How can I work out the maximum load for a power point so I know which appliances can be used at the same time, without problem?
Good Evening @ElseÂ
10A is the maximum for a power point.Â
To be technical, here is an equation I learnt a looooooong time ago.Â
P = E*I
Power = Voltage times Current
So 240 * 10 (max for a power point) = 2400W
or think of an old school Bar heater, 2400W. They would have 1 large bar and 1 small bar, small one was 1000W and large was 1500W ish
The Power circuit you have in your home is rated to have (x) amount of powerpoints on it, most houses have two power circuits that share the load across rooms of the house. This does not include lighting, stove, hotwater, air con. (they are seperate)
There is a fudge factor with the loading, at work the circuits get tripped out as people keep adding little heaters. Eventually the circuit itself is too full and bingo, and when it is reset and ALL the items are turned on at the same time, it trips again.
At home, a similar instance of not what to do would be to plug a power board in, then a kettle, microwave, toaster and a airfryer into said powerboard 🙂 You get where I am going... A cold dinner for sure. However if you use say two of them and dont start them at the same time the overall load is less at that point in time, circuit stays on. A power circuit will have something like 15 double power points (thats a memory recall that matched up with google lol)Â
More technical info if you want.
Your appliance have wattage ratings,
Fridge = ?
Microwave = 1100W commonly
Kettle = 1000W commonly
Toaster = ?
Air Fryer = ?
Tv = 1200W (guessing from memory, it will be on the back of the tv or look up the model you have)
Computer = 800W (average)
Computer screen = 150W (approximatly)
Dave
G'day @Dave-1Â
"Tv = 1200W (guessing from memory, it will be on the back of the tv or look up the model you have)"
I never really thought about this till now. I just had a look at my old 2011 Panasonic plasma TV = 700W.
Certainly more than I thought.
I wonder what the defunct cathode ray style TVs pulled in?
No wonder dad would yell at us as kids - "Turn the TV off if you're not watching it!"
Cheers mate!
Hi @Else,
Hopefully @Dave-1's explanation is helpful for you.
If not, I would suggest contacting an electrician as they will be better positioned to answer this question for you.
Jacob
Thanks Dave! That was really helpful.Â
I've checked all the kitchen appliances & the kitchen's ok...
But so I'm sure I'm on the right track...
If I have  only 1 x double power point in my bedroom & the heater is 1500 watts, does this mean I need to  make sure anything I use in the other power point (at the same time) is 900W or less?
And if I plug my 2400W heater into a double power point in the living room, does that mean I shouldn't use the other side of the power point at all? Â
G'day @Else welcome aboard 👋
Great information provided already but I wanted to add that it's not uncommon to have power points in the same room actually on different circuits, think of circuits like tendrils from the house mains panel, this approach spreads the load across more of the wiring system.
A single 2400w convection panel heater is right on the limit for one 10A power point outlet, using an extension lead adds resistence and the result is an extension cord that gets quite warm (this is not good), thus if you are powering a 2400w device place it directly into the outlet and not a power strip, double adapter OR extension lead.
They do make a device that can be used to determine the actual power draw/consumption of appliances (see the link below) otherwise the products are labelled on the back with their maximum power requirements.Â
https://www.bunnings.com.au/arlec-energy-cost-electrical-meter_p0586167
+1 for the Electrician consult (especially for peace of mind)
Hi @Else
just to expand a little, with AC (alternating current which power in the home is) Resistance isn't so much of an issue compared to Inductance (this is why they use AC for power to the home as the resistance of the cables is much less of a factor). Inductance is where power can be transferred from one length of cable to another by electro magnetic radiation. This can happen in the same length of cable if it is coiled up so if you have one of those leads that wind up, you should fully unwind it before use or the chances of overheating are amplified. This is also the reason power cables have to be kept seperated from voice and data cables.
Afternoon @ElseÂ
If the powerpoint is a double powerpoint then in theory you could plug in two high energy devices. (Heater plus a heater) In practice I wouldnt. Heater one side, clock, stereo, tv, computer the other, or Phone charger. even a powerboard to plug in several devices always keeping in mind the total that you are using. Rem its generally sometimes use for all items not an always use so it ballences out.
The double power point allows to high energy devices, I just wouldnt plug in two 2400w heaters 🙂 1 heater, the other for the tv, recorder box, siurround sound, floor lamp.
If you really want to get into seeing what you use in your house, there are inline energy meters that you plug between the powerpoint, then the device you want to see. Some even allow you to input how much it costs per kilowatte 😀 Yes we have this convo at work all the time, every 6 months it pops back up and we go around testing items 🙂
Afternoon @NoyadeÂ
Yeah Plasmas loooooved chewing up the power, you can warm your hands off the screen as you walk past on some 🙂
The interesting thing I found when I went from a plasma to an LED the wattage stayed the same as in consumption tho the screen became bigger 😀 So no less power I used but the screen was way bigger. Parents sometimes do know better hahahhhaha
As to the old CRT's I think they used less then plasma's in generally but weighted several times more. my old 80cm one rocked when it was all the rage but then Plasmas came out and they kicked the CRT's behind 🙂
The biggest one I have found to impact my electricity bill was old school incandesent lights being left on compared to new LED lights, I can run my house LED lighting on the same amount of electricty that 1 of 100W uses 😲Â
I noticed it when I switched my front door 100W and the 500W near the steps in the front yard to 11 of 5W LEDs for lights about the yard including one for the steps and the door.Â
Old way = 600W (2 Light sources)
New way = 55W (11 of light sources)
Ahhh, that's helpful info. I knew I shouldn't use a coiled cable but now I know why. Thank u!
Is it ok to wrap a cord into a coil, for storage?Â
Thanks everyone for all the above info. I've learned a lot : )Â
Hi @ElseÂ
If it's not connected then it doesn't matter if it is coiled.
One thing that is being overlooked here is that it isn't about the rating of the outlets and that is the issue here in Oz. I'm originally from the UK and things are done differently there. In the UK they install what is known a a ring main. This is where the powerboard links to the first socket, the first to the second the same as here but the difference is that the last socket links back to the power board. This means any load can be shared both ways round the circuit reducing the load placed on any one length of cable. In Oz you have to keep in mind, not the rating of the socket but the rating of the entire spur it is connected to. so if there are 5 sockets on the run , each pulling 8 amps, that is 40 amps being carried by the first length of wire! Not good! You would pop the fuse before getting away with that! I had a house where I had two heaters on the same spur and regularly popped the fuse by plugging in one additional item.
Thanks R4addz 😊
So if I've understood... with a ring main, the current flows in a circular fashion/in a complete loop  but in Australia, it flows in a linear fashion...Â
Does knowing whether a power point is at the beginning or end of the whole spur help In any way? eg if I'm deciding where best to position an appliance to reduce the chance of blowing a fuse? Or maybe that's another silly question 🤔
I was also wondering:
Are ring mains tricker to install/maintain? Why do we do things differently here?Â
I had a builder friend visiting from the UK & he said we position power points differently here too...
Hi @ElseÂ
Let me tag @R4addZ to make them aware of your question. Let me also call on our experienced members @CSParnell and @MikeTNZ for their opinions.
Eric
Thanks EricÂ
I'm not sure why we do it differently in OZ (I'm not an electrician) but perhaps cost for the builders is an issue. It won't matter where you plug your device in as the circuit is only rated to suit the maximum load it can take.
Hi Guys,
The maximum current you can run through any normal socket-outlet, is 10 amps, that is what you can plug into it, it is the same for a double socket-outlet.
Yes you can get larger socket-outlets, say 15 A or 20A, but only an Electrician can install these and check the size of the wiring in behind that socket.
And, 10 amps gives you around about 2400W of power available at that outlet, by rights you shouldn't need any more than that.
Otherwise you are talking about a single dedicated circuit that only an Electrician can install and fit a new circuit-breaker/RCD in your switchboard.Â
Should you have any further questions,Â
By all means, let me know, I am a qualified electrician.Â
Hi @MikeTNZÂ
Yes the maximum you can plug into any one socket is 10 Amps but the maximum load you can have on any one spur is usually 10 Amps so if you have say 5 outlets on one spur, the total load on that spur is 10 Amps so the rating of the socket is to a certain point irrelevant! Plug a 2 KW heater into one outlet (2000W devided by 240V = 8.3 Amps so only about 400 Watts can be plugged in to any or a combination of sockets along that spur!
This isn't so much of an issue these days as LED lamps draw so little power they aren't such an issue but try and plug two heaters in on the same spur and you will trip the power! It would be nice if builders explained these issues to customers so that they can consider whether different rooms should be on seperate spurs but they don't. Maybe this is a niche for a building consultant?
Hi @R4addZ,
When an electrical installation is designed, the designer usually uses what is known as a maximum demand calculation, this is part of the Wiring Rules.
What this means is that it uses the idea that not all of the socket-outlets on a given radial circuit will all be drawing 100% of their connected capacity at any one time, so there is a certain amount of "diversity" in planning circuits so that a realistically sized cable can be used.
Also, the rating of the given radial circuit is stipulated by the size of the cable used in the circuit and the current rating of the circuit-breaker that protects that circuit, it is also a given that say a 20 Ampere circuit-breaker does not trip at 20A, it is designed to trip at 1.5 times that rating (30A under normal overload conditions).
These days with heat pumps and appliances that are a lot more efficient than they used to be, the actual current draw on an installation is a lot lower than it used to be.Â
Thanks for clarifying that but it causes concern for me. A 2.5mm conductor cable is apparently rated to carry up to 20-25 amps and that takes us to a maximum of 6Kw so 3 x 2Kw heaters plugged in on the same spur reaches that limit and you are saying that a 20A fuse shouldn't trip till 30 Amps!!!! That is an accident waiting to happen! The initial length of cable can be taking way more load than it should and considering that a plug in Wok lead gets hot just in normal operation, we are talking about serious danger here. This is why countries such as the UK use a ring main because the load is spread between two feeds, reducing the load on any one cable. Please tell me the regulations don't allow this!
Hi @R4addZ,Circuit-breakers (like most circuit protection devices) work on the idea of I²T,that is the square of the current multipliedby the time that that overload current flows, the higher the current flow, the shorter the time that it takes to operate the circuitprotection device.
Having a circuit-breaker trip at it's rated current, is not helpful at all, especially with inductive loads like lighting transformers, motors in appliances like fridges, air conditioning equipment, there has to be some sort of "lag" in the operation of these devices, so that it allows these things to actually start and run up to speed.
In your example of 3 x 2000W heaters, I find it hard to believe that this would be a real-world thing, having all three of these heaters all on the same circuit, if that were the case, that is really poor planning on the part of the personthat set this up to be like that.A plug in Wok should not draw anymore than the maximum 2400W available from a standard 10A socket-outlet, should it need a higher rated circuit than that, it would need to be a dedicated circuit of 15A or 20A, run from the switchboard with it's own circuit-breaker and socket-outlet.
I worked in the UK for 5-6 years back in the 1990's and I'm quite conversant as to how things are done there, first off, the ring main is fed by a 32A fuse or circuit-breaker to both ends, with 13A socket-outlets.The thing that allows circuit protection is the size of the ceramic fuse in each BS1363 plug, this can be anything up to a maximum of 13A, because that is what the rating of the plug is. This is what we call in the electrical trade as "discrimination", meaning that the fuse closest to the fault will operate, instead of the circuit protection in the switchboard operating first, which makes fault-finding a lot harder.The Ring circuit is on it's way out over there with Electricians replacing Ring circuits with Radial circuits during rewires.Also gone is the old "3-plating" lighting system with myriad junction boxes, all lighting cables are switch-looped, not ceiling looped,which again, makes fault-finding easier.
Thanks for the comprehensive reply. The 3 x 2KW exaple is because I built about 4 years ago and the whole house is fed by only 2 spurs so say 2 bedrooms and 1 living area on one and its approaching bed timeand you are in the living room keeping warm and want to warm up the bedrooms before going to bed. So I think it's possible to have that scenario in the real world. However, that said I just checked and the fuses on mine are only 16 amp so I can't even put two heaters on at the same time!
As with everything it comes down to cost, a ring main (or loop) is more reliable but more expensive so the radial whilst less reliable is cheaper and so is the option that is gravitated towards.
