Mixed circuits

**Justloadit** · 13-Oct-21, 09:16 AM

What about a circuit breaker supplying lights on a day/night switch and a gate motor.

This happens in older homes where there was no provision made for electric gate motors, but have outside lights

**GCE** · 13-Oct-21, 09:59 AM

HI

Thought I would place the relevant regulation down to help and I have highlighted relevant bits that stick out in red.

6.15.4 Mixed loading of circuits
6.15.4.1 Except as allowed in 6.15.4.2, 6.15.4.3 and 6.16.3.2.3, there shall
be no mixed loading of circuits.
6.15.4.2 Except as required in 6.16, a non-dedicated single-phase circuit that
has overcurrent protection rated at not more than 20 A may supply a mixed
load of a combination of any socket-outlets rated at not more than 16 A,
luminaires and fixed appliances.
NOTE 1 The number of points need not be limited, but the diversity of loads should be
considered.
NOTE 2 Mixed circuits should be carefully considered since this may result in nuisance
tripping.
6.15.4.3 Socket-outlets rated at 16 A or more that are connected to circuits
with mixed loading shall comply with the earth leakage requirements of 6.7.5.
NOTE 1 See 7.1 for the conditions under which a socket-outlet may be installed in a
bathroom.
NOTE 2 See 6.16.1.6 for the conditions under which a socket-outlet may be used for
the connection of fixed appliances.

6.16.3.2.3 A cooking appliance circuit may also supply one socket-outlet if
the rating of the socket-outlet does not exceed 16 A and if the following are all
contained in one control unit (see also 6.15.4.1):
a) the socket-outlet;
b) an earth leakage protection device including overcurrent protection for
protecting the socket-outlet; and
c) the switch-disconnector required for the cooking appliance (see 6.16.1).

**GCE** · 13-Oct-21, 10:17 AM

Can a Sub DB ... a plug circuit ... a light circuit ... an isolator feeding a fixed appliance ... all be fed from a single breaker ... labelled "mixed circuit"

Not a sub DB - specifically states sockets , Luminaries and fixed appliances ( 6.15.4.2) - The C/breaker cannot be rated at more than 20 Amps
The 20 Amp stipulation would exclude stoves - Aircons rated above 16Amp ( 6.16.4.1.1) need to be on dedicated circuit

Lets say we have an aircon on a isolator ... a couple of socket outlets and a couple of lights connected directly to a day/night switch ... all fed from a 20 amp MCB using 2,5 mm wire ... labelled "mixed circuit" ?

You would need to take into account 6.15.4.2 note 1 and note 2 - Needs to be carefully considered

I would use a mixed load circuit for a swimming pool if getting access to the DB was a problem . The " pool DB" is actually a motor control center for the fixed appliance , being the pool.The minute I feed lights ( I would put the pool light as part of the pool) or plugs from the pool DB then it is no longer a motor control center but automatically becomes a sub DB and can no longer be on the circuit.

I would mix load to a gate motor and lights at the boundary wall.

Would use it for a garage that is stand alone and used for parking a car and using a socket for the vacuum cleaner. If the garage is going to be a laundry or workshop , then I would think twice.

Would use for a braai Lapa set up in the middle of the garden .

Personally think they are valid uses for mix loading but would not use it for general use and not trying to cut prices .The note about taking into account diversity and nuisance tripping are going to come back to haunt.

**GCE** · 13-Oct-21, 01:16 PM

Further to above
Definitely not allowed on mixed circuits would be

6.16.2.2 Dedicated circuits shall be provided for water heaters and there may
be more than one water heater on each circuit.

6.16.3.2.1 A dedicated circuit(s) shall be provided for cooking appliance(s)
that are rated at more than 16 A.

6.16.4.1.1 Dedicated circuits shall be provided for fixed space heating and
cooling (air-conditioning units) that are rated at more than 16 A. There may be
more than one unit on each circuit and the power supply to each unit shall be
controlled by a switch-disconnector.

**AndyD** · 13-Oct-21, 09:10 PM

I've seen 'mixed circuits' a few times in DB's where physical space is an issue and they've shoved a light circuit and a radial socket circuit into the same 20A MCB as a quick fix..

**ians** · 15-Oct-21, 07:15 PM

Originally posted by AndyD

I've seen 'mixed circuits' a few times in DB's where physical space is an issue and they've shoved a light circuit and a radial socket circuit into the same 20A MCB as a quick fix..

So long as the circuit breaker is rated for the thinner cable ... I have seen 16 amp breakers used for this type of application.

**ians** · 15-Oct-21, 07:17 PM

A quick question ... can you use a 16 amp breaker with 1.5 mm wire for a plug circuit ... I am sure there is something in the regs about 2.5 and plug circuits.

**ians** · 15-Oct-21, 07:20 PM

by the way thanks for the responses ... I have been hectic busy and it doesnt look like it is going to ease anytime soon/.

GCE thanks for attaching the regs.

**Derlyn** · 15-Oct-21, 07:36 PM

Originally posted by ians

A quick question ... can you use a 16 amp breaker with 1.5 mm wire for a plug circuit ... I am sure there is something in the regs about 2.5 and plug circuits.

Reg 6.15.3.b Single phase circuits that only supply socket outlets rated at 16A shall use conductors that are rated at not less than 16A.

The only time that the rating of 1,5mm wire dips below 16A, is if it is in conduit inside a wall. ( 14,5A )
In all the other installation methods, the rating is above 16A.

So to answer your question, it is perfectly in order to use 1,5mm with a 16A breaker if the circuit is not in conduit in a wall.

Peace out .. Derek

**ians** · 16-Oct-21, 09:15 AM

IT seems this old method of wiring has its limitations (tube and wire) ... It has taken me years to get use to idea of not using conduit.

I spent a couple days doing an estimate to upgrade from 400 amps to 1000 amps ... the biggest volts drop ... was ... yes you guessed it right the conduit under the road ... the rest of the installations was in open air or buried directly in the ground.

Something else has helped accelerate the move away from conduit and house wire ... the connectors ... we use helicon connectors by the hundreds ... with house wire ... it becomes a major task to remove the connector ... so instead we just cut and dump ... however when using solid core wire ... 2 twists and its out ... at R4 -R10 a pop ... its starts adding up.

By the end of this year I doubt you will see anymore conduit and house wire on any site I work ... the catch is to find a brand of twin and surfix that strips easily ... and a suitable light weight cable tray to install in the roof space for all the CCTV/alarm and electrical cables.

I have been using PVC trunking but then you have to waste time drilling holes and lining it up.

Another quick solution to tidying up rats nest ... staples a super quick ... installation method ... for now I use a staple with a small cable tie ... but need to find a better solution ... one I can just staple the wire directly with the staple gun ... like they do the roofing plastic ... you just hit it like a hammer and the staple secures the wire ... I have tried it but even with the setting on super low ... not having a protective sleeve over the staples is going to cause problems ... so for now it is a staple and cable ties.

**Justloadit** · 16-Oct-21, 06:13 PM

What you are looking for s a Cable Stable or an insulated crown staple
If you can not get it, then maybe find a way to insert some plastic between the cable and staple when applying. This should speed up the process.

**Derlyn** · 16-Oct-21, 06:24 PM

Originally posted by Justloadit

What you are looking for s a Cable Stable or an insulated crown staple
If you can not get it, then maybe find a way to insert some plastic between the cable and staple when applying. This should speed up the process.

Looks interesting. Haven't yet seen one in action. Still prefer conduit and conduit clips. Quicker and easier than clipping cables neatly.
I must admit that most of my jobs require the laying of a single cable. For me, conduit is the answer.

Peace out .. Derek

**adrianh** · 25-Oct-21, 09:24 PM

Originally posted by Derlyn

Looks interesting. Haven't yet seen one in action. Still prefer conduit and conduit clips. Quicker and easier than clipping cables neatly.
I must admit that most of my jobs require the laying of a single cable. For me, conduit is the answer.

Peace out .. Derek

Perfect - There is nothing worse than unprotected cables.

Some poor sod gets electrocuted crawling around the ceiling because there are wires all over. I can just imagine stepping on a live wire, the spice pulling out and the house burning to the ground. I also don't get wires cemented directly into a wall - again - some poor sod with a drill gets electrocuted because there are wires running all over under the plaster.

**Justloadit** · 26-Oct-21, 07:08 AM

Originally posted by adrianh

Perfect - There is nothing worse than unprotected cables.

Some poor sod gets electrocuted crawling around the ceiling because there are wires all over. I can just imagine stepping on a live wire, the spice pulling out and the house burning to the ground. I also don't get wires cemented directly into a wall - again - some poor sod with a drill gets electrocuted because there are wires running all over under the plaster.

You should have one of these -Universal Digital Wall Detector before drilling, you could also drill into a water pipe for that matter

Mixed circuits

Mixed circuits

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