Electrical Primer for Brewers

[Islandboy85]

Ok, got it. Thanks for bearing with me.


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[Islandboy85]

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.

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]

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.

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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[Hermit]

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?

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.

 

[Islandboy85]

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.

Ok, finally got it. Thanks for taking the time to explain it until I got it.





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[ajdelange]

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.

 

[raouliii]

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? .....

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.

 

[Islandboy85]

I'll could sand some paint off the top of the washer and put the keg on top of it so it's grounded through the frame ground lol.



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[ajdelange]

The big question is whether it's a safe configuration. Imo, it is.

It is probably 99.999% safe. Is 5 nines enough?

But then again, I use propane.

Me too.

 

[Hermit]

It is probably 99.999% safe. Is 5 nines enough?

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.

 

[creekrat]

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

 

[Islandboy85]

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

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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[ajdelange]

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.

 

[Hermit]

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.

 

[ajdelange]

Having checked hundreds of times I can tell you that GE dryers run at about 3 amps difference on the two legs.

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.

Some electric ranges run about half power to the broil element for browning. Just to put some numbers to the imbalance.

30 amp circuit, 10 gauge wire at 0.1 &#937;/100' with 15 amp imbalance implies 1.5 Volts on the neutral.

 

[muhteeus]

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]

Kind of like "Wiring for Dummies" (like me)? I am one that could probably benefit.

 

[muhteeus]

Kind of like "Wiring for Dummies" (like me)? I am one that could probably benefit.

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.

 

[ajdelange]

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.

Nothing to it, really. That's why the NEC is only an inch thick.

 

[muhteeus]

Nothing to it, really. That's why the NEC is only an inch thick.

The sections relating to panels are very short.

 

[Hermit]

I guess I'm at a loss as to what a wiring primer would include. I guess you have to lay out the areas that you don't understand and need elaborated on. Once you know the electrical part then wiring is just the physical aspect.

 

[ajdelange]

The sections relating to panels are very short.

Then all you need to do is list the relevant paragraphs and direct the readers to them with the advice that they be sure to adhere to them. Voila! The manual for dummies. If anything goes awry you can't be sued because you advised that they follow the relevant code sections!

 

[ingchr1]

Here's a post I had in reference to codes for control panels:

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.

 

[muhteeus]

Here's a post I had in reference to codes for control panels:

Not bad ideas!

 

[muhteeus]

I guess I'm at a loss as to what a wiring primer would include. I guess you have to lay out the areas that you don't understand and need elaborated on. Once you know the electrical part then wiring is just the physical aspect.

Typical Post: Hay guys, I bought $500 of parts today. Can anyone send me a diagram of how to wire.

Something that literally just teaches someone how to quickly wire a general circuit, since the wiring seems to be the biggest issue. I'm thinking we just need a RTFM primer.

 

[Hermit]

Typical Post: Hay guys, I bought $500 of parts today. Can anyone send me a diagram of how to wire.

Something that literally just teaches someone how to quickly wire a general circuit, since the wiring seems to be the biggest issue. I'm thinking we just need a RTFM primer.

There is no one diagram though. You place your components and figure out where the wires need to go from there. If you understand the schematic then that should all fall into place. There is a certain level of stuff you need to understand before you buy $500 worth of parts. Helping someone that can't draw out their schematic is not something I personally would attempt.


Again, no one is going to buy all the same equipment and want all the same layout. I don't see a primer. Understanding the circuit IS the primer. If they skipped that, well, their bad.

 

[mattd2]

Agree, and even if you were to write a general wiring primer along the lines of what wire gauge, etc. you would need to over spec 95% of the design to cover the one when someone tries to power 5x 5.5kW elements and wonders why their panel ends up on fire.

 

[muhteeus]

I see. The idea sounded better in my head than in practical application. The existing electrical primer, along with some common sense should cover the basics.

 

[EdMerican]

Unfortunately the problem with common sense is that it is not really all that common.

 

[Aceandover]

So this says that 10awg should handle 30amps but all the 10 awg at my local stores say 20 amps, do I need to find 10 rated for 30 amp or will the 20 amp be ok
Btw I'll be just running the camco 5500w element and a pid, no pump