Drayton Mid Position Actuator MA1

[David]

Merry Christmas one and all.

Staying in another house and there is an ancient and dodgy central heating system.

The valve is a Drayton Mid Position Actuator MA1.

It seems to have two functions; an open/close switch and a three position switch for Heat Mid and Water. I assume that the logic is roughly;

If heating or water is called for the main valve opens and the 3 position valve moves to Heat or Water. If both are called for then the Mid position is selected which allows water to circulate to both.

Digging so far indicates that if the controller calls for heating (with thermostat set above ambient temperature) nothing happens.

If water is called for the main valve sometimes opens and the pump runs.

There are manual overrides for both functions - valve and 3 way selector.

I can (just about) get the cheap plastic piece of shit manual override on the main valve to stay open. The 3 way manual override plastic lever seems to be sticking out of the back of the valve housing - I can see the other end when I waggle it - so I can't move that valve around to see what happens.

At the moment I am assuming that the valve is in the mid way position (otherwise we wouldn't be getting hot water from the tank and some heat from the radiators) and the strange behaviour of the heating is because it only works when the programmer for the hot water is on.

Venting here to see if my conclusions seem reasonable.

One side of the house, the radiators do get hot, Some of the other radiators don't, or at least take a long time (I've only recently put the hot water on constant). Pump is on flat out setting. This suggests that the radiators may not be balanced.

Now some heat is getting to the cold radiators. The new (compared to the others) double radiator is doing something I haven't encountered before. The rear part is heating up but the front part is staying cold. It doesn't have air in because I have bled it (amazingly after a long search I found a bleed screw) and it was full of water.

I assume if the 3 way valve was working properly and the heating side wiring wasn't requesting heating then the 3 way valve would be set to Heat and the central heating wouldn't work. However although I heard the main valve move and watched the plastic lever move, I haven't heard anything from the 3 way valve and the plastic lever seems to be floating.

Anyway having diagnosed this far I'm going to leave it with the central heating and the water heating on full time to see if I can get the temperature in the bungalow up to the expected level.

I'm now trying to remember if for frost protection the water heating was turned off and the central heating thermostat was turned down to 5C. If so that would explain why the house gets cold after a day or so. It also suggest a lucky escape from some freezing if the weather turns bad.

Merry Christmas, everyone!

Dave R

[David]

Supplementary - I'm hoping that it is a faulty thermostat which is clicking but not passing a current. Now if only I'd brought my multi-meter with me.

Access to the wiring is interesting as well. I am used to airing cupboard systems where all the wiring is nicely placed by the door for ease of access. This is behind the clothes shelving half way up the wall behind the boiler and not the easiest place to get to.

Guess what I will be looking for in the Boxing Day sales.

Oh, and that double radiator is still doing my head in. This morning the front is warming up nicely but the rear panel is being slow.

I need to do something to improve the situation because the house will be empty for a time in January and February with a consequent risk of frost damage if the heating doesn't work properly using the thermostat.

Next step wiring diagrams.

Cheers

Dave R

[John Rumm]

Now there is a trick those guys at Victorinox are missing ;-)

[Roger Mills]

I'm not familiar with the Drayton 3-port mid-position valve but if it's like most other makes, it will work like this - as shown in the Y-Plan schematic at

When there is a HW demand but not a CH demand, the valve is un-powered and sits in the HW position. The boiler and pump are powered directly from the cylinder stat.

When HW and CH are calling for heat at the same time, the valve moves to the mid position. The boiler and pump are still powered directly from the cylinder stat.

When there is a CH demand but no HW demand (tank stat satisfied or HW off at programmer) the valve moves to the CH position. A microswitch in the valve actuator switches a live supply to the orange wire - which then powers the boiler and pump.

If the boiler doesn't run when there is *only* a CH demand, it indicates either that the valve hasn't moved all the way to the CH position or that the microswitch isn't working.

The manual lever only moves the valve to the mid position, and is useful when filling or bleeding the system to make sure that all water paths are open. It will flop around when the valve is powered to the mid position or beyond - this is normal.

With regard to the double radiator - unless the two sections communicate at the top, it will have *two* bleed screws - one for each section. You said the first one was hard to find - sounds like the second one is even harder - but it will be there, somewhere! [These are sometimes just over the top on the rear face of each section - often under little circular covers which have to be prized off].

[tabbypurr]

If you've not got a meter yet, you could use a tablelamp. Or better an extension lead that contains a neon.

NT

[David]

Thanks.

Life gets ever more complicated.

First thing in the morning with hot water off the thermostat (tested via twiddling and listening for the click) will turn the boiler and the pump on and off, but not open the shared (flow) valve.

That is, there is a shared (flow) valve which has to open to allow any water to flow, then a second 3 way valve which decides which way the water will flow.

Given that, if the flow valve is permanently open and the 3 way switch is in the middle then water should always flow around the central heating.

However......

For some reason later in the day, with the hot water off and the heating on, twiddling the thermostat does not cause the boiler to fire and the pump to run; I assume causing the pump to run is the critical test because the boiler usually fires a bit after the pump runs.

Nothing like consistent test results.

I still think this Drayton valve is a piece of cheap plastic shit. I am used to the Honeywell valves with metal casings and a nice metal lever arm to lock the valve open which moves firmly and fits firmly into a notch. The Drayton valve has a plastic casing which seems very flimsy, a plastic lever which also feels flimsy and which doesn't locate firmly when locked open, and seems to shake around on the valve body when the pump is running.

Oh, and the 3 position plastic arm is more than just "floppy" - I can see the bottom of it sticking out of the back of the plastic housing so I assume it isn't connected to anything internally.

So I'm still not 100% certain which conditions will make the CH run reliably.

Cheers

Dave R

[tabbypurr]

sounds like a dodgy switch somewhere. Monitor the output of the thermostat to see if it's reliable or not, then ditto the 3 way etc. You'll track it down that way. Intermitten faults just take more time.

NT

[Roger Mills]

I don't understand what this "shared" valve is for. Where is it in the circuit? Any chance you could draw a schematic for the water circuits, and upload it somewhere with a link here to its location? It it's a conventional Y-Plan system, I'd expect to find the pump installed in the flow pipe from the boiler, followed by the 3-port valve - whose 2 outlets go the cylinder coil and radiators respectively. I would then expect to see the outputs from the radiators and coil combine into the boiler return pipe. There shouldn't be any other motorised valves.

[David]

Yes - me getting the flow the wrong way round. So please ignore much of the above. The lever appears to be probably the manual override for the mid port valve and the other strange thing should be used when removing the motorised head.

It looks as though the following thread more or less describes my problem (second post).

or

This suggests that there is probably a dodgy micro switch.

I will test the wiring when my multi meter turns up tomorrow, but it is looking like a new motorised head for the valve.

Regards

Dave R

[David]

<snip>

If you look at this PDF

right at the top there is a diagram of how to fit and remove the head.

For removal it is lock lever (1) and press button (2) then remove the head.

I was assuming that the plastic thing at the mid point of the valve was a valve lock of some kind and got well confused.

It looks easy to replace (for some values of easy) but I have been caught that way before.

gives a good picture which shows the lever on the LHS and the button with the strange black dangly plastic thing by the thumb of the hand.

I hope it is just a replacement of the head because there aren't isolation valves to allow me to remove the complete valve without draining down.

Anyway, how much do you think it might cost to fix this?

I'm noting that I can get the complete unit for around £90 on Amazon, but also for about twice that price. Still looking for the head unit only.

£200 labour £100 parts or am I being optimistic?

Cheers

Dave R

[DJC]

In October I bought Products

1x Drayton MA1 Actuator (23D03) £40.39

from heatingcontrolsonline.co.uk

[tabbypurr]

To replace a few microswitches?

[The Natural Philosopher]

Be aware that the lever will open the valve but NOT actuate the microswitch

DAMHIKT

[David]

To confirm diagnosis, replace head and wire in.

My backstop for being too busy with pressing matters, and also someone who can diagnose further.

I also don't have my DIY tools with me if it needs more than a click off/ click on new with wiring like for like.

[John Rumm]

Many plumbers won't replace the switches... often the best you can expect is swapping the whole valve head assembly.

[David]

Thanks - makes me wonder if an electrician is a better option.

Cheers

Dave R

[tabbypurr]

We however can. The choice is the OP replacing a few switches or paying someone else to replace the head.

NT

[John Rumm]

If you can get the right switch, and don#'t mind lack of heating etc til then. I expect as a DIY exercise, replace the head, but then set about fixing the removed one ready for next time.

[Tim Lamb]

Have we covered *valve not travelling far enough* to operate the microswitch?

[The Natural Philosopher]

I giot a complete valve for less than the cost of the head and simply swapped heads one time.