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

[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.