Cylinder & Room Stat states in wiring diagrams

[GSUK]

Hi there,

I'm trying to work out a Y-Plan wiring diagram with a Honeywell timer.

Honeywell (top left diagram on last page)


What I can't work out is what state the cylinder stat is shown in. I.e is it showing the state of the valve when the water is cold or hot?

Same goes for the room stat as well. Are they showing it closed when the room is below setpoint or above?

I'm guessing it's showing the state of a system that is off with a cold tank and cold room. Correct?

Thanks in advance,
Glenn

 

[spraggo]

Your guess work is correct, they are both calling for heat, normally closed, (nc). They will switch open when temp is satisfied

 

[D_Hailsham]

What I can't work out is what state the cylinder stat is shown in. I.e is it showing the state of the valve when the water is cold or hot?

The cylinder stat is showing the state when the HW is satisfied, i.e up to temperature.

Same goes for the room stat as well. Are they showing it closed when the room is below setpoint or above?

This one's the other way round! It showing the stat calling for heat. When the stat has reached temperature the stat will open.

 

[D_Hailsham]

Your guess work is correct, they are both calling for heat, normally closed, (nc). They will switch open when temp is satisfied

I think you should look a bit closer!

The HW stat is on terminal 2, which is the SAT terminal. If you trace the wiring you will see that terminal 2 connects to the valve grey wire.

What is "normally", in this context? It's not like a relay where normally means unenergised.

 

[spraggo]

Your guess work is correct, they are both calling for heat, normally closed, (nc). They will switch open when temp is satisfied

I think you should look a bit closer!

The HW stat is on terminal 2, which is the SAT terminal. If you trace the wiring you will see that terminal 2 connects to the valve grey wire.

What is "normally", in this context? It's not like a relay where normally means unenergised.

Hi, please correct me if I am wrong but it is my understanding that the grey wire holds the valve in the midi position when both the HW water and CH is calling.

Regards

spraggo

 

[D_Hailsham]

but it is my understanding that the grey wire holds the valve in the midi position when both the HW water and CH is calling.

No.

The grey wire holds the valve in the CH only position. It's the white wire that sends the valve to the mid-position from HW only.

Read How a mid-position valve works