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Sawstop 3hp 220v to dryer outlet

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Forum topic by yasinh posted 08-27-2021 03:22 PM 902 views 0 times favorited 20 replies Add to Favorites Watch
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yasinh

9 posts in 57 days


08-27-2021 03:22 PM

Hello all, I have an electrical question regarding my new table saw. I have a 30amp dryer outlet which has nema 10-30r receptacle. My table saw comes with a cable which has 6-15p plug. Manual says that motor has internal thermal overload protector. I have been checking lots of places and people say that it should be safe to run tool against that receptacle. 1st question: Is it safe to run tool against that circuit?

I bought a dryer extension cord and replaced 6-15p with it. Saw worked perfectly but I didn’t like that setup since dryer extension cord was a bit oversized and power box on the saw didn’t close all way. I would like to change it. I have two options;
1- I can build my own cable setup with one end to the saw. One end to a 10-30p.
2- I can buy adapters with an extension and connect the saw. I feel like this is a safer option. The adapter I am looking at has a 20amp breaker on it. Manual says it is not recommended but as an engineer I would consider they have to write it that way to cover larger cases. I feel like this option and setup safe but still not an electrician and don’t know much about the edge cases.

What do you recommend? Any help much appreciated


20 replies so far

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stevejack

345 posts in 566 days


#1 posted 08-27-2021 03:35 PM

View Fred Hargis's profile

Fred Hargis

7236 posts in 3739 days


#2 posted 08-27-2021 04:10 PM

Running your saw on a 30 amp circuit is fine. If that 20 amp breaker thingy makes you feel better, go ahead and buy it. But you don’t need to. I’d probably buy the extension cord and put a plug on it that fits the dryer outlet. Bam, you’re done. But that’s me…and there will be 30 different opinions offered up…some shaming me for my choice and offering other options. So you’ll just have to choose which one you like and go with it.

-- Our village hasn't lost it's idiot, he was elected to congress.

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MrUnix

8775 posts in 3444 days


#3 posted 08-27-2021 04:39 PM

Using the dryer outlet to power a table saw is common. Sometimes, it’s about the only option available. To use the extension/adapter or not is your call, and perhaps how long you plan on being where you are. I would probably wire up a new, longer cord with the proper plug on it. If you change locations later on, you can always just replace the plug.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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vjc

24 posts in 1632 days


#4 posted 08-27-2021 05:46 PM

$58 is alot of money for an adapter. I agree with Fred Harris. Save some money and either make an extention from parts or put a plug on the the extention cord that fits your dryer outlet.

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controlfreak

2907 posts in 847 days


#5 posted 08-27-2021 05:51 PM

All I can think of is, is the outlet still needed for the dryer to use? if yes, I can’t imagine a table saw that close to the washer dryer (dust). What is your setup?

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yasinh

9 posts in 57 days


#6 posted 08-27-2021 06:17 PM

Is there any plug and cable recommendations? Links would work great.

Dust is manageable. Saw has mobile base on it planning to move it close to garage door and open it. Dryer is in the complete opposite site.

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controlfreak

2907 posts in 847 days


#7 posted 08-27-2021 06:51 PM



Is there any plug and cable recommendations? Links would work great.

Dust is manageable. Saw has mobile base on it planning to move it close to garage door and open it. Dryer is in the complete opposite site.

- yasinh


Dust never sleeps. Gotta watch your wire gauge as you add length to anything feeding a motor. Not an electrician but you need to do the math on this or you could damage the motor. I never did math but always got the biggest gauge cord I could for smaller motors.

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Fred Hargis

7236 posts in 3739 days


#8 posted 08-27-2021 07:05 PM


Is there any plug and cable recommendations? Links would work great.

Dust is manageable. Saw has mobile base on it planning to move it close to garage door and open it. Dryer is in the complete opposite site.

- yasinh

All you need to do is buy that extension you linked above and put this plug on it. This assumes 25’ is long enough, and your spec of the 10-30P plug is correct. Then your saw should just plug into the extension. If you continue to think you need that breaker adapter thingy, just plug it in between the extension and the saw. but it really is not needed.

-- Our village hasn't lost it's idiot, he was elected to congress.

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CaptainKlutz

4904 posts in 2740 days


#9 posted 08-27-2021 09:14 PM

Welcome to LumberJocks!

Can use any of the methods above to connect TS to dryer outlet.

IMHO – Simple is best, buy dryer plug, 10ga SOOW cable, and 6-15/20 receptacle for your saw plug; and make an extension cord.

+1 Dryer plug connection has been used since man started using 3HP motors at home.

Stop reading now if don’t care about electrical code and safety:
————————————————————————————————————————————-

That said; the installation will not follow the code, as none of the options above are code complaint.

Why?

There is much more to this plug conversion than many realize.
Challenge is you have dig really deep into electrical wiring codes to understand.

1) What are electrical ratings on the tool?
TS likely passed electrical code requirements by adding a magnetic motor starter with overload protection. This means the device is protected from an internal failure by relay and overload sensing switch.
Also means you have only way to worry about wiring to tool. :-)

2) NEC section 430 motor wiring code requires circuit protection to be 125% of motor FLC.
Single phase 3HP 230/240v motor FLC (from look up table) is 17A, which means a 21.25A or higher is required. Using a 20A breaker is technically not enough, and since a 25A breaker does not often exist; a 30A breaker is perfect. So your dryer wiring breaker is adequate to protect the wiring to the dryer outlet.

3) Now you have to worry about the wire to tool:
A 30A 208-240v circuit generally uses 10AWG wire. If run is longer than ~150ft, might increase wire size to avoid voltage drop. But since FLC on motor is 17A, on a 30A circuit; you are already oversized ciruit and only need to use larger gauge IF/WHEN voltage measurements show more than 10% reduction.

4) Receptacle/plug in the circuit:
This is a area when MFG always violate codes, and is pet peeve of mine. :)

Per NEC 430.109 plug/receptacles for motorized appliances need to be HP rated:

430.109(F). Cord-and-Plug-Connected Motors. For a cord-and-plug connected motor, a horsepower-rated attachment plug and receptacle, flanged surface inlet and cord connector, or attachment plug and cord connector having ratings no less than the motor ratings shall be permitted to serve as the disconnecting means…

To understand the MFG violation, need to check your plug mfg HP rating. Here is table from Hubbell catalog, but most US mfg have same ratings:

You can see the 6-15p is rated for 1.5HP!
Probably asking yourself, What has the mfg done?

If you look at the 10-30 (3 wire), or 14-30 (4 wire) dryer plug HP ratings in chart, they are only rated for 2HP!
Since dryer motor is usually on 1HP, the plug meets code for dryer, but not a 3HP TS.

Connectors are considered a electrical disconnect in case of emergency. They are supposed to be rated for locked rotor/max surge of the motor. Locked rotor/surge current is often 2-3X the FLC. If you ever are forced to unplug a 6-20P when a 3HP motor is locked and your magnetic starter has failed; will likely burn your hand, and find melting plastic. BTDTGTTS

WTH is this crazy Klutz saying?
IF you plan to, or need to; use the plug as electrical disconnect while the tool is running; the MFG plug and dryer receptacle are NOT NEC code complaint for 3HP motor.

Is this a safety hazard? Maybe, depends, sort of, yes/no?

As noted above:
Appliance with 3HP motor will run OK on a 20A circuit, and is the normal wiring installed for hobby work shop.

This is a ‘locally allowed’ code exception as most modern motors have name plate rating of 15A, and 20A circuit meets code for this name plate rating. As long as tool has self contained overload protection, then likelihood of cascade failure of ALL protection devices that creates a wiring fire is very, very low. Even your residential insurance carrier will consider this wiring ‘design’ low electrical risk.

Another factor is the circuit is TEMPORARY. NEC code only covers permanent circuits. The definition for temporary is usually: only used while some is present. So as long as you unplug the TS from wall when not being used, the risk is temporary and under your control.

Last but not least: IF one never unplugs the motorized appliance WHILE the motor is running, then don’t need a connector rated for Motor HP, only need to satisfy the volt/current ratings for circuit.
If you do happen to unplug a running motor with under rated plug, don’t expect the receptacle/plug to last very long. After only one disconnect, will find melted/burned contacts that can increase connection resistance, and cause over heating issue.

This is why mfg sell tools with improperly rated 6-15 plug! The tool manual usually contains a CYA statement:
User must follow all locally applicable electrical and building codes.

Bottom line:
- Breaker protects wiring, not tool.
- Use proper wire size for circuit protection (in this post – 30A breaker – use 10AWG wire/cable).
- Use connections rated for proper voltage/current.
- Never disconnect plug while tool is running, unless the connection is HP rated, or you are prepared to replace both sides of connection. Use of locking receptacles/plus is great way to avoid accidental disconnects and plug damage.

PS – Electrical nerds are very particular.
Am sure one of the other electrical experts in forum will take issue with my choice of words, or possibly find a mistake made by this old retired Klutz. Apologies in advance if that happens.
So, YMMV

Cheers!

-- 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

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Knockonit

978 posts in 1448 days


#10 posted 08-28-2021 01:27 AM

it taint rocket science for sure, use a cord, min 10ga, put the male plug on for the dryer, the female on for the plug at saw, and make some dust, even if saw is needing only 20 amp, the 30 amp circuit will work, jsut means at pull of 30 amp, which may or may not be too much for saw , breaker will pop, or hope it will pop, but you’d know or should by saw activity, smell ect, if issues arise.

all my trucks have a 100 ft ext cord to hook into clients drier outlets for either welder or 220v equipment, just don’t abuse it.
Rj in az

-- Living the dream

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bigblockyeti

7623 posts in 2966 days


#11 posted 08-28-2021 02:24 AM

I wouldn’t worry about him popping a 30A breaker, that little taiwanese motor will let the smoke out long before that happens.

-- "Lack of effort will result in failure with amazing predictability" - Me

View Madmark2's profile

Madmark2

3097 posts in 1834 days


#12 posted 08-28-2021 03:30 AM

CaptKlutz:
This is why I use twist-loc connectors for the saw and DC. No chance of accidental kick- or pull-out. Saw is NEMA 6-20L while DC is NEMA 5-20L so they can’t cross. I could have rewired the DC for NEMA 6-20 but chose not to just because.

In process of replacing shop breakers with GFCI and arc breakers. $60 a pop for Eaton CH series. Have to hire handyman to change. Not doing ANY panel wiring since pacemaker install! Strictly 12 or 5vdc for me!

I always use UL approved and follow gauge ampacities and deratings, etc., but I’m sloppy about conduit. I tend to string 12-2 w/gnd around the walls and fairly safe from damage. My claim is that the wiring locations “aren’t final” and will have conduit mounted sometime in the future. Mañaña!

I have a switched outlet with indicator on my tool stack. Note highlighting on embossed position label.


Switched outlet with light is used for most hand power tools.

Dead man foot switch has big table router in it in series with switched outlet. Switch disables pedal for fence adjustments, but cord is pulled for anything bit related.

-- The hump with the stump and the pump!

View azwoodworker's profile

azwoodworker

74 posts in 3028 days


#13 posted 08-28-2021 03:38 AM

Captain Klutz: Very thorough and definitive post. I use an extension cable to an enclosed electrical box so I can install the correct connectors and install individual breakers for each tool. Works the best and I always upgrade 220 wall outlets to the highest load. I ignore what the MFG put on and go with the code. Long since abandoned what the MFG was thinking when they pick plugs and cords.

View yasinh's profile

yasinh

9 posts in 57 days


#14 posted 08-29-2021 06:12 AM

Thanks everyone! Especially CaptainKlutz for very detailed explanation. I will build my extension cable as most of you was suggesting. nema 10-30p <> 10ga cable ~25ft <> nema 6-20r receptacle.

CaptainKlutz, I am curious about the safety codes and a follow up question. I understand we should be using correct cable which can carry load. Let’s assume that I don’t have an extension and this was a wall receptacle, how cabling would be different? I would assume that similar to above setup there should be 10ga cable will be connected to 6-20r wall receptacle right? Does 30Amp breaker makes our setup non code complaint or potential of unplugging cable under the load makes it non code complaint?

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controlfreak

2907 posts in 847 days


#15 posted 08-29-2021 09:23 AM

I can’t add anything to the Captain’s code book but thinking out loud here. Probably not code but what if you were to connect some sort of a transfer switch to make ether the dryer outlet or the table saw circuit hot but not both. take the table saw circuit and run it in a surface mounted conduit down the wall to a spot near the door where the saw can do it’s dirty work. No long cords and no plugging and unplugging of cords. I can’t help but think that a dryer outlet is going to fail if it is overused, it is not designed for frequent or daily changes. Also for either use this should probably be a GFCI too if it is in a garage.

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