s plan central heating 3 zone valves

help!!
I am working with a made plumber, he has installed a S PLAN SYSTEM, but with a diverter valve ( witch is a two port eebszone valve ) near the cylinder. so in total there are 3 zone valves apparently this gets wired to the cylinder stat???
cant find any wiring diagrams to follow, they all say two zone valves not 3?
many thanks
feebs73

Unvented cylinder?

yes it is

has he installed three zones

yes he has

- - - Updated - - -

no sorry not three zones,

He also said, this is the new way it is to be done, but I am struggling to find any info on it? Any help would be most appreciated.

feebs73 said:

help!!
I am working with a made plumber, he has installed a S PLAN SYSTEM, but with a diverter valve ( witch is a two port eebszone valve ) near the cylinder. so in total there are 3 zone valves apparently this gets wired to the cylinder stat???
cant find any wiring diagrams to follow, they all say two zone valves not 3?
many thanks
feebs73

Click to expand...

"Hello feebs73",

Please don`t be offended by the `Tone` of this message - I am trying to prevent You getting into a VERY Serious situation.


Please be VERY Careful what You do regarding wiring this Heating and Hot Water System !


IF this Third Zone Valve is installed on the Primary Heating Pipework [Flow and Return] to an Unvented Hot Water Cylinder the following applies:

The additional Zone Valve is part of the `EMERGENCY CUT OFF` Process for an Unvented Hot Water Cylinder it operates in the event of the Cylinder becoming Overheated to prevent Over-pressurisation and possible `Exploding` of the Cylinder IF the Pressure Relief Valve was Faulty.

The Unvented Hot Water Cylinder`s `Safety Zone Valve`is controlled by the EMERGENCY `High Limit Thermostat` on the Unvented Hot Water Cylinder ONLY - Nothing at all to do with the Heating System Controls.


I am a Heating Engineer - But I would not be prepared to advise You on wiring the Zone Valve on this Forum even if I was Electrically Qualified - as it is VITAL that this is done correctly - as will be shown in the Unvented Hot Water Cylinder Installation Instructions.

The Instructions for the Unvented Hot Water Cylinder MUST be followed `to the letter` for wiring the Unvented Cylinder`s Safety Zone Valve.


THIS IS A VERY SERIOUS MATTER - THESE UNVENTED HOT WATER CYLINDERS CAN BECOME `BOMBS` OF RAPIDLY EXPANDING STEAM IF THEY RUPTURE BECAUSE OF BECOMING OVER-PRESSURISED DUE TO OVERHEATING !

IF AN UNVENTED HOT WATER CYLINDER WERE TO OVERHEAT TO ABOVE BOILING POINT [POSSIBLE BECAUSE AT HIGHER PRESSURE THAN ATMOSPHERIC PRESSURE] AND THEN RUPTURE BECAUSE OF THE VAST INCREASE IN PRESSURE THAT COULD OCCUR [IF THE PRESSURE RELIEF VALVE FAILED TO OPERATE] THE RESULT WOULD BE THAT THE WATER WOULD INSTANTLY TURN TO STEAM AND `EXPLODE` / EXPAND RAPIDLY TO 1600 TIMES THE CYLINDER VOLUME !

THIS HAS OCCURRED IN THE PAST DUE TO THE `SAFETY CONTROLS` EITHER NOT BEING FITTED - OR NOT BEING WIRED CORRECTLY - OR A COMBINATION OF BOTH.



Unvented Hot Water Cylinders have at least TWO forms of `Emergency Controls` - these are a Pressure Relief Valve AND an Overheat Protection System - an High Limit Thermostat controlling a `Safety Zone Valve` to prevent Overheating of the Hot Water and Over-pressurisation of the Unvented Cylinder.

If an Immersion Heater is fitted these MUST have a `High Limit` `Cut Off` Thermostat - for the same reason as above - and should be supplied by the Manufacturer of the Unvented Hot Water Cylinder.


I should mention that the Plumber who has installed this System / the Unvented Hot Water Cylinder should be Registered - Trained and Assessed for `Unvented Hot Water Systems` - otherwise He should NOT be Installing them - this is a requirement of the Building Regulations.

If He is `Trained - Assessed and Registered` - He should certainly have been able to let You know that this `Zone Valve` / `Safety Zone Valve` was ONLY to be operated by the Unvented Hot Water Cylinder `High Limit Thermostat` !


And He should have been able to let You read the Installation Instructions regarding the Electrical wiring of the `Overheat Safety Zone Valve` - it would definitely be shown.


Just as a matter of interest could You let Us know what You mean by a `made Plumber` ?



I hope that this is helpful to You and other Members - as I mentioned Please don`t be offended by the tone of My message - I am NOT trying to be pedantic - but this is a VERY serious issue IF the wiring of the `Safety Zone Valve` is not done correctly.


Regards,

Chris - Heating Engineer and Registered Gas Engineer [Plus Registered for Unvented Hot Water Systems].

Hi Chris

Fantastic answer to this question, very informative
Cheers Mate

T&Earth said:

Hi Chris

Fantastic answer to this question, very informative
Cheers Mate

Click to expand...

"Hello T&Earth",


Thanks for the compliment - I do try to answer these kind of questions where somewhat `specialised` knowledge of Heating - Gas - Plumbing or in this case Unvented Hot Water Systems is required.

Especially as in this case where there is the potential for a VERY serious situation to be created regarding the `Safety High Limit Thermal Protection` system possibly not being wired correctly.


However I do get a little disappointed when I don`t receive a reply from the person that I am trying to help - especially because I type using only ONE finger and a post such as My one above obviously takes a LONG time for Me to compose and type.


Thanks again.


Regards,


Chris

Hi Chris

As a fellow one finger typist with dyslexia I agree entirely. A simple thank you makes all the difference. Thank you.

Steve

chris murphy said:

"Hello T&Earth",


Thanks for the compliment - I do try to answer these kind of questions where somewhat `specialised` knowledge of Heating - Gas - Plumbing or in this case Unvented Hot Water Systems is required.

Especially as in this case where there is the potential for a VERY serious situation to be created regarding the `Safety High Limit Thermal Protection` system possibly not being wired correctly.


However I do get a little disappointed when I don`t receive a reply from the person that I am trying to help - especially because I type using only ONE finger and a post such as My one above obviously takes a LONG time for Me to compose and type.


Thanks again.


Regards,


Chris

Click to expand...

Don't be disheartened mate, your posts are always really informative, helpful and to the point, it's priceless having you around to help on these kind of questions.

To the OP, I would question the design with the installer and ask him to provide you with a wiring diagram for the system.

chris murphy said:

"Hello feebs73",

Please don`t be offended by the `Tone` of this message - I am trying to prevent You getting into a VERY Serious situation.


Please be VERY Careful what You do regarding wiring this Heating and Hot Water System !


IF this Third Zone Valve is installed on the Primary Heating Pipework [Flow and Return] to an Unvented Hot Water Cylinder the following applies:

The additional Zone Valve is part of the `EMERGENCY CUT OFF` Process for an Unvented Hot Water Cylinder it operates in the event of the Cylinder becoming Overheated to prevent Over-pressurisation and possible `Exploding` of the Cylinder IF the Pressure Relief Valve was Faulty.

The Unvented Hot Water Cylinder`s `Safety Zone Valve`is controlled by the EMERGENCY `High Limit Thermostat` on the Unvented Hot Water Cylinder ONLY - Nothing at all to do with the Heating System Controls.


I am a Heating Engineer - But I would not be prepared to advise You on wiring the Zone Valve on this Forum even if I was Electrically Qualified - as it is VITAL that this is done correctly - as will be shown in the Unvented Hot Water Cylinder Installation Instructions.

The Instructions for the Unvented Hot Water Cylinder MUST be followed `to the letter` for wiring the Unvented Cylinder`s Safety Zone Valve.


THIS IS A VERY SERIOUS MATTER - THESE UNVENTED HOT WATER CYLINDERS CAN BECOME `BOMBS` OF RAPIDLY EXPANDING STEAM IF THEY RUPTURE BECAUSE OF BECOMING OVER-PRESSURISED DUE TO OVERHEATING !

IF AN UNVENTED HOT WATER CYLINDER WERE TO OVERHEAT TO ABOVE BOILING POINT [POSSIBLE BECAUSE AT HIGHER PRESSURE THAN ATMOSPHERIC PRESSURE] AND THEN RUPTURE BECAUSE OF THE VAST INCREASE IN PRESSURE THAT COULD OCCUR [IF THE PRESSURE RELIEF VALVE FAILED TO OPERATE] THE RESULT WOULD BE THAT THE WATER WOULD INSTANTLY TURN TO STEAM AND `EXPLODE` / EXPAND RAPIDLY TO 1600 TIMES THE CYLINDER VOLUME !

THIS HAS OCCURRED IN THE PAST DUE TO THE `SAFETY CONTROLS` EITHER NOT BEING FITTED - OR NOT BEING WIRED CORRECTLY - OR A COMBINATION OF BOTH.



Unvented Hot Water Cylinders have at least TWO forms of `Emergency Controls` - these are a Pressure Relief Valve AND an Overheat Protection System - an High Limit Thermostat controlling a `Safety Zone Valve` to prevent Overheating of the Hot Water and Over-pressurisation of the Unvented Cylinder.

If an Immersion Heater is fitted these MUST have a `High Limit` `Cut Off` Thermostat - for the same reason as above - and should be supplied by the Manufacturer of the Unvented Hot Water Cylinder.


I should mention that the Plumber who has installed this System / the Unvented Hot Water Cylinder should be Registered - Trained and Assessed for `Unvented Hot Water Systems` - otherwise He should NOT be Installing them - this is a requirement of the Building Regulations.

If He is `Trained - Assessed and Registered` - He should certainly have been able to let You know that this `Zone Valve` / `Safety Zone Valve` was ONLY to be operated by the Unvented Hot Water Cylinder `High Limit Thermostat` !


And He should have been able to let You read the Installation Instructions regarding the Electrical wiring of the `Overheat Safety Zone Valve` - it would definitely be shown.


Just as a matter of interest could You let Us know what You mean by a `made Plumber` ?



I hope that this is helpful to You and other Members - as I mentioned Please don`t be offended by the tone of My message - I am NOT trying to be pedantic - but this is a VERY serious issue IF the wiring of the `Safety Zone Valve` is not done correctly.


Regards,

Chris - Heating Engineer and Registered Gas Engineer [Plus Registered for Unvented Hot Water Systems].

Click to expand...

Hi Chris
Please accept my appologise, i have been out of reach recently. I have read your reply with much intrest, i did look through the cylinder book but just found a normal wiring diagram nothing about this cylinder cut off valve. i always want to do my job properly so went looking on line asked the plumbers i know, but with no luck.
could you point me in the wright direction where i could find this information as i still have not found this wiring diagram.
Just out of interest has this method been in place long as i am working on two 5 bed 3 ensuites, 1 bathroom, with under floor heating on ground floor, the 1st and 2nd each have a room stat and a zone valve for each floor, but not a cylinder zone valve, is this write??
the "made plumber" should of been "mad plumber" i have fat fingers.

Thank you once again
feebs 73

- - - Updated - - -

chris murphy said:

"Hello feebs73",

Please don`t be offended by the `Tone` of this message - I am trying to prevent You getting into a VERY Serious situation.


Please be VERY Careful what You do regarding wiring this Heating and Hot Water System !


IF this Third Zone Valve is installed on the Primary Heating Pipework [Flow and Return] to an Unvented Hot Water Cylinder the following applies:

The additional Zone Valve is part of the `EMERGENCY CUT OFF` Process for an Unvented Hot Water Cylinder it operates in the event of the Cylinder becoming Overheated to prevent Over-pressurisation and possible `Exploding` of the Cylinder IF the Pressure Relief Valve was Faulty.

The Unvented Hot Water Cylinder`s `Safety Zone Valve`is controlled by the EMERGENCY `High Limit Thermostat` on the Unvented Hot Water Cylinder ONLY - Nothing at all to do with the Heating System Controls.


I am a Heating Engineer - But I would not be prepared to advise You on wiring the Zone Valve on this Forum even if I was Electrically Qualified - as it is VITAL that this is done correctly - as will be shown in the Unvented Hot Water Cylinder Installation Instructions.

The Instructions for the Unvented Hot Water Cylinder MUST be followed `to the letter` for wiring the Unvented Cylinder`s Safety Zone Valve.


THIS IS A VERY SERIOUS MATTER - THESE UNVENTED HOT WATER CYLINDERS CAN BECOME `BOMBS` OF RAPIDLY EXPANDING STEAM IF THEY RUPTURE BECAUSE OF BECOMING OVER-PRESSURISED DUE TO OVERHEATING !

IF AN UNVENTED HOT WATER CYLINDER WERE TO OVERHEAT TO ABOVE BOILING POINT [POSSIBLE BECAUSE AT HIGHER PRESSURE THAN ATMOSPHERIC PRESSURE] AND THEN RUPTURE BECAUSE OF THE VAST INCREASE IN PRESSURE THAT COULD OCCUR [IF THE PRESSURE RELIEF VALVE FAILED TO OPERATE] THE RESULT WOULD BE THAT THE WATER WOULD INSTANTLY TURN TO STEAM AND `EXPLODE` / EXPAND RAPIDLY TO 1600 TIMES THE CYLINDER VOLUME !

THIS HAS OCCURRED IN THE PAST DUE TO THE `SAFETY CONTROLS` EITHER NOT BEING FITTED - OR NOT BEING WIRED CORRECTLY - OR A COMBINATION OF BOTH.



Unvented Hot Water Cylinders have at least TWO forms of `Emergency Controls` - these are a Pressure Relief Valve AND an Overheat Protection System - an High Limit Thermostat controlling a `Safety Zone Valve` to prevent Overheating of the Hot Water and Over-pressurisation of the Unvented Cylinder.

If an Immersion Heater is fitted these MUST have a `High Limit` `Cut Off` Thermostat - for the same reason as above - and should be supplied by the Manufacturer of the Unvented Hot Water Cylinder.


I should mention that the Plumber who has installed this System / the Unvented Hot Water Cylinder should be Registered - Trained and Assessed for `Unvented Hot Water Systems` - otherwise He should NOT be Installing them - this is a requirement of the Building Regulations.

If He is `Trained - Assessed and Registered` - He should certainly have been able to let You know that this `Zone Valve` / `Safety Zone Valve` was ONLY to be operated by the Unvented Hot Water Cylinder `High Limit Thermostat` !


And He should have been able to let You read the Installation Instructions regarding the Electrical wiring of the `Overheat Safety Zone Valve` - it would definitely be shown.


Just as a matter of interest could You let Us know what You mean by a `made Plumber` ?



I hope that this is helpful to You and other Members - as I mentioned Please don`t be offended by the tone of My message - I am NOT trying to be pedantic - but this is a VERY serious issue IF the wiring of the `Safety Zone Valve` is not done correctly.


Regards,

Chris - Heating Engineer and Registered Gas Engineer [Plus Registered for Unvented Hot Water Systems].

Click to expand...

Hi Chris
Please accept my appologise, i have been out of reach recently. I have read your reply with much intrest, i did look through the cylinder book but just found a normal wiring diagram nothing about this cylinder cut off valve. i always want to do my job properly so went looking on line asked the plumbers i know, but with no luck.
could you point me in the wright direction where i could find this information as i still have not found this wiring diagram.
Just out of interest has this method been in place long as i am working on two 5 bed 3 ensuites, 1 bathroom, with under floor heating on ground floor, the 1st and 2nd each have a room stat and a zone valve for each floor, but not a cylinder zone valve, is this write??
the "made plumber" should of been "mad plumber" i have fat fingers.

Thank you once again
feebs 73

Is this not an S plan plus.

Thought OP said it was an unvented cylinder too

Hi there
when you say a s plan plus, do you mean an extra zone with a zone valve controlling it?. If that is the case than no it isn't
Many thanks
feebs73

Make you mind up, you clearly mention the use of 3 'zone valves' in your opening post.

TBH never heard of an 'eebszone valve'

This 2 port valve near the cylinder is usually for you hot water control, switched by the cylinder stat.

What would this diverter valve be diverting?

I can't see how you can have a system with a 2 port valve and a 3 port valve. As the 3 port can't be closed.

Whos got a 3 port valve?

Have seen a few clacker valves in the past, always seem to be ceased up though

Ok mid position valve

Wasn't having a go Will, its just that the OP reckons he has 3 2 port valves only, yet only to zones?

This is what throws me out.

feebs73 said:

Hi Chris
Please accept my appologise, i have been out of reach recently. I have read your reply with much intrest, i did look through the cylinder book but just found a normal wiring diagram nothing about this cylinder cut off valve. i always want to do my job properly so went looking on line asked the plumbers i know, but with no luck.
could you point me in the wright direction where i could find this information as i still have not found this wiring diagram.
Just out of interest has this method been in place long as i am working on two 5 bed 3 ensuites, 1 bathroom, with under floor heating on ground floor, the 1st and 2nd each have a room stat and a zone valve for each floor, but not a cylinder zone valve, is this write??
the "made plumber" should of been "mad plumber" i have fat fingers.

Thank you once again
feebs 73

- - - Updated - - -



Hi Chris
Please accept my appologise, i have been out of reach recently. I have read your reply with much intrest, i did look through the cylinder book but just found a normal wiring diagram nothing about this cylinder cut off valve. i always want to do my job properly so went looking on line asked the plumbers i know, but with no luck.
could you point me in the wright direction where i could find this information as i still have not found this wiring diagram.
Just out of interest has this method been in place long as i am working on two 5 bed 3 ensuites, 1 bathroom, with under floor heating on ground floor, the 1st and 2nd each have a room stat and a zone valve for each floor, but not a cylinder zone valve, is this write??
the "made plumber" should of been "mad plumber" i have fat fingers.

Thank you once again
feebs 73

Click to expand...

"Hello again feebs 73",


From your description and taking it that the Heating and Hot Water system has an UNVENTED `INDIRECT` [Heated by a Flow and Return from Heating System] Hot Water Cylinder installed:

There should be `Zones` for the Heating System which from your description should be:


1. First Floor Heating circuit / zone - Zone Valve and Room Thermostat - Ideally a Programmable Room Thermostat* - regarding both Timed / Temperature Control of that Zone.

2. Second Floor Heating circuit / zone - Zone Valve and Room Thermostat - Ideally a Programmable Room Thermostat* - regarding both Timed / Temperature Control of that Zone.

* Programmable Room Thermostats may NOT be suitable for some Householders regarding their Time and Temperature setting requirements - and some people find understanding the setting requirements too complicated *

3. UNVENTED Hot Water Cylinder [Zone] - Zone Valve - usually SUPPLIED BY Cylinder Manufacturer and MUST be wired as the Unvented Cylinder Installation Instructions state - This should include wiring for the `Thermal Cut Out` / High Limit Thermostat on the Unvented Cylinder.

4. Underfloor Heating - Zone Valve - Room Thermostat [Programmable* ? or plus Timeswitch] - Pump - Manifold - Thermostatic Mixing Valve etc.

I have identified these Zones with the Underfloor Heating as No.4 because it may be wired seperately from the S Plan Plus wiring - ?


The MUCH more knowledgeable Members will be able to verify whether I am correct in this regarding the Electrical wiring / operation for the Thermal Cut Out / High Limit Thermostat on the Unvented Cylinder:

I believe that the Unvented Cylinder TWO PORT VALVE [Zone Valve] is wired to the Heating & Hot Water Controls as in the Honeywell `S Plan` BUT ALSO there is wiring from the Unvented Hot Water Cylinder `Thermal Cut Out` / High Limit Thermostat which will `Interrupt the Power Supply` to that Zone Valve in the event of the High Limit Thermostat reaching Temperature - STOPPING the Heat / Flow to the Unvented Cylinder Coil.



I misworded My explanation in My first message to You when I wrote about the Cylinder Zone `Safety` Valve wiring being `nothing to do with the Heating Controls wiring`:

I meant that the wiring for the Unvented Cylinder `Thermal Cut Out` / High Limit Thermostat was seperate / additional to the Heating Controls wiring.

That additional wiring from the Thermal Cut Out / High Limit Thermostat controls the CLOSING of the Cylinder Zone Valve by interupting the Power in the event that it operates at a High Temperature - it then OVER-RIDES the Heating System Controls.


Please make sure that You get the EXACT Wiring Instructions before proceeding with this Unvented Hot Water Cylinder wiring - regarding the Dangers that I detailed in My previous message to You.

I do NOT have the Electrical Knowledge / Expertise to advise You any further regarding Wiring up the Controls to this Heating System / UNVENTED HOT WATER CYLINDER - because of the additional wiring for the Underfloor Heating Controls etc.

Hopefully now that I have attached the example wiring diagram for the Heatrae Sadia Megaflow Unvented Hot Water Cylinder one of our Electrical Expert Members will be able to advise You on the additional Zones - converting the Diagram to an `S Plan PLUS` with the additional wiring to the Underfloor Heating Controls.


I am attaching an example of a wiring diagram for a Heatrae Sadia Megaflow Unvented Hot Water Indirect Cylinder here and I am including a link to the webpage which has athe wiring Diagram - wired to an `S Plan` Heating System / Controls system.

PLEASE READ THE DETAILS ABOUT THIS WIRING DIAGRAM ON THE WEBPAGE IN CONJUNCTION WITH THE DIAGRAM.

This would have to be adapted to an `S Plan PLUS` wiring plan AND whatever is required for wiring the Underfloor Heating Controls [?] - that Zone is probably going to be completely seperate from the `S Plan Plus` wiring[?].

The wiring for the `Main` Heating System Pump may have to be altered from the S Plan if the Boiler has a Pump Over-run - because the Pump would then have to be wired to the Boiler as indicated in the Boiler Installation Instructions.

The wiring diagram for the Unvented Cylinder Zone Valve on an `S Plan`is on this webpage on Megaflow Unvented Hot Water Cylinders:

Megaflo Unvented Direct & Indirect Hot Water Cylinders



I hope that You can get further advice on this from the extremely Expert and Professional Members on here - BUT - PLEASE remember the situation regarding the Cylinder Zone Valve being wired to the Cylinder Thermal Cut Out / High Limit Thermostat.


I hope that this is of some help.


Regards,


Chris


P.S. Who is the Manufacturer of the Unvented Hot Water Cylinder and the Model ?

High Tower said:

Don't be disheartened mate, your posts are always really informative, helpful and to the point, it's priceless having you around to help on these kind of questions.

To the OP, I would question the design with the installer and ask him to provide you with a wiring diagram for the system.

Click to expand...

"Hello High Tower",

Thanks very much for the compliment - it is always nice to feel that what I write is appreciated - especially when that appreciation comes from a `Fellow Professional` such as You and other Members of the Electrical Profession.


I have now been replied to by feebs 73 and as You can see the thread is `Ongoing` - awaiting the input required to adapt the Wiring Diagram that I attached above to an ` S Plan Plus` with the Unvented Cylinder`s Thermal Cut Out / High Limit Thermostat wiring.

The wiring for the Underfloor Heating Controls may have to be seperate from the S Plan Plus wiring plan ? - because it needs to be able to operate `independantly` of the other Zones of the Heating System.

Also the Pump wiring being connected `via` the Boiler IF a Pump Over-run is required [?].

Regards,

Chris

Hi again Chris
I have just read that last thread. I have taken on board what you have said, I can see the diagram but I don't see that third zone valve ( safety valve) I hope I have read and under stood your message correctly as I can see a lot of time and effort has been put in to the reply, I would like to thank you for taking so much time in replying to me, I find this website very informative and have a good read though some of the threads, I guess we never know every thing and we are always learning.
Thanks feebs 73

feebs73 said:

Hi again Chris
I have just read that last thread. I have taken on board what you have said, I can see the diagram but I don't see that third zone valve ( safety valve) I hope I have read and under stood your message correctly as I can see a lot of time and effort has been put in to the reply, I would like to thank you for taking so much time in replying to me, I find this website very informative and have a good read though some of the threads, I guess we never know every thing and we are always learning.
Thanks feebs 73

Click to expand...

"Hello again feebs 73",

The attached Diagrams [Screenshot] are of an `S Plan PLUS` which shows TWO Heating Zone Valves and a Cylinder Zone Valve - as these are Screenshots You might want to use the Snipping Tool to create am image that You can Enlarge - when I found the Colour version I did not know how to delete the Black and White Diagram.

I did look for an S Plan Plus wiring diagram in the Central Heating section where there were some Heating Wiring Diagrams [in PDF form ?] very kindly posted by a Member / Moderator but they seem to have disappeared [?].


Here is a Link to a Honeywell Wiring Plans webpage for the `S Plan Plus` wiring method:

Sundial S Plan Plus - Honeywell UK Heating Controls



Please get confirmation from the Electrical Professionals on here on how exactly to adapt this to include the Unvented Hot Water Cylinder `Thermal Cut Out` / High Limit Thermostat wiring.

The Unvented Cylinder`s Hot Water Thermostat AND the Thermal Cut Out Thermostat are usually a combined unit - so it may be that the wiring would go to the same wires / terminals on the `Wiring Centre` / Terminal Block as is shown on the Diagrams for the conventional Cylinder Thermostat - ?


Although as there are more terminals shown in the Heatrae Sadia Megaflow wiring Diagram - this would have to be clarified by an Electrical Professional - it might be that You would still be able to use a `10 Way` Terminal Block ?.

IT IS VITAL THAT THIS IS WIRED CORRECTLY - THESE ARE ONLY MY SUGGESTIONS - YOU MUST GET EXPERT ELECTRICAL ADVICE ON THIS BEFORE CARRYING OUT THE WIRING FOR THE UNVENTED HOT WATER CYLINDER.


ALSO the wiring for the Underfloor Heating needs to be identified and described how it should be connected - as I previously mentioned this would probably be wired seperately from the `S Plan Plus` [?].



I was trying to explain in My previous message that the Wiring Diagram example is for an `S Plan` - TWO Zone Valves - One Zone Valve for the Heating and One Zone Valve for the Unvented Cylinder.

I attached the Wiring Diagram on My other message so that You and the other Members could see the `Thermal Cut Out` / High Limit Thermostat wiring `TO` the Unvented Cylinder`s Zone Valve - That is the `Additional / Safety Protection wiring that is necessary for the `Safety / Thermal Protection` of the Unvented Hot Water Cylinder.

It is that wiring from the High Limit Thermostat on the Unvented Cylinder that turns the Cylinder Zone Valve into the Unvented Cylinder `Safety Zone Valve` in the event that the High Limit Thermostat operates and interrupts the power to the Zone Valve - Closing it via the `Spring Return` and preventing further Heating of the Hot Water.


Where there are more than TWO Zone Valves on a Heating / Hot Water System the Wiring Plan is called an `S Plan PLUS` - as in Your question and the Wiring Diagram above.


What we now need is for an Electrician / Electrical Engineer to adapt and explain the `S Plan PLUS` wiring diagram [as above] to show the THREE Zone Valves - TWO for the Heating Zones that are controlled by the Room Thermostats [First and Second Floors in your system ?] and ONE Zone Valve for the Unvented Cylinder AND:

Also ADD the wiring for the THERMAL CUT OUT THERMOSTAT ON THE UNVENTED CYLINDER / Hot Water Thermostat.

AND the Underfloor Heating Zone / Controls - which may be seperate from the S Plan Plus ?

I also mentioned that it may be required that the Pump wiring goes `via` the Boiler because there may be a Pump Over-run - this would mean that the Boiler also needs a Permanent Live supply to achieve this - which is another alteration to the `S Plan Plus` wiring plan - there is a segment on the Black and White S Plan Plus Diagram regarding that.


THIS MIGHT BE A `BIG ASK` TO HAVE SOMEONE FULLY EXPLAIN THIS TO YOU [?].


To help with this You should find out whether the Boiler does require a Pump Over-run and also find out what Controls are being used on the Underfloor Heating - and obtain the Underfloor Heating Wiring Diagram.


I hope that I have made this a bit clearer with these details - I know that My previous VERY Long message AND THIS have probably been a bit `daunting` to wade through - But believe it or not I was actually trying to write as `Brief` an explanation as possible !

However I needed to write ALL that I posted in these messages in order to `Fully Explain` - Sorry that it does not seem to have worked out that way from Your point of view.

Please don`t be offended by My use of Red / Blue / Highlighted Text - I am trying to emphasise what I perceive to be the Important points - it also helps Me when I am composing the Messages to see IF I have covered the Important points.


Regards,


Chris - Heating Engineer


P.S. You can see from My lack of Electrical Terminology that I am NOT an Electrician !

The easiest way of wiring in the UFH is just to treat it as a third zone in the heating. So assuming this underfloor heating is just one zone you would take a live (and poss a neutral) to a programmable room stat, take the switched live (and neutral) back to a 2 port zone valve; this operates the motor of the zone valve. Then all you have to do is connect the grey and orange,(the switch inside the valve) in parallel with the grey and orange of the other valves.

Post 13 advised of tthe Splan plus, then in post 14 OP comes back and says no its not.

Think we're on a merrygoround here.