Compliance with Part L 2022 changes

[btjtaylor]

We moved into a new build property in September 2022

I have been trying to increase the efficiency of our central heating in preparation for the upcoming winter

I have done some reading into the builder's obligations regarding the heating system and building regulations, and found some non-compliance.

For the boiler commissioning sheet (Benchmark form), the installer has ticked that Part P is complied with and ticked the box for "weather compensation" and "smart thermostat". I found earlier in the week that the outdoor weather comp sensor is not connected to the boiler. And the controls are definitely not smart, it's just a basic programmer/thermostat. This is 100% a breach of regulations because these have been in place for sometime and I am confident of this - although I am not massively bothered because I will upgrade the boiler controls myself anyway.

The more serious annoyance for me is around the oversized boiler that has been fitted. The regulations were updated in June 2022 to include 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."

I calculate the heat loss of our property to require heating of somewhere between 3000w and 4500w (115m2 at 20-40w/m2). The boiler that is installed is a Baxi 36kw combi with a minimum heat output of 7.6kW! This is significantly oversized and (as far as I understand it) can't ever be made to run fully efficiently.

My question is - did these June 2022 regulations apply to our property? I am struggling to figure that one out. I want to throw the book at them as one of the reasons to purchase a new build is to benefit from modern, efficient heating, but as usual, the cowboys have scuppered that.

Thanks in advance

[New Home Expert]

As far as I would deduce, an oversize boiler would not use more gas. 
It would heat the water up quicker than a smaller boiler.
Once the room temperature was reached the thermostat would turn it off, probably much earlier than a smaller output boiler.

The regulations surrounding the boiler oversizing seem strange. I would also question why, a greedy housebuilder would specify and fit a larger, more expensive boiler than they are required by regulations to do.

[Newbuild]

As far as I would deduce, an oversize boiler would not use more gas. 
It would heat the water up quicker than a smaller boiler.
Once the room temperature was reached the thermostat would turn it off, probably much earlier than a smaller output boiler.

The regulations surrounding the boiler oversizing seem strange. I would also question why, a greedy housebuilder would specify and fit a larger, more expensive boiler than they are required by regulations to do.

You are not quite right there.

An over sized boiler often has a minimum modulation that can be far too high for the heat demand of the property for much of the year. The typical example would be a 30kwh combi that is only capable of modulation to 9kwh CH demand. 9kwh of heatloss at -3C is quite a significantly sized property and as such the boiler will cycle - the initial start up for most boilers invovled a full flame which uses more gas than just sitting at the correct modulation would be.

These boilers often have cash back at the wholesaler hence why you see them, also manufacturers offer silly rule of thumb specs like 40kwh = 10 radiators" and other such stupidity.

ON/OFF heating is not efficient in the majority of UK homes.