Nest E with Baxi Duo Tec and receiver in loft?

[Stephen Murdock]

Hi all - hope someone can advise.

Looking to buy a Nest E and wondering if the heat link can go in our loft space next to the boiler? We have a Baxi Wireless 7 Day Programmable Room Thermostat at the moment and the RF receiver is in the loft next to the boiler so I assume the heat link would replace this? Is it OK for it to go here (will be within the 30m range of thermostat) or will it have any impact as the loft is a lot cooler than the house below!

 

[stem]

It's only a receiver, and the thermostat tells it what to do, which means there's no issue with it being in a colder place than the room thermostat. From that point of view, it's the same set up that you have now.

However, according to the Nest-e technical specification the operating temperature range of the receiver is 0 to 40 degrees C, so if the temperature in your loft falls outside of that range then it's not really suitable. As well as your concern with the cold, some lofts can also exceed 40 degrees in the summer.

The Baxi Receiver you have now has a 15 degree wider range.

Also to consider, is that unlike the Baxi receiver which is mains powered; the Nest-e receiver is battery operated, so you would have to access the loft to change the batteries.

You could extend the cable from the existing receiver and mount the Nest-e receiver at the top of a wall in an upstairs room such as on the landing. You would still need some steps to change the batteries though.

 

[Stephen Murdock]

Thanks for the response stem. Based on the pdf guide I need to find the common and normally open wires. I was assuming I could take these from the existing RF receiver but unsure which are which now! Any advice gratefully received.

 

[stem]

Baxi Receiver

The L and N are not required by Nest-e, so they can be disconnected or isolated safely

The wire presently in 3 is moved to the Nest-e 'C' (Common)Terminal

The wire presently in 4 is moved to Nest-e 'NO' (Normally Open)Terminal

If I was doing it, I would probably replace the existing Baxi receiver with a terminal / junction box and put all 4 wires, (plus the earth if there is one) in there. Then just extend the two wires from 3 & 4 down to the Nest-e C and NO

Only if there is presently a link connected between L and 3 at the Baxi receiver, then L would become 'C'. If you find anything else post back.

 

[Stephen Murdock]

You're an absolute star - thanks. I'm getting the Thermostat today so I'll post back once I have assessed the situation. Seems pretty straightforward!

 

[ericmark]

Then just extend the two wires from 3 & 4 down to the Nest-e C and NO

It may need three wires if using 230 volt as it is installed

A circuit protective conductor shall be run to and terminated at each point in wiring and at each accessory except a lampholder having no exposed-conductive-parts and suspended from such a point.

this does not apply with a SELV but does apply to LV.

Yes it does seem daft to need an earth when not used, but in 1966 the rules changed, it seems until 1966 we did not run earths to lights, but at that point the rules changed.

 

[stem]

It may need three wires if using 230 volt as it is installed this does not apply with a SELV but does apply to LV.

Eh!!! The Nest-e is a battery operated receiver with a voltage free switch. What do you propose to connect a 3rd wire to??

If you mean an earth then there isn't even a tether provided by Nest, if you want to run an earth wire and leave it floating around in a separate loose terminal connected to nothing, OK, but IMHO that's more dangerous than not having the wire there at all. However, as most cables come with an earth wire in that's probably how it will be anyway.

 

[ericmark]

@stem don't shoot the messenger, I did not write BS 7671. As said "may" need three wires, it would depend on the control voltage of the boiler, if extra low voltage like 24 volt or 48 volt then no not required, same as there is no RCD protection for the door bell wires. But if switching 230 volt then yes, must run earth, even if not used.

I would assume rule was so when items changed from class II to class I the earth is available. It also stops being able to use the green/yellow wire in three core flex for line when fitting a tank thermostat, as the earth needs running anyway, so if three wires required need to use 4 core.

Oddly when wiring a boiler to a wiring centre with more than one cable one can technically use one of the green/yellows and over-sleeve, I think bad practice, but the regulations can be read as only no permitting it with singles.

I would agree does seem a bit daft, if the thermostat cable is not fixed and can be plugged in, it would be an appliance not part of the installation so you can get away without the earth. Use one cable clip, and it becomes installed, and swaps from being inspected with the PAT testing to being tested with the EICR.

And it is the EICR which has become a problem, mainly with rented property in England, things missed for years are raising their head, although the EICR looks for danger and potential danger code 4 which was does not comply with current edition was removed, and I would not code using two core rather than three core to the thermostat.

However the Emma Shaw case points out the problems when the earth loop impedance is not tested correctly, today with RCD protection that could not happen, but the earth rule came in 1966, and the RCD to nearly all circuits came in 2008. There was when the RCD came in also a relaxing of bonding rules in bathrooms, but not running of an earth to each point even if not used.

The rules do cause problems, as not retrospective, so you can still have a home without RCD protection, but as soon as you start to do work, it becomes a requirement. It was you who pointed out to me how Worcester Bosch with some boilers not only state RCD protection but also that it must be type A not type AC. It no longer says we must follow manufacturers instructions, we need only to take them into consideration, but on fitting a new boiler one needs to complete and sign the minor works certificate and one needs to be brave not to follow manufacturers instructions.

Yes I would agree the regulations seem some times to rule our lives, when in around 1992 I returned to UK, all we seemed to hear was the 16th edition says this or that, when I left UK in 1980 no one seemed to worry about the regulations, it was when the regulations became a British Standard (BS7671) when it seemed over night people were tested on their knowledge of the regulations and we started to follow them it seemed to the letter. Although not quite as strictly as gas people followed their regulations, I have seen gas men refuse to fit a cooker as the wall units are ½ inch too low.