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One thing that i noticed that you have wrong is the ampacities for wire in used in transmission vs chassis wiring. The numbers you have listed are for transmition wiring so they would be the correct sizing for the cables that go to the panel and to the different elements and pumps. But for chassis wiring you can use smaller wire.

#14 THHN copper wire is good for up to 25 Amps
#12 THHN copper wire is good for up to 30 Amps
#10 THHN copper wire is good for up to 40 Amps

These ratings come from The Handbook of Electronic Tables and Formulas for American Wire Gauge. This data is also in NEC Table 310-16.
 
crazyirishman34 said:
One thing that i noticed that you have wrong is the ampacities for wire in used in transmission vs chassis wiring. The numbers you have listed are for transmition wiring so they would be the correct sizing for the cables that go to the panel and to the different elements and pumps. But for chassis wiring you can use smaller wire.

#14 THHN copper wire is good for up to 25 Amps
#12 THHN copper wire is good for up to 30 Amps
#10 THHN copper wire is good for up to 40 Amps

These ratings come from The Handbook of Electronic Tables and Formulas for American Wire Gauge. This data is also in NEC Table 310-16.
Click to expand...

glad you found those

now go to the National Electrical Code and find out all the rules and regulations for installing those wire sizes
how to derate, etc

plus if you were to look in the notes of table 310,16 you will see that 14 gauge wire can only be used for 15 amps, 12 gauge for 20 amps and 10 gauge for 30 amps, no mater what they are rated for.

and those figures are just a start, we can only use 80% of allowable rating
we figure the fill of the box in devices and wires, how the wires are installed and derate them further

it is not as easy as just reading a table.
 
Why is it so hard for people to understand that NEC table 310.16 only applies to wire in conduit, raceways, cables (romex, BX) and direct bury. NEC Table 310.15 is the chart that is used for chassis wiring.

Refers to the maximum constant load on a circuit. So even though you can run a 7200w element on a 30a 240v circuit that max constant load allowed is 5760w.
 
For this type of wiring i would only use a ratcheting type wire crimper. You can get a really decent one for about $20 on amazon or ebay.

Also I would only use THHN stranded wire in a chassis wiring application. Solid core wire is really only good for house wiring.
 
crazyirishman34 said:
Why is it so hard for people to understand that NEC table 310.16 only applies to wire in conduit, raceways, cables (romex, BX) and direct bury. NEC Table 310.15 is the chart that is used for chassis wiring.

Refers to the maximum constant load on a circuit. So even though you can run a 7200w element on a 30a 240v circuit that max constant load allowed is 5760w.
Click to expand...

What year code book are you referencing? In the 2011 code 310.15(B)(16) is the old 310.16.... Are you referring to TABLE 310.15(B)(17) (formerly Table 310.17) Allowable Ampacities of Single-Insulated Conductors Rated Up to and Includluding 2000 Volts in Free Air, Based on Ambient Temperature of 86*F? If so there's a note to Refer to 240.4(D) for condutor overcurrent protection limitations For #14, #12 and #10.

240.4(D) shows the 18 being fused at 7amps, #16 at 10amps, #14 at 15amps, #12 at 20amps and #10 at 30amps.
 
This may have been brought up, but if one were to follow code/industry standards in building their control panel, wouldn't the proper codes/standards be: NEC Article 409 (Industrial Control Panels) and UL508A (Standard for Industrial Control Panels). NEC Article 300.1(B) leads me to believe that Article 300 would not apply to the internals of the control panel.



I don't have access to UL508A, but it would be intersting to see what their ampacity tables list, conductor sizing and circuit protection.
 
ingchr1 said:
This may have been brought up, but if one were to follow code/industry standards in building their control panel, wouldn't the proper codes/standards be: NEC Article 409 (Industrial Control Panels) and UL508A (Standard for Industrial Control Panels). NEC Article 300.1(B) leads me to believe that Article 300 would not apply to the internals of the control panel.



I don't have access to UL508A, but it would be intersting to see what their ampacity tables list, conductor sizing and circuit protection.
Click to expand...

Thanks for pointing that out... I'll have to read through that this weekend but glancing through I did notice that under "409.21 Overcurrent Protection (A) General. Industrial control panels shall be provided with overcurrent protection in accordance with Parts 1, 2, and 4 of Article 240"... good find... As far as UL508A goes I would have to say that it's not relevant to the general public since our control panels aren't going to be UL listed but I could be wrong.
 
Jerz said:
As far as UL508A goes I would have to say that it's not relevant to the general public since our control panels aren't going to be UL listed but I could be wrong.
Click to expand...
Correct, no one building their own panel is going to go for a UL listing, but as far as following good industry standards and practices I would think it would be very good place to look if one had questions on what size wire to use, how to protect it and control circuit design.

I did find a couple of guides that quote sections of the standard:

Schneider Control Panel Technical Guide
Eaton Control Panel Design Guide

So, per the above guides it looks like the UL Standard gives the following ampacities: #14 = 15A, #12 = 20A and #10 = 30A.
 
crazyirishman34 said:
Why is it so hard for people to understand that NEC table 310.16 only applies to wire in conduit, raceways, cables (romex, BX) and direct bury. NEC Table 310.15 is the chart that is used for chassis wiring.
Click to expand...
If you are referring to the Single Conductor Free Air Table 310.15(B)(17) (formerly Table 310.17) then I think the problem may be that the NEC does not define what "Free Air" means. In my opinion this table means that you have a single conductor cable that has no impediments to the air flow around it. Once you have multi-conductors, more cables, conduit, dirt, enclosure, etc. then you are no longer in Free Air, and the table does not apply. It's those impediments that could ultimately affect the cooling around the cable and thus it's ampacity rating. Hence the need for two tables, with the Free Air table having higher ampacity listings.
 
The reason why I used the general wiring table versus the chassis table was to keep it simple. I dare not assume that the vast majority here know the difference between different insulator types and how they affect current rating. My logic was that if they followed the general wiring / power transmission table that no matter what type of wire they picked up at the big box stores it would be sufficiently de-rated and safe to use.

The cost savings resulting from using a wire gauge size or two smaller according to the chassis table is negligible to some one doing a one off panel. That and it just adds more confusion. Bottom line is that by using the general table no one is doing anything unsafe. If your knowledgeable enough about the NEC to take advantage of all the caveats then more power to you. However, the information provided here is more than sufficient.

And solid core sucks...
 
So, from what I've gathered here let me make sure I understand this. My apartment built about twelve years ago must not be to spec because the range and dryer have three pronged outlets. Because of this I can't use them to run power to a spa disconnect with GFCI because the neutral has power on it. I would need another wire for ground, disconnect the neutral from the hot, and install 4 pronged outlet. Did I get that all straight?


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It probably is to code as there was an exception to the rules for washer/dryers allowing bonding of the frame to neutral (rather than earth) because the a-symmetric load (110 stuff) was so small. After some cutoff date 4 wire receptacles were required but you are 'grandfathered' in and most modern appliances can be installed in either a 3 wire of 4 wire system (jumper inside the unit). You are correct that for safest operation you would need to run an earth/ground wire bonded to the neutral in the panel. An alternative is to move the neutral to earth (so that you have phase/phase/earth instead of phase/phase/neutral) and derive 120 V from a transformer in your panel. You should not use an outlet once so modified for a dryer, however.
 
ajdelange said:
. You should not use an outlet once so modified for a dryer, however.
Click to expand...

So, would it be codger to then use the range outlet, and ground the keg through one of the 110 outlets? This actually sounds really really non kosher to me now that I've asked it... I hate renting sometimes. I need a house for a garage for all my hobbies.



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ajdelange said:
Would it provide a good earth? Yes. Is it kosher? No, I wouldn't think so.
Click to expand...


Yeah, "kosher." I just woke up. Fingers aren't quite doing what my brain want yet ha ha ha. So, there is no way to ever hook up a GFCI breaker to a 3 conductor circuit because it monitors current between the neutral and line which are tied together in the case of 3 wire plugs? I need the 4 wire plug so I can separate the neutral from the line and have a true ground. Right?


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Islandboy85 said:
Yeah, "kosher." I just woke up. Fingers aren't quite doing what my brain want yet ha ha ha. So, there is no way to ever hook up a GFCI breaker to a 3 conductor circuit because it monitors current between the neutral and line which are tied together in the case of 3 wire plugs? I need the 4 wire plug so I can separate the neutral from the line and have a true ground. Right?


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Click to expand...

From another thread but here is PJ's explaination of going from 3 wire HHN to 4 wire HHN+E via a spa panel / GFCI breaker
P-J said:
Couple of options: Get this for $49.00
HomeDepot GE 50A spa panel

And wire it like one or the other of these images show:

power-panel-5.jpg



power-panel-6.jpg
Click to expand...
 
mattd2 said:
From another thread but here is PJ's explaination of going from 3 wire HHN to 4 wire HHN+E via a spa panel / GFCI breaker
Click to expand...


Thanks for that. I dig pictures and diagrams. All I'm used to working on is DC at work. My AC theory is weak.


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Islandboy85 said:
....the range and dryer have three pronged outlets. Because of this I can't use them to run power to a spa disconnect with GFCI because the neutral has power on it. I would need another wire for ground, disconnect the neutral from the hot, and install 4 pronged outlet. Did I get that all straight?
Click to expand...
No.

The neutral has no "power" or voltage on it. It is at 0volts but can carry current.
Neutral is not connected to hot.

What you have is a Hot,Hot,Neutral, HHN, 3wire 240v receptacle. Neutral is connected to ground within the main panel and both are at 0volts and that is why it can be strapped to the chassis of an appliance as a ground. When a 240V appliance is plugged in, the neutral only carries current when an internal 120v module within the dryer, like a timer, exists. And therein lies one of the hazards; that if the neutral was somehow interrupted, or a high resistance was created, between the receptacle and the main panel, that 120V based current could find a path to ground through a person touching the "grounded" chassis.

Islandboy85 said:
.....So, there is no way to ever hook up a GFCI breaker to a 3 conductor circuit because it monitors current between the neutral and line which are tied together in the case of 3 wire plugs? I need the 4 wire plug so I can separate the neutral from the line and have a true ground. Right?
Click to expand...
Wrong. Neutral and line(hot) are not connected together.

What you're not supposed to do is replace the 3-prong receptacle with a 4-prong receptacle. However, you CAN create an appliance cord that includes a spa-panel/GFCI breaker that essentially converts the 3-prong receptacle to a 4-prong receptacle based on the previous post containing P-J's diagrams. You would wire according to the bottom one. This would mitigate the above hazard and provide you with a safe, usable, 120/240vac source.
 
raouliii said:
No.



The neutral has no "power" or voltage on it. It is at 0volts but can carry current.

Neutral is not connected to hot.



What you have is a Hot,Hot,Neutral, HHN, 3wire 240v receptacle. Neutral is connected to ground within the main panel and both are at 0volts and that is why it can be strapped to the chassis of an appliance as a ground. When a 240V appliance is plugged in, the neutral only carries current when an internal 120v module within the dryer, like a timer, exists. And therein lies one of the hazards; that if the neutral was somehow interrupted, or a high resistance was created, between the receptacle and the main panel, that 120V based current could find a path to ground through a person touching the "grounded" chassis.



Wrong. Neutral and line(hot) are not connected together.



What you're not supposed to do is replace the 3-prong receptacle with a 4-prong receptacle. However, you CAN create an appliance cord that includes a spa-panel/GFCI breaker that essentially converts the 3-prong receptacle to a 4-prong receptacle based on the previous post containing P-J's diagrams. You would wire according to the bottom one. This would mitigate the above hazard and provide you with a safe, usable, 120/240vac source.
Click to expand...
Ok, so since the neutral is tied to ground in the main box how can you have a real neutral for 120/240 after the spa disconnect?





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raouliii said:
No.



The neutral has no "power" or voltage on it. It is at 0volts but can carry current.

Neutral is not connected to hot.



What you have is a Hot,Hot,Neutral, HHN, 3wire 240v receptacle. Neutral is connected to ground within the main panel and both are at 0volts and that is why it can be strapped to the chassis of an appliance as a ground. When a 240V appliance is plugged in, the neutral only carries current when an internal 120v module within the dryer, like a timer, exists. And therein lies one of the hazards; that if the neutral was somehow interrupted, or a high resistance was created, between the receptacle and the main panel, that 120V based current could find a path to ground through a person touching the "grounded" chassis.



Wrong. Neutral and line(hot) are not connected together.



What you're not supposed to do is replace the 3-prong receptacle with a 4-prong receptacle. However, you CAN create an appliance cord that includes a spa-panel/GFCI breaker that essentially converts the 3-prong receptacle to a 4-prong receptacle based on the previous post containing P-J's diagrams. You would wire according to the bottom one. This would mitigate the above hazard and provide you with a safe, usable, 120/240vac source.
Click to expand...
Ok, so since the neutral is tied to ground in the main box how can you have a real neutral for 120/240 after the spa disconnect?





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Islandboy85 said:
Ok, so since the neutral is tied to ground in the main box how can you have a real neutral for 120/240 after the spa disconnect?
Click to expand...
240 is delivered to your house from a center tapped transformer. The center tap is grounded and is your neutral (reference) for the 240. From end to end is 240V. Either end to the center tap (neutral) is 120. The ground wire is (in theory) separate from that three wire system. You should see three wires coming into your house. Two hot and a neutral. The power company doesn't run a ground to your home.

|<-----------------240------------------->|
(L1)WWWWW(N)WWWWW(L2)
|<------120------>|<-------120----->|

Ground is not from the transformer. It is an independent system. Yes, both neutral and ground go to earth in the end but for safety purposes they are two different systems.
 
Hermit said:
240 is delivered to your house from a center tapped transformer. The center tap is grounded and is your neutral (reference) for the 240. From end to end is 240V. Either end to the center tap (neutral) is 120. The ground wire is (in theory) separate from that three wire system. You should see three wires coming into your house. Two hot and a neutral. The power company doesn't run a ground to your home.

|<-----------------240------------------->|
(L1)WWWWW(N)WWWWW(L2)
|<------120------>|<-------120----->|

Ground is not from the transformer. It is an independent system. Yes, both neutral and ground go to earth in the end but for safety purposes they are two different systems.
Click to expand...
Ok, finally got it. Thanks for taking the time to explain it until I got it.





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The big problem I see with the second picture in #178 is that someone plugging something into a 120 V outlet in a system connected to this panel is duped into thinking that it is properly grounded and it isn't. The ground wire on any outlet downstream of the box is connected to the neutral. The neutral carries a-symetric load current (from a 120 V pump for example) and, if its impedance and the a-symetric load are appreciable the neutral voltage and thus the voltage of anything connected to the 'pseudo ground' (such as the frame of a pump and the kettle) will be at non zero potential relative to earth. In most cases (I believe we are in an apartment here) the length of the neutral should be fairly short (in fact one often finds the panel located in or near the same space as the laundry equipment) and the a-symetric loads should be small (this is why the exception is allowed for dryers and ranges) so you should not have a large potential differnce.

The best thing to do, of course, is pull a new four wire cable from the panel and hook things up properly. Probably second best would be to get the ground from an adjacent 120V outlet. This would put the panel and anything plugged into it at true earth potential. I doubt this satisfies code (but there are cases where a separate ground can be brought in - you'd have to research the code) but it at least seems safer that tying the frames of things to the neutral.
 
Islandboy85 said:
Ok, so since the neutral is tied to ground in the main box how can you have a real neutral for 120/240 after the spa disconnect? .....
Click to expand...
All neutrals in a 120/240 main panel are tied to a neutral bus bar, which is tied to the ground bus bar.

In the configuration depicted in the second P-J diagram, the 4-wire neutral and ground are connected together. The hazard associated with using the same conducter as a current carrying conducter (neutral) and a non-current carrying, safety, conducter (ground) is the issue. The GFCI mitigates this hazard by monitoring the currents on both hots and the neutral. Essentially, if ANY of the current is unaccounted for, it is assumed to be a ground fault and it trips. As ajdelange indicates, it can be described as a pseudo-ground.

The big question is whether it's a safe configuration. Imo, it is. But then again, I use propane.;)
 
ajdelange said:
It is probably 99.999% safe. Is 5 nines enough?
Click to expand...
Over 30 years in appliance repair and I only remember seeing one dropped neutral. Then there was the case where the 'electrician' hooked the neutral and ground together in the receptacle. I get a call because every time the woman opened the fridge door it blew a fuse. Well, turns out he hooked hot and ground together. Every time she opened the door it moved enough to hit the cold air return under the fridge. Old house in Cleveland. Since the fridge's exterior was hot it shorted to ground.
 
If this has already been mentioned then sorry but feel it's improtant.

In a single phase system, a lot of the circuits that are pulled from opposite hot legs will share a neutral. This means that the circuit you are working on could be dead but you can still have current flowing back to the panel through your neutral. To verify this you would need an ampmeter to check the current flow. A NEUTRAL WITH CURRENT THROUGH IT CAN AND WILL KNOCK THE CRAP OUT OF YOU! Just a heads up that because the hot is dead you can still get bit
 
creekrat said:
If this has already been mentioned then sorry but feel it's improtant.



In a single phase system, a lot of the circuits that are pulled from opposite hot legs will share a neutral. This means that the circuit you are working on could be dead but you can still have current flowing back to the panel through your neutral. To verify this you would need an ampmeter to check the current flow. A NEUTRAL WITH CURRENT THROUGH IT CAN AND WILL KNOCK THE CRAP OUT OF YOU! Just a heads up that because the hot is dead you can still get bit
Click to expand...


I am assuming another option is why some designs I've seen have a contactor either before or after their SSR and pump relays. It seems like most of them are also wired to E-stop kill switches as well.


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This is a gross exaggeration. If the asymetric load is, as might typically be the case here, a fractional horsepower pump motor the load (1/20 hp) would be about 50 watts and the current half an ampere. If the neutral run were 100 ft to a panel using 14 gauge wire the impedance would be 0.25 &#937; and the voltage, relative to ground, on the neutral (1/2)(1/4) = 1/8 volt. That isn't going to knock the crap out of anyone even if he is standing in a puddle of water. Clearly if it would the NEC would not have permitted the grandfathering of this connection scheme for clothes dryers and ranges (where the asymetric load is lights, timers etc.).

It is, of course, best that the neutral be allowed to go to whatever voltage it needs to while still having a true earth available for the frame of equipment - i.e. a complete 4 wire hookup.
 
Having checked hundreds of times I can tell you that GE dryers run at about 3 amps difference on the two legs. Some electric ranges run about half power to the broil element for browning. Just to put some numbers to the imbalance.
 
Hermit said:
Having checked hundreds of times I can tell you that GE dryers run at about 3 amps difference on the two legs.
Click to expand...

30 Amp circuit, 10 gauge wire at 0.1 &#937;/100' with 3 amp imbalance implies 0.3 Volt on the neutral for a 100 foot run to the panel.

Hermit said:
Some electric ranges run about half power to the broil element for browning. Just to put some numbers to the imbalance.
Click to expand...

30 amp circuit, 10 gauge wire at 0.1 &#937;/100' with 15 amp imbalance implies 1.5 Volts on the neutral.
 
Could we do a wiring primer? I.E. the basics of how to wire a panel.

There are hundreds of questions a week on "Can I get a wiring diagram for X?" when all people need to know is how to redirect energy simply.

I would be willing to write and/or assist.
 
rodduley said:
Kind of like "Wiring for Dummies" (like me)? I am one that could probably benefit.
Click to expand...

Wiring isn't too bad once you have a good feel for what is going on!

The only trick to wiring is making sure that you have adequate protection for your wire, and safety for yourself.
 

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