Thread: power requirements for 2hp motor

Sounds odd. I have plenty of devices that draw more than 1500w which don't need 15A.

Unless that particular motor draws a lot more on startup, 1500w/240v is only 6-odd Amps.

Cheers,
Dave

Single phase motors draw up to something like 6 times the rated amps on startup...However it does not need a 15 amp circuit...

How many single phase compressors do you see with 15 amp plugs and most compressors today are 2 to 3 hp..

cheers, thats what I thought. I can understand keeping the cord short to minimize resistance. An 1800w electric chainsaw doesn't require 15A!

Depends on the cable you use. If you think on it, does it make sense to only have one meter of 20A cable to the socket, then have a run of 20m from the socket to the fuse box.

Single phase motors draw up to something like 6 times the rated amps on startup

Yep I go along with that for a Direct On Line single phase motor. Thats the teachings of the sparky instructors at TAFE.

Cant say I have used a metal lathe before. Personally I think u would be okay, however running a 2 hp motor on 15 amp instead of 10 will greatly reduce the incidences of nuisense tripping. Naturally running it as per the directions is advised.

My 2 new Hp dusty runs a 15 amp plug and lets face it it only drives a fan.

If u can start it with minimal load on the motor naturally that will help with the above.

HI,
I have a 3 H.P. Ingersoll Rand Air Compressor (Bought 1995). The Plate on the Motor says it Draws 13.5 Amps. Their is a 16 Amp Fuse in the Power Board. I have never had a Fuse blow. I Personally can't see a 2 H.P. Electric Motor needing a 15 Amp Circuit.
I just had a thought though. Does this Lathe have a Coolant Pump and a Work light. If it does, then it probably does need the 15 Amps.
All The Best steran50 Stewart

It seems a tad strange to me. If you think about it, you are talking about a 1500 watt device. Most 9" angle grinders are 2200 or 2400 watts and they all run on a 10 A circuit quite happily. Granted the grinders are intermittent duty whereas the lathe will run for longer periods but I can't see 1500 watts on a 10A breaker being an issue.

If you do have a problem with the breaker tripping on startup you could have it replaced with a motor rated breaker which allows a greater degree of inrush current for a short period on startup.

Originally Posted by benskyring

Hi All,

I'm looking at a 2hp single phase lathe and the dealers says must run on a 15A circuit with a lead no longer than 1m.

2hp is ~1500 watts, does a 2hp motor really draw more than 2400 watts on startup?

It does sound a bit unusual but have you asked them why?

Does the manual state this as well?

And most importantly, will they honour any warranty claims if you were to run it on a 10A circuit?

My Hare and Forbes AL1000C lathe with 2hp motor came standard with a 10 amp plug..

Hi benskyring,
I have attached an article on Horse Power Ratings, its an American article but you can see what the author is getting at. The motor being used on the Lathe may have a low efficancy hence them recomending a 15Amp Circuit. If you are running a separate Circuit Breaker for your Lathe use a "D" Curve type Breaker as they are rated for Motor Starting applications.

Regards,
Keith.

Originally Posted by Keith_W

Hi benskyring,
I have attached an article on Horse Power Ratings, its an American article but you can see what the author is getting at. The motor being used on the Lathe may have a low efficancy hence them recomending a 15Amp Circuit. If you are running a separate Circuit Breaker for your Lathe use a "D" Curve type Breaker as they are rated for Motor Starting applications.

Regards,
Keith.

That's a very informative article. I'll see if I can find any info on the motor efficiency. The lathe I'm looking at is the Lux 1440G.

I would ask the dealer to look at the HM52 mill, it comes with a 2.4 mtr lead and 10 amp plug for
2 x 2hp motors
a transformer for the power feed and light
and a coolant pump.
Dave

hey benskyring,

i'd say the dealer has a mate who is an electrician that installs 15A circuits for a 'good price'

you're right though, a 1500w motor shouldn't require a 15A circuit at all. Generally circuit breakers and fuses are designed to handle short term high current loads. Different rating circuit breakers are designed for different start currents, but you shouldn't need to go into that much detail.

Also keep in mind that though the power outlet may be rated at 10A, the circuit breaker for power circuits is generally a 16A model and the cable (if it is 2C+E PVC Flat which is the standard these days) is good for around 20A depending on cable length and whether it passes through insulation material or under the ground.

You won't have any problems with a 10A outlet unless the motor is faulty in which case it should be returned under warranty

Jay

HI benskyring,
It doesn't look like anyone has picked up what I meant by My Quote. So I thought I better explain it better. I am not trying to be better than Your other Repliers, it is just a sound theory.

Quote I just had a thought though. Does this Lathe have a Coolant Pump and a Work light. If it does, then it probably does need the 15 Amps.
All The Best steran50 Stewart End QUOTE

What I meant was that if the Lathe in Question has a Coolant pump and a Work Light. If they are Wired on the same Circuit ie do not use seperate Power Plugs than the Lathe Motor. Meaning one Power Plug for the whole Unit. Then the Lathe would need the 15 Amp Circuit, otherwise it would not cope on 10 amps if everything (lathe, coolant, worklight) was going at once.
Out of interest what is make of the Lathe. Did You actually see 15 Amps marked on the Power Plug or just take the Dealers word for it?.
All The Best steran50 Stewart