating on is to turn the thermostat up on the hot water tank.

Could this be something else??

I replaced the thermostat in the livining room yesterday, this is the only room themostat in the house, this has made no difference.

I thought the circuitry in the valve maybe faulty.

seco services · 9 Feb 2009

turn the heating/hw on programmer off.
then turn the power to the heating system off, then turn back on. this will reset the valve to relaxed position.

the lever on the end is it floppy or has it got resistance on it when you push it across ?
also the marker lever on the side what is it pointing to W M H ?

MikeHayward1 · 9 Feb 2009

OK,

Done that the lever remained in the position marked W with the electric on and off. There is resistence when moving the lever mannualy.

MANDATE · 9 Feb 2009

HI Mike! I've read it that you can not remove the head of a 679H340 3OLO.
New drayton valves now come with removable head.
If you do a search for the author 'gooseander' it should confirm that.
Now 'grindstone' had problems for a year and finally got it down to the mid position valve and he has a drayton 679H340 3OLO.
He made the mistake of purchasing a head MA1 which he could not fit.(should have got and replaced complete valve with head).
However he did manage to exchange the inards of the old valve for the new one.
It's best if you have read of 'grindstones' thread

seco services · 9 Feb 2009

put the heating on a programmer lever will move to H.
if boiler don't fire up micro switch sounds like the faulty part.

MikeHayward1 · 9 Feb 2009

put the programmer to heating, the lever remains at W, the boiler hasn't fired up.

I'll look into the issues rasied by MANDATE regarding the head being unreplacable.

Thanks for the advice guys.

seco services · 9 Feb 2009

if you turned heating on at programmer, wall stat up, and no boiler firing
then the motor has failed.

under a tenner job done.

MikeHayward1 · 9 Feb 2009

I recognise that!!

Where do I get one from?

seco services · 9 Feb 2009

any plumbing shop

MikeHayward1 · 9 Feb 2009

Great thanks.....

I'll update a progress report at a later date.

MANDATE · 9 Feb 2009

MikeHayward1 said:
I recognise that!!

Where do I get one from?

You'll see them at Wickes or B & Q about £18.

MikeHayward1 · 13 Feb 2009

I'm back.

Replaced the motor, which was simple enough. I'm now getting the lever moving fully between H M and W which I don't think it's ever done.

The radiators have got hot whilst the water is heating up but once the water has reached temperature the boiler is not firing to continue heating the central heating.

what next??

seco services · 13 Feb 2009

once the water is at temp what does the marker on the side go to W M H ?

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Central Heating: Replacing Drayton 3 Way Mid Position Valve

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