Central heating peeps.....hot water issue

[digitalfailure]

I have a hot water / heating system that uses water heated by the boiler to heat the cylinder in the airing cupboard, except this morning it didn't!

I thought i'd heard the boiler fire up this morning before i climbed out of my pit......but maybe I was mistaken as it was soon apparent the water was cold when I jumped in the shower

Ive been reading the net and it seems common for the mid position valve to fail, mine is a british gas branded Drayton Ma1 unit.

Before I attack it, I want to be a bit clearer on a couple of things as the water heated up when i had a fiddle with the valve while the controller was set to ON as opposed to it's timed setting.

1. The small lever on the side should rest in W (water) with power off and move with moderate force before returning on it's own to the W position , is this with heating turned off by the controller...or heater electrically isolated (fuse out). Mine's currently living in the M (mid-both) position and refuses to move with moderate force while the programmer is turned off (but still powered)

2. On the end furthest from the wires there's a stubby lever which is referred to by drayton as the lock, what's it's purpose and where should it rest while in normal operation. I know it's not the quick release button because thats adjacent to the W M H lever on the side. It was this Lock lever i fiddled with and when the water was heating I assumed it had freed something off but not sure if it's actually in the correct position or not now as theres no labelling on the case.

This evening when the timer clicked in for the water to heat up (CH still set to off) the boiler kicked in OK but the rads all around the house were much warmer than usual (the upstairs rads have always been warm to the touch when the water heats but downstairs stayed cold)

Any help is appreciated
Df

 

[andyred]

Hi Brian

I'm not a plumber or expert by any means - so If I'm wrong, apologies ...

Sounds like a similar set up to ours, where the boiler fires up and in the airing cupboard there is a 3 way valve - which either diverts the hot water from the boiler to the rads or to the cylinder or both (depending on which is calling for it) - do you have a thermostat on the cylinder ?

If you have, I would suggest, switch you're heating on, and make sure your room thermostat (rads) and hot water cylinder are turned down so nothing is calling for the boiler to fire up, then turn the thermostat on the cylinder up in temperature and you should hear a click (from the thermostat) and then your boiler should fire up, the 3 way valve should then move to the cylinder heating only and away it goes.

If no click, could be a faulty cylinder thermostat - not calling for hot water, therefore the valve won't move...

If a click, but the valve doesn't move, then this suggests a faulty valve...

This is the process I went through a few years ago, when I suspected an issue with ours and worked a treat and showed the 3 way valve was playing up, changed this and no issues with it since...

Hope it's of some help
A

 

[andyred]

This evening when the timer clicked in for the water to heat up (CH still set to off) the boiler kicked in OK but the rads all around the house were much warmer than usual (the upstairs rads have always been warm to the touch when the water heats but downstairs stayed cold)

Any help is appreciated
Df

This would suggest to me the valve is stuck in a mid position - hot water being sent to both rads and cylinder even when it's just the cylinder calling for it - my rads don't get warm if it's just the hot water calling for it ...

 

[Suvv]

1. the valve which the lever is connected to is sprung loaded to the W position so with no power at all it should got to W. With the system switched on and calling for hot water the lever should stay at W and the boiler and pump should start. Only the Cylinder should warm up, if the rads are also getting warm the valve is not closing off the heating fully.

2. The lock lever locks the valve and prevents it from being pulled by the spring back to the W position, as soon as power is applied to the valve it becomes unlocked. You can use this to set the valve to the mid position manually, disconnect the valve and have the heating and water heated while you sort a problem out.

If you turn the whole system off the lever should go to W under the spring tension. If you then turn on just the hot water, making sure that the cylinder stat is calling the boiler should fire and the lever should remain at W, if you then turn on the heating and turn the heating stat to call the lever should go to M, where the driving motor is electrically stalled, and you should have hot water going to both cylinder and rads. If you then turn the hot water off the lever should go to the H position and only the rads should get hot.

If you get warm rads when only the hot water cylinder is calling then the valve is letting by as it is not electrically driven to the W position it is solely the spring which pulls it across.
The valve actuator, which contains the spring, motor, micro-switches and pcb is clipped to the top of the actual valve and can be changed without any plumbing work, just electrical connections, however if the valve is letting by then that will not solve that problem.

 

[digitalfailure]

Im sure I posted a reply to this thread earlier from my phone and it's not showing here.......I've probably posted it on another site and someones having a wtf moment trying to understand why theres an unrelated central heating question in a thread

When I got home this evening about 20 mins after the water should have finished heating the rads downstairs were cold (as expected with no demand for heat made to the CH), but the water didn't feel as hot as expected. Flicking the heating on with a 22 degree call for heat the little lever on the side of the actuator moved to the right and the rads warmed as expected.
The lock lever thing on the end is still over to the left but now feels a bit floppy (2-3mm movement) when the heating is running.
I seem to be getting every failure mode possible from the pesky thing, I never minded the warmth on the upstairs rads when the water has heated, especially on cold days when you're getting out of bed......the downstairs rads always stayed cold. Most reports of these failures suggest hot water is maintained and heating is lost as the valve defaults to W

for what the bits look to cost on screw fix I might just bite the bullet and renew the mid position actuator and the cylinder thermostat and have done with it....... then if it's still acting up it's time to start thinking of a call out

 

[Suvv]

floppy is good! The manual lever should be floppy in normal use so that's OK.
The warm rads when only HW is called for is just the valve letting by a little bit If it does not bother you then that's OK.
When the all the rads were hot even though the CH was off it is possible that the lock was still engaged and the valve was locked in the M position, that is the mid position to give both HW and CH. So possibly that's OK.
The only problem then is that the HW was not hot in the morning, the normal faults are either the HW cylinder stat or the 3 way valve.

Carry out the following steps and see what happens after each.:
Turn the whole system off and the lever should go to W
Turn the HW and CH stats down and turn the system on again, the lever should stay at W with no pump and no boiler
Turn the HW stat up and the pump and boiler should run with the lever staying at W
Turn the CH stat up and the lever should move to M with both pump and boiler running.
Turn the HW stat down and the lever should move right across to H with both pump and boiler running.

 

[Darkroom]

Remove the actuator head and turn the valve spindle and see if it turns freely. If it's jamming, move it from lock to lock a few times and it might free itself up. If it's still very stiff/jamming or takes a lot of effort to turn then the complete valve will probably need replacing. If it moves freely then the actuator part is probably faulty. It's also possible to get just the motor in the head if rest of the head mech is fine.

 

[digitalfailure]

Sods law dictates that it's working correctly now since i fiddled with the levers. Guess it must have been sticking and it's freed off now.

I've book marked this thread, the law of sod is sure to be invoked again when it's below 0 and the shops are shut !

Thanks all for the help

 

[shapeshifter]

Remove the actuator head and turn the valve spindle and see if it turns freely. If it's jamming, move it from lock to lock a few times and it might free itself up. If it's still very stiff/jamming or takes a lot of effort to turn then the complete valve will probably need replacing. If it moves freely then the actuator part is probably faulty. It's also possible to get just the motor in the head if rest of the head mech is fine.

That is what I do as the valve spindle sticks.I just remove the actuator(two screws) and use some pliers to spin the valve spindle at the same time as applying some DW40.If you do not free the valve spindle up it will burn the actuator motor out. It's easy to do.