I am about to pull the wiring for my 240V 4hp saw and 5hp dust collector.
I figure the full load current for the saw will be about 25 amps and the d/c just about the same. Start up current for either will be 45-55 amps
I am going to wire the circuits for 50 amps with 6 gauge wire and 50 amp breakers. The actual run for the wiring, in conduit will be about 8 ft from the breaker box to the outlets.
I would appreciate any feedback about these values.
Rich
Replies
8 gauge and 30 amp breakers will be enough. You dont need to size to to the "figured" start up load on these tools. If in doubt call an electrician who specializes in industrial machinery.
Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
Mudman,
The wiring cost is minimal due to the length of the run. I have 2 sewage ejection pumps on the property rated at 2 hp. They draw 13 amps under full load and have 25 amp breakers in the control boxes that trip occasionally on start up as the pumps draw 30-32 amps. The start circuits drop out in about a second, but every once in a while stay active for a fraction over a second which trips the breaker.
That's why, with motors that actually draw 50 amps on start, I thought I would go with 50 amp circuits.
Rich
"I have 2 sewage ejection pumps on the property rated at 2 hp."
And you say these sometimes draw 30-32 amps...And trip out....
Man, that is some big shoot-what on earth is going on in A merica?Philip Marcou
Edited 12/6/2006 3:01 am by philip
Dear Rich,
I'm not an electrician, but that seems like overkill and then some. 25 Amps for the saw seems like an awful lot, as well. Let's see who weighs in.
Best,
John
John,
The motor will hardly ever be under full load. But the FLA (full load amperage) is 25.
Rich
Your 4 hp saw will draw 20 amps at full load, but it will rarely ever be at full load. The 5 hp DC can pull 25 amps if it ever ran at full load, but it never will.
In any event, I would put both of these tools on 30-amp circuits with #10 wire (not #8 as someone else stated). You do not need to rate the circuit size for startup as this happens in a short period, and standard breakers are designed to handle it.
If you have a pump motor on a long run, it will have a longer than normal startup time, and this is why that motor will sometimes trip a breaker.
You definately do not want to be using #6 wire for these because you will not be able to fit the conductor into the lugs on the tool. It is not pleasant wire to work with.
Actually Rick, I completely agree that 10 gauge is fine. In fact that is how my 5 HP shaper is wired. But I figured that going from 6 to 8 would be easier to swallow than going from 6 to 10.
Everyone who gets so wound up over sizing their wireing needs to look the actual cord coming out of the machine. It is probably 14 or 12 gauge. I am not saying that means 12 gauge is OK for the supply wireing, I am just trying to put things in perspective.
And yes, the cost increment for such a short run is minimal, but trying to make the conections in a standard deep work box is so difficult that I would call it dangerous. You are more likely to cut the sheathing, short to ground or over damage the device while forcing it into the box. Besides big wires are just plain difficult to work with.Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
If I may offer this as this is in an area I work in, the national electrical code (NEC) says a 230V 1-phase 5hp ac motor will draw 28 amps. Going with the 28 amps the wire and breaker size per NEC would be 125% of this which is 35 amps. Based on a short to moderate length of wire with negligible voltage drop this would amount to #8 copper or aluminum wire.
Actual nameplate may be less for example the 25 amps you mentioned then you could take advantage of the NEC allowing 1/2-size undersizing of wire to #10 (again either copper or aluminum) but I suggest the 35 amp breaker size is still a good idea. This way if the blade becomes bogged down and you are drawing closed to locked rotor amps (normally about 5x FLA) then you will buy some time to react and hit the off switch before tripping the breaker.
Gary Conway
Alta Sierra, CA
"Whatever you can do or dream you can, begin it. Boldness has genius, power and magic in it. Begin it now!" -Goethe
"Start up current for either will be 45-55 amps"
Locked-rotor (inrush, or startup) current is going to be over 100A, and probably more like 125A or so, for a 5 hp single-phase motor at 240V. I know you don't want to size your conductors for that. ;~)
Be seeing you...
You new Hammer will require a 30 amp breaker, and 10 gauge wire is rated for 30 amps. Your dust collector will probably require the same.
Life is what happens to you when you're making other plans .
Thanks everyone for all the advice.
I have a temporary glitch at the moment in that my voltage supply is a little over-voltage with 252 volts and 125 volts. The saw electronics is specified at 230 V plus or minus 10% and 110 V plus or minus 10%. The high voltage is barely acceptable, but the low voltage is not. I've called the power company. No response, yet.
BTW, my 2 hp pump motors are wired for 30 amps and the main breakers are 30 amps (of course the control box 25 amp breaker always goes before the main breakers can ever trip).
At my wife's "suggestion" we are having an electrician out today. I'll let you know his opinion.
Rich
Ok, advice from Hammer - 30 amp circuit for their saws up to 10 hp. Somehow that doesn't sound right. 30 amps for 4 hp, ok. But 10 hp? The plate on the 4 hp motor in the saw says it draws 16.5 amps. That's a pretty effecient motor if that's FLA. Rich
Actually the higher voltage is helping your cause. Higher voltage = less current for a given load. Motors are rated 230V. Std US 1 phase voltages are 120/240V. 240V plus 10% = 264V. Your 252V is well within tolerance. Now consider the low side. Std US 3 phase voltages are 120/208V. It is common in industrial applications to run up to 5hp single ph 230V motor on 208V which could run as low as 187V. Therefore the voltage range for a standard 230V motor is 187-264V. If you're tripping 30A breakers with 2hp motors then the problem is elsewhere.John O'Connell - JKO Handcrafted Woodworking
The more things change ...
We trained hard, but it seemed that every time we were beginning to form up into teams, we would be reorganized. I was to learn later in life that we tend to meet any new situation by reorganizing; and a wonderful method it can be for creating the illusion of progress while producing confusion, inefficiency, and demoralization.
Petronious Arbiter, 210 BC
John,The problem with my overvoltage situation is that it's outside the range for the low voltage control circuits in the Hammer electrical package. And the sales contract states that they will not guarantee the functional and operational safety of the system.Rich
It still sounds fishy to me. If the product is intended for the US then it would be built for a 240V nominal system and all should be well. Even if 230V is the base line it should be good for +/- 10% which is 253V on the high end and 252 is still within tolerence. If you're 100% sure you need to lower the voltage without the power company, then get a 240V - 240V transformer with taps to adjust the voltage for that machine. Size it per the largest motor, ie. 5 KVA for 5hp or 4 KVA for 4 hp.John O'Connell - JKO Handcrafted Woodworking
The more things change ...
We trained hard, but it seemed that every time we were beginning to form up into teams, we would be reorganized. I was to learn later in life that we tend to meet any new situation by reorganizing; and a wonderful method it can be for creating the illusion of progress while producing confusion, inefficiency, and demoralization.
Petronious Arbiter, 210 BC
A hard-wired 5hp motor at 240V requires #8 wire and 40A breaker. This is mainly because of the 125% rule in the code for motor circuits. It also requires running overload protection other than the breaker, which is where the starter comes in. On the other hand if you use a cord and plug connection then it's no longer a motor circuit and #10's w/ a 30A breaker will work just fine and meet the NEC. On the 10's you will have 3% voltage drop at 103.7 feet, so no worries about voltage drop at 8'. My three 240V machines (5, 3, & 2 hp) are all wired with #10 SO cord and 30A twistloks on 30A circuits.
John O'Connell - JKO Handcrafted Woodworking
The more things change ...
We trained hard, but it seemed that every time we were beginning to form up into teams, we would be reorganized. I was to learn later in life that we tend to meet any new situation by reorganizing; and a wonderful method it can be for creating the illusion of progress while producing confusion, inefficiency, and demoralization.
Petronious Arbiter, 210 BC
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