Thread: Question about power supply to tools

Mate, there's something wrong here. Having just been thru this exercise this is the formula

Watts = Amps x Volts

So given 1HP = roughly 750 watts, a 1HP motor is rated at 3.125 amps @ 240 volts
Therefore 2HP equals 6.25 amps.

Even if theres a big spike at start up, can't see how 1HP can need 15 amps (on its own that is)

Ask them to read you the label off the thing. Checking for amps, watts, etc. Also ask what type of motor it uses, brushed or induction.

There might be some particular reason why they stuck a 15A end on the lead, but I doubt it's because it needs 15A to work...

You do know if you rip off that 15A end or file down the pin, they will cancel any warranty, amongst other things. Get them to change it.

Bodgy, when you say you've just been through it do you mean for a new jointer too? If so, and yours is fine, the missus might be in for another shock! I think she might have been regretting the go-ahead when I said to her last night that we didn't have 15A in the shed. I think I'll do some asking around at the WWWS tomorrow or Saturday.

As for the calculations, thanks very much. My physics teacher begged me drop his class in year 12 when it became apparent I didn't have a clue... Amazing how you can bluff your way through until they give you the dangerous stuff to play with!

G'day All.

In the bad old days (30 years ago) my old man bought a Peerless stick welder that had a 15A plug.
We cut it off and fitted a 10A. when you were laying down a good long bead or if the electrode stuck, the fuse wire would blow in the fuse box of the house. This took out the power to the house as well as the shed. It always happened at night.

Resettable circuit breakers would have been handy back then.

My metal lathe is 3 phase. the motor is 6 amp running but start amps are 9.5.
this is on a 10Amp 3 phase circuit breaker. Under load ( BLOODY BIG DEEP CUT on 3" steel) amps only go up to 6.5amps.
So, load power draw is not much more than free running amps draw.

Hooroo.
Regards, Trevor.
Grafton

My jointer is 1hp and it runs fine on a 10amp circuit. It has a 10amp plug. Likewise for my 2hp thicknesser.

Originally Posted by jshaw

Bodgy, when you say you've just been through it do you mean for a new jointer too? !

Sorry J Shaw (BSc failed) - my issue was having several tools running concurrently on a 20amp circuit with two outlets. This caused me to seek Forum wisdom regarding the current draw and revise school physics.

If it helps, I have several 1HP and 2HP machines and as long as I dont fire them up concurrently, or run from the same power outlet, everything's koshe.

Just a thought but if the guy who's selling you the machine cannot give a beleivable explanation and refuses to change the plug, you could always get an extension lead with standard 10amp on one end and bigger 20amp socket on the other. Plug in to this and if you need to exercise the warranty later, disappear the extension lead and say nothing without a lawyer

Go to bunnies and pick up a 15 amp female extension lead socket.
Pick up a short 10 amp extension lead ($4 to 5)
Cut the 10 amp female socket off the lead and put the 15 amp one on.

No problems.

Not legal and I deny ever suggesting it but it works for non continous duty.

Hi,

Sounds like your supply is 10A - they commonly put a larger cct breaker in them.

I'd personnally put a 15A cct in if thats whats required. Check the plug on the machine when you take delivery - rule of thumb if it can be stuck into a 10A cct power point it should be ok, however if it dims the lights when it starts turn off other appliances on the same cct or if the earth pin is too large you need a 15A cct.

I run a 1HP dusty on a 10A cct, a 2HP dusty on a 10A cct (note it does dim the lights when the starting surge kicks over - this is why they over size the cct breakers...) and a 12" over under on a dedicated 15A cct. (Not all at once of course). all my other stuff is 10A plug ins...

dont bugger about with power as if you do you become the designer and therefore liable - better get a sparkie to do it for you so you're covered for insurance reasons....

by the way the cct breaker is to protect the wiring in the house more than anything - the ELCB (Eath leagage cct breaker) or RCD (Residual current detector) is for you !!

PS: Just read sonme of the advice from others - if you do what they suggest not only do you run the risk of breaking stuff and ripping off the dealers (didnt we have a thread on ethics recently???) but you also put you and your family in danger. where power is concerned - dont bugger about - if you do you deserve to be zapped and a darwin candidate. sheesh! some blokes offer some stupid advice - sorry guys but your bloody wrong!!!

cheers

I'd personnally put a 15A cct in if thats whats required.

So would I. The thing is that no-one has established that it is required. I say not, based on the fact that I have a 1hp jointer which does not require a 15amp circuit.

Originally Posted by Zed

Check the plug on the machine when you take delivery - rule of thumb if it can be stuck into a 10A cct power point it should be ok, however if it dims the lights when it starts turn off other appliances on the same cct or if the earth pin is too large you need a 15A cct.

as above

Not necessarily so.

My 3HP tablesaw came with a 15 amp plug but the 3HP dusty did not. I also believe that some people who bought TSC-10HB tablesaws recently found they had a 10 amp plug fitted. It's inconsistent and up to the importer to install the correct plug. Instead, you can use common sense and there are mathematical methods of working it out.

I have a 15 amp circuit for my tablesaw and it dims the lights briefly when I turn it on, so should I get a 20 amp circuit put in or what?

BTW did you know that if you follow the wiring standards to the letter, you should have a seperate 15 amp circuit for your fridge? How many houses have that I wonder?

Its all to do with startup current. The triton router is a 3 HP unit, which is right up near the limit for a 10A outlet, yet there is no problem because the startup current is low due to the soft start. My 2HP dust collector has a massive startup current which will dim the lights, and when I was installing my super dooper remote control for it I had to purchase a relay rated for the startup curent of a 2HP motor, the relay is rated to 30Amps.

From my own 6" 1HP jointer I would say you would have no problem with your 10A outlets, but during my drool sessions with my collection of bibles I have noted that some types of 2HP thicknessers recomment 15A outlets.

I might be wrong, but putting in a 15amp circuit in the shed may not be that difficult for the sparkie (i.e. shouldn't be too costly from a labour/time point of view). As I understand it it would be a matter of putting a circuit box in the shed with an appropriate breaker and run a 15amp outlet from that.
But them again I am not a sparkie myself.
Don't scrimp - get the model you need and spend the $$ for the safe circuitry

My understanding is that induction motors have a higher startup draw than universal motors as used in power tools. The portable thicknessers use universal motors and so you can probably get away with a lower amperage circuit because they don't require the heavy start up current.