60amp 240v only sub panel... grounding rod?

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Old 12-08-18, 11:55 AM
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Question 60amp 240v only sub panel... grounding rod?

I have a detached garaged with buried 20amp 120v service coming from my 100a mains panel inside the house in the basement.

I needed a 30a 240v source in the garage to run a smaller welder so with future welder upgrade in mind ran 50ft of 6/2 undergroud feeder line to the garage , using pvc conduit to enter into both structures on a 50amp double pole breaker at the main panel. In the garage i have a single 6-50 welder outlet.

Problem is... I am now looking at a 240v electric heater for garage that calls for 10g/30a.
I planned to just wire the heater with the same 6-50 plug as my welder and in rare occasions i need to weld while heater is running to just unplug heater and plug welder in.

Just wondering if I would be better off running a 60amp breaker on the main panel (UF 6g wire good for 55amps I believe) and installing a sub panel in garage labeled as "240v ONLY, NO NEUTRAL" that way I could run welder and heater on there own 30a breaker and be able to disconnect at the garage. Would I need to drive in a grounding rod at the sub panel or just tie into ground from main?

Any other thoughts?
Thanks
 
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Old 12-08-18, 12:30 PM
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You can not have two power feeds to a detached structure The 120v feed will need to be abandoned and a 4-wire 120/240 feed (H-H-N-G) run to the garage.. A 60 amp feed will probably be adequate. You will need an EGC ground from the house and a GEC earth ground at the sub panel.
 
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Old 12-08-18, 02:34 PM
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You may not substitute a 50 amp plug for the original 30 amp plug on the heater. Same for the future smaller welder if that also comes with a 30 amp plug.

The 30 amp plug implies that the maximum amperage circuit that the heater may be used on i s 30 amps.

The "first" panel in the detached building needs ground rods.

Running a 240 volt only feed to the detached building is almost certainly short sighted. Surely in the near future you will wnat to use 120 volt power there.
 
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Old 12-08-18, 07:45 PM
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I already had 120v buried circuit going to garage. I was told if adding a 240v line to garage to stay 6ft + away from current line and trench needed to be 18" deep , and had to use pvc elec conduit coming from ground up foundation to where it enters buildings. All of which I did. So I got bad info? Id hate to have to dig up both lines to run a single 6/3.

As for the 6/50 plug.... Several hobart (handler 190, mvp 210) and similar amperage 240v welders come with the 6-50 plug even though they are 28amp peak machines. Dont see what the difference there would be, using one on a 30amp elec heater for a temporary solution untill getting sub panel installed. I currently have 50amp breaker- 6gauge wire rated for 50amps, and the nema 6-50 receptacle .... so dont see what the issue would be since the heater will only ever use peak 30amps. I would understand that using 50amp plug on 30amp circuit would be wrong.
I think i will swap the 50amp breaker for a 30amp tomorrow just to be closer to actual load until i install sub panel and figure this mess out
 
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Old 12-08-18, 09:32 PM
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Allanj: You may not substitute a 50 amp plug for the original 30 amp plug on the heater. Same for the future smaller welder if that also comes with a 30 amp plug.

The 30 amp plug implies that the maximum amperage circuit that the heater may be used on is 30 amps.
That is nonsense.

Circuit wire size from electric panel determines rating of breaker or fuse used, not plug on loads. Using an over sized plug is good way to lower contact resistance and reduce problems on high current items.

Residential portable electric heaters rated at 1500 watts draw ~12 .5 amps. Their plugs often overheat. When one does I replace with 20 amp plug. If that over heats replace receptacle.

Moderator note: This is personal opinion..... not in particular what is correct.
 

Last edited by PJmax; 12-09-18 at 10:34 AM.
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Old 12-08-18, 10:32 PM
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I would feel better with breaker in garage so think ill pick up one of these panels ...
https://www.farmandfleet.com/products/034162-square-d-homeline-100a-indoor-main-lug-load-center.html?feedsource=3&gclid=EAIaIQobChMI0-bUuYCS3wIVDIhpCh2enATnEAQYAyABEgLSIfD_BwE

Plan to run 60amp breaker at main, using 6ga wire rated for 55amps.
At sub panel I will hardwire the electric heater (which is what it calls for anyway) to 30amp breaker at the panel, this will get rid of the plug debate.
Ill wire my welders 6-50 (30amp welder that came with this 6-50 plug) outlet to another 30 amp breaker.

I dont think the panel comes with a grounding bar and assume the neutral bar shouldnt be used???

Ill clearly label the panel and all outlets, my only question now is how to ground?
There is no neutral. I have 2 hots and the ground only coming from main. Do i just ground the sub panels ground bar with the ground coming from house, or drive a new ground rod in ground for the sub panel? If I drive in a new ground for sub do I tie it AND the mains ground to the sub panels ground bar?

Im pretty sure back in the day you would ground with ground wire coming from the main but thought I read recently to not even use ground from main and that sub panel had to have grounding rod so Im confused on this aspect.

thanks
 

Last edited by deezdrama; 12-08-18 at 10:48 PM.
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Old 12-08-18, 10:41 PM
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I already had 120v buried circuit going to garage. I was told if adding a 240v line to garage to stay 6ft + away from current
That was WRONG. You can ONLY have one feed if it is not attached to the house.You must run a 4-wire feed, hot-hot-neutral-ground. The 120 volt feed must be abandoned. You will need to buy and add a ground bar to the subpanel. The neutral bar will be isolated (not bonded to panel) and used only for neutrals.
 
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Old 12-08-18, 11:01 PM
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I will have to rectify the 2 feed issue when the ground thaws.
Does the sub panel need a grounding rod in the earth at the sub panel or just use the ground wire coming from main panel? Or both? Ive read several threads stating "must use main panels ground" and read several threads stating "must use grounding rod in earth at sub"
 
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Old 12-08-18, 11:09 PM
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Depending on your local AHJ you will need one or two ground rods for lightning in addition to a low resistance ground wire from the main panel to clear faults to metal parts of equipment.
 
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Old 12-09-18, 12:00 AM
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I will have to rectify the 2 feed issue when the ground thaws.
The old feed doesn't need to be removed from the ground just disabled. You could wire correctly now by going overhead with UF-b. That could be reused when weather permitted for direct burial.
 
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Old 12-09-18, 07:26 AM
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dada dada dada
That is nonsense.
Every light, appliance, tool, device, and even receptacle has a maximum amperage for the branch circuit on which it may be used. (Some also have a minimum amperage circuit specified.) For common U.S. lights and appliances with "ordinary" plugs, that maximum circuit rating can't be less than 20 amps due to the prolific use of 20 amp branch circuits nowadays, and safety rating agencies such as Underwriters Labs should take that into account. Materials, insulation, etc. in the device determine the maximum circuit amperage rating.

(I don't have handy now the NEC table listing what amperage receptacles may be installed on what amperage branch circuits.)

For hard wired appliances the instructions or the name plate should state this amperage.

Among other things this limitation will disallow using one 50 amp circuit to power three or even just one 12 amp heaters.

Yes I have experienced a out-of-the-box ordinary appliance (a heater) having its plug and the receptacle melt due to overheating. The reason was a defect in manufacture; the cord wires were not properly attached (they used screws which were untightened) to the plug. After I fixed the problem the plug did not overheat.
 

Last edited by AllanJ; 12-09-18 at 07:44 AM.
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Old 12-09-18, 10:33 AM
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Allanj: You may not substitute a 50 amp plug for the original 30 amp plug on the heater. Same for the future smaller welder if that also comes with a 30 amp plug.
This is 100% correct. You CANNOT put a larger than normal plug on an appliance.

Example..... There is a 240v 50A circuit and receptacle available for a welder. You decide to put a 50A plug on a 30A heater because it's heavier duty. Then you plug a 30A heater into a 50A circuit. That is not good.

If you want devices to handle the current they are designed for without getting hot..... use spec grade or commercial grade devices.
 
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Old 12-09-18, 11:07 AM
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Given the number of electric based fires and injuries, the bottom line should be safety. Codes and Underwriter Labs are focused on safety, not endurance.

Manufacturing is about constantly cutting costs to increase profits. Product is cheapened until it just works. Company's exposure typically ends there.

To some this may be nonsense.

In the big picture of modern life this is a small issue. I cannot change the world, but can use a safer plug with higher current rating. Duh duh duh
 

Last edited by doughess; 12-09-18 at 12:38 PM.
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Old 12-10-18, 08:28 PM
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