Drayton MA1 Mid Position Valve

[S&M]

Hi

Not an uncommon problem - I have heating but no hot water.

I have discovered that if I remove the motorised valve and manually turn the little brass bit there is a very loud 'clunk' as the valve changes position. I then get hot water.

Is this 'clunk' normal when operating the valve manually?

Could it be the actual brass valve that is the problem for me rather than the controller or motorised valve?

Mark

 

[D_Hailsham]

Just to clear up terminology, the whole assembly is the motorized valve; the box on top, which you have removed, is called the "actuator" or "powerhead".

The clunking sound is due to the valve paddle being free; when it's connected to the actuator it will not be able to move so freely. Nothing to worry about.

Does the valve spindle turn easily using your fingers? It will only turn a small amount, say from 11 to 1 on a clock.

When hot water only is called the MV is not used as it is in the hot water only position. The boiler is turned on and off by the thermostat on the side of the hot water cylinder (normally set to about 60C). Set the controls to HW only ON and try turning the cylinder stat up and down. The boiler should light when turned up and go off when turned down. If this doesn't happen, either the stat is faulty or no elctricity is getting to the stat.

Do you have a multimeter, and know how to use it?

 

[S&M]

Thanks for clarifying what the various bits are called.

Good news that the clunk is nothing to worry about.

The valve turns fairly easily - probably about 45 degrees total movement.

I'll try your suggested test this evening when I get home.

I do have a multimeter and know how to use it.

 

[D_Hailsham]

I do have a multimeter and know how to use it.

That will be a great help.

If the cylinder thermostat test works, check the temperature at which it turns on and off (depends on how hot the water is in the cylinder). There should be about 8-10 degrees difference. If the boiler will not light, proceed to the meter test.

Hopefully all components are wired into a large junction box (aka wiring centre or w/c). Most measurements can be done there.

Turn of power at main switch for the ch/hw system
Remove lid from w/c (240 volts inside)
Check all terminals are done up tight
Turn power back on
Set controls to HW only permanently ON (i.e not timed) and CH OFF
Trace the 3 wires from the cylinder stat cable:

1. connects to orange from valve;
2. connects to valve grey;
3. connects to HW ON terminal of timer.

All voltages are measured to Neutral

1. Measure voltage on wire 3: should be 240Vac.

1 not OK: turn power off, remove timer from backplate; check all connections are done up.
1 OK, also check when HW is set to timed ON. If that fails, the problem is with the timer.​

2. If 240V on wire 3

turn cylinder stat to max
measure voltage on wire 1: Should be 240V and boiler should light​

3. Move probe from 1 to 2: Voltage should be 0.

Turn cylinder stat right down:Voltage should be 240V and boiler (if lit) go off.​

If you do not get the correct voltages on wires 1 and 2, check that the connections are done up at the cylinder stat (turn power off first)
If they are OK, the cylinder stat is faulty and should be replaced. (Make a note of stat make and which cable goes to which terminal)

 

[S&M]

Thanks! I'll try to run your suggested tests this evening.

Appreciate your responses.