Sticking central heating valve (y-plan)?

Blimey, these things always happen over a cold weekend, don't they?

Are the heads to Honeywell 3-port valves interchangeable? I know they are removable, mostly, but is a new one the same as one from 1985 (I guess)?

My tenant called to say the heating wasn't working and I've just been over to try to see if I can work out what's wrong. The hot water seemed to be on all the time and the central heating only coming on intermittently. Obviously I need to get this fixed sharp-ish (they have small children, as we do).

It's just a "y plan" system. House built in 1985, not quite big enough for multiple heating zones. It's an open vent system with a boiler and timer-controller in the kitchen, and pump/valve/junction box all in the airing cupboard with the cylinder.

One question: does the manual override lever on a mid-position valve do anything? The lever on this valve is permanently loose whether the heating/water are on/off. On a 2-way valve (as I have at home here) I know I can energise the valves with the lever.

I'm not entirely sure that I could detect the valve energising or doing anything when fiddling with the heating controls.

Is it a typical fault for the valve to get stuck and fail to operate the heating? If the motor fails, the valve sticks in the water only mode, or the heating only mode?

After kicking the motorised valve and switching the hot water permanently off at the timer-controller, the heating circuit appeaered to come on and the water circuit appeared to start cooling down - but it seemed to take a long time for heat to get to the radiators and by the time I had to leave again, only the upstairs was getting warm. The tenant had bled all the radiators and the result was horribly black, so think I shall have to get someone in to give the whole thing a proper flush.

Michael

Reply to
Michael Kilpatrick
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If it has a 'nipple/knob' on one end of the top plate, then the actuator can be taken off without draining down. If it is a flat top plate, then it'll be a drain down to take it off, so better to change the whole lot rather than just the actuator.

Reply to
A.Lee

Yes, forgot to put it in, they shoudl be a straight swap.

Reply to
A.Lee

BTW Al, thanks for the info re these valves, got one for £42 valve + actuator at my local PM. Half the price I found online.

Reply to
The Medway Handyman

"manual overide" is a bit of misnomer it ought to be called a "filling lever" or similar. It's there to crack the valve open so that air doesn't get trapped when filling. It can be used to have the valve open should the control system fails but if the valve gets motored it will unlatch.

That sounds more like a failed pump and you are only getting gravity circulation around the heating.

Has it got inhibitor? Has that bee topped up occasionally over the years. I wouldn't worry too much about black if it has inhibitor.

Reply to
Dave Liquorice

Highly likely. Mine are 1988 installation and I've had to change the motor units more than once.

Reply to
charles

Thanks very much. I appreciate the answer but I'm not sure I know what you mean by the top plate! However, I did take the steel cover off the actuator unit to look inside breifly (just one screw, and lift the side outs to extract) and it looked as though the actuator screwed onto the brass valve body.

Michael

Reply to
Michael Kilpatrick

But the pump certainly appears to be pumping. It's rather quiet but it's definitely vibrating and water is circulating. The pump failed three years ago, if I recall, and so it's a reasonably recent replacement.

Michael

Reply to
Michael Kilpatrick

Look at the picture here:

The U shaped cover has a small nipple in the middle of the top of the plate. That is the indication that the actuator can be replaced without draining the sytem. If your top cover is flat, then you'll need to drain down, as once you undo the screws holding the actuator to the valve, the water will come out. I've no idea when the design changed, but check before you undo any screws that go into the valve body.

Reply to
A.Lee

Ah, I think I see what you mean.

I've just found another picture which is taken from the right angle to see the bobble very clearly, and an explanation:

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thanks,

Michael

Reply to
Michael Kilpatrick

On 24/03/2013 18:20, A.Lee wrote:480

Tenant reports the existence of a lump on the cover. Good news. I guess I can get a replacement at a builder's merchants etc in Cambridge in the morning and try and fit it myslef, then do some diagnostic tests on the electrics. Then get someone in to flush the system.

Michael

Reply to
Michael Kilpatrick

As a responsible landlord with a duty of care why have you not brought in a plumber? As the tenant has small children this should be of concern?

Reply to
Mr Pounder

I wouldn't expect many plumbers to respond as quickly as the OP. He's clearly intending to sort out the problem tomorrow, so I'm left wondering what is the problem?

It sounds like you're a disgruntled tenant?

Reply to
Fredxx

I'm not a tenant but I know that many landlords like to do things on the cheap. I could tell you some horror stories.

Reply to
Mr Pounder

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