Unvented system wiring help

[davesparks]

Hi, this system is not connected to the boiler, it's stand alone hot water, does that not make it a direct system as the water is heated directly by the source ( element).

If it's not connected to the boiler then why does it have a flow and return pipe connected to it, and a two port valve?

That is an indirect cylinder, not a direct one.

 

[davesparks]

Every unvented has a 2 port, fail safe / safety device

Only indirect cylinders do. There is nothing for a valve to operate on in a direct system.

The safety cutout on a direct system is incorporated in the immersion heater thermostat.

 

[Sparkgap]

Every unvented has a 2 port, fail safe / safety device

All unvented cylinders have mechanically operated temperature/pressure relief valves. I have also seen more recently cylinders with two-port motorised valves on the hot water outlet with an over temp thermostat which shuts it if the water gets too hot. This is because even if the overtemp cutout on the immersion heater works you still have a cylinder full of too-hot water.

 

[Toneyz]

Reading this post has not answered the OP question.
These unvented cylinders should have immersion heaters with H/L stat built in.
How is the domestic hot water being heated the impression I get is direct from the immersion heater in which case as Davesparks posted the pump is secondary hot water pump via time clock which makes sense. What is the valve for ?.

 

[davesparks]

Reading this post has not answered the OP question.
These unvented cylinders should have immersion heaters with H/L stat built in.
How is the domestic hot water being heated the impression I get is direct from the immersion heater in which case as Davesparks posted the pump is secondary hot water pump via time clock which makes sense. What is the valve for ?.

That is an indirect cylinder, the motorised valve is on the flow connection.
The yellow pump is a secondary pump,