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Is it possible to run a 2hp Dust Collector and Saw on a single 240v/30amp dryer circuit?

4127 Views 31 Replies 10 Participants Last post by TopamaxSurvivor, Mar 30, 2021

JonCrafting

Discussion Starter · Mar 29, 2021 (Edited by Moderator)

I am sure this is a common delimma for a lot of growing woodworkers, but due to the amount of other electrical questions about 240v this and 120v that and dust collectors and table saws in general, I have not been able to sift through the search results to find a post that directly addresses this question.

As the title states, I have a typical 240v/30amp circuit wired to my garage intended for an electric dryer. I would like to repurpose this circuit for use with my 2HP/12amp dust collector and 2HP/7.5amp table saw. I have been looking into this question for several weeks now and am still not sure I have a clear understanding.

While I would love to hire an electrician to upgrade my main panel, run a new 100amp circuit to the garage with a new sub-panel, and totally rewire the garage with outlets for everything, that will need to wait as there are other priorities higher on the totem pole. I understand that the running amps listed on the DC and TS do not account for the surge of amps they will draw on start up. I am wondering if both pieces of equipment are not turned on at the same time, if the 30amp breaker could work.

I would love to know what others have done or tried to do to deal with this scenario. Assuming that it is possible, I'm wondering how one would go about re-wiring the outlet(s) in series.

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HokieKen

· #2 · Mar 29, 2021

In short, yes. I see no reason you can't run both of those on a single 30A circuit. Even with startup loads, the spike should be short enough that it wouldn't throw the breaker. Running a second outlet is the same as running a 115V outlet with the exception that there's an extra wire and the wire will be larger. Just use a pigtail to split the line at the first outlet and run it to the second outlet.

This of course is dependent on local codes. I think in most locations that multiple outlets are allowed on a single 230 circuit but you should check and make sure for your locale.

misbeshavings

· #3 · Mar 29, 2021

Absolutely you could do that. You could also put a junction box there, take out the dryer plug, and run conduit and 220 receptacles closer to your machines. That's what I did in my first garage shop. Second one didn't have a dryer outlet, so I had to run a line all the way across the house from the outside box. Still worth it!

WhyMe

· #4 · Mar 29, 2021

Are both the dust collector and tablesaw 120V? If so and the dryer circuit is 4 wire, 2 hot, neutral and a ground you can split the circuit into two 20A 120V circuits with a shared neutral. The 30A breaker will need to be changed to a 2 pole 20A breaker or two single pole 20A breakers with a handle tie. Obviously the circuit will no longer be used for a dryer. If you are on the International Residential Code multiple outlets on a single circuit are not allowed if over 20A.

PlentyFarmLLC

· #5 · Mar 29, 2021

You are only supposed to use 80% of the circuit, so 24A. 12A (DC) + 7.5A (TS) - you are fine. The DC will have a higher start load for an instant to get the blower wheel turning. You may have to run the machines in that order: Start DC first, then start TS.

CaptainKlutz

· #6 · Mar 29, 2021

- Yes.
Per NEC 430, need 125% of FLC (not FLA) for a motor circuit. (2) 2HP motors have 12A FLC * 125% = 30A

- NEC code only allows multiple receptacles on 20A building wire circuits.
Can not make a permanent circuit with more than one 30A receptacle, though you can permanently connect more than one machine with dedicated wiring to a circuit greater 20A, that meets code requirements.

You can use a temporary cable with 30A plug, and several 15/20A receptacles.
Leviton makes this easy with a #5822 duplex 2 wire 240v 20A receptacle. They also make #16462 Decora version. Can place one of these in an outdoor junction box, and use 10-3 SOOW cable with a 30A matching dryer plug on end. If cord length exceeds 120ft, then suggest 8-3 SOOW cord to avoid voltage drop.

PS - Not an licensed electrician. Only a EE that has played with power and learned some codes.
If any of the above does make sense, hire a professional to help you.
YMMV

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WhyMe

· #7 · Mar 29, 2021

"- NEC code only allows multiple receptacles on 20A building wire circuits."
There is no such NEC restriction. The IRBC limits multiple outlets to 20A.

JonCrafting

Discussion Starter · #8 · Mar 29, 2021 (Edited by Moderator)

Thanks for all the responses and advice.

@WhyMe I'm so sorry, I thought I had clarified in my post that both the DC and TS would be running on 240v, but apparently not.

@HokieKen, @Ruscal That would be great if i don't have to worry about timing the start up times. I guess the only way to tell would be to test and see.

@misbeshavings I like this idea, and imagine it would be better/safer than long dropcords.

@CaptainKlutz I like the idea of the duplex receptacle, but it is unclear if the 20A rating on the receptacle is signifying the output or input. I could be wrong, but as the circuit is 30A, I would be hesitant to put anything rated less than 30A in the line.

ibewjon

· #9 · Mar 29, 2021 (Edited by Moderator)

A 2 hp motor on 240 v draws 12 amps, so your table saw is not 2 hp. Is it a Craftsman where they sell you 'developed' hp? A 1 hp draws about 8 amps on 240. I would have a sub panel installed with separate breakers for each motor, as long as you have a grounding conductor. In rush / start up current for a motor is about 3x running current.

HokieKen

· #10 · Mar 29, 2021

As WhyMe and CaptainKlutz stated, you can't add outlets to that circuit. I was unaware there was a 20A cap when I originally replied. I think I would pull another 20A circuit or make a pigtail extension cord to plug the machines in. Having a code violation could be bad if there's a fire or something even if it's totally unrelated.

WhyMe

· #11 · Mar 29, 2021 (Edited by Moderator)

The building wiring is governed by the NEC, so a 240V 30A dedicated single outlet circuit needs to have a 30A or greater amp outlet. A 20A outlet on a 30A circuit is a no go. Using an adapter cord going from a 30A plug to a 20A socket end is an option. The correct way is to mount a small subpanel fed by the 30A circuit and have two 240V 20A circuits from that subpanel. Or one 240V 20A with multiple 20A outlets.

ibewjon

· #12 · Mar 29, 2021

An adapter cord with a 20 amp female is not an option without changing to a 20 amp breaker. There are adapter plugs at big box stores that allow plugging a 20 amp cord into a 15 amp receptacle. It is not UL listed.

TopamaxSurvivor

· #13 · Mar 29, 2021 (Edited by Moderator)

I could be wrong, but as the circuit is 30A, I would be hesitant to put anything rated less than 30A in the line.

- JonCrafting

That is correct. 20A outlet needs to be protected by a 20A breaker or fuse.

Edit: The only place that overrated fuse protection is allowed is branch circuits with several 15 amp outlets protected by a 20 A breaker. If the 15 amp outlet is on a circuit by itself. it would require 15A protection.

JonCrafting

Discussion Starter · #14 · Mar 29, 2021

Thanks for the additional comments.

@iblewjon Not sure, where your info comes from, but "2 HP, 120V/240V (prewired for 120V), single-phase, 15A/7.5A " is strait off of the grizzly website, for the Shop Fox W1837. I can't argue based on personal experience, I'm just going off of the specs that have been made available.

@HokieKen If by "cap" you mean maximum capacity, your first understanding is correct and the cap is 30A not 20A. I was however responding to CaptainKlutz's who linked a 20A receptacle as a possible solution to put on my 30A circuit.

@WhyMe I agree that the best scenario might be to create a 240v/30A sub panel in the garage. That does sound a bit more costly though, so I will need to price it out to see.

TopamaxSurvivor

· #15 · Mar 29, 2021 (Edited by Moderator)

Thanks for the additional comments.

@iblewjon Not sure, where your info comes from, but "2 HP, 120V/240V (prewired for 120V), single-phase, 15A/7.5A " is strait off of the grizzly website, for the Shop Fox W1837. I can t argue based on personal experience, I m just going off of the specs that have been made available.

- JonCrafting

That is probably the National Electrical Code rating. About 15 or 20 years ago all the power tools HP doubled. I believe they started using locked rotor current instead of full load to rate HP ;-((

JonCrafting

Discussion Starter · #16 · Mar 29, 2021

Thanks for the additional comments.

@iblewjon Not sure, where your info comes from, but "2 HP, 120V/240V (prewired for 120V), single-phase, 15A/7.5A " is strait off of the grizzly website, for the Shop Fox W1837. I can t argue based on personal experience, I m just going off of the specs that have been made available.

- JonCrafting

That is probably the National Electrical Code rating. About 15 or 20 years ago all the power tools HP doubled. I believe they started using locked rotor current instead of full load to rate HP ;-((

- TopamaxSurvivor

Thanks TopamaxSurvivor. So you are saying that either the HP or the Amp draw listed on the Grizzly website is not accurate and is based on an older formula? I can understand companies picking and choosing the formula they use for different specs in order to improve marketing, but was not aware this was the case for Grizzly/Shop Fox.

ibewjon

· #17 · Mar 29, 2021 (Edited by Moderator)

2 hp is 2 hp. Amps should be close to the same for both motors. Companies can claim what they want to sell. Who will challenge them? That is how sears Craftsman shop vacs are rated 5 hp, and able to run on 15 amp 120 volt circuit. My info comes from a starter / breaker / fuse calculator put out by Square D, a very reliable electrical equipment manufacturer. Much more trustworthy than Griz or Craftsman. Kind of like milage for a car. Do you ever get what is on the window
stickerr? The tag on my 2 hp dust collector states 2 hp, 12 amps on 240 volts.

WhyMe

· #18 · Mar 29, 2021 (Edited by Moderator)

An adapter cord with a 20 amp female is not an option without changing to a 20 amp breaker. There are adapter plugs at big box stores that allow plugging a 20 amp cord into a 15 amp receptacle. It is not UL listed.

- ibewjon

Why is the 6-30 to 6-20 adapter not an option? You can buy them; and what code prohibits their use? No they are not UL listed. Not the best option, but it is an option.
PS: If the saw and dust collector motors have their own overload protection (reset buttons) I'd run then on a 30A circuit with no concerns. If they don't have independent overload protection I don't recommend plugging them into a 30A circuit.

TopamaxSurvivor

· #19 · Mar 29, 2021 (Edited by Moderator)

I am IBEW too. ;-)) I use the same data Square D publishes based on the National Electrical Code requirements. Power is basically Amps x Volts with lots of other minor factors for AC vs DC. Like ibewjon points out a Sears Craftsman shop vac rated at 5 hp can't run on 15 amp 120 volt circuit. 5hp at 120 volts draws 56 amps and 28 on 240. When my Sears 5 hp-peak vacuum started on my 15 amp circuit remodeling the bath last year it dimmed the lights slightly starting. My electrical panel is Cutler Hammer. They have thermal (as most do) and magnetic (most don't expect Square D) overload protection. Square D and CH breakers trip so quickly on overload you cannot see a spark with a dead short most of the time. There is no way that vacuum will run drawing 5 hp worth of amps (56) on 120 v. I did not measure it, but I doubt it is drawing more than 9 or 10, a 1/2 hp worth on 120 v.

Your 2HP/12amp dust collector should be 2 old-fashioned hp at 240 v. or 3/4 at 120v. The 2HP/7.5amp table saw could be 1 old-fashioned hp at 230 volts or a 1/3 old-fashioned hp at 120 v.

I have no idea how they claim a 5 hp vac can run on a 15 amp circuit. I suppose they use lock roto amps or may peak staring amp, but those are not really measurment so of horse power produced.

Edit: Many many moons ago a customer had a 5n hp compressor I wired. There is not enough room in the top of my Sears Craftsman shop vac for a 5 hp motor ;-))

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Lazyman

· #20 · Mar 29, 2021

While we are on the subject…what is the difference between a 6-15 and 6-30 receptacle? I know one is rated for 15 amps and the other 30 but they look like the same plugs on the charts? Is there a subtle difference that prevents the 6-30P from plugging into a 6-15R or even 6-20R receptacle?

1 - 20 of 32 Posts

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