How to wire Programmable Room Thermostat to Heating System without Zone Valves ?

[chris murphy]

Hello",

THIS VERY LONG POST IS DEFINITELY A ONE OFF - I NEEDED TO FULLY EXPLAIN MY VERY UNUSUAL CIRCUMSTANCES FIRST - I WOULD NOT BE POSTING LIKE THIS AGAIN - EXPLANATION TO ADMINISTRATORS AND THE CONTRIBUTERS:


This is a `Plea` for Help from a Plumber & Heating Installer [Gas Safe Registered] to his `Professional Colleagues` in the Electrical Industry - I feel that I HAVE TO Explain My Present Circumstances in order to Avoid being viewed as a `DIYer` who should NOT be dealing with Electrical Work:


I am Registered and Trained to carry out Electrical Wiring etc. under the CORGI Defined Scope Electrical Scheme / Competant Persons Scheme although I did not do My own Heating System Wiring - preferring to use a Registered Electrician - `Each Trade to their own Work` and I would always require a Certificate for the Wiring etc.


I need to TEMPORARILY wire up a Programmable Room Thermostat - Horstmann DRT2 - Directly to My Potterton Netaheat Electronic Boiler / A Junction Box - It MUST be able to Operate Without having Zone Valves on the System -
Here is Why:

I am a Plumber & Heating Installer - I am at present unable to Work because of a SEVERE Back Injury - I had stripped out the Zone Valve / Pump Configuration and quite a lot of Pipework in the Summer to Replace My Boiler in a Different Position in the House and then I suffered this Severe Back Injury - I have JUST About managed to pipe up the Flow & Return to the Boiler and Pump - A REALLY `Challenging` task - I was having to LAY down on the Floor - CRAWLING about on My Stomach to do the Pipework as I cannot Bend Down - My Back is So Bad that I could `Hurt Myself Badly` even Dressing or putting on Shoes etc.

For the last 23 Years I have been Self Employed and I have Always believed in using a Qualified and Registered [Last 6 - 7 Years] Electrician to do ALL of My Heating Controls and Power Wiring - I am Trained and Registered in Electrical Work for Heating Sysytems under the CORGI Defined Scope Scheme and their Competant Persons Scheme and about 10 Years ago I did take an ACOPS Course in `Essential Electrics` and `Electrical Wiring for Mechanical Services` - Because of the Notion that we should be Electrically Safe in order to Work on Gas Appliances.

I have Never really been Interested in doing what I consider to be `Another Trades` Work - And I have always wanted to have Certification for All of the Electrical Work that is Associated with My Heating Installations - So hence the Qualified and since approx. 2004 Registered Electricians have been used for EVERYTHING `Electrical` that I required.

Sorry for the LONG Explanation - The `Short of It` is that I have NO Idea how to Wire Up what I am Asking about - I have never done any Boiler Repair / Fault Finding / Fixing Work - Where I obviously would have needed to Know about Controls Wiring - And since I was Injured My Electrician has gone `Travelling` abroad - I have No one to Ask about this:



I NEED to be able to Operate My Home`s Boiler / Heating System this Winter just using the Programmer / Pump and Programmable Room Thermostat - OR I will have NO Control to Stop the Boiler Continuously `Cycling` to keep the Water in the Heating System at the Boiler Thermostat Setting ! - Obviously I just cannot afford that.


I Now NEED to know how / If I can just Wire the Programmer - Honeywell ST 9400 C and the Pump and Programmable Room Thermostat either Directly to the Boiler Electrical Terminal Block [And If so - How to do it Please] - OR possibly more likely Wire them using a Junction Box / Connector Blocks in an Enclosure -- ?

This request is because I CANNOT Install the Zone Valves etc to make My Homes Heating System into a Honeywell `S Plan` - My Back Problem has `Totally Disabled Me at present - Reconnecting the Pipework has caused Me to not even be able to get out of Bed without using Crutches.

I have Disguarded the `Old` Zone Valves when I did the `Strip Out` because it was My Intention to Install New ones - So I cannot even Wire Up the Zone Valves `Out of Position` - Unless doing so is My ONLY Way - But as I have not been Working I could do without the Expense of purchasing those at this time.


The ONLY reason that I Cannot find this Information anywhere is because it would obviously NOT be an `Approved / Energy Efficient` method that any Boiler Manufacturer would Recommend - That is All - There would be Nothing `Dangerous` about Wiring the System in this way - there are NO Zone Valves and the Feed and Expansion Pipes are correctly installed - the System has been running well for 24 Years ! - I will be Sorry to see the Netaheat Go next Year - IF I have recovered enough to Install the New Boiler [?].


Can I Ask My `Professional Colleagues` to Help Me in My `Hour of Need` - "Please" - I would need EXACT Instructions Please on which Wire goes where:



Potterton Netaheat Electronic 10 / 16 - Honeywell ST 9400C Programmer - Horstmann DRT2 Programmable Room Thermostat - Battery Operated / 2 Wire Connections - [Grundfos Pump]


Thank You for your Time in Reading this LONG Question / Details - I Hope for an Answer - I really am `Desperate` to get the Heating Wired and Working before We have a Weather Change.


Regards,


Chris

 

[telectrix]

sorry to hear about your back trouble.wish you a speedy recovery. unfortunately, i do not myself know enough about heating systems to help, but i'm sure if you hang on a while, geordie spark or others will be able to give you good advice.

 

[chris murphy]

Hello telectrix,

Thank You for your comment about My Back Injury.


I am sure that some of the Very experienced Electricians / Electrical Engineers on the Forum will be able to Help Me with this - I am fairly sure that what I need to achieve will be a Very Simple wiring task - So simple that I hope they will understand that I need to know where EVERY Wire goes.

At present the Programmer - Boiler and Pump have been wired up to enable the Heating to be Run - initially to Heat & Circulate the System Cleanser that I always use after Installing a System - or in this case after reconnecting the Heating Flow and Returns to the Boiler in a Temporary Fashion - And after that to Run the System again Circulating the Corrosion Inhibitor which I added after Draining out the Cleanser and Flushing out the System.

Basically Power is being supplied via a Plug-in cable to the Honeywell ST 9400C Programmer Backplate - From there a cable supplys the Timed Feed to the Potterton Netaheat 10 / 16 Electronic Boiler and the Pump is wired to the same terminals within the Boiler Terminal Block as the Timed Feed - So the Programmer turns on both the Boiler and Pump.

I cannot afford to Run the Heating System like this in the Winter - As at present the Boiler would keep Cycling to satisfy the setting on the Boiler Thermostat - EXTREMELY Expensive !

This is why I am DESPERATE to learn how to wire in the Horstmann DRT2 Programmable Room Thermostat - to have Temperature Control over the Boiler - This Thermostat has only 2 Wires - the Operation Settings are powered by Batteries.



It has occurred to Me to remove the Timed Feed from the Programmer Backplate and connect a wire from the Programmable Room Thermostat to that `Timed Feed` terminal - then connect the other wire from the Stat to the Timed Live Feed to the Boiler.

At the Programmable Room Thermostat - connect the appropriate 2 Wires to the CORRECT Terminals [When I KNOW which is which] - The Thermostat Installation Instructions - a Diagram the size of a Matchbox shows terms that are unknown to Me as someone NOT doing Electrical Work on a regular basis.

What I have written is Me almost thinking out loud - I really do need someone to inform Me of EXACTLY Which Wire goes where - "Please".


I look forward to some Expert Help - Thanks to All who will read this.


Chris.

P.S. I hope that You don`t mind Me using My Reply to You to elaborate on My Post

 

[topquark]

Live from the boiler down to the room stat (you'll need at least two core and earth, but would suggest using three core and earth). On the stat you'll have connections for Common (live from boiler) and an NO and NC terminal, brown from boiler live down to stat and return from stat (NO terminal) back to the boilers switched live, call for heat or supply return (whatever terminology they're using).

 

[topquark]

Here's the two documents you may need to refer to:
http://www.horstmann.co.uk/download.../ThermoStats/DRT2UserandInstallationGuide.pdf
http://www.ultimatehandyman.org/PDF...onic-6-10-10-16-16-22-installation-manual.pdf
I can't vouch for the source of the second one though.

 

[SPARTYKUS]

topquark you sure know your stuff, I struggle (but do eventually suss it) when all the heating wiring diagrams and the stuff itself is laid out in front of me. Doing it by proxy like this .... fair play man.

 

[topquark]

topquark you sure know your stuff, I struggle (but do eventually suss it) when all the heating wiring diagrams and the stuff itself is laid out in front of me. Doing it by proxy like this .... fair play man.

Just done one this week mate, so was fresh in mind

 

[chris murphy]

Hello topquark,

Thank You very much for your Reply - I do have the Netaheat Installation Instructions as the Boiler is in My own Home and I was the Installer - albeit 24 Years ago - I really appreciate you taking time to post the Link for it.

I also have the Horstmann Installation Instructions as I purchased the Programmable Room Thermostat to Install after I changed My Boiler - But again Thank You for taking the time to post Me a Link to that.

When I researched this Thermostat on the Horstmann website it was stated to require only 2 Wires - the Operation / Settings are Battery Operated and I already have the 1mm Twin and Earth Cable run through the House [Months ago] - Deliberately to suit this Thermostat.

Although from what I read on this Forum while trying to research how I might wire the Thermostat I would have run a 3 Core and Earth if I had seen the Views of You and your Colleagues previously - regarding any Upgrade of the Thermostat - I am already regretting not having a Stat with a Backlight Facility.


From what You describe in your Post - I am hoping that this is the same as I was trying to describe:

I am hoping that I am correct in thinking that what I described in one of My Posts about connecting the `Live Wire` for the Programmable Room Thermostat to the Switched Live Terminal on the Programmer backplate and then connecting the other wire FROM the Programmable Room Thermostat to what was the Switched Live Wire to the Boiler and Pump [Previously connected to the Switched Live from Programmer to Boiler and Pump].

Then at the Programmable Room Thermostat `End` connect the Switched Live from the Programmer to the COM Terminal and the other wire to the NO Terminal.

Please excuse My `Non Electrical Terminology`.


Could You Please confirm IF that is what You have explained ?


IF this is as You are describing [?] - Thank You very much - Something that slightly threw Me was the `Wiring Diagram` which seems to show 3 Wires - regarding : Live [Switched ?] to COM - NO to Heater - and Neutral to Heater - ?? - But I am sure that I am just not used to seeing a Diagram like this [Hopefully]

I am going to try to Attach the `Diagram` so that You will see what I mean - I am sure that People will think that this is the `Simplest` Diagram that I could EVER be looking at - Why can`t I understand it ? - But IF I am correct in My description of what to do with the Wiring [?] - Why would there not just be the 2 Wires showing between the `Heater` [Boiler] and the Programmable Room Thermostat ?

It is not Important to Me to `Go Into` that - IF I have the Wiring Connections Correct - I just mentioned it to show why I was slightly confused by that.


"Thank You Very Much topquark" - Could You Please confirm - Or Otherwise IF I have got the connections Correct for wiring the Programmable Room Thermostat ?

Also could You Please let Me know if there is ANY Chance of causing the Boiler PCB to be damaged / ruined by an Error during the Wiring - NOT that I am not confident in what I will be doing - JUST in case My `Non Electrical Terminology` causes You to misunderstand what I have described - You think that I have understood your description and just `reworded it` - But I do something wrong - Could I cause the PCB to be damaged or would the Glass Fuse within the Boiler just `Blow` ??

I ask this because then I would have NO Heating - without paying for an Expensive [If still available] PCB - So I would like to make sure that I have everything Correct re. the Wiring ?

"Sorry about the Very Long Posts" - It will ONLY be for this Subject - Which as I have stated is of `Vital Importance` to Me.


Chris

 

[topquark]

Yep, you've got it. You can use the two core (+earth) for the job, but won't be able to upgrade to a neutral reqd stat in the future. So brown will go in the com terminal on the programmer and the sleeved blue into the NO (Normally Open) terminal. The other end of the brown to the wiring centre (normally terminal 4) and the (again sleeved) blue to the terminal in your wiring centre for switched live (that will also run the the pump and any valve-normally terminal 5). HTH.

The diagrams can be a little confusing. If you look at the bit you've pasted it shows two devices, the boiler on the left and the programmable stat at the top. The only added confusion is that you'll have a wiring centre in the middle (which is usually just a large 10 terminal connector block).

The boiler (or wiring centre) will usually have a neutral, live feed and switched feed terminal. When the boiler is shipped it will normally be jumpered between live and switched live (so no stat required). So you'll need to remove the link and replace with the core from/to the programmable stat respectively.

edit:

as for the damage, yes there is a chance if you introduce a neutral into the equation and connect it to the wrong point.

Please ensure the boiler is completely isolated before doing any work and double check all of the connections.

As this particular device is battery powered it will most likely not have an earth terminal as it'll be a plastic casing.

 

[chris murphy]

"Hello topquark",

Thank You very much for your I really appreciate your Expert Help with this.

I would just like to show You a couple of Photos of the Existing Wiring - this was just to allow the Heating to operate when I was `Cleansing` after repiping the Heating Flow & Return and so that I could circulate the Fernox Corrosion Inhibitor.

The Photos show the Programmer Backplate with the `Power In` - Live Neutral & Earth and Terminal 4 has the Switched Live to the Boiler and Pump which are connected together on the Boiler Terminal Block [ L N E ] - which is the other Photo.


I don`t have plans to use a Junction Box - Just change the connection to the Switched Live on the Programmer Backplate from the Live to the Boiler and Pump to the Switched Live to the Programmable Room Thermostat - Programmer Backplate Terminal 4


Then at this `End` [Programmer Backplate] of the 2 Wires From the Programmable Room Thermostat connect the Wire from NO [Stat] to the Switched Live to the Boiler and Pump - this Wire was previously connected to the Programmer Backplate Terminal 4 Switching On both the Boiler and Pump [These are wired together on the Boiler Terminal Block]

I am Sorry If My explanation is NOT as clear as it would be if I was using more conventional Electrical terminology.

I hope that the Photos will make what I mean more clear.


I really appreciate Your involvement "Thank You" - You will have made the difference to whether I could [just about] Afford to run My Heating System this Winter - As You know running a Heating System using the Boiler Thermostat as the ONLY Temperature Control would be Prohibitively Expensive I would simply NOT be able to Afford that.

If it is Not Clear what I mean about the Connections could You Please point that out to Me and ask Me to Clarify anything that you need to know I MUST be 100% that what I plan to do will be Correct - "Thanks Again".


Chris

 

[topquark]

I don`t have plans to use a Junction Box - Just change the connection to the Switched Live on the Programmer Backplate from the Live to the Boiler and Pump to the Switched Live to the Programmable Room Thermostat - Programmer Backplate Terminal 4


Then at this `End` [Programmer Backplate] of the 2 Wires From the Programmable Room Thermostat connect the Wire from NO [Stat] to the Switched Live to the Boiler and Pump - this Wire was previously connected to the Programmer Backplate Terminal 4 Switching On both the Boiler and Pump [These are wired together on the Boiler Terminal Block]

First observation is, you have pvc/pvc cable at the backplate, you don't really want to be taking that into the boiler direct. I'd suggest still having a wiring centre (may be co-located with the boiler) so you can convert to heat resistance flex to go into the boiler with.

 

[topquark]

Ah, I can see from the picture now that the cable runs up conduit into the boiler, that's fine, that should offer it sufficient protection.

 

[chris murphy]

"Hello topquark",

Sorry that I forgot to say the existing wires are purely temporary - I do plan to rewire the whole Programmer Backplate and wiring into the Boiler - Using Heat Resistant Cable to the Boiler.

I do realise that even running the Boiler temporarily to Heat and Circulate the Cleanser and Corrosion Inhibitor while wired with PVC Flex was `Incorrect` - BUT it was purely to achieve those tasks and I would NEVER leave the PVC Flex in place permanently - although it was not in contact with any Hot Surfaces I do realise that PVC Flex is NOT Rated to be in what will be a `Warm Environment` - `Warmer` than a Home`s Ambient Temperature.

But Thank You for pointing that out - Just in case I had not been aware of this Important Point - or for the benefit of other readers of this subject.

As the Boiler is located in a large cupboard at present [Well Ventilated] I will take Your advice and use a Junction Box - I have plenty of wall space to locate it on adjacent the Boiler - to connect up the Wiring and then just take the Switched Live to the Boiler using Heat Resistant Cable.

I wonder if You or any other Member know of any National Electrical Materials Supplier that will sell 1mm Twin & Earth Heat Resistant Flex / Cable in Cut Lengths ? - As I will only need about 2 Metres MAX. - I don`t really want to have to Buy 50 Metres - Any suggestions ?

Can I take it that My explanation of what I plan to do regarding the Wiring of the Programmable Room Thermostat did make sense and that I have described everything correctly ?


If You could Please give Me the "O.K" that I am going to be correct when I do what I described - I would appreciate the Confirmation - "Thanks Again".


I really cannot Thank You enough for your Help - What may seem a Very Simple thing to You and others on the Forum will have a profound affect on whether We are `Warm` this Winter at an Affordable Cost - Because of My Severe Back Injury I have not been Working for Many Weeks and will probably NOT be able to Work for Many more MONTHS - My Financial Situation WILL become `Dire` - The Confirmation about the Programmable Room Thermostat Wiring really will have a Beneficial Affect regarding being able to Run My Heating System this Winter - "Thank You topquark"


Chris

 

[topquark]

I think I've digested what you've said now, so here goes.

Firstly, for your CH you are ostensibly going to be ignoring the original programmer completely (you'll need to set the CH programming on it to permanently off). So for the purposes of this discussion it is not going to be used. In fact from the looks of the backplate wiring, it was only using that one channel anyway for CH (maybe just to enable your cleansing cycle to run?) and not using the HW channel at all.

So for your temporary bypass, you can take your live feed to the new programmer from the third terminal down on the boiler connector(L) OR more correctly, link down from terminal 3 to terminal 7 and take the live feed from terminal 7 (connected to com in the new programmer).

On some programmers a link is needed from com to NC (that doesn't appear to be needed here for the horstmann though).

I'm assuming that the boiler connection (switched live) has been placed into the right hand side of terminal three currently. If correct you'll need to move that to terminal 8 (right hand side) and connect the core from NO on the stat to the left hand side of that terminal (enabling the stat and built in timer to control the boiler).

IF that's not what's been done then I can't tell from the picture what's controlling the boiler.

If that was correct then you'll just need to wire the pump and any valve in to terminal 8 to control them.

 

[chris murphy]

"Hello topquark",

I was hoping to not have to completely change everything as I thought that I had finally understood what I could alter from the existing wiring in order to make the Programmable Room Thermostat operate.

The Existing Programmer will be used and it operates as I describe in the next paragraph - there is no Hot Water Zone - because there is No Pipework to the Cylinder and No Zone Valve - The Programmer only operates the Boiler and Pump at present.


At present the Programmer Backplate wiring enables the Programmer to either Turn On the Boiler and Pump using the Timed Settings OR the Constant Setting - So this would be `O.K.` as wired for operating the Heating System via the Honeywell ST 9400C Programmer.

The Switched Live Wire on the Programmer Backplate at Terminal 4 is the `On` from the Programmer to the Boiler and Pump.

I was hoping that I would be correct in wiring the Switched Live from that Terminal 4 on the Programmer Backplate TO the COM Terminal on the Horstmann Programmable Room Thermostat - Having Disconnected the existing Switched Live to the Boiler and Pump from Terminal 4 - And then wire from the NO Terminal TO that WIRE that was previously the Switched Live connected to Terminal 4 at the Programmer Backplate [Switched Live to Boiler and Pump]

It would be very Helpful if You could let Me know IF the above would Work - without Me having to try and understand how to do this a completely different way ?

I have described connecting to the Switched Live WIRE that was previously connected to Terminal 4 at the Programmer Backplate - Just so that I can try and explain exactly what I mean - But I would carry out the connections within a Junction Box - BUT - Not one of the Honeywell Wiring Centres - where there are `Dedicated Terminals` for every componant,
just connector blocks within a Box.

I hope that this is correct - without having to try and understand any complete changes in the wiring - When You mention Terminals 3 - 7 & 8 this will completely confuse Me If it is `O.K.` to do the Wiring in the way that I have described ?

Thanks Again,


Chris

 

[topquark]

Yes, you can do that, however then the programmer side on either the programmable stat or orig programmer would need to be set to 24H ON. You're effectively placing them in series (so they'd both need to be "on" for the boiler to fire).

I rather assumed (more fool me) that the reason for getting a programmable stat was that you'd be replacing the boiler with a combi eventually .... otherwise you could have just used a normal stat (no need to be programmable if you're keeping the orig programmer). Unless, ultimately you want to have more than the one CH zone I guess

Terminals 3, 7 and 8 refer to inside the boiler, if you look at the picture you've posted it appears that the boiler has had it's switched live wired into the live supply (and is hence on permanently).

 

[chris murphy]

"Hello topquark",

Thanks for Your Reply.

Regarding the Programmer and Programmable Room Thermostat having to Both be ON - Programmer On 24 Hours - Why could the Programmer not just be On Timed - As the Programmable Room Thermostat Settings are Battery Operated the Thermostat would only be Operating on the Temperature Settings [Re. Turning the Boiler and Pump On & Off] when the Programmer Turns ON the Heating System / Bolier & Pump [ Through the Thermostat]

The Programmable Room Thermostat does not need Electrical Power to keep the Time or Temperature Settings - So although the Thermostat would be Operating `Internally`- going through the Settings throughout the Day & Night - Only when the Switched Live from the Programmer was going through the Programmable Room Thermostat would it Switch the Boiler and Pump On & Off at the Temperature Settings for each Time Period - I hope that this is Correct ?

Could You Please let Me know if what I have described about the Operation of the Programmer and Programmable Room Thermostat [Above] is Correct.

From a Heating Engineers point of view the idea of having a Programmable Room Thermostat is so that when the Heating is `On` the Programmable Room Thermostat would Control the Firing of the Boiler at whatever Temperature was Set for a particular Time Period on the Thermostat.

Imagine the Weather is particularly Cold - The Heating needs to be On for most of the Day & Night :

For example perhaps: Heating comes On at 06:00 Hrs - In order to Heat Up the House as quickly as possible the Programmable Room Thermostat is Set at 24 Degrees between 06:00 Hrs and 08:30 Hrs.

At 08:30 Hrs until 16:00 Hrs You want the House to be Heated - But NOT to the Highest Temperature - Perhaps Set the Temperature on the Programmable Room Thermostat to 18 Degrees for that Time Period [Temperatures as You know are a Very Personal Choice]

At 16:00 Hrs You want the House to `Warm Up` more for People coming in from Work - Set the Programmable Room Thermostat to 23 Degrees from perhaps 1600 Hrs to 00:00 Hrs.

This Temperature can be Manually Adjusted at the Programmable Room Thermostat if required when People are at Home in the Evening [At any Time]

As I mentioned the Temperature Choices are a Very Personal thing - People would get used to what Temperatures that they need to use - I am NOT recommending the Temperatures that I used in this example.

With regard to the use of a Programmer as well as the Proigrammable Room Thermostat - There will be a Hot Water Zone when I Install the New Boiler [Not a Combi] - So it will become a Fully Pumped `S Plan` Heating System [2 Zone Valves] which will need a Programmer.

My Honeywell ST 9400C Programmer has been Controlling the Heating System at my Home - which was previously a Fully Pumped S Plan System - Until I stripped Out the Zone Valves - Pump and quite a lot of Pipework during the early Summer - getting ready to Install a New Boiler in a different Area of my Home.

It is because I removed the Zone Valves and Pump configuration that I need to wire up the Programmable Room Thermostat as I have asked about.


Thank You Very Much for your Help with this - I Apologise If this has been `Frustrating` regarding My lack of Electrical Terminology and My `Explanations / Descriptions of what I wanted to do with the Wiring of thre Thermostat - I really appreciate You persevering with Me.

Would it be O.K. to Send You a Private Message IF I want to confirm anything when I start to carry out the Wiring ? - I would NOT bother You unless I had to.


"Thank You topquark" - As I previously mentioned You have done Me a VERY BIG FAVOUR here - I will NOT Forget that.


Chris

 

[topquark]

It depends how they are wired: OK, say programmer one is set to turn on CH from 00:00-11:59 and programmer two is set to turn on from 12:00 to 23:59. Then if they are wired in series the CH will never come on. If you set one to 24H and the other is then used to program it, it will work as expected. That's why I suggest setting one of them to 24H (not both). You can of course connect them in parallel (so that either could fire up the boiler). In which case you'd set one to permanently off and use the other to control the "true pattern" of on/off.

PM's are fine, if it's generic then best put a post here as it'll get help from whoever is around and others will see it when they research problems.

For others benefit, the programmable stats are just stats with built in time periods, they don't send any temp info to the boiler (as I'm sure you're aware). The water temp from the boiler is set at the boiler (and controlled by the boiler PCB logic).

 

[chris murphy]

Hello topquark",

I can see what You are saying - Because I would ONLY be using the Programmable Room Thermostat to Control the Temperature of My Home it would ALWAYS have a Setting for ALL Time periods - Without Me having mentioned this [and My NOT having looked at the Horstmann Setting Instructions since You mentioned this] I was wondering what You meant - Now I know.

It was Definitely correct to mention this - as other People might get very confused if they tried to use one of these Programmable Room Thermostats without realising what You have stated.

In My case I will have ALL Time Periods of the Days `Set` with a Temperature - So when the Programmer turns ON the Boiler and Pump on a Timed OR Constant Setting [ via the Programmable Room Thermostat] - The Programmable Room Thermostat will Always be `Calling for Heat` [Unless the Temperature Setting is Low enough to be already`Satisfied`]

Wired as We have discussed - The Programmer will Turn On the Boiler and Pump IF the Programmable Room Thermostat is `Calling for Heat` There will ALWAYS be a Temperature Setting on the Thermostat NO `Off Periods`.

Whatever the Programmable Room Thermostat is `Showing` / Set At will not matter IF the Heating System is OFF at the Programmer because the Switched Live from the Programmer TO the Programmable Room Thermostat will NOT be Switched On.

When the Programmer Switches ON the Heating System the Programmable Room Thermostat [If Calling for Heat] will allow Power to the Boiler and Pump and Turn the Boiler and Pump`On / Off` at whatever Temperature Setting is for that particular Time period.


FOR OTHER READERS THIS IS PURELY HOW I WANT TO OPERATE MY HEATING SYSTEM - ON A TEMPORARY BASIS I DO NOT RECOMMEND THIS METHOD OF WIRING OR `CONTROL` OF OTHER HEATING SYSTEMS - MY CIRCUMSTANCES HAVE DICTATED THIS - PLEASE READ MY ORIGINAL POST ABOUT THIS MATTER.

Most Modern Boilers would NOT be suitable to use a Thermostat which is wired in this way as they would require a Pump Over-Run which disipates Heat from the Boiler Heat Exchanger after the Burners stop firing.


Because this method of Settings was always my intention - I did NOT even think about any other possible problems for other People wanting to Operate their Heating Systems in a different way.

"Thanks Again topquark" - This is EXACTLY WHY I like to Liaise with Experts such as Yourself - What You mentioned would NOT be a Problem for the way that My Heating will be `Set` - But could easily be a problem for others.


Chris

 

[alarm man]

you could ask some of the sparks you gave work to help you out.