Heatslave 15/19 - rads on when hot water only selected

[IAEGMOOH]

Have a Heatslave 15/19 and have a problem in that when the 2 channel programmer is set to hot water only (CH off) some of the rads still get hot.
The diverter valve (Has a Drayton ZA3 actuator on it) runs to the HW position when demand for HW is given, when the demand stops the boiler goes off and the valve runs back to the HW/CH position. I realise this is opposite to normal convention but my question is should it stay in the HW position when there is no demand but the timer is still "ON" thus preventing hot water going to the rads (I assume by gravity/convection as the pump is off) ?

 

[dcawkwell]

Normal position and operation of the divert valves is hot water default
with the valve not having to move.

Mid position and then central heating only.

 

[IAEGMOOH]

When the valve runs open it heats the hot water only , switching on the CH as well it runs back to the non powered position and the CH heats as well So is that a programmer fault giving the wrong signal to the valve at the wrong time or the actuator at fault. The actuator is the 3 wire type with no mid position, and I had read somewhere on the great www that these are powered to the HW position and default (non powered) is HW & CH
As i said when the HW is satisfied the valve runs back to default which is HW & CH so giving a path through the rads for the hot water to circulate by gravity

 

[stumpydick]

which model is it, how old, ?

 

[IAEGMOOH]

Heatslave 15/19 on front panel not sure of age (old) we bought a house that we have been renovating (major works) since last Nov so not really been using it and only noticed this problem the other day as we wanted some hot water.
The valve actuator is a Drayton ZA3 and looking on the web that valve body and actuator is not advertised for a 15/19, also just looked at the wiring diagram in the manual and it shows a 5 wire actuator and the troubleshooting flow chart states the valve is off with HW only so maybe someones fitted the wrong valve cos its all he had in the van !!

 

[IAEGMOOH]

The main board will only accept a 3 wire diverter valve see this photo of a similar one on fleabay
http://www.ebay.co.uk/itm/WORCESTER...arden_Hearing_Cooling_Air&hash=item2a0a24f6a2

 

[stumpydick]

diverter is faulty. sounds like an ancient boiler where the diverter energises for hot water, and is not energised for c heating. therfore the c heating port is not being fully sealed off during hot water demand p.s.. there is no mid position.

 

[IAEGMOOH]

when the HW is on and the valve is energised the rads stay cold but when the HW is no demand and the valve runs back then the hot water slowly goes to the rads (the pump is off), so with the valve at default the port is open to CH so the water can circulate, think i need another shut off in the CH pipe to stop it just need to sus out how to wire it in

 

[stumpydick]

turn off rad valves to cure temporarily . does pump continue to run after flow switch has opened and dhwtank stat satisfied? ie no demand for hot water ? if so it could be relay fault on pcb.

 

[stumpydick]

sorry just noticed yuo said pump is off must be gravity circulation.