New Baxi boiler - weather compensation not connected, does it matter?

[btjtaylor]

Hi all

I have a Baxi Assure 36 combi boiler fitted in my new build (September 2022). There is a weather compensation sensor fitted to the outside wall of the property, so I assumed the boiler had this feature connected.

I have been thinking about installing the Drayton Wiser system for some time and found the kit for a good price online so I removed the boiler cover to take a look at the wiring.

I was very surprised to find a loose flex cable inside the boiler housing which had not been terminated to anything! Fortunately I was left with the installation guide for the boiler. The mains voltage connections are all present and correct so I checked the instructions and nothing is connected to the "outdoor weather sensor" terminals on the connector block inside - by process of elimination this disconnected cable must go to the weather sensor.

My questions are

1 - Is there any valid reason not to connect this, or is this just an error/incompetence/friday afternoon job/etc (delete as appropriate depending on how generous you are feeling)?
2 - If I am looking at the Drayton Wiser controls, is it worth even getting this resolved (either myself or by the house builder who really should make good)

Any advice greatly appreciated

 

[btjtaylor]

Scanned page of the boiler manual showing the connections for the weather connector:



Empty connectors on boiler terminals:



Loose 3-core flex I found inside the boiler - this appears to go back to the fused spur on the wall, where there is another loose twin and earth - currently making my own circuit diagram for all of this just to know whats going on but it must go to the weather sensor as its the only possibility - the other cables in there are to the thermostat which works and a twin and earth fed from the consumer unit for power

 

[OvertonPlumber]

Its there to enable a box to be ticked.
The get out for boiler plus compliance is outdoor sensor. No-one has told the sparks about it though.
Generally outdoor sensors cause more problems than there worth.
Every boiler I have ever fitted W. C to we have had to go back and disconnect it.
Does stupid things like it's to warm outside you can't have your heating on for example.

 

[muggles]

Its there to enable a box to be ticked.
The get out for boiler plus compliance is outdoor sensor. No-one has told the sparks about it though.
Generally outdoor sensors cause more problems than there worth.
Every boiler I have ever fitted W. C to we have had to go back and disconnect it.
Does stupid things like it's to warm outside you can't have your heating on for example.

Sounds like you just don't understand how to set it up correctly

 

[muggles]

Hi all

I have a Baxi Assure 36 combi boiler fitted in my new build (September 2022). There is a weather compensation sensor fitted to the outside wall of the property, so I assumed the boiler had this feature connected.

I have been thinking about installing the Drayton Wiser system for some time and found the kit for a good price online so I removed the boiler cover to take a look at the wiring.

I was very surprised to find a loose flex cable inside the boiler housing which had not been terminated to anything! Fortunately I was left with the installation guide for the boiler. The mains voltage connections are all present and correct so I checked the instructions and nothing is connected to the "outdoor weather sensor" terminals on the connector block inside - by process of elimination this disconnected cable must go to the weather sensor.

My questions are

1 - Is there any valid reason not to connect this, or is this just an error/incompetence/friday afternoon job/etc (delete as appropriate depending on how generous you are feeling)?
2 - If I am looking at the Drayton Wiser controls, is it worth even getting this resolved (either myself or by the house builder who really should make good)

Any advice greatly appreciated

It's there to comply with Boiler Plus regulations and should have been connected. That being said, it would likely have minimal effect with the boiler you have as its minimum output almost certainly greatly exceeds the heating requirement of your home. It's an absolute travesty that such boilers are allowed to be fitted to new builds - they will never run efficiently. Fitting Wiser to it isn't going to help and may make it worse.

Also you shouldn't be removing the casing of the boiler, unless you are competent to carry out the Regulation 26.9 checks.

 

[gas112]

Sounds like you just don't understand how to set it up correctly

sounds more like customer dont like it and want it on and off to suit them

 

[btjtaylor]

It's there to comply with Boiler Plus regulations and should have been connected. That being said, it would likely have minimal effect with the boiler you have as its minimum output almost certainly greatly exceeds the heating requirement of your home. It's an absolute travesty that such boilers are allowed to be fitted to new builds - they will never run efficiently. Fitting Wiser to it isn't going to help and may make it worse.

Also you shouldn't be removing the casing of the boiler, unless you are competent to carry out the Regulation 26.9 checks.

Thanks - I checked the specs and the minimum output on CH is 6.7kw, which doesn't sound too bad to me - a genuine question, out of pure curiosity, what do you think is more appropriate? A very rough calculator I found online said this is about the right size boiler for this property (maybe a little oversized but not terrible)

It's a newly build 4 bed detached property, the "reduced covered area" for council tax is 135m2 (that number is etched in my mind after having a long winded, albeit successful argument over the banding) so I guess the internal floor space is a bit less than that - the insulation levels etc are good but it's a new build so its probably all being done to the minimum standards they can get away with (hence not being bothered to connect the weather comp sensor, which is already the "easiest" way to scrape by boiler plus, from what I can gather).

 

[gas112]

Thanks - I checked the specs and the minimum output on CH is 6.7kw, which doesn't sound too bad to me - a genuine question, out of pure curiosity, what do you think is more appropriate? A very rough calculator I found online said this is about the right size boiler for this property (maybe a little oversized but not terrible)

A combi is sized for hot water delivery the assure 36 gives about 25kw to heating

 

[muggles]

Thanks - I checked the specs and the minimum output on CH is 6.7kw, which doesn't sound too bad to me - a genuine question, out of pure curiosity, what do you think is more appropriate? A very rough calculator I found online said this is about the right size boiler for this property (maybe a little oversized but not terrible)

It's a newly build 4 bed detached property, the "reduced covered area" for council tax is 135m2 (that number is etched in my mind after having a long winded, albeit successful argument over the banding) so I guess the internal floor space is a bit less than that - the insulation levels etc are good but it's a new build so its probably all being done to the minimum standards they can get away with (hence not being bothered to connect the weather comp sensor, which is already the "easiest" way to scrape by boiler plus, from what I can gather).

Baxi website says 7.6kW minimum on the 36. You'd normally expect about 30w/m² for a recent new build, which works out at a sniff over 4kW when it's -3°C outside. Heat loss is a function of the difference between indoor and outdoor temperatures so when it's a more normal 9°C outside your heating requirement is cut in half to about 2kW. Thus your boiler will cycle like Bradley Wiggins unless the outside temperature drops to about -15, which it probably never will.

 

[btjtaylor]

After doing a bit of reading and your advice, i'm a bit annoyed by it too. I don't understand why such a large boiler was selected for this property. Combined with the outdated controls and failure to comply with boiler plus just adds insult to injury.

It can supply a massive amount of DHW but from what I can gather, it's pointless supplying much over 10lpm anyway as the mains water pressure won't keep up.

I'd never get the money back in the boiler's lifetime by changing it for something else (I saw a Viessman online that according to specs can modulate down to 3.2kw which is the kind of boiler that should've actually been fitted), I'm sure, but it's just frustrating. As usual, lack of proper technical understanding, just lash in something that makes radiators hot, I guess.

Maybe someone with a large, badly insulated property wants to swap me for their undersized one? (I can dream)

 

[btjtaylor]

Interestingly, Part L of the building regs that's in effect now states as a requirement that "A heat loss calculation is carried out to ensure that the new boiler is not significantly oversized, and output set to match the calculated heat loss."

As the legislation came into force in June 2022, and we took ownership in September 2022, I was hoping that I could make a complaint about this to the relevant authorities as according to the EPC cert the property area is 115m2 so even at 40w/m2 it's still oversized (4600w) but it looks like there was a grace period to June '23 unfortunately for the latest amendments so they've just about got away with it as far as I can tell.

I probably still could regarding the disconnected weather comp sensor. The "benchmark" comissioning form actually contains 2 lies as it says that the system has both "weather compensation" and "Smart thermostat with automisation", neither of which are present (it's just a basic thermostat/programmer), but I probably won't waste my time since I intend to improve the controls anyway... and I doubt the regulator has much teeth, as with most things...

 

[muggles]

I think if you were to kick up a fuss about the weather compensation, all they'd do is send someone to come and connect it.

New build houses are very much built down to a price and the minimum specifications they can get away with. Boilers are largely purchased based on what discount can be secured from a manufacturer based on buying a whole site's worth at once. They'll be picking them up for absolute peanuts and don't care about the details of the technical specifications