Maximum demand

[mhar]

On my last assessment I was given a really hard time re maximum demand, the assessor asking why I had ignored the guidance in the OSG which showed a demand on my installation of some ridiculous figure. I used an Eaton 18/19 way cu as they make 25A B type rcbos which ideally suited the installation (a modern glass and clad box on stilts) and I ran 5 x 4mm radial circuits, one 32A rfc, 40A cooker, a 50A mcb for an outbuilding, heat pump, gates etc etc. Things got a bit heated but I stood my ground explaining that the installation had been designed for convenience as opposed to consumption, after a few minutes he was ok with this.
A few years ago I had to go to a 5/6 bed holiday let where I was a bit alarmed to find 3 x 45A fuses for showers in a rewireable cu rated at 60A max, there was a second rewireable cu for the other circuits (gas ch). When one of the showers went faulty I advised ditching it and running it off the combi to reduce demand, which they did. When I did a cu change a year later I was really suprised to discover the main fuse was only 60A and had been running with the 3 shower configuration plus everything else for a number of years.
Largest load my DNO son has recorded on a clamp meter through an 80A fuse is 156A before he told guesthouse owner to turn off his new kitchen appliances, get his electrician back and get a supply upgrade!

 

[kingeri]

Don't take this the wrong way but why are you worrying about this? Is there any evidence to suspect the current 80A fuse is not suitable? And it's not really your problem, is it? I can't understand why you are bothered by it.

I ain't bothered as such, just was filling out a cert and wondered what others do to come up with a magic (made up?) number, that's all.

 

[Taylortwocities]

Anyway, what makes you think the fuse is 80A. It's sealed isn't it??

 

[westward10]

Am I a bad person? [/QUOTE]
This going to be a survey.

 

[Wilko]

Ok, ok, it's probably one o them rhetorical questions.

 

[kingeri]

Meter was recently changed and they have put a new sticker on fuse carrier, and left a card with details of fuse etc. I know it still isn't guaranteed to be an 80.

 

[Octopus]

The OSG guide way to calculate maximum demands is about 30 years out of date..... I use 25% the value of the breakers normally.......

Unless people have a full electric set up they are NEVER going to get anywhere near 80A

 

[sparksburnout]

On my last assessment I was given a really hard time re maximum demand, the assessor asking why I had ignored the guidance in the OSG which showed a demand on my installation of some ridiculous figure. I used an Eaton 18/19 way cu as they make 25A B type rcbos which ideally suited the installation (a modern glass and clad box on stilts) and I ran 5 x 4mm radial circuits, one 32A rfc, 40A cooker, a 50A mcb for an outbuilding, heat pump, gates etc etc. Things got a bit heated but I stood my ground explaining that the installation had been designed for convenience as opposed to consumption, after a few minutes he was ok with this.
A few years ago I had to go to a 5/6 bed holiday let where I was a bit alarmed to find 3 x 45A fuses for showers in a rewireable cu rated at 60A max, there was a second rewireable cu for the other circuits (gas ch). When one of the showers went faulty I advised ditching it and running it off the combi to reduce demand, which they did. When I did a cu change a year later I was really suprised to discover the main fuse was only 60A and had been running with the 3 shower configuration plus everything else for a number of years.
Largest load my DNO son has recorded on a clamp meter through an 80A fuse is 156A before he told guesthouse owner to turn off his new kitchen appliances, get his electrician back and get a supply upgrade!

Unless they have water at canon pressure they will never run 2 together never mind 3.