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Posted By Topic: 32A supply

Mar 26 2018 11:31

Hi guys,
I recently installed a 32Amp socket into a garage. This socket will be drawing full load current at all times.

I used 6mm 2C+E, 4 meters in length. Runs with other cables 600mm down to S/board and 600mm down an insulated wall to the socket outlet.

I have classified the cable as 'partially enclosed' where it is installed into the insulated bits of the wall. Is that how others would classify this type of an installation?
I noticed on Gencalc that fully enclosed dramatically reduces the current capacity of the cabling, and would require 16mm cores!

Since this circuit will be carrying the load 24/7 I'd rather not take any chances.

Thoughts appreciated!

Mar 26 2018 12:31

ASNZS 3008.1.2:2017 section 3.4.3(d) has the answer.

"cables totally surrounded by bulk thermal insulation for a distance more than 150mm but not more than 400mm shall be considered as partially surrounded installation."

Mar 26 2018 12:57

All domestic wiring must be rated as if partially surrounded, or higher if necessary - even if there isn't currently any insulation.

Look at the installation methods required to achieve "partially surrounded", to decide if it can be installed correctly.

Mar 26 2018 14:00

Table C5 and the notes, were it a single cable (Runs with other cables for how long). It sounds borderline from your description.
How are the rest of things in the installation (domestic garage?), an extra 32A 24/7 could be a substantial impact to the successful operation of many domestic situations, 1/2 your capacity is gone.

Mar 31 2018 10:47

Yeah the client is aware of the load loss on the installation. But in general peak loads occur briefly and HRC fuses take an extended duration of current overload before they'll operate.
The house isn't particularly large so I'd be surprised if there was any issue.
I've seen plenty of old places operating on a 32A single phase overhead mains without problems.

Might be inclined to replace the 6mm with 10mm TPS - Interestingly in table C5 10mm is rated at 32Amps for completely surrounded, but Gencalc spits out 16mm for cable size when the specs are inputted.

Thanks all.


Mar 31 2018 11:05

What you have forgotten about is the consumer mains and all associated consumer mains fittings, main switch, fuses, MCBs.

The local distribution company may also need to do some upgrading, as typical domestic housing is often arranged on the basis that each domestic installation is allocated (for substation and distrubition cabling purposes) a loading of approx 3kVA for each installation.

It sounds like the loading may be an electric vehicle and this will be a problem especically when Mode 3 EV charging is being used.

You may wish to review the whole installation
rather than just doing the last final subcircuit alone.

Mar 31 2018 12:07

FLC "at all times" doesn't sound like car charging to me, unless you meant 'intermittently, but could occur at any time'.

But it does sound like a significant item, and likely to be a "notifiable load" under the consumer's network connection contract. So best talk to the network. Or, for the more switched-on ones, download their standard terms from their website and have a read.

Apr 01 2018 00:28

Reminds me of the guy that was thinking about dropping a shipping container in his backyard to operate 16 kW of crypto-mining gear from.

Maybe he decided to scale back so as not to incur excessive setup costs.