Help please wiring Honeywell thermostat CM907

[Broadswordsman]

I am replacing a Horstmann centaursat wall thermostat in my fully pumped conventional boiler system. Timer controlled, Gravity fed, no zone valves. There are three wires to the centaurstat wired to terminals 1,2 and 4 . Diagram here

http://www.tlc-direct.co.uk/Technical/DataSheets/Horstmann/CS1_7_I.PDF

I am replacing it with a CM907. Both of these thermostats are battery powered. I have transferred the existing 1 to the CM907 terminal A, 2 to B and 4 to C (there are only three CM907 terminals). I have also tried disconnecting C so only A&B are connected but it does not appear to work wired either way e.g it does not fire up the boiler when temperature is reached I have now reconnected the centaurstat with the three wires and it works fine.

How should I transfer the wires across to the CM907 (wiring diagram here)

http://europe.hbc.honeywell.com/products/pdf/en0h8547uk07r0906.pdf


Many thanks!

 

[snb]

1 goes to A and 2 to B 4 needs to be either taped with insulation tape as this neutral

 

[D_Hailsham]

If you originally connected 1 to A, 2 to B and 3 to C, then you may have blown the CM907 as Live (A) would be shorted to Neutral (C) when the required temperature has been reached.

If you look at the wiring diagram for the CM907 you will see that A connects to the common of a two-way switch; B and C are the Call and Satisfied connections. You will also see that the CM907 does not have a Neutral connection but the Horstmann does. As snb says, wrap the neutral in insulating tap.

 

[Capvermell]

If you look at the wiring diagram for the CM907 you will see that A connects to the common of a two-way switch; B and C are the Call and Satisfied connections. You will also see that the CM907 does not have a Neutral connection but the Horstmann does. As snb says, wrap the neutral in insulating tap.

My situation is similar to the OP except that I have managed to blow up the old Drayton Digistat that I was trying to replace with the Honeywell CM907 as after removing the Drayton Digistat and looking at online articles I rather took fright about connecting the right wires to the Honeywell CM907. The Honeywell CM907 has not yet been attached to the wiring.

The situation is also complicated by the fact that originally before the Drayton Digistat there was a Satchwell or Honeywell stat that also had green and yellow wires attached to it. That dated from 1970. They (the blue and green wires) were taped up and taken out of use when the analogue stat was replaced with the Drayton Digistat in the mid 1990s.

The bottom line is that when I had what I believe was the red wire attached to terminal 1/L and the black wire attached to terminal 3/SAT this arrangement fried the Drayton Digistat but when I also had the Blue wire attached to Terminal 4/N of the Digistat as well earlier it did not fry.

So does it sound to you as though my blue wire may actually be the terminal B wire for the Honeywell CM907 and the black wire is the one I should be taping. In other words were the wrong wire colours used by the original installers?

What testing equipment could I buy at a DIY shed that might let me establish for sure which is the Neutral Wire and which is the Demand wire and also make sure that the red wire is the Live wire?

Or would I be better to ring round electricians and central heating servicing guys and see who would give me the most reasonable quote. Obviously having someone in on the old hourly rate trick could land me with a bill for several hours of their time at £50 per hour or whatever.

 

[Whitespirit66]

quote="Capvermell";p="1643296 Obviously having someone in on the old hourly rate trick could land me with a bill for several hours of their time at £50 per hour or whatever.

Good heavens, having to lower yourself to employ one of us crooked tradesmen.

If you whitter on in conversation like you ramble on in your posts, the poor fellow could be there for days!

 

[Capvermell]

If you whitter on in conversation like you ramble on in your posts, the poor fellow could be there for days!

I'm some how missing where you actually offered me any help with my problem. Surely the whole point of this forum is in order to avoid the use of over priced trades persons. Also any genuinely over priced tradesperson keen for us to use their services and be ripped off would surely be unlikely to be found giving any help for free here?

The bottom line is yes I have screwed up and lost track of which wire is my Neutral wire and which was the Black wire and am confused about whether the Black was connected to 2/DEM or 3/SAT. However I did manage to substitute the original 5 wire connected Satchwell stat for the 3 wire Drayton Digistat set up 15 years ago though.

What electrical tester do I need to work out which of the red, black and blue wires do what and so how I attach them to the CM907 terminals? I expect you are now going to tell me I will need a link between some of the terminals on the CM907 or some such hideous thing.

Bottom line is the heating set up here is out of date and the hot water circuit probably needs a valve installing to stop it running all the time the heating is on. Also no doubt it could do to be a two pipe system but it is only one pipe at the moment. But all of those things are much less likely to happen than the installation of the CM907 stat. This would be a simple but still worthwhile improvement. It only cost me £33 off an Ebay seller.

The main point of the programmable Digistat is that my mum is forever having to manually alter the current stat including the nonsense with the original Drayton Digistat only being changeable in on direction until it rolls over to the bottom when it gets to 86 degrees F. On top of this the programming would allow the stat to be at the right temp during the hours when the main Drayton programmer has the heating circuit turned on. Due to the hot water circuit limitations I doubt my mum will run the heating circuit 24/7.

 

[Whitespirit66]

If you whitter on in conversation like you ramble on in your posts, the poor fellow could be there for days!

I'm some how missing where you actually offered me any help with my problem. Surely the whole point of this forum is in order to avoid the use of over priced trades persons. Also any genuinely over priced tradesperson keen for us to use their services and be ripped off would surely be unlikely to be found giving any help for free here?

95% of the people giving advice on here are the over priced 'trades persons' that are out to trick you. Surely you wouldn't be able to trust their advice either.

 

[Capvermell]

95% of the people giving advice on here are the over priced 'trades persons' that are out to trick you. Surely you wouldn't be able to trust their advice either.

No they aren't.

95% of the posters on here are the 5% of tradespersons who are not overpriced and don't like to see a customer ripped off for hundreds of pounds for what was actually a simple job that they could have done in only 30 minutes to an hour.

But it seems that you are clearly in the 5% of tradespersons here who resent members of the public who try to DIY to avoid being ripped off by overpriced trades persons.

 

[heatserve]

What electrical tester do I need to work out which of the red, black and blue wires do what and so how I attach them to the CM907 terminals? I expect you are now going to tell me I will need a link between some of the terminals on the CM907 or some such hideous thing.

A multimeter. What what what m'lud

Doffs cap and tugs forelock furiously

 

[Capvermell]

A multimeter. What what what m'lud

Doffs cap and tugs forelock furiously

Many thanks for the useful advice what, what my dear old thing but do these multimeter chappies come with instruction leaflets and what is their usual price compared to hiring one of the more reasonably priced members of your profession for an hour or so?

My concern would be that surely the multimeter will only tell me that the red wire is live but how will it clarify for me which of the blue and black wires is a Neutral and which wire is the switched circuit to the heating pump?

To be honest the whole heating system is years out of date and in need of probably spending a fair bit on a major update that would save a lot on oil costs. But persuading my mother of this is quite another matter.

My mistake here has been to meddle in someone else's heating system as an amateur. Had I done it to my own system then it would not be an especially big deal. But as noted way back I did fit the Drayton Digistat that I am now replacing 15 years ago and it has run for all these years up to now without any incident. I also replaced a failed 24 hour Honeywell central heating programmer on my own home system with a 7 day one a few years ago successfully and that had a hell of a lot of wires attached to it so I must surely have some vague idea of what I am doing.

 

[heatserve]

I would expect that you're looking at £50-60 for someone to come out and do it for you.

You can use the multimeter to check for both mains current and continuity - this allows you to trace the wiring at your connection site back to the wiring centre. Wiring a battery powered programmable room thermostat isn't usually a big deal at all. Generally you use it to switch a live to the motorised valve and adapt the wiring to bypass the heating circuit of your programmer.

Usually it's quite obvious which wire is what when you take the cover off the wiring centre, but depending on what sort you've got, these can sometimes be a bit of a nightmare and this is where the MM is essential.

P.S. Oops, a cheapo MM is about £15-£20 and they don't usually come with instructions.

 

[Capvermell]

Usually it's quite obvious which wire is what when you take the cover off the wiring centre, but depending on what sort you've got, these can sometimes be a bit of a nightmare and this is where the MM is essential.

The problem that I'm really facing is all the redundant wires that are associated with the original Satchwell or Honeywell analogue stat that then controlled a driven motorised valve on the downstairs circuit and the duplication of red and black wires (some in use and some covered in plastic sticky tape) at the connection point. And it does seem that the black wire that was still in use on the Drayton Digistat is a Neutral and the blue wire the one to the heating pump that should go on the CM907 B terminal. But having already seen one room stat blown up I'm now not feeling at all brave. It sounds like to test the circuitry I would have to disconnect cables at the pump end too and most of it is in a metal sleeve that would probably bring down the wall with it if I tried to open it. My mother is also unfortunately here and would never allow it.

So its either risk connecting the red and blue wires and hoping there isn't another loud bang or call in a suitable tradesperson. I suppose I could buy the cheapest analogue stat going at B&Q to test the point and return it if I don't manage to blow it up. My only other concern is could I have damaged the heating circulation pump in the last bang that took out the old Drayton Digistat?

 

[simond]

I think your view of tradespeople has queered your pitch here, mate.

95% of tradespeople are honest, not the other way round. Most of them are reputable tradesman, trying to earn a living. And many participate in this forum.

You are a bitter penny pinching type, who knows nothing about tradesmen - or wiring - or plumbing.

You can string a few dull words together though, credit where it is due.

 

[heatserve]

My only other concern is could I have damaged the heating circulation pump in the last bang that took out the old Drayton Digistat?

I wouldn't have thought so.

Why not take a few decent quality photos of the problem areas, you might get a bit more help then - I'm having difficulty understanding quite what the problem is TBH.

 

[Capvermell]

Why not take a few decent quality photos of the problem areas, you might get a bit more help then - I'm having difficulty understanding quite what the problem is TBH.

Good idea. I just need to track down the right lead to connect my cam and the PC. I know its around somewhere.