Cylinder thermostat wiring - Wiring Centre

[stu550]

I have a CH/HW programmer wired into a Honeywell wiring centre.

There are three wires into the 'CYL STAT' terminals, 'C', '2' and '1'.

I think I am right in saying that the cylinder stat is a single pole double throw, hence the 3 wires?

I want to be able to add a switch (to work in series with the programmer) so I can switch the Hot Water on or off without having to adjust the programmer. I don't want to override or 'boost' the hot water. Just do the same job as switching the Hot Water between 'Auto' and 'Off' on the programmer.

Can I do this by adding a wire to one of the wires to the cylinder or is more complicated than this because it is a SPDT?

I.e. does the hot water programmer in the 'off' position actually close the valve?

Having got a wiring digram for the wiring centre I know that the '2' on the cylinder stat goes to the grey and the 1 on the stat goes to the brown on the mid position valve.

I'm just getting a bit confused now!

Thanks.

 

[picasso]

Is your programmer difficult to get at ? I cant see another reason for an extra switch but anyhoo a single pole change over switch is what you need, if you connect the output from the programmer to com when the switch is in one position it will run as it normally would through the cylinder stat and in the other position will send 230 to the valve shutting it off.

 

[D_Hailsham]

I.e. does the hot water programmer in the 'off' position actually close the valve?

The simple answer is NO.

For a fuller explanation read How a mid-position valve works

 

[stu550]

Not difficult to get at, I just want guests (in a rental property) to be able to turn the hot water on/off but not adjust the programming.

Not sure i follow the above I'm afraid. Maybe m reading it wrong but the two answers contradict each other? Or maybe they don't?!

Thanks

Stuart

 

[picasso]

If you turn the hot water off on the programmer it will close the valve to the cylinder exactly the same if the cylinder stat is satisfied, the grey wire on the 3 port is "hot water off" so if you put 240v (on the grey ) the valve will close leaving just the central heating port open.

 

[D_Hailsham]

I.e. does the hot water programmer in the 'off' position actually close the valve?

The simple answer is NO.

Don't know what I was thinking when I wrote that!

I just want guests (in a rental property) to be able to turn the hot water on/off but not adjust the programming.

I can see Picasso's solution working for turning the water OFF when it is ON at the programmer; but not sure about it turning the water ON when OFF at the programmer.

Does the programmer not have an "Advance" button? This sets the programmer to the next timed event, so if it is ON it will turn off and if it is OFF it will turn on, which is what you want.

Or is it? I'm getting confused now.

I'm beginning to think that what you want is to allow your guests to turn the water on and off as they wish, irrespective of what the programmer says. Is this correct?

 

[ianmcd]

No it wont work with a mid position valve as when the programmer switches the HW off it then sends power to the HW off terminal, if you just interrupt the HW on terminal with a switch then the valve will not move untill the cylinder stat reaches temp, you could change your system over to an S plan with two x 2 port valves instead and then it will work but you will have to leave the programmer set to 24 hours On

 

[ukrobj]

You would need to alter your wiring altogether, if you just wanted a simple solution yes, you could take 230v to your guest house switch, then to "c" (Com) on the cylinder stat.

The trade off to that would be regardless of what the programmer was doing, if the guest house switch was on, so would be the hot water (until the cylinder stat became satisfied) as long as the timer was on for hot water. So your adding too many if's an but's if you take my meaning.

Instead of a switch, put in a timer, without a permanent on switch. This way it would only be on very a varied period.

 

[matt1e]

Picasso's solution will work
He is on about using a 2 way switch wired to interrupt the hotwater on signal to the cylinder stat with the other leg of the switch connected to the hotwater off leg
draw it out you will see what he means

Matt

 

[stu550]

I'll explain more...!

The unvented tank is heated overnight wtih off peak electric for hot water. This will use an off peak timer. When guests are here this will supply morning hot water or all day hot water if its not used much- there is an electric shower.

If the house is full and more hot water is needed I want the guests to have the option to flick a switch that will then heat the water using the boiler- the programmer will be set to come on 2 or 3 times a day. If we know the house will be ful, the switch will already be on. There are other reasons too but I won't complicate it further at ths stage!

So I want this switch to work in series with the programmer so it will only heat the water when the programmer is set to auto and on between x and x hours. It should not be a constant 'ON'. Just doing the same job as switching between 'OFF' and 'AUTO'.

Hope that makes more sense!

Thank you for the answers so far!

Stuart

 

[stu550]

Rob says:

You would need to alter your wiring altogether, if you just wanted a simple solution yes, you could take 230v to your guest house switch, then to "c" (Com) on the cylinder stat.

The trade off to that would be regardless of what the programmer was doing, if the guest house switch was on, so would be the hot water (until the cylinder stat became satisfied) as long as the timer was on for hot water. So your adding too many if's an but's if you take my meaning.



The above is what in trying to do. So all I need to do is switch the "c"?

 

[D_Hailsham]

So I want this switch to work in series with the programmer so it will only heat the water when the programmer is set to auto and on between x and x hours. It should not be a constant 'ON'. Just doing the same job as switching between 'OFF' and 'AUTO'.

So, if the programmer is in a ON phase, the switch can turn the HW ON/OFF; but if the programmer is in an OFF phase it stays OFF, irrespective of what the Switch says??

If that's correct, then Picasso's solution will work. Here a wiring diagram:

Untitled

• D_Hailsham
• 14 Apr 2013
• 1

 

[stu550]

Thanks for the diagram. Makes slightly more sense - I think!

Only thing is, I have a mid position valve wired in so I assume I need to wire it in to the grey for off and brown for on as opposed to the orange?

Here is my wiring centre...

Untitled

• stu550
• 15 Apr 2013
• 2

 

[D_Hailsham]

Only thing is, I have a mid position valve wired in so I assume I need to wire it in to the grey for off and brown for on as opposed to the orange?

I didn't realize that you were using that particular wiring box. Unfortunately you will not be able to do what you want as it would involve breaking connections on the back of the circuit board..

For example: CYL STAT C is permanently connected to Programmer HW ON.

The only way would be to use a standard 10-terminal wiring centre.

 

[stu550]

Oh, I thought I could just wire the cyclinder stat into my new switch then take a new cable and wire one wire into the CH off, and the other into the CH on where the cylinder stat wires into C, 1 and 2?