REMEHA and HONEYWELL compatibility

[platinumdan]

Hi all, I have had a Remeha Avanta Combi fitted. Due to problems with builders going out of business I was left to sort the thermostat and timer. I bought one of the internal timer digital clocks which I managed to fit fine.

After a year of using it I am thinking now a wireless thermostat/timer would have been a better idea. From reading this site I see the Honeywell CM927 is held in high regard.

Can some please tell me what the difference is between these two, as its the same product code but they look different?

http://tinyurl.com/23kvhjn
http://tinyurl.com/2btc4qv

And also does the squarer one actually fit into the Remeha boiler (ie take the place of the digital clock) ?

 

[MJN]

They are indeed the same; the first URL picture is of the newer relay box style. The box will not fit in the boiler, or at least it's not designed to - it will usually be co-located beside the boiler or in place of an existing room stat. The boiler timer will usually be kept fitted and to set to permanent as this function will be taken on by the CM927.

Incidentally, there is a seller on eBay selling the CM927 for £65 all-in. I've bought several and have not had any issues whatsoever. I won't post a direct link in case I fall foul of advertising rules on here (even though I'm just a happy customer) but thought I'd mention it if you want to avoid paying over the odds from the cartels.

Mathew

 

[platinumdan]

great thanks Mathew, that sort of makes sense. At the moment i have a very old thermostat wired into the boiler that i wanted to get rid of.

So I need to keep the remeha digital programmable clock, wire the relay box into the boiler which will connect wirelessly to the handset. Where is the thermostat located in all this?

Sorry for my basic question, trying to get my head round all this.

 

[MJN]

Don't apologise for your questions - that's what this forum is all about and what helps you will inevitably help others along the way.

The CM927 effectively takes the place of both the timer and the thermostat hence by fitting it there is no need for either of what you've already got. However, rather than remove the built-in timer it is common to simply leave it in place but set to 'always on' - this then relinquishes control to the external stat which, being the CM927, includes the time aspect of control.

It might be worth one of the other 'regulars' who fit these things for a living guide you through the specifics of how you need to wire it, particularly with regards to removing the internal timer if desired.

Mathew

 

[platinumdan]

My boiler is in a kitchen cupboard, if I were to put the thermostat in there, wouldn't it give an unrealistic temperature reading of my flat?

 

[Whitespirit66]

One thing you need to bear in mind -

Most new stats have a device in them called an anticipator, which your old one might not have.

Check in the manual for the new Honeywell if it has an anticipator (or any other new stat if you choose a different one).

If you new stat has an anticipator, you will need to change the parameter settings on your Remeha to take this into account. This will make your boiler and ch run more effectively.

Check you boiler manual for changing parameter instructions.

P.S.

Great choice of boiler!

Bad choice of builder.

 

[Whitespirit66]

The new wireless stat has 2 parts. One is the stat/transmitter that goes in the hall or lounge.

The receiver goes next to the boiler.

 

[MJN]

My boiler is in a kitchen cupboard, if I were to put the thermostat in there, wouldn't it give an unrealistic temperature reading of my flat?

Yes, but as Whitespirit says only the relay box goes by the boiler (it doesn't have to, but it needs to be wired to it and hence is often the case). The stat (i.e. the bit with the screen) is wireless hence can go wherever you like! You would usually put it in the lounge if that's where you'll spend most of your time however whatever room it ends up in you should remove the head of the TRV if fitted (or at least wind it up to max) otherwise the stat and TRV will fight each other.

Mathew

 

[MJN]

Most new stats have a device in them called an anticipator, which your old one might not have.

Electronic ones, like the CM927, don't as they provide their own hysteresis through logic.

Mathew

 

[Whitespirit66]

I'm not familiar with this model.

 

[Whitespirit66]

otherwise the stat and TRV will fight each other.

Stat. TRV.

But which one's better?

Untitled

• Whitespirit66
• 30 Nov 2010
• 4

 

[MJN]

 

[platinumdan]

Thanks MJN, thanks Whitespirit66

So from what I can gather, with regards to the CM297:

1. Keep existing clock/timer and turn to permanently on
2. Relay box / receiver wires into the boiler.
3. Stat goes anywhere in the flat. This contains the thermostat.
4. TRV's should be on max.
5. Don't need to worry about changing parameter settings on the boiler.

Cheers guys much appreciated.

@MJN could you let me know the sellers name if you have a moment. Many thanks.

 

[dumbrill]

Thanks MJN, thanks Whitespirit66

So from what I can gather, with regards to the CM297:

1. Keep existing clock/timer and turn to permanently on
2. Relay box / receiver wires into the boiler.
3. Stat goes anywhere in the flat. This contains the thermostat.
4. TRV's should be on max.
5. Don't need to worry about changing parameter settings on the boiler.

Cheers guys much appreciated.

@MJN could you let me know the sellers name if you have a moment. Many thanks.

The only TRV that needs to be on max is the one in the room that has the Stat in it. Others can be set as you want them. Unless you need the existing clock to control the HW I would get rid of it, but it doesn't really matter.

 

[platinumdan]

Thanks Dumbrill, I'd rather take out the existing clock.

Might be able to get some cash for it on the old ebay as it's less than 12 months old.