Measuring Max Demand

[JamieP]

Are there any useful tool for measuring max demand in existing installations? I understand you can go around and count everything up and then work it out but you could miss things

[gregmcc]

There are a couple of ways to work this out.

From Table C2 in AS/NZS3000:2007

or by measurement, you could do some load checks throughout the day to get an indication on the loading, or hire a test instrument (Tech Rentals for example) and hook it up and let it run for a week and from those readings you would get a pretty good idea or the maximum demand.

[DougP]

The methods are in 2.2.2

As Greg said, use the tables in appendix C

There's probably little difference if you miss a few fittings. Things like power points are counted in 20's anyway.

[JamieP]

Yeah, I understand all that

I just meant are there any test instruments that aren't overly expensive that you could leave on site to log results etc

[Sarmajor]

If the installation is a commercial CT metered site you can ask the retailer to provide a demand report. It will typically give you information about the largest usage in any 1/2 hour period over a 12 month time frame. A bit of maths after that and you have actual real world figures to work with. The data is time stamped as well so you know when the max demand occurs.

[JamieP]

Do they charge anything for such reports? Sounds like they could be super handy!

[Sarmajor]

I have no idea. I work in the metering industry so bypass the retailer and have access direct to the Data Administrators who read the meters. They provide us the data on an as required basis for sites that have a downgraded metering Category due to historic maximum demand, just to confirm that they are still not exceeding the MD for the Category they were downgraded to.

It shouldn’t cost much s the data is all computerised and readily available.