S plan not firing boiler for hot water

[mrlennie]

Hello all!

I'm a plumber and have a customer where the s plan is working fine for both zones (ground floor, 1st floor + cylinder) but not firing the boiler when hot water demand from the cylinder is operated. 2 port valve opens and pump runs but boiler shows no demand for heat. Any ideas why? Id be very grateful

When I turn programmer on for one of the heating zones the cylinder does begin to heat up...

 

[Leesparkykent]

The hot water valve is obviously opening if its being asked to by the programmer/cylinder thermostat if its heating up when one of the other zones is calling for heat. Seems a little strange the pump is working but not firing the boiler as the pump would either be connected to the pump live terminal in the boiler which means the boiler would have to be receiving a call for heat or connected to the oranges of the valves which only becomes live when the valve opens because it closes the switch between the grey and orange (grey being permanent live). Are you sure the pump is operating just on the hot water call?

 

[growler]

is this an existing heating system or new ?

 

[HandySparks]

When you turn up the cylinder stat, does the pump run immediately or only when the valve has motored open?

 

[mrlennie]

Wow thanks for all your replies. Im not sure that the pump was working on hot water only!
Existing system
40kw heat only boiler

 

[mrlennie]

Handy sparks I didn't check that but i can do when I'm there next?

 

[growler]

is there a reset button on the cylinder ? might have tripped

 

[Leesparkykent]

need to start digging in the wiring centre with your voltage tester I think. check for voltage on the orange of the HW valve when its calling for heat with just HW turned on, on the programmer and the cylinder thermostat turned up.

 

[mrlennie]

Reset button is

is there a reset button on the cylinder ? might have tripped

Overheat stat has not tripped

 

[mrlennie]

need to start digging in the wiring centre with your voltage tester I think. check for voltage on the orange of the HW valve when its calling for heat with just HW turned on, on the programmer and the cylinder thermostat turned up.

I will do. So no voltage would suggest 2 port valve not communicating with wiring centre and message not getting back to the boiler?

 

[Leesparkykent]

I will do. So no voltage would suggest 2 port valve not communicating with wiring centre and message not getting back to the boiler?

Yeah if there is no voltage on the orange but there is voltage on both the brown and grey and the valve has opened it would suggest the micro switch in the valve head is shagged. If there is voltage on the orange check if there is voltage at the switched live terminal in the boiler if there is no voltage at this terminal it would suggest a shyte connection between the orange and the boiler switch live.

 

[mrlennie]

Yeah if there is no voltage on the orange but there is voltage on both the brown and grey and the valve has opened it would suggest the micro switch in the valve head is shagged. If there is voltage on the orange check if there is voltage at the switched live terminal in the boiler if there is no voltage at this terminal it would suggest a shyte connection between the orange and the boiler switch live.

You sir are a genius. I will try this and report back.

 

[Leesparkykent]

You sir are a genius. I will try this and report back.

Let us know what you find