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Current Requirements for a 935TS and 1340GT

wrmiller

Chief Tinkerer
H-M Supporter-Premium
#1
Hey all,

Finally making progress on getting the new garage wired up for my machines. It's been a loooong 6 months.

Anyway, I originally wanted to run one 10gauge 30A circuit for both machines, like I had in my CO garage, but for whatever reason we had a brain glitch and ran separate runs to each receptacle. I don't have the extra amperage in my sub-panel for another 30A breaker, so I am thinking of putting a 20A breaker on each machine.

Reading the motors on the machines shows 8.8A on the mill, 6.6 on the lathe. Both are run via VFD. I would think 20A should suffice?

TIA
 

JimDawson

Global Moderator
Staff member
Director
#2
Hi Bill, happy to hear you're getting things back together.

I'm not quite sure what gauge wire you used to wire the machines, but putting a 20 amp on each machine should be fine. On the other hand, the total amperage of the breakers, added together, in the panel can exceed the available power. The breakers protect the wiring downstream of the individual breakers. The breaker feeding your sub-panel protects the wiring to the sub-panel.
 

Kiwi Canuck

H-M Supporter - Premium Content
H-M Supporter-Premium
#3
If you are running off a sub panel, the breaker in the main panel feeding the sub panel will determine the total load possible, what is the rating on that breaker?

Even if it's only 40 Amps you can still run (2) 30 amp breakers off the sub panel, you can't draw more than 40 Amps total without the main breaker tripping.

Guess it depends on if you have 30 amp breakers already or you still need to purchase them and then a 20 Amp breaker should be OK and less expensive.

David.
 

Chris Bettis

Active Member
Active Member
#4
Bill, what kind of panel do you have, there are alot of companies thin breakers tp add circuits to panels without extra room? They also sell load centers for hot tubs. For about 30 bucks. You can take a 60 amp from your main panel. Out to a sub panel that splits into 2 30 amp circuits for about 45 dollars total.
Its good to see you posting again. I was just telling my dad while working this weekend, "I gotta check in and see how Bill is doing"

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wrmiller

Chief Tinkerer
H-M Supporter-Premium
#5
The breaker feeding the sub-panel is 80A, and we ran 10-3 (4 wire) for the 240v circuits.

I have two 30A breakers, but can take them back. :)
 

Chris Bettis

Active Member
Active Member
#8
Its a small breaker box usually they install for hot tubs with room for between 2-4 circuits depending on the model or 1-2 circuits in a 2 pole 220v configuration
Basically you mount it right next to your existing sub panel. Put your mill and lathe runs into it, then wire it up into your existing panel.

OR. you buy a couple of single pole double sided breakers and consolidate a few of your single pole circuits into those to gain room for adding the second 30amp 2pole breaker.

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Chris Bettis

Active Member
Active Member
#11
Actually just buy a junction box and set it on the wall by the sub panel and split one line into 2
Then one breaker feeds both runs.

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mksj

Active User
H-M Supporter-Premium
#12
The VFD specify 30A breakers, although I use a 20A on my WJ200-015SF. I would use a 30A breaker for a WJ200-022SF. As others mentioned, the breaker protects the wire and usually not the device. The total amperage of the breakers does not add up to the total amperage of the panel, so I use a 100A sub panel with the total breaker amperage of 150A. Each breaker is rated to the branch circuit wiring and the start up motor ratings for my non-VFD machines. If you are short on slots, they have half sized breakers or 4 pole quads that fit a standard dual breaker slot. So you would be fine with either two 30A breakers or a 20A and a 30A. A 20A for a 3 Hp VFD motor would probably work, but based on the wiring gauge there is no reason why you couldn't use a 30A dual pole breaker.
 

Kiwi Canuck

H-M Supporter - Premium Content
H-M Supporter-Premium
#13
Hey all,

Finally making progress on getting the new garage wired up for my machines. It's been a loooong 6 months.

Anyway, I originally wanted to run one 10gauge 30A circuit for both machines, like I had in my CO garage, but for whatever reason we had a brain glitch and ran separate runs to each receptacle. I don't have the extra amperage in my sub-panel for another 30A breaker, so I am thinking of putting a 20A breaker on each machine.

Reading the motors on the machines shows 8.8A on the mill, 6.6 on the lathe. Both are run via VFD. I would think 20A should suffice?

TIA
Bill, just to confirm, when you stated "I don't have the extra amperage in my sub-panel for another 30A breaker" did you mean the value of all breakers exceeded the sub panel rating (which is not a problem) or did you mean there was no physical space left for an additional double pole breaker.

Both questions are answered above but it would be easier to clarify if we knew what was your original concern.


David.
 

wrmiller

Chief Tinkerer
H-M Supporter-Premium
#14
I'm not a electrician (if you saw my wiring on my lathe/VFD you'd agree...), so I'm not sure what the requirements are, but to answer your question: I thought the sum of the circuit breaker ratings could NOT exceed the main breaker supplying the sub-panel (100A)

New panel, so I'm not out of breaker slots. :)
 

Chris Bettis

Active Member
Active Member
#15
I'm not a electrician (if you saw my wiring on my lathe/VFD you'd agree...), so I'm not sure what the requirements are, but to answer your question: I thought the sum of the circuit breaker ratings could NOT exceed the main breaker supplying the sub-panel (100A)

New panel, so I'm not out of breaker slots. :)
Noo no it means the panel is only rated to pull x amount of amps at any given time. You could have 300 amps worth of breakers on a 100 amp panel and be fine so long as your actual usage is less than 100 amps. For instance my shop ( compressors, welders, mill, and lathe plus lighting and all electrical sockets everuthing) are all on a 100 amp sub panel. And im nowhere close to maxing it out at any given time..
The way that is usually calculated is to install a clamp meter over the mains to record amperage. Turn everything you could possibly be using at once on.
And see how much amperage you are actually using.
Ive got way more heavy draw equipment in my shop and ive never come close. To flickering the lights while using anything.
Moral of the story, wire it up and forget about it, your fine..

My house has a 200 amp main panel with 60 slots for breakers if I loaded it up with 60 5 amp breakers it the breaker rating would be 300 amps (5 is the smallest breaker you can buy). They wouldn't sell panels like that if it were the case. Plus the supply breaker on the mains would trip before any of the others would if you could even plug enough crap in to draw that much power.
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