jambo

[jambo]

just spent the last hour arguing with a developer about motorised valves at the moment he has a worcester 27cdi reg boiler tapped into a 90 ltr open vented cyl he reckons you cant have heating and hot water at the same time its either one or the other can some one clear this up so i can put him straight

 

[grahamgas]

He probably has an old style diverter valve instead of a mid- position valve.

Graham

 

[davetheplumber]

Mid position valve or zone valves

 

[jambo]

two 2 port motorised valves

 

[migoplumber]

if both valves are open, then they will share the heat source. if it was a 3 port valve it would be different

 

[quality]

. if it was a 3 port valve it would be different

mid position has three ports

 

[stevetheplumber]

with two two ports it should be possible to have either or both

 

[Cds]

It might be wired to give Hot Water Priority so that the cylinder will recover quicker.

 

[jambo]

can someone please explain the three port mid positioned vale in some detail please thank you

 

[doitmyself]

can someone please explain the three port mid positioned vale in some detail please thank you

Water enters up the T (port AB) and exits via the side ports (A and B)

When the valve is unenergised port B is held open by a spring. This port is usually connected to the central heating cylinder. Port A connects to the radiator circuit.

When only HW is ON at the timer and the cylinder stat calls for heat, the switch live from the Call terminal of the cylinder stat turns on the boiler. The valve stays unenergised.

If CH is required at the same time as HW the room thermostat will apply 230v to the White wire of the valve. This causes the motor to turn and move the valve from Port B open towards Port A open. Half way across a microswitch trips in the valve and brings into play a clever circuit which stops the motor, thus holding the valve in mid-position with both port A and port B open. The boiler is still turned on by the cylinder thermostat.

If HW then goes off 230v is applied to the grey wire of the valve. This can be either from the SAT terminal of the cylinder stat (HW up to temperature) or from the HW OFF terminal of the timer (HW turned OFF at timer). This then applies 230v to the motor which moves over until only port A (CH) is open. this moves a second microswitch in the valve, which applies 230v to the orange wire, which also turns on the boiler.

Hope that good enough.

 

[jambo]

thanks a lot brilliant info