Problems with diverter (Radiators warm up, then cool down)

[vern]

I have the similar problem as jezbo's problem.

My radiator heated up then stop heating until the next start.

I think the problem comes from the diverter (mid-position valve).

It has W-M-H. When the central heating is just turned on, it switched to H.
Then after it runs for a while it switches to W and stays there, which mean theres no water going to my central heating anymore...

I wonder what causes the problem...since its a new fitted boiler, clock, thermostat and mid position valve.

boiler is a vaillant thermocompact 620, and the clock & stats is Drayton.

any help is appreciated ! many thanks.

 

[brumylad]

sounds a bit like the wiring is set up as a W plan and there is perhaps a fault on the cylinder thermostat ?

Anyway just ignore that waffle, tell us more.

What are the settings on the timer when this happens (water on heating on etc.)?,

is the pump running at this point?

have you tried turning up the room stat.?

 

[vern]

I am now thinking if its the boiler that causes the problem? because it just switched on ONCE from cold , then when the water is heated and CH is hot enough. It then switched Off and stays Off.... until the next program starts again from cold.

On the timer theres HW override and CH override.

If the just press the HW override button, nothing will happen.
Only if I press the CH button the boiler will comes on.

When the boiler is ON, the diverter switches to H and lever goes In. When its off it switch back to W with the lever come out.

I tried turning up the room stat but still no luck.

 

[corgigazza]

wiring on prog incorrect (3 port valve) wiring should have perm live +neutral+hw on+hw off+ch on normally hw off missing meaning when cylinder stat satisfied ch stops.

 

[vern]

corgigazza, I think you are right.

I opened up the control unit, and here are the diagram :

N L 1 2 3 4

1- HW OFF
2- CH OFF
3- HW ON
4- CH ON

currently there are connection for N, L, 1, 3, 4

So what does it mean? How should I do to correct the wiring?

 

[corgigazza]

the wiring is correct in the prog, check wiring centre the hw off (1) should go to the gray wire on the three port valve and also the hw satisfied from the clinder stat, get hold of wiring diagram and check all wires.