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Electrical Question About Contactor Box


WalledLakePatient
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I currently have a CAP contact0r box which isn't UL listed. I live in a trailer and am scared to death of electrical fires (and fires in general). I'm making my own box, but can't seem to get past this one point. If I have 50 amps going in to supply power for 8 lights I need a 50 amp breaker, but if one of my 15 or 20 amp outlets or the 1' of wire leading to them shorts the breaker won't throw. What are my options, I know other industries must have already figured this out.

 

Question #2: I always use the 120v wire on my ballast because it says its good up to 600V. I have 240 outlets that will hook up to this. My question is, since 240v is really just two 120v circuits could I use a high quality 120 outlet instead? I know this works short term because I've done it to see. If you say no, its not safe please have a reason or a link that I can read.

 

Thanks a lot,

 

WLP

Edited by WalledLakePatient
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The easiest solution to your first problem is to run the 50 amp circuit to a sub panel. If you want you could find a 50 amp rated contactor and use a time clock to turn the entire sub panel on and off for you lights. As long as you only plan to use the panel for lights or other devices which don't need 24 power you are ok. If not then use multiple 30 amp contactors to turn your 20 amp light circuits on and off with a time clock.

 

The rating on the power cord that is labeled 600 volt has to do with the insulation on the wire. If for example it was only rated 300 volts and you used it for 480 volts it could short out internally. Regardless of the voltage outlet you are using it would be a good idea to spend a little more for the better quality outlets. The internal construction is of much higher quality and will last much longer.

 

There are a couple reasons not to use a 120 volt outlet for 240 volts. One the rating is wrong so you risk overheating the outlet. Second is if you accidentally plug a 120 volt device in to the incorrectly wired outlet you could start a fire and it might not be immediately. Third the internal construction is different. The higher the voltage the better the insulation between conductors must be to prevent arcing. As voltage goes up it will "jump" further to short out. Remember that a neutral is also considered a current carrying conductor. I'm sure I could find other reasons if I spent more time but I would think that is enough not to incorrectly wire an outlet.

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  • 2 weeks later...

I currently have a CAP contact0r box which isn't UL listed. I live in a trailer and am scared to death of electrical fires (and fires in general). I'm making my own box, but can't seem to get past this one point. If I have 50 amps going in to supply power for 8 lights I need a 50 amp breaker, but if one of my 15 or 20 amp outlets or the 1' of wire leading to them shorts the breaker won't throw. What are my options, I know other industries must have already figured this out.

 

Question #2: I always use the 120v wire on my ballast because it says its good up to 600V. I have 240 outlets that will hook up to this. My question is, since 240v is really just two 120v circuits could I use a high quality 120 outlet instead? I know this works short term because I've done it to see. If you say no, its not safe please have a reason or a link that I can read.

 

Thanks a lot,

 

WLP

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Do not use a 120 volt receptacle for 240 volt apllication. A 120 volt (standard wall receptacle ) either 15 or 20 amp is rated at 15 or 20 amps at 120 volts. A 240 volt receptacle and circuit rated at 20 amps/240 is actually using more than 20 amps. Using the 80% method would allow for 16 amps for a 20 amp circuit.

However the 20 amp/240 circuit is capable of 16 amp on each 120 volt leg. So the total amount potential is 32 amps. The 120 volt phases are 180 degress out of phase so they cancel each other out as the power is consumed at the appliance connected. The neutral will carry no load. If you were to disconnect the neutral the 240 appliance will still work. Example is a water heater.

 

240 volt applications require 240 volt receptacles.

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That response leads one to a false understanding of how electricity works. Even in a 120 volt outlet the "neutral" conductor still carries all of the amperage that is carried by the "hot" conductor. The load on each line is the same. And the 220 volt outlets that would be used for ballast in this case has no "neutral" conductor.

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That response leads one to a false understanding of how electricity works. Even in a 120 volt outlet the "neutral" conductor still carries all of the amperage that is carried by the "hot" conductor. The load on each line is the same. And the 220 volt outlets that would be used for ballast in this case has no "neutral" conductor.

What do mean a false understanding of how electricity works? Please explain if I have missed somthing. 120volts times 16 amps = 1920 watts

240 volts times 16 amps = 3840 watts. A 240 volt circuit twice the power potential. The ballast or its fixture will have a bare coper equipment ground which goes back and connects to the neutral buss in the panel. Call it what you want ( equipment ground or neutral ).

 

My point is that in a 240 volt appliance configuration ( when no 120 volt electric is connected or used ) the neutral and bare copper equipment ground carries no load. And that the 240 volt receptacle and circuit have the ability to provide twice the power as a 120volt circuit and receptacle. Meaning that the 240 volt receptacle is built to take more power and would be better served for this purpose than using a standard wall receptacle. All 240 volt appliances have an equipment ground. The allows for an alternative path back to the panel in case of a short from equipment failure.

Yes a 120 volt circuit the neutral carries power, but not in a 240 volt configuration. So yes the ballast assembly will have a third wire ( equipment ground ) going back to the panel. Yes it is easy to use both words interchangeably to describe the the neutral or equipment ground. Which is commomly done in the electrical vocation.

An example is an older clothes dryer which has only three wires. Two hot and a bare copper equipment ground or neutral. The timer uses the bare copper euipment ground to carry the 120 phase for the timer. The bare copper is an equipment ground and a hot leg for the 120 volt timer, serving as both a neutral carring conductor and equipment ground. So in actual use of the appliance in this configuretion the equipment ground and the neutral are the same wire. This is why NOW the clothes dryers and ranges have both a separation of the equipment ground and neutral, and wired with four wires.

Really the equipment grounding is a moot point for this configuration as all fixtures should be grounded.

 

What is important is that 16 amps at 240 volts is not the same load as 16 amps at 120 volts. (240 volt @ 16 amps)is 3840 watts verses (120volts@ 16 amps)is 1920 watts.

So if you were to use a 20 amp 120 volt receptacle which is rated for max 2400 watts it is not recommmended or capable of the continuous load at 240 volt at 16 amps which is 3840 watts.

 

The 32 amp potential may have not been explained well in my intial answer and at first glance might cause one to ponder, A 240 volt 20 amp circuit is quite capable of suppling two - 120volt circuits at 16 amps to each leg which add up to 32 amps for a total. So in a 240 volt/16amp configuration you are using 32 amps of 120 volt power.

32 amps times 120 volts equals 3840 watts.

Edited by orion
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There is a difference in purpose between the "neutral" and the ground. The confusion comes in because we have chosen to reference the "neutral" to ground for safety. Which is a different issue all together. They are not the same and they serve two very different purposes. I have yet to meet a trained electrician who confuses the two.

 

A 240 volt 20 amp circuit is not the same as two 120 volt 20 amp circuits. This way of thinking is due to the ground reference of the "neutral". In reality all that matters is the voltage difference between the two current carrying conductors, whether they are grounded current carrying conductors, i.e. "neutral, or not. The "neutral" does not need a ground reference to operate. You claim that it is because both legs would have current on it but so would the line conductor and the "neutral" in a 120 volt circuit and it would be the same on each conductor as well. If there is 10 amps on one then there will be 10 amps on the other what phase they are at is irrelevant. It's just a misunderstanding in the way AC electricity works. Your example of a 240 volt circuit having a 32 amp potential is false, there is only 16 amps being used not 32 amps.

 

As for the reference to an electric dryer well the dryers that the original 2 wire with ground circuits were meant for used a mechanical timer that was not powered. That is why there was only a ground and no "neutral". When the manufacturers began incorporating electronics in to the machines to add more options it caused a problem and the NEC responded with a reasonable solution. Knowing that people would not replace their circuits just because the new dryers needed a neutral an exception was created. As long as the circuit was not modified and stayed in its original location the neutral and ground could be bonded at the dryer to allow the electronics to operate. But this is not the best solution so if you move that circuit or install a new circuit you must include the "neutral".

 

The NEC rule is that a 20 amp circuit can be used for up to 20 amps. That's what it's rated for. But there is an exception based on certain conditions. That would be if the load on the circuit will operate for more than three hours you must not exceed 80% of the circuit rating. This applies for any circuit. Again it's a reasonable exception to the rule of circuit ratings. If you exceed 80% of the circuit rating for more than three hours then the thermo-overload in the circuit breaker may trip due to heat. As well other electrical connections may overheat and potentially cause damage.

 

These are really common misunderstandings. I can't tell you how many times some one with a 100 amp service tried to convince me that it's really a 200 amp because you can draw 100 amps on each phase. But it's doesn't really work that way. For the purposes of this site it really doesn't matter except that by claiming a 20 amp 240 volt circuit would use 32 amps when maxed out you might confuse those who want to operate their lights at 240 volts. All that matters is watts used, that's how you are billed.

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Hi Jayt, Thanks you for your thoughts and response.

My initial response was somewhat ambiguously written and lacked some explanation, However the math and physics are correct.

Using a 120VAC circuit at 32 amps is the same power consumption as operating a 240VAC circuit at 16 amps. The wattage or power consumption is the same (3840 watts). The electric meter will read the same using either configuration.

A 240 VAC circuit is comprised of two 120VAC circuits that are 180 degrees out of phase.

When using a 16 amp 240 VAC circuit there is 16 amps on both 120VAC legs that mathmaically equals 32 amps at 120VAC. ( 3840 Watts )

 

 

What is relavant is the actuall power being consumed. In regards to the original question whether to use a standard wall receptacle in place of a 240VAC receptacle, this is why you cannot use a 20 amp 120VAC receptacle. It is not designed for (3840 watts) which is the max potential for a ( 20 amp circuit ) using 16 amps ( 80 % of 20amps ) at 240VAC .

 

.

 

In regard to the electric dryers and electric ranges that were wired with three wires. These appliances were manufactured in the past with electric operated timers and clocks that used the bare copper equipment ground/neutral as a current carring conductor. The power consumption was small and in most cases not a problem. Until a plumber came into contact with a gas pipe that had been energized due to a defective timer in an electric range. The ranges equipment ground was energized from the timer, which energized the ranges frame and thus energized the gas pipe. The plumber died from electricution from comming into contact with the gas pipe and his physical person being in a wet crawlspace.

 

This led the NFPA ( National Fire Protection Association )to investigate and make recommendations.

The NFPA writes both the National Electric Code ( NFPA-70 ) and the National Fuel Code.

This situation along with the addition of electronics caused the revision of the NEC in regards the separation of the equipment ground and neutral. It also required the gas code to required the gas pipe be bonded/connected via a bare copper wire back to the neutral/ grounding lug in the main service panel.

 

In final note. I do not believe I have confused anyone from using a 240 volt circuit. They most likely have decided , and will not use a standard 120VAC wall receptacle in place of a 240 receptacle for a 240 volt application..

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  • 3 weeks later...

Using NEMA 5-15 receptacles @ 240v:

 

NEMA 5-15 (the standard 12-v receptacles installed in your home) are listed for 125v, 15 amp use & can be connected to a 20A circuuit per NEC code. "Listed" meaning that they have been through the UL testing and are approved by every regulatory agency & juristiction in the US for use in construction.

NEMA 6-15 receptacles are rated for 250v/15A.

The contacts or blades inside the high quality NEMA 5-15 & 6-15 receptacles are .032" to .050" brass. The plastic case of both receptacles are built to exactly the same specifications if they are of the same product line of any given manufacturer. The only difference between the 5 & 6 series receptacles is the configuration of the blade assembly & plastic cover (the shape of the blade entrance). The dielectric or insulation properties of the 250V receptacle is in NO WAY superior to the same manufacturer's product line 125V receptacle.

Aside from the obvious hazard of human error (plugging a 120v device into a 240v outlet), there is electrically no danger of using the 125 volt cord and plug for your 240v ballasts. In fact it is, in at least one regard, safer to use a given cord and plug device at 240v rather than 120v -Take a 1000w ballast for example: drawing 9.2 amps at 120v or 4.6 amps @ 240v, according to the laws of power, as long as the insulation of the cord and devices are capable of the 240v (they are), the voltage drop and, therefore the heat created in the plug, receptacle & cord is one-half of the same load running at 120v -meaning that as long as the insulation is sufficient, in regard to the voltage drop, the 240v circuit is safer.

Being that the ballasts & all of the cords, etc are expected to be out of the reach of visitors to your home, there is little dange in using your 120v cord, plug & receptacle for 240v operation. I would NEVER wire your living room like this, but the only danger is that of human error.

If you do use the 5-15 @ 240v be sure to cover any unused recept's with those child-proof covers & label everything 240V to avoid any mishaps because the previous author is correct in saying that it could be hours later that some 120v device could burn up if it doesn't immediately get fried.

 

Is it a good idea to use your 120v cord & plugs @ 240v?

Unless you can be 100% assured that somebody will not come along & connect a 120v device to the circuit, NO!

 

Reasons to use the 120v connectors for 240v:

The only reason is the cost of replacing all of your ballast cords OR replacing the plugs (cord caps) on your present cords.

If you are building your own lighting controller you will find that the NEMA 6-15 duplex receptacles are not available at your local Home Depot and the price at the electrical distributor might be $20 or more (compared to $2 for high quality, spec grade NEMA 5-15 receptacles).

 

Reasons to use only the proper NEMA 6-15 connectors for 240v:

NEC code requires it; No chance of somebody plugging your new 120v, $300 vortex fan into 240v & frying it -or worse!; doing otherwise gives the greedy-gentlemen at the insurance company ANOTHER reason not to pay for damage caused by a grow-room fire (not that they will pay a dime anyway). Replacing the cord caps on your existing cords is cheap and easy (if you don't feel comfortable doing it, enlist the help of a friend who does).

 

It's a good idea to use the proper connectors -not because it's electrically dangerous not to but because some idiot might make a mistake!

*********************************************************************************

 

My customers request that I install NEMA 5-15 receptacles on their 240v lighting controllers all the time and I do it. I also be sure to use a different color receptacle and stick warning labels all over the place. Many of the commercial manufacturers offered their controllers built like this and now use the "x-plug" which is a really low grade chinese receptacle made by Zhejiang trimone electric -upon inspection of the receptacle (did I say it was low grade?), I found that it has a UL number on it! The number actually belongs to a NEMA 5-15 receptacle made by the same company. The x-plug receptacle will accept NEMA 5-15, 5-20, 6-15 & 6-20 plugs. There are also the multi-receptacles made by Wonpro which will accept all of those as well as the plugs from almost every country in the world with the exception of the big Nigerian plug.

 

I would personally feel better using a high quality, American made, spec-grade or better NEMA 5-15 receptacle for my HID lighting than a crappy chinese UL listed NEMA 6-15 plug.

 

 

The NEC doesn't allow 240v lighting to be used inside of a dwelling unit. NEC and most local codes don't allow HID lighting to be used inside of a dwelling either.

 

In my opinion the shape of the plug is much less important than things like: proper grounding; having the sense not to stand in water while toughing ballasts & other electric devices; keeping your ballasts off the wet floor; installing smoke/fire alarms with new batteries; a plan to get your family out of the house if a fire should arize -using common sense.

 

The FLAME DEFENDER

I hate advertising for National Garden Wholesale but everybody who chooses to grow in their home should invest in at least one Flame Defender automatic fire extinguisher per grow room. They are available everywhere and are REALLY CHEAP! So cheap in fact that, after being entirely sold on them I contacted the manufacturer and found that I can buy them for less from my local grow store at retail than I can buy factory direct in pallet quantity. This tells me that NGW must be selling them for cost or making a very low profit on them (I must give credit when due).

 

I'm finished writing my book!

DX

Edited by dxhydro.com
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