I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag on
the motor housing says it is 12.5 amps at 230V. (It also says it will
operate on a minimum of 203v at 13.7amps. It has an over-heat shutoff.)
Does this mean I can use a 20amp double pole breaker? What difference
would it make if I used a 30amp? I think I'll use #10/3 wire (romex-type).
I need to wire a plug-lead from the saw's mag switch. I reckon a 20amp/230v
male plug with recepticle to match would be correct. Again: what
difference would it make if I used a 30amp setup?
Oh yeah, something else: I have two (unused) 15amp breakers. If I gang
them with a tie bar, does this make the setup function as a double pole
30amp breaker?
I will appreciate comments and recommendations.
Best,
David
"dpb" <[email protected]> wrote in message news:[email protected]...
> Doug Miller wrote:
>> In article <[email protected]>, "Leon"
>> <[email protected]> wrote:
>>> "dpb" <[email protected]> wrote in message news:[email protected]...
>>>> Doug Miller wrote:
>>
>> No, I didn't.
>>>> I see no sane reason to limit the breaker size to less than what the
>>>> circuit wiring is rated for, either.
>>
>> Please trim and quote more carefully. Those are dpb's words, not mine.
>
> On top of which, I have no idea what was the point trying to be made... :)
>
> (And, btw, I knew you knew the previous point, only figured it should be
> clarified/corrected for the record...)
LOL
"David Todtman" <[email protected]> wrote in message
news:lvAQi.52835$th2.375@pd7urf3no...
>I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag on
>the motor housing says it is 12.5 amps at 230V. (It also says it will
>operate on a minimum of 203v at 13.7amps. It has an over-heat shutoff.)
>
> Does this mean I can use a 20amp double pole breaker? What difference
> would it make if I used a 30amp? I think I'll use #10/3 wire
> (romex-type).
>
> I need to wire a plug-lead from the saw's mag switch. I reckon a
> 20amp/230v male plug with recepticle to match would be correct. Again:
> what difference would it make if I used a 30amp setup?
>
> Oh yeah, something else: I have two (unused) 15amp breakers. If I gang
> them with a tie bar, does this make the setup function as a double pole
> 30amp breaker?
>
> I will appreciate comments and recommendations.
>
> Best,
> David
>
No problems with anything until you came to the two 15 amp breakers, you
need a double 30 amp breaker for this setup.
Myself, I would go with the 20 amp breaker 12 gauge wire, and an appropriate
20 amp plug, socket, and cord, but if you want to up it all to 30 amp
breaker, 10 gauge wire and 30 amp socket, plug and cord I would not have a
problem with that either. Assuming the length of run of the circuit is not
excessive.
The breaker is there to protect the wire, not necessarily what is connected
to the circuit.
Greg
"David Todtman" wrote:
>I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag on
>the motor housing says it is 12.5 amps at 230V. (It also says it will
>operate on a minimum of 203v at 13.7amps. It has an over-heat shutoff.)
>
> Does this mean I can use a 20amp double pole breaker? What difference
> would it make if I used a 30amp? I think I'll use #10/3 wire
> (romex-type).
10-2 with ground, a 30A plug and receptacle will make your life easy.
It is legal to use a tie handle most places, but DON'T do it.
A 2P-30A c'bkr with internal tie is not that expensive and offers added
protection.
You're on the right track standardizing on 30A circuits.
Have fun.
Lew
"Toller" wrote:
> Everyone says that, but why shouldn't it also protect what is connected?
By definition, a circuit protective device, protect the insulation on the
conductors of the distribution system.
Overload devices provide the protection for the device.
About the only thing they have in common is protection, but they of
necessity, approach it from different directions.
Lew
"David Todtman" wrote:
>I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag on
>the motor housing says it is 12.5 amps at 230V.
Basic rule of thumb for c'bkrs used on motor circuits:
A c'bkr needs to be sized about 2.5-3.0 as large as the FLA of the motor,
rounded up to the next std size c'bkr, in order to handle the inrush current
of the motor.
Thus, FLA=12.5 x 2.5 = 31.25A
And, FLA=12.5 x 3.0 = 37.25A
I'd try a 2P-30A; however, would not be surprised with an ocasional trip.
You could very easily use a 2P-40A for this application and be legal.
Lew
What does the saw mfg spec?
Lew
Lew Hodgett wrote:
> Basic rule of thumb for c'bkrs used on motor circuits:
>
> A c'bkr needs to be sized about 2.5-3.0 as large as the FLA of the motor,
> rounded up to the next std size c'bkr, in order to handle the inrush current
> of the motor.
It doesn't "need" to be sized that big.
For dedicated motor loads it's *permitted* to use an oversized breaker
should it be required. I have a 3HP motor on a 20A circuit, and I've
yet to trip the breaker.
Chris
This question is OT to the original post:
Based on the OP's motor's description, what information on the tag for the
Baldor motor is missing that would make one suspect the motor is really a 3
ph, 3hp motor?
For example, I find a 3hp motor at a flea market, and the seller claimed it
was from a table saw, what clue would I look for to tell me it is 3 phase?
(and thus should put it down, since I ain't going to get 3 phase in my
house, no way, no how.)
Wouldn't a 3 phase also be listed as input voltage 203 to 230 VAC
phase-to-phase?
Phil
"David Todtman" <[email protected]> wrote in message
news:lvAQi.52835$th2.375@pd7urf3no...
>I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag on
>the motor housing says it is 12.5 amps at 230V. (It also says it will
>operate on a minimum of 203v at 13.7amps. It has an over-heat shutoff.)
>
> Does this mean I can use a 20amp double pole breaker? What difference
> would it make if I used a 30amp? I think I'll use #10/3 wire
> (romex-type).
>
> I need to wire a plug-lead from the saw's mag switch. I reckon a
> 20amp/230v male plug with recepticle to match would be correct. Again:
> what difference would it make if I used a 30amp setup?
>
> Oh yeah, something else: I have two (unused) 15amp breakers. If I gang
> them with a tie bar, does this make the setup function as a double pole
> 30amp breaker?
>
> I will appreciate comments and recommendations.
>
> Best,
> David
>
"Chris Friesen" wrote:
> It doesn't "need" to be sized that big.
>
> For dedicated motor loads it's *permitted* to use an oversized breaker
> should it be required. I have a 3HP motor on a 20A circuit, and I've yet
> to trip the breaker.
INRUSH!
Totally dependant on application.
Most wood working applications do not start under load, so the application
is not that severe.
Lew
> Chris
"Doug Miller" <[email protected]> wrote in message
news:[email protected]...
> In article <[email protected]>, "Greg O"
> <[email protected]> wrote:
>
>>No problems with anything until you came to the two 15 amp breakers, you
>>need a double 30 amp breaker for this setup.
>>Myself, I would go with the 20 amp breaker 12 gauge wire, and an
>>appropriate
>>20 amp plug, socket, and cord, but if you want to up it all to 30 amp
>>breaker, 10 gauge wire and 30 amp socket, plug and cord I would not have a
>>problem with that either.
>
> Except that it's a Code violation to put the 20A receptacle he intends to
> use
> on a 30A circuit...
>
> --
> Regards,
> Doug Miller (alphageek at milmac dot com)
>
> It's time to throw all their damned tea in the harbor again.
That is why I said, "but if you want to up it all to 30 amp breaker, 10
gauge wire and 30 amp socket, plug and cord I would not have a problem with
that either." My intent was everything was to be 30 amp. I suppose it could
be translated otherwise.
Greg
"dpb" <[email protected]> wrote in message news:[email protected]...
> Doug Miller wrote:
>
> I see no sane reason to limit the breaker size to less than what the
> circuit wiring is rated for, either.
What is the point??? The circuit breaker is not a good protection for an
appliance, it is not finely tuned enough for that purpose and it has no idea
if the tool is getting too hot or not since the wiring near it is not
getting too hot. A tool can get damaging hot and not draw too many amps to
trip the breaker.
Toller wrote:
>> The breaker is there to protect the wire, not necessarily what is
>> connected
>> to the circuit.
>
> Everyone says that, but why shouldn't it also protect what is connected?
>
>
Four reasons:
1. The circuit breaker has no way of knowing what is plugged into it,
might be a 5 watt night light, might be toaster oven, might be an
arcwelder. Generally there are multiple sockets tapped off each branch,
with who knows what plugged into them. You don't want the circuit
breaker to pop until the current is enough to overheat the wires.
2. Electric motors draw enormous amounts of current getting started. To
avoid popping circuit breakers, you want to furnish the motor plenty of
current to start with. The starting load only lasts a few seconds while
the motor is coming up to speed. Your 12 amp motor might draw 30-40
amps at startup, and then drop down to a couple of amps after to getting
going. If you put it on a 12 amp breaker, it will pop that breaker on
every startup.
3. The house circuit breaker is supposed to prevent house fires.
Without protection, a short circuit will heat the wire, running thru
the wooden studs of your wall, up to red hot. Then the studs catch fire
and your house burns down. Circuit breaker size is set by the branch
wire size. Rule of thumb: 14 gauge wire = 15 amp breaker, 12 gauge wire
= 20 amp breaker, 10 gauge wire = 30 amp breaker. Doesn't matter what
you plug into the branch circuit, choose a breaker that's right for the
wire.
4. Stationary saw motors always have a thermal protection switch built
into them that shuts the motor down if it gets too hot. They don't need
any more protection. Speaking of which, should the thermal overload
pop, you want to be aware that it might spontaniously reset, starting
the saw up again. You want to keep your hands clear of the blade until
you unplug the tool.
Was it me, I'd run your 220 volt saw on a 12 gauge branch circuit
protected with a pair of 20 amp breakers, one in each hot lead. Use two
conductor plus a ground wire cable. I'd make sure the iron frame of the
saw was connected to the green ground wire. Back at the terminal box
make sure the green ground wire goes to ground.
David Starr
"Leon" <[email protected]> wrote in message
news:[email protected]...
>
> "Toller" <[email protected]> wrote in message
> news:[email protected]...
>>
>>> The breaker is there to protect the wire, not necessarily what is
>>> connected
>>> to the circuit.
>>
>> Everyone says that, but why shouldn't it also protect what is connected?
>
> Because, it is designed to protect the wiring. If you want to protect
> what is connected you should buy the tool with it's won built in
> protection.
>
> If the breaker was designed to protect the tool, you would only be able to
> plug "1" tool into a circuit at a time. Many tools only pull 7 amps. Are
> you going to put in 7 amp breakers and what if you want to plug in 2, 7
> amp tools into the same circuit? What if you want to run a dust collector
> and a TS on the same circuit? You can't have a breaker that will protect
> both and not trip when both are on.
I know what it designed to protect, but why the heck not put a 15a breaker
on the circuit instead of a 20 or 30? Doesn't cost anything so you pick up
protection for free. I am not saying it required, or even necessary, but
that doesn't mean it isn't preferable.
If he wanted to run a DC and a TS on the same circuit he would wouldn't have
asked about wiring a 12a TS. And if he did want to run both, the 20a
circuit wouldn't be adequate either!
"Phil-In-Mich." <[email protected]> wrote in message
news:[email protected]...
> This question is OT to the original post:
>
> Based on the OP's motor's description, what information on the tag for the
> Baldor motor is missing that would make one suspect the motor is really a
> 3 ph, 3hp motor?
>
> For example, I find a 3hp motor at a flea market, and the seller claimed
> it was from a table saw, what clue would I look for to tell me it is 3
> phase? (and thus should put it down, since I ain't going to get 3 phase in
> my house, no way, no how.)
>
> Wouldn't a 3 phase also be listed as input voltage 203 to 230 VAC
> phase-to-phase?
>
> Phil
+
The nameplate will say 3 PH
Voltage can vary from 208 to 480. Typical single phase won't go over 230.
On Mon, 15 Oct 2007 13:30:45 -0700, "Lew Hodgett"
<[email protected]> wrote:
>
>"Chris Friesen" wrote:
>
>> It doesn't "need" to be sized that big.
>>
>> For dedicated motor loads it's *permitted* to use an oversized breaker
>> should it be required. I have a 3HP motor on a 20A circuit, and I've yet
>> to trip the breaker.
>
>INRUSH!
>
>Totally dependant on application.
>
>Most wood working applications do not start under load, so the application
>is not that severe.
Then the relevance of factoring it into your "recommendation" in this
discussion is...?
--
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
Proud participant of rec.woodworking since February, 1997
email addy de-spam-ified due to 1,000 spams per month.
If you can't figure out how to use it, I probably wouldn't
care to correspond with you anyway.
In article <[email protected]>, "Toller" <[email protected]> wrote:
>
>> The breaker is there to protect the wire, not necessarily what is
>> connected
>> to the circuit.
>
>Everyone says that, but why shouldn't it also protect what is connected?
Because that's not what it's there for. Do you want a 1/2 amp breaker to
protect the circuit that you have a 60W table lamp plugged into?
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
Doug,
Your previous comment is right on target--I was subject to the confusion you
referenced. You saved me the extra expense of the 3 conductor wire. I'm
getting 12/2. Thanks.
"Doug Miller" <[email protected]> wrote in message
news:[email protected]...
> In article <m8NQi.61695$th2.25502@pd7urf3no>, "David Todtman"
> <[email protected]> wrote:
>>
>>Thanks everyone. I plan to use 12ga wire, 20amp 2-pole breaker, and
>>matching plug/receptacle.
>
> 12-2, right? Not 12-3?
>
> Excuse me if I'm telling you things you already know, but there is
> occasional
> confusion on this part. For premises wiring such as NM cable (Romex), the
> number after the dash indicates the number of current-carrying conductors,
> and
> does *not* include the ground. Thus, 12-2 Romex has three wires in it, and
> 12-3 has four.
>
> xx-3 cable is used for electric dryers, cooktops, ovens, etc. because
> those
> appliances also have 120V circuits (timers, motors, etc.) which need a
> neutral.
>
> Pure 240V loads, such as a table saw or electric baseboard heater, use
> only
> the two hot conductors and thus need only xx-2 cable. With ground, of
> course.
>
> --
> Regards,
> Doug Miller (alphageek at milmac dot com)
>
> It's time to throw all their damned tea in the harbor again.
It's a single phase. (Indicated on the info plate along with the other
stuff.)
"Phil-In-Mich." <[email protected]> wrote in message
news:[email protected]...
> This question is OT to the original post:
>
> Based on the OP's motor's description, what information on the tag for the
> Baldor motor is missing that would make one suspect the motor is really a
> 3 ph, 3hp motor?
>
> For example, I find a 3hp motor at a flea market, and the seller claimed
> it was from a table saw, what clue would I look for to tell me it is 3
> phase? (and thus should put it down, since I ain't going to get 3 phase in
> my house, no way, no how.)
>
> Wouldn't a 3 phase also be listed as input voltage 203 to 230 VAC
> phase-to-phase?
>
> Phil
>
> "David Todtman" <[email protected]> wrote in message
> news:lvAQi.52835$th2.375@pd7urf3no...
>>I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag
>>on the motor housing says it is 12.5 amps at 230V. (It also says it
>>will operate on a minimum of 203v at 13.7amps. It has an over-heat
>>shutoff.)
>>
>> Does this mean I can use a 20amp double pole breaker? What difference
>> would it make if I used a 30amp? I think I'll use #10/3 wire
>> (romex-type).
>>
>> I need to wire a plug-lead from the saw's mag switch. I reckon a
>> 20amp/230v male plug with recepticle to match would be correct. Again:
>> what difference would it make if I used a 30amp setup?
>>
>> Oh yeah, something else: I have two (unused) 15amp breakers. If I gang
>> them with a tie bar, does this make the setup function as a double pole
>> 30amp breaker?
>>
>> I will appreciate comments and recommendations.
>>
>> Best,
>> David
>>
>
In article <KTGQi.357$cI5.309@trnddc06>, "dadiOH" <[email protected]> wrote:
>David Todtman wrote:
>> I have to wire for a 3hp cabinet saw. The motor is a Baldor and
>> the tag on the motor housing says it is 12.5 amps at 230V. (It
>> also says it will operate on a minimum of 203v at 13.7amps. It has
>> an over-heat shutoff.)
>>
>> Does this mean I can use a 20amp double pole breaker? What
>> difference would it make if I used a 30amp? I think I'll use
>> #10/3 wire (romex-type).
>
>
>Same as my saw which is on a 20 amp circuit. Starting the saw will
>occasionally trip the circuit breaker.
Curious: what's the nameplate amperage rating on the saw? How far is the
receptacle from the breaker box? And is the circuit wired with 12ga wire as it
should be?
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
David Todtman wrote:
> I have to wire for a 3hp cabinet saw. The motor is a Baldor and
> the tag on the motor housing says it is 12.5 amps at 230V. (It
> also says it will operate on a minimum of 203v at 13.7amps. It has
> an over-heat shutoff.)
>
> Does this mean I can use a 20amp double pole breaker? What
> difference would it make if I used a 30amp? I think I'll use
> #10/3 wire (romex-type).
Same as my saw which is on a 20 amp circuit. Starting the saw will
occasionally trip the circuit breaker.
--
dadiOH
____________________________
dadiOH's dandies v3.06...
...a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico
"Toller" <[email protected]> wrote in message
news:[email protected]...
>
>> The breaker is there to protect the wire, not necessarily what is
>> connected
>> to the circuit.
>
> Everyone says that, but why shouldn't it also protect what is connected?
Because, it is designed to protect the wiring. If you want to protect what
is connected you should buy the tool with it's won built in protection.
If the breaker was designed to protect the tool, you would only be able to
plug "1" tool into a circuit at a time. Many tools only pull 7 amps. Are
you going to put in 7 amp breakers and what if you want to plug in 2, 7 amp
tools into the same circuit? What if you want to run a dust collector and a
TS on the same circuit? You can't have a breaker that will protect both and
not trip when both are on.
In article <m8NQi.61695$th2.25502@pd7urf3no>, "David Todtman" <[email protected]> wrote:
>
>Thanks everyone. I plan to use 12ga wire, 20amp 2-pole breaker, and
>matching plug/receptacle.
12-2, right? Not 12-3?
Excuse me if I'm telling you things you already know, but there is occasional
confusion on this part. For premises wiring such as NM cable (Romex), the
number after the dash indicates the number of current-carrying conductors, and
does *not* include the ground. Thus, 12-2 Romex has three wires in it, and
12-3 has four.
xx-3 cable is used for electric dryers, cooktops, ovens, etc. because those
appliances also have 120V circuits (timers, motors, etc.) which need a
neutral.
Pure 240V loads, such as a table saw or electric baseboard heater, use only
the two hot conductors and thus need only xx-2 cable. With ground, of course.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
"Toller" <[email protected]> wrote in message
news:[email protected]...
> I know what it designed to protect, but why the heck not put a 15a breaker
> on the circuit instead of a 20 or 30? Doesn't cost anything so you pick
> up protection for free. I am not saying it required, or even necessary,
> but that doesn't mean it isn't preferable.
Ok, you asked why shouldn't it also protect what is connected.
I explained why it shouldn't, not that it could not be done. It shouldn't
be done because the breaker is used as a last resort to protect you home
wiring. It shouldn't be done because of the reasons I mentioned.
It can be done, but it shouldn't.
Additionally, The protection needs to be located at or very near the motor.
The farther away it is the slower it will react to an overload especially if
the tool that is overheating is doing so slowly.
Breakers tend to not work very quickly. I regularly run a 1100CFM dust
collector, a 15 amp router, fan, and radio on a 15 amp circuit. No problems
as long as the DC and Router are started and brought up to speed 1 at a
time. Breakers are designed to take overloads and not trip immediately and
are usually rated at less than what the wiring in the house will handle.
That may not be fast enough to save a tool. Thermal protection built into
a tool tends to work at the threshold.
In article <[email protected]>, "Greg O" <[email protected]> wrote:
>No problems with anything until you came to the two 15 amp breakers, you
>need a double 30 amp breaker for this setup.
>Myself, I would go with the 20 amp breaker 12 gauge wire, and an appropriate
>20 amp plug, socket, and cord, but if you want to up it all to 30 amp
>breaker, 10 gauge wire and 30 amp socket, plug and cord I would not have a
>problem with that either.
Except that it's a Code violation to put the 20A receptacle he intends to use
on a 30A circuit...
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
In article <[email protected]>, "Lew Hodgett" <[email protected]> wrote:
>"David Todtman" wrote:
>
>>I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag on
>>the motor housing says it is 12.5 amps at 230V.
>
>Basic rule of thumb for c'bkrs used on motor circuits:
>
>A c'bkr needs to be sized about 2.5-3.0 as large as the FLA of the motor,
>rounded up to the next std size c'bkr, in order to handle the inrush current
>of the motor.
>
>Thus, FLA=12.5 x 2.5 = 31.25A
>And, FLA=12.5 x 3.0 = 37.25A
So according to you, my 14.5A table saw should be on a 40A breaker.
>
>I'd try a 2P-30A; however, would not be surprised with an ocasional trip.
Oddly enough, I've had that saw on a double-pole 30A breaker for five years
now, with no trips -- even when ripping 12/4 hard maple. I'd be *very*
surprised if the OP ever trips a 30A breaker.
>
>You could very easily use a 2P-40A for this application and be legal.
As long as he uses a 40A receptacle, yes.
He could also use a double-pole 30A or 20A and be legal, and still not have to
worry about nuisance trips.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
On Mon, 15 Oct 2007 09:29:19 -0600, Chris Friesen
<[email protected]> wrote:
>It doesn't "need" to be sized that big.
>
>For dedicated motor loads it's *permitted* to use an oversized breaker
>should it be required. I have a 3HP motor on a 20A circuit, and I've
>yet to trip the breaker.
>
>Chris
3HP motor (Jet JTAS10) on a 240V/20A circuit now for more than 5 years
without a single trip, nuisance or otherwise.. I don't know where all
this "gotta have a huge breaker to avoid nuisance trips" BS is coming
from unless they're thinking about a 110V circuit.
There could be some justification in that case, 'cause a 110V/20A
circuit might be a little undersized for the FLA of a 3HP motor.
3HP = 2238 Watts = 20.35 Amps at 110 Volts (ignoring Power Factor,
Efficiency, etc.)
Tom Veatch
Wichita, KS
USA
In article <lvAQi.52835$th2.375@pd7urf3no>, "David Todtman" <[email protected]> wrote:
>I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag on
>the motor housing says it is 12.5 amps at 230V. (It also says it will
>operate on a minimum of 203v at 13.7amps. It has an over-heat shutoff.)
>
>Does this mean I can use a 20amp double pole breaker?
Yes.
>What difference
>would it make if I used a 30amp? I think I'll use #10/3 wire (romex-type).
You'll spend more on wire (you may use 12ga wire with a 20A breaker, but you
must use 10ga wire with 30A), and you will be required to use 30A receptacles.
Using 10-3 (or 12-3) is pointless -- a 240V motor doesn't have, or use, a
neutral. All you need is two hots and a ground. 10-2 (or 12-2) is sufficient.
>
>I need to wire a plug-lead from the saw's mag switch. I reckon a 20amp/230v
>male plug with recepticle to match would be correct. Again: what
>difference would it make if I used a 30amp setup?
Again: you'll spend more on wire, and you'll be required to use 30A
receptacles. Code does not permit the use of anything but 30A receptacles on a
30A circuit.
>Oh yeah, something else: I have two (unused) 15amp breakers. If I gang
>them with a tie bar, does this make the setup function as a double pole
>30amp breaker?
No. That will function as a double-pole 15A breaker.
>
>I will appreciate comments and recommendations.
Use a double-pole 20A breaker. Whether you use 12ga or 10ga wire is up to you,
but unless the saw is a long way from the breaker box, you're not likely to
see any benefit from the 10ga. Either way, though, use a 20A breaker, not a
30A.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
In article <[email protected]>, "Greg O" <[email protected]> wrote:
>
>
>"Doug Miller" <[email protected]> wrote in message
>news:[email protected]...
>> In article <[email protected]>, "Greg O"
>> <[email protected]> wrote:
>>
>>>No problems with anything until you came to the two 15 amp breakers, you
>>>need a double 30 amp breaker for this setup.
>>>Myself, I would go with the 20 amp breaker 12 gauge wire, and an
>>>appropriate
>>>20 amp plug, socket, and cord, but if you want to up it all to 30 amp
>>>breaker, 10 gauge wire and 30 amp socket, plug and cord I would not have a
>>>problem with that either.
>>
>> Except that it's a Code violation to put the 20A receptacle he intends to
>> use
>> on a 30A circuit...
>>
>That is why I said, "but if you want to up it all to 30 amp breaker, 10
>gauge wire and 30 amp socket, plug and cord I would not have a problem with
>that either." My intent was everything was to be 30 amp. I suppose it could
>be translated otherwise.
Right, I gotcha -- but the OP had already stated his intent to use a 20A
receptacle, and I wanted to emphasize that that was a no-go with a 30A
circuit. Sorry for any confusion.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
Doug Miller wrote:
> In article <[email protected]>, "Toller" <[email protected]> wrote:
>
>> I know what it designed to protect, but why the heck not put a 15a breaker
>> on the circuit instead of a 20 or 30?
>
> Because that would limit him to using 14ga wire. ...
No. A _smaller_ breaker only limits the circuit load to less than what
it could otherwise be used for.
I see no sane reason to limit the breaker size to less than what the
circuit wiring is rated for, either. One never knows what may come down
the road as a desired addition, so having to go back and replace the
breaker to take advantage of the circuit's full capacity is simply an
unnecessary pita and cost (although not huge, another breaker for no
reason other than undersizing it originally just makes _no_ sense).
--
Doug Miller wrote:
> In article <[email protected]>, "Leon" <[email protected]> wrote:
>> "dpb" <[email protected]> wrote in message news:[email protected]...
>>> Doug Miller wrote:
>
> No, I didn't.
>>> I see no sane reason to limit the breaker size to less than what the
>>> circuit wiring is rated for, either.
>
> Please trim and quote more carefully. Those are dpb's words, not mine.
On top of which, I have no idea what was the point trying to be made... :)
(And, btw, I knew you knew the previous point, only figured it should be
clarified/corrected for the record...)
--
Phil-In-Mich. wrote:
...
> For example, I find a 3hp motor at a flea market, and the seller claimed
> it was from a table saw, what clue would I look for to tell me it is 3
> phase? (and thus should put it down, since I ain't going to get 3 phase
> in my house, no way, no how.)
...
Well, if it has the manufacturer's tag on it, number of phase will be
marked. And if it doesn't have the tag, I'm not buying any motor for
anything other than junk, basically, unless there's a way to test the
operation at what is being claimed is the operating voltage/phase...
--
On Mon, 15 Oct 2007 14:47:14 -0700, "Lew Hodgett"
<[email protected]> wrote:
>"LRod" wrote:
>> Then the relevance of factoring it into your "recommendation" in this
>> discussion is...?
>
>CYA.
>
>For the amount of effort required to do the wiring, makes no sense trying to
>cut corners with tinkertoy components to save a couple of $.(Wire & wiring
>devices only)
A 20A circuit in the case of the OP certainly isn't "cutting corners."
In fact, it's more than adequate. 30A is decidedly overkill for 3HP @
240V (and will get Rick Christopherson positively apopleptic--and
rightly so). YOU recommended 40A. CYA? Please. That was just plain
nuts.
--
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
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email addy de-spam-ified due to 1,000 spams per month.
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In article <[email protected]>, dpb <[email protected]> wrote:
>Doug Miller wrote:
>> In article <[email protected]>, "Toller" <[email protected]>
> wrote:
>>
>>> I know what it designed to protect, but why the heck not put a 15a breaker
>>> on the circuit instead of a 20 or 30?
>>
>> Because that would limit him to using 14ga wire. ...
>
>No. A _smaller_ breaker only limits the circuit load to less than what
>it could otherwise be used for.
Of course you're right -- I hadn't had my coffee yet when I posted that. :-(
A 15A breaker would subject him to nuisance trips, though.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
In article <[email protected]>, "Leon" <[email protected]> wrote:
>
>"dpb" <[email protected]> wrote in message news:[email protected]...
>> Doug Miller wrote:
No, I didn't.
>
>>
>> I see no sane reason to limit the breaker size to less than what the
>> circuit wiring is rated for, either.
Please trim and quote more carefully. Those are dpb's words, not mine.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
In article <[email protected]>, duckecho@gmail-dot-com wrote:
>Unless Doug corrects me, I believe the use of a 6-15 receptacle on a
>20A 240V circuit is permitted by the same exception as the 2-15 on a
>20A 120V circuit is. Those -15 receptacles aren't "rated" for 15A,
>they're "keyed" for 15A. In any event, I think all of that goes out
>the window if it's a single receptacle and the only one on the circuit
>(note a duplex receptacle is not a single receptacle).
Exactly right, LRod.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
On Mon, 15 Oct 2007 00:26:18 -0700, "Lew Hodgett"
<[email protected]> wrote:
>"David Todtman" wrote:
>
>>I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag on
>>the motor housing says it is 12.5 amps at 230V.
>
>Basic rule of thumb for c'bkrs used on motor circuits:
>
>A c'bkr needs to be sized about 2.5-3.0 as large as the FLA of the motor,
>rounded up to the next std size c'bkr, in order to handle the inrush current
>of the motor.
>
>Thus, FLA=12.5 x 2.5 = 31.25A
>And, FLA=12.5 x 3.0 = 37.25A
Cite, please.
>I'd try a 2P-30A; however, would not be surprised with an ocasional trip.
>
>You could very easily use a 2P-40A for this application and be legal.
Puhlease. A 3HP saw occasionally tripping a 30A breaker? In what
universe do you think that can happen? You'd be unlikely to ever get a
trip on a 20A circuit with a 3HP saw. Maybe if he had 200' of feed,
but not in a normal run. 40A is more than twice as ridiculous as 30A
is in this application.
--
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
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email addy de-spam-ified due to 1,000 spams per month.
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On Mon, 15 Oct 2007 19:46:11 GMT, "Edwin Pawlowski" <[email protected]>
wrote:
>
>"Phil-In-Mich." <[email protected]> wrote in message
>news:[email protected]...
>> This question is OT to the original post:
>>
>> Based on the OP's motor's description, what information on the tag for the
>> Baldor motor is missing that would make one suspect the motor is really a
>> 3 ph, 3hp motor?
>>
>> For example, I find a 3hp motor at a flea market, and the seller claimed
>> it was from a table saw, what clue would I look for to tell me it is 3
>> phase? (and thus should put it down, since I ain't going to get 3 phase in
>> my house, no way, no how.)
>>
>> Wouldn't a 3 phase also be listed as input voltage 203 to 230 VAC
>> phase-to-phase?
>>
>> Phil
>+
>
>The nameplate will say 3 PH
>
>Voltage can vary from 208 to 480. Typical single phase won't go over 230.
>
Unless you're in Canada, and perhaps other countries where 3ph is
600v. I just had a lesson on this recently.
Jeffo
long time lurker, occasional poster
On Mon, 15 Oct 2007 17:36:04 GMT, [email protected] (Doug Miller)
wrote:
>In article <m8NQi.61695$th2.25502@pd7urf3no>, "David Todtman" <[email protected]> wrote:
>>
>>Thanks everyone. I plan to use 12ga wire, 20amp 2-pole breaker, and
>>matching plug/receptacle.
>
>12-2, right? Not 12-3?
>
>Excuse me if I'm telling you things you already know, but there is occasional
>confusion on this part. For premises wiring such as NM cable (Romex), the
>number after the dash indicates the number of current-carrying conductors, and
>does *not* include the ground. Thus, 12-2 Romex has three wires in it, and
>12-3 has four.
>
>xx-3 cable is used for electric dryers, cooktops, ovens, etc. because those
>appliances also have 120V circuits (timers, motors, etc.) which need a
>neutral.
>
>Pure 240V loads, such as a table saw or electric baseboard heater, use only
>the two hot conductors and thus need only xx-2 cable. With ground, of course.
In addition to that labeling confusing a lot of people, back in about
1960 when I worked in a hardware store, if you wanted a ground with
your NMC you had to state "with ground." If you asked for 12-2, you
got a two conductor wire, no ground. If you wanted a ground wire, you
had to ask for 12-2 w/ground. That's no longer the case--now you get a
ground with your NMC whether you want it or not (and why wouldn't
you?).
In those days, two wires went to your electric water heater or your
pool pump--both hot. I know--I grew up in a house in FL which we built
in 1956. We had a pool installed in 1960 (which, watching the
electrician, who was the dad of a classmate, was the beginning of my
education on electricity). There was no ground required.
Obviously, that, too, is no longer the case.
--
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
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email addy de-spam-ified due to 1,000 spams per month.
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"LRod" wrote in message
> Puhlease. A 3HP saw occasionally tripping a 30A breaker? In what
> universe do you think that can happen? You'd be unlikely to ever get a
> trip on a 20A circuit with a 3HP saw.
... and, in the past the plug that comes standard on the 3HP Delta Unisaws
is a NEMA 6-15P. It will work with a 6-15R, 15A receptacle, as well as a 20
amp, 6-20R receptacle.
--
www.e-woodshop.net
Last update: 9/30/07
KarlC@ (the obvious)
On Mon, 15 Oct 2007 06:13:34 -0500, "Swingman" <[email protected]> wrote:
>
>"LRod" wrote in message
>
>> Puhlease. A 3HP saw occasionally tripping a 30A breaker? In what
>> universe do you think that can happen? You'd be unlikely to ever get a
>> trip on a 20A circuit with a 3HP saw.
>
>... and, in the past the plug that comes standard on the 3HP Delta Unisaws
>is a NEMA 6-15P. It will work with a 6-15R, 15A receptacle, as well as a 20
>amp, 6-20R receptacle.
Not just the Uni--I have that same plug on my DJ20 and on my
DC380--all 3HP motors.
Unless Doug corrects me, I believe the use of a 6-15 receptacle on a
20A 240V circuit is permitted by the same exception as the 2-15 on a
20A 120V circuit is. Those -15 receptacles aren't "rated" for 15A,
they're "keyed" for 15A. In any event, I think all of that goes out
the window if it's a single receptacle and the only one on the circuit
(note a duplex receptacle is not a single receptacle).
--
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
Proud participant of rec.woodworking since February, 1997
email addy de-spam-ified due to 1,000 spams per month.
If you can't figure out how to use it, I probably wouldn't
care to correspond with you anyway.
On Mon, 15 Oct 2007 02:45:37 GMT, "David Todtman"
<[email protected]> wrote:
>I have to wire for a 3hp cabinet saw. The motor is a Baldor and the tag on
>the motor housing says it is 12.5 amps at 230V. (It also says it will
>operate on a minimum of 203v at 13.7amps. It has an over-heat shutoff.)
>
>Does this mean I can use a 20amp double pole breaker?
Yes, if the circuit is wired with 12ga or larger wire
> What difference would it make if I used a 30amp? I think I'll use #10/3 wire (romex-type).
If you use a 30amp breaker, you need 10ga or larger wire. 30 amps is
more than you need for this application, and 10ga wire is larger than
needed unless you have an excessively long wire run from the breaker
to the outlet.
>
>I need to wire a plug-lead from the saw's mag switch. I reckon a 20amp/230v
>male plug with recepticle to match would be correct.
Yes, NEMA 6-20 configuration, if you use a 20 amp breaker
>Again: what difference would it make if I used a 30amp setup?
You'll need a 30amp receptacle, NEMA 6-30
>
>Oh yeah, something else: I have two (unused) 15amp breakers. If I gang
>them with a tie bar, does this make the setup function as a double pole
>30amp breaker?
NO, it would function as a 15amp breaker.
>
>I will appreciate comments and recommendations.
>
>Best,
>David
>
Tom Veatch
Wichita, KS
USA
"Toller" <[email protected]> writes:
> I know what it designed to protect, but why the heck not put a 15a
> breaker on the circuit instead of a 20 or 30? Doesn't cost anything
> so you pick up protection for free. I am not saying it required, or
> even necessary, but that doesn't mean it isn't preferable.
In the case of power tools, the rated current is usually less than the
startup current, so you don't want the circuit to be *too* close to
the rated current, or you risk occasionally tripping the breaker when
you start the tool.
Hence, read the manual and do what they recommend.
"Toller" <[email protected]> writes:
> Everyone says that, but why shouldn't it also protect what is connected?
Consider a 20 amp circuit. Beyond 20 amps, the wire may melt and
cause fire. Below 20 amps, all is safe.
Consider what you plug into a 20 amp circuit. It could have *any*
current rating, from a tiny lamp cord to a power tool. The breaker
can't protect what's plugged in unless everything you plug in is
capable of carrying 20 amps safely.
So, devices plugged into a circuit which desire overcurrent protection
must provide a *suitable* protection themselves.
Note that in the UK every device has a suitable fuse in the plug,
which protects the device.
To recap, a circuit breaker...
* CAN protect the hardwired circuit
* MAY protect some plugged-in devices
* CANNOT protect ALL plugged-in devices
"David Todtman" <[email protected]> writes:
> Oh yeah, something else: I have two (unused) 15amp breakers. If I gang
> them with a tie bar, does this make the setup function as a double pole
> 30amp breaker?
Even if that were legal and wise, it would still only give you a
double pole 15 amp breaker, not 30 amp.
"David Todtman" <[email protected]> writes:
> Does this mean I can use a 20amp double pole breaker?
Yes. Doesn't the saw's manual tell you what size breaker to use?
> What difference would it make if I used a 30amp?
You can't use a bigger breaker without ensuring that everything after
it is also rated for 30 amps, at least the hard-wired stuff (wire and
outlet). The purpose of a breaker is to protect the house from wire
insulation failing from heat, and starting a fire. The breaker is NOT
intended to protect your tools, although it can.
> I think I'll use #10/3 wire (romex-type).
You can use bigger wire with a smaller breaker, to get the protection
you need yet reduce the resistance of the wire. You can't use a
larger breaker with a smaller wire, though.
> I need to wire a plug-lead from the saw's mag switch. I reckon a
> 20amp/230v male plug with recepticle to match would be correct.
> Again: what difference would it make if I used a 30amp setup?
Unless you're really far from the breaker, a larger wire won't make
that much difference. Larger wire reduces the resistive losses
somewhat, but the shorter the wire, the less an impact this will have.
A larger breaker won't do squat for you.
Larger wire is, however, more expensive and harder to work with.
In article <[email protected]>, "Toller" <[email protected]> wrote:
>I know what it designed to protect, but why the heck not put a 15a breaker
>on the circuit instead of a 20 or 30?
Because that would limit him to using 14ga wire. It will take forever for the
saw to spin up. (You're always talking about the importance of avoiding
voltage drop -- think it through.)
> Doesn't cost anything so you pick up
>protection for free. I am not saying it required, or even necessary, but
>that doesn't mean it isn't preferable.
No, but the slow startup speed for the saw *does* mean that.
>
>If he wanted to run a DC and a TS on the same circuit he would wouldn't have
>asked about wiring a 12a TS. And if he did want to run both, the 20a
>circuit wouldn't be adequate either!
Nonsense. 20A would be perfectly adequate for his TS and any DC up to about
2hp.
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
"Phil-In-Mich." <[email protected]> wrote in message
news:[email protected]...
> This question is OT to the original post:
>
> Based on the OP's motor's description, what information on the tag for the
> Baldor motor is missing that would make one suspect the motor is really a
> 3 ph, 3hp motor?
>
> For example, I find a 3hp motor at a flea market, and the seller claimed
> it was from a table saw, what clue would I look for to tell me it is 3
> phase? (and thus should put it down, since I ain't going to get 3 phase in
> my house, no way, no how.)
>
> Wouldn't a 3 phase also be listed as input voltage 203 to 230 VAC
> phase-to-phase?
Something else to consider when buying from a flea market, you need to be
sure of the spin direction. Left and right tilt saw motors spin in opposite
directions.