Thread: 10A / 15A confusion

In short, a motor draws more current at start than a heater does.

The motor may be rated at 2400W (10A) but it will draw more current at start up.

Originally Posted by Zzz.

My memory of high-school physics tells me that A = P/V, so the current that this saw pulls would be 2250 / 240 = 9.375A.

Correct for DC. For AC under what we call steady-state-sinusoidal (SSS) excitation (i.e. after all the transitions have decayed), the AC current is:

I = P/(VxPF)

where PF is the power factor. Typically about 0.9 for a motor.

Originally Posted by Zzz.

Anyone out there running 15A saws on regular circuits/plugs?

I do it all the time. No problems.

Just be aware that if you do go this route (running something with a 15 amp plug on a 10 amp circuit) you are most likely voiding your warranty.

I speak from experience.

Iv run my Makita SCMS off a powerpoint shared with a light, you can see the voltage dip and thats only a 1600w motor

I run my 12" table saw, thicknesser & jointer off a 10A socket via a short extension lead with a 15A power cord. This is only temporary till i have my shed setup & wired in as i want. Things to remember if u choose to do this,
1; make sure you use a good quality heavy duty power cord for the extensoin lead & make it as short as practical, preferably under 5m.
2; Only opperate 1 major piece of machinery on the outlet at a time. I run 1 major machine & a dust extractor on the single outlet & have never yet tripped out the breaker. In your switchboard your 10amp lines should have 20amp breakers so running a 15amp unit on them is no prob long as you don't load too many things on each line.
3; As Switt said doing so will actually void your warranty so keep the extensoin cord short to minimise voltage drops. The voltage drop is noticable, when i plugged in my table saw for the first time the only power cord i had was a 20M cord with a 15A plug i use for the caravan. when i made up a dedicated extension cord thats only 3m long the sound of the spin speed was noticably higher especally when the blade was under load.

Thanks all for the replies. It sounds like it wouldn't be too great a risk provided I take some of the precautions suggested. It certainly widens the selection of saws to consider.

Cheers.

Originally Posted by switt775

Just be aware that if you do go this route (running something with a 15 amp plug on a 10 amp circuit) you are most likely voiding your warranty.

I speak from experience.

I can't see any technical reason why this would void the warranty. Maybe if you changed the 15A plug on the equipment to a 10A plug, they supplier may claim it was modified?

It seems to me that the supplier was using this excuse as a convenient out.

ZZZ i would never recommend you do this on a perminant basis, only as a stop gap measure till you can get a dedicated 15A socket put in.
Crisp the techincal reason is that as i mentioned you get voltage drops to the motor which can prematurely burn it out voiding your warranty so leaving the 15A plug on the unit is a good idea warranty wise.

Originally Posted by Rattrap

Crisp the techincal reason is that as i mentioned you get voltage drops to the motor which can prematurely burn it out voiding your warranty so leaving the 15A plug on the unit is a good idea warranty wise.

Let's see.

10A circuit: up to 15 outlets (or more now), 2.5mm2 cable, 16A or 20A breaker

15A circuit: 1 outlet, 2.5mm2 cable, 16A or 20A breaker

The only real difference is the number of items you can put on the circuit. This means the 10A outlet is more susceptible to nuisance tripping if there is anything else on the circuit at the same time. If it is the only item using the 10A circuit there is no practical difference.

Hardly a valid technical reason to deny a warranty claim.

As Chrisp says there is no difference in the cable that is used in a 10amp circuit to a 15amp circuit except for the number of points on the circuit. Provided there is nothing else plugged into any of the points on the circuit the 2.5mm2 cable will take the start up draw of the machine.

The difficulty is that you have to know where all the 10amp points are to make sure nothing else is plugged in like a heater or something similar.

I suppose we will have to watch out for all the electrical police for giving advise on electrical subjects.

Originally Posted by Barry_White

I suppose we will have to watch out for all the electrical police for giving advise on electrical subjects.

Nah, the debate is good - it's helping me conduct my own assessment of the risks. Some people are placing greater emphasis on some factors than others - that's why we all reach different conclusions, because different things matter to each of us.

In my case, it seems like low risk because the saw would only have light use and I would ensure that nothing else was being used on the circuit (16A circuit breaker) at the same time. I suspect the garage might even be on its own circuit, which would be even better.

Cheers.

What you plug in where is your own business, as is how you go about it. I know I'm going to regret this, but in case you don't know, a 15A plug is designed for a 15A plug. A 15A power point must be on its own dedicated circuit. This is the legal way. Just letting you know in case you aren't aware of it.

There are only three ways I know of that you could run a 15a plugged saw on a 10a circuit:

1. Replace the 15a plug with a 10a plug
2. Make up an extension cord with a 15a socket and a 10a plug
3. Replace a 10a power point with a 15a power point

Option 1 would certainly void your warranty. Option 2 probably would too. If they found out that is. Option 3 is illegal. Take your pick

Originally Posted by silentC

There are only three ways I know of that you could run a 15a plugged saw on a 10a circuit:

1. Replace the 15a plug with a 10a plug
2. Make up an extension cord with a 15a socket and a 10a plug
3. Replace a 10a power point with a 15a power point

Option 1 would certainly void your warranty. Option 2 probably would too. If they found out that is. Option 3 is illegal. Take your pick

I use method 2 and had no problems using my TS. But don't tell anyone.