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

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Forum topic by JonCrafting posted 03-29-2021 06:44 PM 1350 views 1 time favorited 31 replies Add to Favorites Watch
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JonCrafting

17 posts in 402 days


03-29-2021 06:44 PM

Topic tags/keywords: table saw dust collector dc ts tablesaw 250v 240v 220v 30amp garage electrical dryer drier

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.


31 replies so far

View HokieKen's profile

HokieKen

19055 posts in 2348 days


#1 posted 03-29-2021 06:51 PM

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.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View misbeshavings's profile

misbeshavings

32 posts in 3854 days


#2 posted 03-29-2021 08:01 PM

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!

View WhyMe's profile

WhyMe

1409 posts in 2771 days


#3 posted 03-29-2021 08:31 PM

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.

View Ruscal's profile

Ruscal

109 posts in 388 days


#4 posted 03-29-2021 08:48 PM

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.

-- Have a hobby? You should have a business.

View CaptainKlutz's profile

CaptainKlutz

4854 posts in 2704 days


#5 posted 03-29-2021 08:58 PM

- 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

-- If it wasn't for bad luck, I wouldn't have no luck at all, Doom, despair, agony on me… - Albert King - Born Under a Bad Sign released 1967

View WhyMe's profile

WhyMe

1409 posts in 2771 days


#6 posted 03-29-2021 09:38 PM

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

View JonCrafting's profile

JonCrafting

17 posts in 402 days


#7 posted 03-29-2021 10:02 PM

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.

View ibewjon's profile

ibewjon

2587 posts in 4003 days


#8 posted 03-29-2021 10:05 PM

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.

View HokieKen's profile

HokieKen

19055 posts in 2348 days


#9 posted 03-29-2021 10:18 PM

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.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View WhyMe's profile

WhyMe

1409 posts in 2771 days


#10 posted 03-29-2021 10:21 PM

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.

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ibewjon

2587 posts in 4003 days


#11 posted 03-29-2021 10:39 PM

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.

View TopamaxSurvivor's profile

TopamaxSurvivor

22070 posts in 4886 days


#12 posted 03-29-2021 11:17 PM

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.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View JonCrafting's profile

JonCrafting

17 posts in 402 days


#13 posted 03-29-2021 11:26 PM

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.

View TopamaxSurvivor's profile

TopamaxSurvivor

22070 posts in 4886 days


#14 posted 03-29-2021 11:44 PM


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 ;-((

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View JonCrafting's profile

JonCrafting

17 posts in 402 days


#15 posted 03-29-2021 11:52 PM


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.

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