alfredeneuman
Well-known member
That's a valid point. I apologize
How about: "Anyone that believes the NEC is just designed to sell to more products is misinformed" instead?
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220v 40 amp to 15amp
- Thread starter Stevematt21
- Start date
That's a valid point. I apologize
How about: "Anyone that believes the NEC is just designed to sell to more products is misinformed" instead?
The problem with keeping a 40 or 50 amp feed .. is the feed wire to the device.
If you read the table saw I'm sure it will say to install a 12G wire feed wire -- some come with 14G (15amp) wire installed and no plug (since they don't know if you will use 110 or 220) I have a 220 grinder and the instructions say 15amp.
If you use an adapter and connect the tool to a 40 or 50 amp feed .. an internal fault has the potential to quickly overload the feed wire ... I have seen them melt and flame at 30 amps. The motors don't always trip .. and sometimes its the switch .. or you can damage the wire by dropping something.
Same problem with extension cords connected to 40-50 amp outlets.
If you read the table saw I'm sure it will say to install a 12G wire feed wire -- some come with 14G (15amp) wire installed and no plug (since they don't know if you will use 110 or 220) I have a 220 grinder and the instructions say 15amp.
If you use an adapter and connect the tool to a 40 or 50 amp feed .. an internal fault has the potential to quickly overload the feed wire ... I have seen them melt and flame at 30 amps. The motors don't always trip .. and sometimes its the switch .. or you can damage the wire by dropping something.
Same problem with extension cords connected to 40-50 amp outlets.
Charles (in GA)
Well-known member
IF the OP has FOUR wires run to the garage 240v circuit, (white, red, black, green) then it would be easy enough to install a small subpanel and single and double pole breakers for anything the OP wants to use.
Charles
Charles
alfredeneuman
Well-known member
And if he only has 3 wires (without the neutral) he could install a 240 volt only subpanel
sberry
Banned
Some can have a 12 wire and 50A and the HF welder that comes with a 6-50 has a 12 cord
Jeff Ivers
Well-known member
In all my studying of electricity, I have never heard of a "40 amp feed". What I have studied is that you have a circuit with a specified wire size from the outlet to the breaker with the breaker sized to prevent the wiring from melting in the wall if the item plugged into the outlet draws more current than the wire is capable of handling. People plug .5 amp draw items into a 20 amp circuits all the time with no safety issues. So why would a 15 amp draw plugged into a 40 amp circuit create a safety issue? It does not. The same is true of using an extension cord. Where people get in trouble is when they plug an item that is designed to draw 20 amps without burning up into an extension cord rated at 15 amps and then plug that into a 20 amp circuit. The OPs original question pertains to having a 40 amp outlet and wanting to use more that one item (one at a time) that draw much less current - just like plugging your cell phone charge into a 20 amp wall outlet circuit.
^ ^ ^ It's still a jerry rig . . . . not the right way to do it.
OP should have just told electrician he was going to have multiple 240v devices with different amperage/plug and right then the electrician would have recommended SUBPANEL in the garage !!
Is this ATTACHED or DETACHED garage??
OP . . . you need to listen to Alfred/PattenP/Charles(GA) as they know what the hell they're talking about !!
OP should have just told electrician he was going to have multiple 240v devices with different amperage/plug and right then the electrician would have recommended SUBPANEL in the garage !!
Is this ATTACHED or DETACHED garage??
OP . . . you need to listen to Alfred/PattenP/Charles(GA) as they know what the hell they're talking about !!
alfredeneuman
Well-known member
I'm going to repost #32:
From the instruction manual:
Plug your table saw into a 220-240 V, 15 amp., 3-prong receptacle. Make certain the receptacle is connected to a 240 V, AC power supply through a 240 V branch circuit
having at least a 15 amp capacity and protected by a 15 amp time-delay fuse or circuit breaker.
That pretty much eliminates any of the "alternative methods" mentioned here.
The receptacle is limited to a breaker size of 15 amps if a single receptacle is used, and 20 amps if multiple receptacles are installed.
______________________________________________________________
The manufacturer's instructions supersede everything else.
END OF STORY, CASE CLOSED!
Thank you for explaining the welder label requirements. So I assume that I'm up to code with the 6-50p on the 40 amp circuit without any special markings? If yes, I'll peal the label off.
Most electrical items are purchased with cords and plugs --- The plug determines the volts and amps. You can't plug a 15 amp plug into a 40 amp circuit outlet. Many stationary power tools do not come with plugs because they can be wired different ways .. but the manual will tell you what plugs to install. The plug becomes the limiting factor.
The problem is not with the wire in the wall or the outlet ... it is with the wiring in the tool. If the tool says to install a 20 amp plug .. and you somehow make a connection to a 40amp outlet controlled by a 40amp breaker, the feed wire could easily melt and flame if a short occurred.
I have seen shorted out 12g extension cords on fire with a 40 amp breaker. 40 - 50 amps is a lot of power and can be very dangerous.
A 15 or 20 amp breaker would quickly trip.
I had a neighbor in the city who hired a contractor who connected his 220v sander up to a dryer outlet and almost burned down the block when the cord melted and set the steps on fire.
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alfredeneuman
Well-known member
Lucky1 said: I believe you have to label it as such..for example "Welder Only"
Not saying it's not a good idea, but nothing in the Code says this
Not saying it's not a good idea, but nothing in the Code says this
sberry
Banned
A phone charger s designed to be plugged in to a 20A. The problem here again, back to code basics is that the cord cannot be plugged in to 40A unless it is 12 or better and its not because of general overloading but due to short circuit interruption ratings. A fult really doesn't overheat a wire unless the ground bond is missing.
We confuse many of these types of circuits with general 20A with multiple recepts where there is a potential for multiple pieces to be added to the same circuit to overload the wire. Almost,,, none of that applies to a specialized circuit,, the load is determined and controlled by the connected device and the breaker acts as short circuit protection and as a switch.
The first part of the quote above is essentially correct but its not really an overload in the general sense.
sberry
Banned
Lincoln AC welder, 50A breaker, 50A plug on a 12 cord and no secondary thermal. All the secondary is designed for shorts to 50 and protected from overload by duty cycle. A 200 mig, 12 cord, 50A plug and breaker but lots of fine internal wiring, goes to cord to double pole switch to thermal and if one really reads the instruction manual will see that the machine only needs a 14 wire to operate but,,,,,,,,,,,,,, once you do this must change the breaker to 30.
My steamer, comes with 5 hp motor, 10 wire, 30A plug with instruction for 30A breaker. The only secondary is on the furnace motor and they spec leads which are normally 16 to 14 for this application despite the draw being 1/2 the amp it would be at 120,,, not allowed to connect 16 wire above 20A
My steamer, comes with 5 hp motor, 10 wire, 30A plug with instruction for 30A breaker. The only secondary is on the furnace motor and they spec leads which are normally 16 to 14 for this application despite the draw being 1/2 the amp it would be at 120,,, not allowed to connect 16 wire above 20A
sberry
Banned
Where is a 12 cord connected to this breaker and what is it connected to? Is the cord being overloaded by the device connected to it???????? This is the same for a 16 extension cord,,, the user is sposed to realize he is connecting a cord to an appliance which must have a bigger cord in order to overload it????? On generals this could be a 3 way installed by the operator.
If this is shorted out and on fire there is something wrong with the grounding and in general theory the breaker would have to be well above 50A not to trip.
sberry
Banned
This isn't just about the OP but to a general understanding of how some specialized circuits are designed. Why when you see a larger breaker on some circuits its not always wrong.
There are some specialized 120 circuits (hence the 30A breaker) but they are not to have multiple general outlets on them, they are for motor and some lighting circuits which are usually hard wired and in some cases even have secondary fusing you may see n some old 4 lamp flo fixtures. If I am not mistaken they actually make a 50A single pole breaker for lights.
There are some specialized 120 circuits (hence the 30A breaker) but they are not to have multiple general outlets on them, they are for motor and some lighting circuits which are usually hard wired and in some cases even have secondary fusing you may see n some old 4 lamp flo fixtures. If I am not mistaken they actually make a 50A single pole breaker for lights.
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An alarm clock is plugged into a 15 amp circuit. The cord of the clock is not 14 gauge. If a fault developed in the clock, the cord could overheat and melt, causing a fire which will level the city of Chicago and kill cute puppies.
The difference here is that back in the day, makers of alarm clocks did not say to put the clock on a 1 amp circuit breaker.
That's because the breaker is there to protect the wire in the wall, not the cord of the clock.
If the OP's table saw did not have that one sentence about the 15 amp breaker would the naysayers be happy? If OP buys a table saw that runs on 240 that does not have that sentence will you all still complain? Does every one here wait at the crosswalk light till it says “WALK” even if no traffic is coming?
The difference here is that back in the day, makers of alarm clocks did not say to put the clock on a 1 amp circuit breaker.
That's because the breaker is there to protect the wire in the wall, not the cord of the clock.
If the OP's table saw did not have that one sentence about the 15 amp breaker would the naysayers be happy? If OP buys a table saw that runs on 240 that does not have that sentence will you all still complain? Does every one here wait at the crosswalk light till it says “WALK” even if no traffic is coming?
sberry
Banned
This is why there are a list of calcs for multiple motor loads,,, there are cases you may wire multiples to a circuit but they need to meet certain conditions,, some are cord size and secondary protection.
You could but motors on with 6A draw but,,,,,,,,, they still need a 12 cord and additional thermal if they go on a 40, 14 cord for 30 and max of 20 for a 16 even if the load is an amp.
sberry
Banned
The alarm has a cord heavy enough to fault a 20, right after that a fuse to keep the fine internal wiring from going up in smoke. Its not the breaker.
sberry
Banned
The wording can be funny and the original writer may leave something out,, min or max etc. The 200 compact wire welder is confusing in language,,, it doesn't mean max breaker but specifically when used with the minimum wire which is too small for a 50.
I suspect the OP table saw wording to be similar in nature and could be I spose if the motor has no secondary ( Not familiar with every motor rule) but I think its required?????? on these small hp motors?
sberry
Banned
Ok, here is a simple one,,, where is a 10,, or a 12 for that matter, wire allowed to carry hundreds of amps and no breaker in it?
sberry
Banned
Christmas tree lights, super fine wire running at 120 on a 120 circuit but,,, a 2 amp fuse in the plug.
I was being sarcastic, sorry.
Jeff Ivers
Well-known member
I think your post goes to the heart of the matter here. Persons trained in the electrical code are prone to look at a situation from a "rules and regulations" point of view. I suspect that the codes for "specialized circuits" are geared to industrial applications. The reality is that 120 or 240 volt circuits are alike in that there is no reason you can't have one or more lower rated items on the same circuit without changing the circuit breaker (providing the total load rating is less that the rating of the circuit breaker. Anybody here familiar with motor homes and the cords used to plug them into a home or campground receptacle? Ever seen the pigtail adapters sold to convert them to a different amp rating receptacle? If it were my table saw and it is rated to operate at 115 or 220 and I choose to run it at 220 and I have a 40 amp receptacle, I would not put a 40 amp plug on the saw, because that makes the saw unusable if I want to load it into a truck and take it to another site to work. If I installed a 40 amp receptacle because I anticipate having an item that requires that power that I would be using occasionally and exclusive of the saw, I would create an appropriate sized adapter pigtail with a 220v/15amp receptacle on one end, 12 gauge wire, and a 200v/40amp plug on the other end.
Jeff Ivers: Your are not getting what a few of us are saying.
... and the cords on RV are designed to handle the load.
The issue is not ... if it will work ... it will. The issue ... IF a short should happen .. it could start a fire.
Fused plugs are not common in the USA .. that is how it is taken car of in other countries. Xmas lights are a great example in the USA -- they have a fuse in the plug to prevent the wire from overheating and starting a fire.
When I lived in the UK everything used large 220 plugs w/ fuses..
... and the cords on RV are designed to handle the load.
The issue is not ... if it will work ... it will. The issue ... IF a short should happen .. it could start a fire.
Fused plugs are not common in the USA .. that is how it is taken car of in other countries. Xmas lights are a great example in the USA -- they have a fuse in the plug to prevent the wire from overheating and starting a fire.
When I lived in the UK everything used large 220 plugs w/ fuses..
Jeff Ivers
Well-known member
Yeldogt: Quite the contrary. I get what you are saying and totally disagree with you. If you have a tablesaw designed to draw 15 amps, it will have a cord designed for that load. That cord will be the same or lighter duty than the pigtail I propose. If there is a short, and something internal to the saw does not burn up and go open circuit first, the cord on the device is going to go next, before the pigtail. Any device plugged into an electrical outlet has the potential to cause a fire. The risk is no higher in this situation than a 1500 watt hair dryer plugged into 115 volt 20 amp or 30 amp circuit. It may be code in an industrial environment to require matching the circuit breaker to the device, but in a home environment, there is absolutely no such need based on scientific fact.
^ ^ You still don't get it. Having grossly overpowered 240v circuit that OP wants to share skimpy appliance is not MATCHING the entire circuit/wiring/appliance for the intended use. Appliance manufacturers surely don't want their cord to be the "protecting device" if 50 amps are shorting across a motor in 15 amp table saw !! That's the job of circuit breaker.
That's the job of circuit breaker. Exactly correct. Make an adapter and move on.
You are completely incorrect .. A device -- like a hair dryer plugged into a 20amp controlled circuit will trip with the supplied line -- if you plug that same device into a 40 or 50 amp controlled line -- it may never trip.
If you take a 14 cord and tie the two wires together and plug it into a 50 amp line -- it will light up like a bulb .. and never trip.
As another illustration: remember the old 12/2 with really skinny ground Romex from the 60s? They found that the little ground would burn in two before tripping a 20a breaker. So now we have full size grounding conductors.
Jeff Ivers
Well-known member
^ ^ You still don't get it. Having grossly overpowered 240v circuit that OP wants to share skimpy appliance is not MATCHING the entire circuit/wiring/appliance for the intended use. Appliance manufacturers surely don't want their cord to be the "protecting device" if 50 amps are shorting across a motor in 15 amp table saw !!
CNGsaves: OK - you are absolutely right. I don't get it. Apparently I never learned anything in my college electrical engineering courses. Apparently the houses and shop I have wired (that subsequently passed inspections) don't indicate any level of skill or knowledge.
When you finish patting yourself on the back, will you do this forum a favor? Please, immediately go unplug your cell phone charger and call an electrician to come fix your unsafe wiring. Why? Because that cell phone charger is rated at 1 amp or less and you have it plugged into a 15, 20 or maybe even a 30 amp circuit. So, by your definition it is "overpowered" by at least 15 to 1.
The OPs table saw would be "overpowered" by 45 to 15 (3 to 1). You are in imminent danger! Please, based on your logic, make sure your electrician replaces your circuit breaker with a 2 amp or preferably a 1 amp to get you in a safe range. And, if you really care about us ignorant types, please post up here what your electrician charges you to fix this problem so we will know how to make ourselves safe.
Jeff -- the cell phone charger is plugged into a max 20 amp line with a full amp conductor line -- or it has a directly connected transformer with a secondary line. What are you talking about?? I'm at a loss to understand how you don't understand this.
The properly installed disconnect / line and outlet is not the problem.
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alfredeneuman
Well-known member
404,
I just read your occupation. This explains it all.
A ME at a Manufacturing Plant where I used to do work had the same thoughts about those "unnecessary breakers" as you, connected his haywire rig up directly to a 100 amp receptacle, and left it overnight. This, although there were receptacles from 20amps up, he chose the biggest one available to him
These are the results:
The fire caused the alarm and fire sprinklers to activate, and a 100,000 sq ft manufacturing plant flooded (the valve controlling the sprinklers wouldn't shut off).
Their production was down for a couple of days.
PS The breaker never tripped
I just read your occupation. This explains it all.
A ME at a Manufacturing Plant where I used to do work had the same thoughts about those "unnecessary breakers" as you, connected his haywire rig up directly to a 100 amp receptacle, and left it overnight. This, although there were receptacles from 20amps up, he chose the biggest one available to him
These are the results:
The fire caused the alarm and fire sprinklers to activate, and a 100,000 sq ft manufacturing plant flooded (the valve controlling the sprinklers wouldn't shut off).
Their production was down for a couple of days.
PS The breaker never tripped
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sberry
Banned
This is important,,, more than individual questions but is the essence. I am sure yall can wire a house, I had inspection passes yesterday and barely know an amp from a volt.
But I am sure guys understand this in its own way and I figured it out backwards from a code standpoint. The sizes are moveable here but its likely that the 14 shorted will trip the 50 or it should but somewhere they found out and come to the conclusion it should be a 12. Its to do with speed too. Some to do with mechanical connections and some for V drop.
Many are very confused by the difference between thermal and short,,, the wire has to be able to carry enough current to serve the load for a dedicated and big enough to sustain a thermal in the case of a general multi outlet that can become overloaded. Different than 2 wires turning in to a toaster. We want to prevent that via fault before it happens.
But I am sure guys understand this in its own way and I figured it out backwards from a code standpoint. The sizes are moveable here but its likely that the 14 shorted will trip the 50 or it should but somewhere they found out and come to the conclusion it should be a 12. Its to do with speed too. Some to do with mechanical connections and some for V drop.
Many are very confused by the difference between thermal and short,,, the wire has to be able to carry enough current to serve the load for a dedicated and big enough to sustain a thermal in the case of a general multi outlet that can become overloaded. Different than 2 wires turning in to a toaster. We want to prevent that via fault before it happens.
Robert Duncan
Member
- Joined
- Feb 26, 2015
- Messages
- 7
If it gives you heartburn put a 6" #12 pigtail on each end of the #8 and use a 20 amp breaker and receptacle.
Actually, the QO220 Square D breakers are rated to a single #8 wire at the terminal, so you only need the pigtail at one end.
I personally would have no problem running the larger breaker.
Actually, the QO220 Square D breakers are rated to a single #8 wire at the terminal, so you only need the pigtail at one end.
I personally would have no problem running the larger breaker.
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