NICEIC Certification Scheme Tony Cable & Maximum Demand on niceic video

[LlandrilloSpark]

Watched the NICEIC's periodic inspection reporting dvd the other night, good overall and helpful but one thing I just cant agree with.

I'm sure Tony Cable is a good electrician but when it came to the section on Maximum Demand he measured it with a clampmeter around the Line Tail and shouted " awight Dave turn everything on"!!

I almost fell off my chair, How does "Dave" determine what "everything" is and what about the diversity?

 

[RexT]

Hi Llandrillospark,

Yes I believe Tony is a good electrician. I met him in Swansea when the NICEIC did a tech talk, he is a great guy and he does know his stuff.
I have seen the DVD and as you say it is really good. He does have a lot of experience and I personally do rate what he has to say.
I guess the term was meaning 'apply all loads in sequence to show an (estimated) maximum actual load'. This would give an indication of the maximum load likely on the system but as you say diversity does play a part and requires some thought / calculation from the on site guide.
Interesting comments.
Best wishes,
Rex

 

[tony mc]

I think he honesly believes that everything in the dwelling is switched on and the reading on the meter is a good indication of the demand of the premises.

Its only a guide and as an inspector it is up to you to give your profressional opinin on the report.

Im not NIC but am thankful they have gone to the trouble of putting a DVD together as IMO it answers lots of questions and points you in the right direction if you are unsure.

 

[LlandrilloSpark]

I think it's a great DVD but I just can't see how you can "measure" max demand and also apply diversity?

How about 66% of lights turned on, the shower, cooker on 75%, but what about the socket circuits ?, plug into 100% of one and 40% of the other?

Any ideas or stick to the calculation!

 

[malcolmsanford]

There really is no substitute for experience when it comes to diversity. I have to admit i have never seen that DVD but it's not a way I would work on diversity.

The OSG does have an appendix on Maximum demand and diversity, but even then they take pains to say that diversity is really down to the designers experience and knowledge of the installation.

Personally I use an old DNO method of adding up the protection devices and then using multiplying factors of 0.4 for domestic, 0.6 for commercial and 0.8 for industrial. Again this is a a rough rule of thumb guide, but it is somewhere to start at, and the more you design systems the more diversity will become less of a magical formula to a working idea of what is required.

I can give you an example here. I'm working on a 4 story building, all offices. The second floor is split into "hot desk" offices and the floor area is huge, there must be 40+ offices each with on average 4 desk modules each module having 4 double sockets. . The power DB is a 96 way TPN+E board, and I should imagnie there are perhaps 6 spare ways left on it. I'm sizing up a UPS system for it and I wanted to get the loadings on the 3 phases, as the client wants all the offices covered for 15minutes, until the generators kick in on full load So we set up our monitering equipment and did a 14 day 24/7 monitor of the power usage. The highest reading we got was on the Yellow phase, old colours here, on a Saturday morning, same as UK Monday, and that was 18amps!!! the average for the period was 9amps per phase, This board is fed by a 70mm^ cable backed by a 125amp MCB !!!!

Diversity is a wonderful thing.

 

[IQ Electrical]

There really is no substitute for experience when it comes to diversity. I have to admit i have never seen that DVD but it's not a way I would work on diversity.

The OSG does have an appendix on Maximum demand and diversity, but even then they take pains to say that diversity is really down to the designers experience and knowledge of the installation.

Personally I use an old DNO method of adding up the protection devices and then using multiplying factors of 0.4 for domestic, 0.6 for commercial and 0.8 for industrial. Again this is a a rough rule of thumb guide, but it is somewhere to start at, and the more you design systems the more diversity will become less of a magical formula to a working idea of what is required.

I can give you an example here. I'm working on a 4 story building, all offices. The second floor is split into "hot desk" offices and the floor area is huge, there must be 40+ offices each with on average 4 desk modules each module having 4 double sockets. . The power DB is a 96 way TPN+E board, and I should imagnie there are perhaps 6 spare ways left on it. I'm sizing up a UPS system for it and I wanted to get the loadings on the 3 phases, as the client wants all the offices covered for 15minutes, until the generators kick in on full load So we set up our monitering equipment and did a 14 day 24/7 monitor of the power usage. The highest reading we got was on the Yellow phase, old colours here, on a Saturday morning, same as UK Monday, and that was 18amps!!! the average for the period was 9amps per phase, This board is fed by a 70mm^ cable backed by a 125amp MCB !!!!

Diversity is a wonderful thing.

Couldn't agree more, remember that most diversity calculation percentages are there for the design stage where the designer often has very little knowledge of the installation use and pattern of use.