Cylinder thermostat

I take it that the "Calling" signal will be live if the water temp has dropped to low in th cylinder??? What should "Satisfied" signal be during this???

Then what happens when cylinder temp is ok with respect to "Calling" and "Satisfied" signals.

Also how does this correspond to my thermostat which is marked "Common" , "1" and "2" THANKS

If you are not sure which connections to terminate on?

Use your continuity meter on terminal marked common © and either terminal (1) (2) Turn the dial on the cylinder stat to a higher setting and you should get continuity on the terminal that will call for heat, turn the dial down and you should loose it hope this helps CJS

I take it that the "Calling" signal will be live if the water temp has dropped to low in th cylinder??? What should "Satisfied" signal be during this??? Then what happens when cylinder temp is ok with respect to "Calling" and "Satisfied" signals.

Also how does this correspond to my thermostat which is marked "Common" , "1" and "2" THANKS

Click to expand...

(1)Turn stat to MAX & select hot water only at programmer

(2) Should now be live on terminal 'COM' and terminal 1 & approx. 20V at terminal 2

(3) Select heating only at programmer

(4) All terminals should have no voltage

Job done.

(1)Turn stat to MAX & select hot water only at programmer(2) Should now be live on terminal 'COM' and terminal 1 & approx. 20V at terminal 2

(3) Select heating only at programmer

(4) All terminals should have no voltage

Click to expand...

Sorry, not so. We need to know if we are talking S plan or Y plan.

2) above is only true for a Y plan and 4) is only true on S plan

As PCelectrics says, we need to know what sort of valve arrangement you have? Do you have separate motorised valves for Heating & Water? Or one 3-port mid-position valve? This will effect the voltages you will get at the cylinder terminals.

Doc H.

Thanks all! its a 3 port mid position valve fitted.

How can i tell if its "S" or "Y" plan just by looking cheers.

Think s plan is 2 2 port valves and y plan is just one mid position valve but not 100% so stand to be corrected. Cheers

Thanks all! its a 3 port mid position valve fitted.How can i tell if its "S" or "Y" plan just by looking cheers.

Click to expand...

3 Port Mid position valve is a 'Y' plan..

This is the one where you can get what appears to be unexpected voltages at the cylinder stat..

As you say earlier..

'C' on your cylinder stat is the 230v trigger from the programmer 'Water ON'

'1' on your cylinder stat is the 230v output to fire the boiler while the water is cool.

'2' on on your cylinder stat is the 230v output to the Grey wire on the valve to position it all the way over for heating only, while the water is hot.

The first confusing bit comes because you get 230v on '2' when the Hot water is switched off at the programmer;

This is because 230v is needed on the grey wire as stated above..

(and the grey is common to '2' on the cylinder stand AND the water OFF at the programmer.)

The second confusing bit comes because you get 230v on '1' when the Hot water is switched off at the programmer and the heating is switched on.

This is because 230v is fed via the orange on the valve to the boiler..

and the orange is common to '1' on the cylinder stat AND the boiler live trigger.

So it is possible to be getting 230v reading with respect to earth in a varied bunch of situations NOT just your water on/off requests..

The Honeywell drawings are in the downloads section..

If you look at the ones for the 'y' plan it "hopefully" will make more sense!

:Salute

Just to confirm as well that P/L = perm live and S/L=switched live?

PL can also be pump live

Just something I thought I`d throw in - not connected to the O/P but......

If you have an unvented cylinder, there are generally 2 seperate thermostats on the cylinder: 1 standard and 1 resettable overheat stat.

Now- many people will wire these two stats up in series; however it isn`t a good idea. Why?

Because if the overheat sta has tripped, the householder may not realise, and could think the 2 port valve is faulty - so they open it manually. This would throw heat back into the cylinder; which cannot be controlled by the stat; as the stat is usually wired up in the supply to the 2 port valve.

So - the correct way to do this is to wire the hot water stat in the usual way; but put the valve`s microswitch contacts through the overheat stat. Then manual operation of the valve will not fire the heat source, as the microswitch path is interrupted by the overheat stat.

KME