Hot water not getting from pump to hot water tank

[Charlie]

Currently I don't seem to have any hot water getting into the hot water tank (CH OK). I've had a look and firstly does any one know what this box does:

sits immediately after the pump (which seem to be running OK), on the front it has the letters "H M W" printed and a black switch set to H. There is also a black switch on the side - I couldn't get any of these to move. What is this box?

From this box there are two pipes, the first to the CH (I think) and the second to half way down the hot water cylinder. Now this second pipe has a tap on it which is fully open. However the pipe is hot before the tap and cold afterwards, despite the tap being fully open.

Here's a little pic (sorry it's not perfect, I had trouble getting in there with my phone):

a couple of questions?

1) What's the white box thingy? Is the problem here? 2) Is there a blockage in the tap - can't think why - the tap hasn't been touched. Is it just pipes that are hot before the tap rather than the water inside them?

Any help gratefully received, lack of hot water not going down very well at present :-(

[ARWadsworth]

It is called a "miss-position" valve. There is a 99% chance that the fault is in the valve

There could be, but it is only a 1% chance. It is probably just thermal conduction that makes this pipe hot

[Tim]

It's a motorised three way valve that diverts hot water from your CH boiler to your CH circuit, your HW tank or to both. More than likely the motor within it has died. They do this periodically. Depending on the model, it should probably be possible to either replace just the motor or the whole "head" without having to disturb the plumbing.

Wiser folk than me can probably identify the make and model.

Tim

[ARWadsworth]

It's a Drayton, but not all of the heads can be swapped. ISTR that the older ACL Drayton heads could not be removed.

[Stephen H]

Most common fault is the motor failing on the 3 port mid-position valve or one of the microswitches failing open circuit. There are two microswitches in it.

Also another common fault is the cylinder thermostat on the hot water cylinder. So this is worth testing.

Also, your motorised valve is upside down. This is considered bad practice in case the the water carrying pipework starts to leak. The leaking water then dribbles into the electronics underneath.

I'm told on good authority that when water gets into the electronics in motorised valves, they can literally explode.

The little black bit you see for H M W is an indicator of what state the motorised valve is in. H is Heating, W is Hot Water and M is Mixed.

There should be a small metal lever somewhere on the side of the motorised valve. This is an emergency manual override lever for when the motor fails. If you move this lever to one side, it will put the valve into mid position to give you both heating and hot water, and start the boiler. Useful if you have a cold snap and the heating engineer can't come out straight away.....

Regards,

Stephen

[ARWadsworth]

They won't explode. But yes the valve is incorrectly installed.

Is M not for Mid-position?

That sometimes works.

[Stephen H]

Yes you're right, M i s mid position....

Provided the microswitches are OK........

[John Rumm]

your particular system:

It sits immediately after the pump (which seem to be running OK), on

Zooming in to that picture, it looks like the indicator on the valve is set at the heating position. If you ensure that the programmer is calling for heat, and the cylinder stat is also on, you should see that move to the middle or the W position.

Probably...

Unlikely to be the tap - that does not look like the type of tap that has a habit of failing "shut"...

Most likely, the valve, second the cylinder stat, third the programmer, or fourth the wiring.

If you have a multimeter and are happy using it to read mains voltages, then you could follow the wiring diagram I linked to above and see exactly which bit is failing.

However chances are its the valve. You may find even shifting the manual leaver on the side is enough to free it up enough to work again.

[Charlie]

Yeah, just noticed that the gate valve under the pump (above the motorised value) is leaking very slightly. I guess this is what has caused it to fail.

Have shoved a massive blanket in between to get me through tonight and will have a go/call a plumber tomorrow.

[Charlie]

Yeah agree, if not I can always stick on the immersion. Almost certain the problem is caused by a slight leak to one of the pump gate values which I also noticed

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D\

=A0 =A0 =A0 =A0|

=A0 =A0 =A0 =A0|

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D/

[John Rumm]

If its dripping onto the electrical bit of the valve, then it certainly won't do it any favours ;-)

[Stephen H]

Heres the source of where I found out that 3 port or 2 port valves can explode....

chap that runs the repair service is after some Drayton ACLs as apparently one is suspected of causing a fire and he wants to do some failure analysis for a firm of solicitors.

If you scroll down the page, you will see cremated/exploded valve pictures.

Regards,

Stephen.