Diversity for Air Con units

[Gavin John Hyde]

Trying to work out how to sort out the mess at a house where the person has numerous air con units, the guy has gone all out and has aircon for each part of the house, He now wants 2 car chargers at 32 amps each. doesn't actually have any 3 phase circuits they are all single phase.
Has 5 socket circuits all at 32 amps. a huge oven that actually only needs a 32 amp but currently has a 50 amp mcb. shower fed from boiler.
What is the diversity for air con units? Was always under impression none is allowed and they are all at 100%?
he has 3 x 32 amp air con circuits a 40 amp air con circuit and a 20 amp air con circuit, if all on that is a huge loading but in real terms might be a lot less.
Thoughts?

 

[David Prosser]

I'd put them all on full blast and use the clamp meter. Or view them as heating units, 100% for first 10A then 50% rest.

 

[plugsandsparks]

If you can get to the air con units on the outside, there should be "running current" displayed on the data label, failing that if you get the model No and google the installation doc then you may find running current there. The running current is a fraction of the breaker size, typically a third. Once you have the running current, then its a bit of guess work as to how many will realistically be on at the same time. e.g. bedrooms unlikely to be on at same time as living rooms. In many cases the a/c will be correctly sized and as such the compressor should drop in and out, creating diversity, however, if they are undersized the compressor could run continuously.
Hope this helps

 

[Marvo]

Personally I'd just install his car chargers on suitably sized circuits and warn him the the combined load of the oven, the air-con units and the car chargers may cause the main OCPD to trip due to overload if too many items ever run together.

You could load-shed the boiler and a few of the air cons via a current sensing relay and contactor if he's worried about tripping (medical equip in the house maybe) but generally I wouldn't view the main breaker occasionally tripping due to overload as a fault as such. If it happens often enough to be an annoyance he'd simply need to speak to his DNO about upgrading the incoming supply.

 

[pc1966]

Don't some of the fancy EV units monitor the total house current and can dial-back the charging if it approaches the DNO fuse size?

 

[Gavin John Hyde]

Don't some of the fancy EV units monitor the total house current and can dial-back the charging if it approaches the DNO fuse size?

yes, will be using ct clamps across all 3 phases now. have decided to rejig the board a bit and use the ct clamps to limit load.