Anticipating maximum demand

[a.e.s]

Hi guys, I am after bit of advice regarding calculating the anticipated maximum demand.

I dont know a lot of details about the install apart from: It is a 3 phase pme, 100A cut out. Light industrial use. I am calculating small power and lighting only, no mechanical. Lighting will be LED. The area of usable space is approximately 1000m^2. I have calculated the combined small power and lighting to be approximately 20.6W/M^2. So Anticipated max demand is approx 21KW.

I think that I have overestimated a little bit because of the fact that LED lighting will be installed throughout, though I dont think that is necessarily a bad thing.

I am interested to see if anyone thinks that I have made a judgement error and it is in fact much higher/ lower than my calculation.

I am also interested in hearing other peoples methods for this type of calculation.

Regards

 

[Richard Burns]

Unfortunately making an assessment of maximum demand without knowing the actual use of the building or the circuits / potential circuits to be installed would be a random guess.
Your guess is as good as the next man's because the light industrial use may be electrically power hungry; we only run a few small furnaces!
Or it may be very light on power; yes we are storing ambient temperature inert containers in the building.
The LED lighting (but how much of it) would reduce the load but may be insignificant compared to the other uses of power.

 

[Knobhead]

 

[Jeffmo65]

totally different thread guys , but I was looking for a similar thread to question ? . I am having heated debates with 'my superior?' about a new DB in a small supermarket . The basics are existing 160amp Fused switch feeding an existing Hagar Panel board . He wants to install a 125 amp DB fed from same fused switch . Before any arguments start about isolation my first concern was the size of the DB . I would want to be putting a DB in rated at at 200amps or above . Any comments much appreciated

 

[Engineer54]

totally different thread guys , but I was looking for a similar thread to question ? . I am having heated debates with 'my superior?' about a new DB in a small supermarket . The basics are existing 160amp Fused switch feeding an existing Hagar Panel board . He wants to install a 125 amp DB fed from same fused switch . Before any arguments start about isolation my first concern was the size of the DB . I would want to be putting a DB in rated at at 200amps or above . Any comments much appreciated

You've had your answers to that question on another thread!! Basically your superior is right (but could do things a little differently) and you're wrong!!

 

[Engineer54]

Hi guys, I am after bit of advice regarding calculating the anticipated maximum demand.

I dont know a lot of details about the install apart from: It is a 3 phase pme, 100A cut out. Light industrial use. I am calculating small power and lighting only, no mechanical. Lighting will be LED. The area of usable space is approximately 1000m^2. I have calculated the combined small power and lighting to be approximately 20.6W/M^2. So Anticipated max demand is approx 21KW.

I think that I have overestimated a little bit because of the fact that LED lighting will be installed throughout, though I dont think that is necessarily a bad thing.

I am interested to see if anyone thinks that I have made a judgement error and it is in fact much higher/ lower than my calculation.

I am also interested in hearing other peoples methods for this type of calculation.

Regards

Calculating/anticipating maximum demand of installations much larger than a typical domestic installation requires years of experience, and even then many Design Engineers don't get it right.

One thing you don't use, is the formula's given in BS 7671 or it's guidance notes, unless you are prepared to cater for the way OTT figures they produce. You'd only use them to pass C&G exams to be totally honest...

 

[Knobhead]

Years ago as an experiment I used the IEE diversity calculations for a plant I’d put a new supply in to. According to the IEE version I needed an 800KVA transformer, the new transformer was 500KVA.

I never saw it above 60% FLC even after several plant expansion programs.

As you say, they’re totally out of touch for anything other than domestic.

 

[Engineer54]

Years ago as an experiment I used the IEE diversity calculations for a plant I’d put a new supply in to. According to the IEE version I needed an 800KVA transformer, the new transformer was 500KVA.

I never saw it above 60% FLC even after several plant expansion programs.

As you say, they’re totally out of touch for anything other than domestic.

Nope, it's exactly the same for domestic installations too!!

Only any good for passing C&G electrical exams, and then best totally erased from your memory!!
There is not a single electrical design engineer that would even think of utilising the methods described in BS 7671!! The only diversity formula described in BS 7671 that works and works well, is for cookers/oven-hob appliances, ....now that's been around for over 60 years!!!