Honeywell CM927 with Vokera combi boiler

jem16 · 9 Mar 2010

I have a Vokera Linea 28 combi boiler with a Lifestyle LP711 timer.

I would like to get a programmable thermostat and have been recommended the Honeywell CM927 - first of all I assume it is compatible?

I need it fitted as it's not something I could do myself.

1. What is involved in fitting it? Would it replace existing timer or work in conjunction with it. Boiler is in garage - LP711 is wired from boiler into house.

2. How much would I expect to pay someone to fit it if I supplied it?

D_Hailsham · 9 Mar 2010

jem16 said:
I would like to get a programmable thermostat and have been recommended the Honeywell CM927 - first of all I assume it is compatible?

Yes

1. What is involved in fitting it? Would it replace existing timer or work in conjunction with it. Boiler is in garage - LP711 is wired from boiler into house.

It would replace the existing timer and, if you have one, the existing thermostat.

The CM927 is a wireless prog stat, which is in two parts: control unit and receiver. The receiver can go where the LP711 is located - provided there is good radio reception from the control unit's location. The installer will check this for you.

2. How much would I expect to pay someone to fit it if I supplied it?

It should not take more than an hour to fit, so about £40. Make sure the person who fits it is familiar with heating installation electrics - not all electricians are.

jem16 · 9 Mar 2010

D_Hailsham said:
The CM927 is a wireless prog stat, which is in two parts: control unit and receiver. The receiver can go where the LP711 is located - provided there is good radio reception from the control unit's location. The installer will check this for you.

The LP711 is located in a small cupboard under the stairs, next to the door of this cupboard. Would wiring need to be altered to change over from the LP711?

I would imagine wireless reception should be fine from there to the living room where I would put the thermostat itself.

2. How much would I expect to pay someone to fit it if I supplied it?

It should not take more than an hour to fit, so about £40. Make sure the person who fits it is familiar with heating installation electrics - not all electricians are.[/quote]

OK - thanks.

One person I have spoke to so far wanted to fit a Vokera 411 as it just fitted into the boiler - don't fancy that to be honest.

D_Hailsham · 9 Mar 2010

jem16 said:
The LP711 is located in a small cupboard under the stairs, next to the door of this cupboard. Would wiring need to be altered to change over from the LP711?

Do you have a thermostat at the moment, if so where is it located?

The CM927 does not use the same base plate as the LP711 so this will have to be changed. The CM927 receiver requires a four wire cable: two for the supply (L and N) and two to the boiler.

I would imagine wireless reception should be fine from there to the living room where I would put the thermostat itself.

If there are only a couple of walls between the receiver and control unit, you should have no problems.

One person I have spoke to so far wanted to fit a Vokera 411 as it just fitted into the boiler - don't fancy that to be honest.

I know nothing about the 411 so I can't comment. I do know that the CM927 is a good product. You're paying so get them to install what you want.

jem16 · 9 Mar 2010

D_Hailsham said:
Do you have a thermostat at the moment, if so where is it located?

No thermostat at the moment.

The CM927 does not use the same base plate as the LP711 so this will have to be changed. The CM927 receiver requires a four wire cable: two for the supply (L and N) and two to the boiler.

Looking at the LP711 it has a fused mains socket beside it. Mains cable comes from that into the LP711 and mains wire, labeled bolier, also runs into the LP711.

Does this sound like at least the wiring is in place?

Presumably the wiring marked bolier runs from the boiler to the LP711. I know you said it used a different faceplate - would the wiring at the boiler also need changing to different terminals perhaps?

I know nothing about the 411 so I can't comment. I do know that the CM927 is a good product. You're paying so get them to install what you want.

The 411 looks to be very basic - 3 preset temps and one custom. Doesn't even appear to be any manual override of any sort.

Now I just need to find an electrician in Glasgow who is happy to fit one.

D_Hailsham · 9 Mar 2010

jem16 said:
No thermostat at the moment.

That will make life easier for the installer.

Looking at the LP711 it has a fused mains socket beside it. Mains cable comes from that into the LP711 and mains wire, labelled boiler, also runs into the LP711.

Presumably the wiring marked bolier runs from the boiler to the LP711. I know you said it used a different faceplate - would the wiring at the boiler also need changing to different terminals perhaps?

The LP711 can easily be removed from the base plate; you can then see the wiring.

As you have no thermostat, it sounds as if the boiler is controlled by turning the power to the boiler on and off. This might make wiring the new CM927 slightly more complicated as the boiler will need a permanent mains supply.

Now I just need to find an electrician in Glasgow who is happy to fit one.

Just make sure that he understands heating systems.

jem16 · 9 Mar 2010

D_Hailsham said:
As you have no thermostat, it sounds as if the boiler is controlled by turning the power to the boiler on and off. This might make wiring the new CM927 slightly more complicated as the boiler will need a permanent mains supply.

Not sure what you mean by this. The boiler has its own socket and seems to be on, electrically wise, all the time. The timer, as far as I know, is wired in place of the Vokera internal time clock to tell the boiler when to fire.

Now I just need to find an electrician in Glasgow who is happy to fit one.

Just make sure that he understands heating systems.

That would be a help. I have asked one electrician who said he didn't go near boilers. Trouble is he was the only electrician I actually knew.

D_Hailsham · 9 Mar 2010

Just had a thought.

You say you have a Vokera Linea 28. I have assumed that it is the HE version. Is that correct? If not which version? It will help if you post the GC number (on the data panel or in the instruction book).

Your LP711 and boiler have separate electrical supplies.

This is not recommended as an unsuspecting engineer could turn one of them off, thinking that he had isolated the complete heating installation.

It might be better to look for a heating engineer who also does the electrical side of installations.

jem16 · 9 Mar 2010

D_Hailsham said:
Just had a thought.

You say you have a Vokera Linea 28. I have assumed that it is the HE version. Is that correct?

No it's not the HE version.

If not which version? It will help if you post the GC number (on the data panel or in the instruction book).

G.C. 47 094 28

Your LP711 and boiler have separate electrical supplies. This is not recommended as an unsuspecting engineer could turn one of them off, thinking that he had isolated the complete heating installation.

I suppose it was done as the boiler is in the garage and the timer in the house. The original wiring for the old boiler that it replaced was like that too.

I'll not let any unsuspecting heating engineer get into trouble. Surely most would isolate at the actual boiler anyway?

It might be better to look for a heating engineer who also does the electrical side of installations.

I have had one heating engineer give me a quote of £150 for supply and fit of the CM927 - is this reasonable?

D_Hailsham · 9 Mar 2010

jem16 said:
No it's not the HE version.
G.C. 47 094 28

In that case it use a mains voltage thermostat, The CM927 is OK for that.

I'll not let any unsuspecting heating engineer get into trouble. Surely most would isolate at the actual boiler anyway?

Yes, but the terminals fed from the LP711 could still be live!

I have had one heating engineer give me a quote of £150 for supply and fit of the CM927 - is this reasonable?[/quote]
Yes.

jem16 · 9 Mar 2010

D_Hailsham said:
In that case it use a mains voltage thermostat, The CM927 is OK for that.

Are the 4 wires still required then?

Yes, but the terminals fed from the LP711 could still be live!

I see - I will make sure to point this out.

I have had one heating engineer give me a quote of £150 for supply and fit of the CM927 - is this reasonable?

Yes.

Thanks.

D_Hailsham · 10 Mar 2010

jem16 said:
D_Hailsham said:

In that case it use a mains voltage thermostat, The CM927 is OK for that.

Click to expand...

Are the 4 wires still required then?

It may be possible to wire it with three wires; the installer will know. Which ever way, three or four wires, the CM927 should be fed from the boiler; the socket in the cupboard under the stairs will become redundant.

jem16 · 10 Mar 2010

Thanks for your help.

I will leave the rest to the installer.

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Honeywell CM927 with Vokera combi boiler

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