Tab extension cord & step down from 30Amp to House questions

ScottG

I think we are getting a little afield of @northwestinatab's original question, but it's a good discussion regardless.

A 120/240V 50A receptacle found in a campground would be no different that that used on an electric range in your home. Since 120/240V 50A and 120V 30A services are standard in RV parks, those adapters (below) are pretty easy to come by.

However, you would be far less likely to find a 120/240V 30A receptacle (typical dryer receptacle) in a campground, so a commercial 120/240V 30A to 120V 30A adapter might be harder to find.

Further confounding this issue is that older 120/240V receptacles had holes for only three prongs, making them strikingly similar to a modern 120V receptacle. This is where things go south fast if you are trying to wire up your own adapter without understanding how electricity is distributed in a typical residential (or campground) system.

Residential wiring isn't particularly difficult, but you had better know exactly what you are doing--and why--before attempting it.

JEB

Sharon_is_SAM said:

And, sorry, I don't agree that you should abstain from a surge protector - even at your home.  I simply can't think of any reason to not use one.

I agree.  I have a dedicated 30A circuit in my garage that I had an electrician install a few years ago and I always use a surge protector.  It has saved my butt on more than one occasion when energy use in the neighborhood was high and voltages dropped.

ScottG

kaylevine1 said:

when I tried to run the air conditioner off the 15 amp regular socket in my garage it would kick in n run awhile but then would get too hot n trip the circuit breaker-I didn't feel it was safe so had a regular 30 amp rv outlet put in at the back of my driveway on the side of the house.

...

@kaylevine1, what breaker was tripping, the one in the T@B or the one in your house?

And what exactly got "too hot?"

JEB

ScottG said:

I think we are getting a little afield of @northwestinatab's original question, but it's a good discussion regardless.

A 120/240V 50A receptacle found in a campground would be no different that that used on an electric range in your home. Since 120/240V 50A and 120V 30A services are standard in RV parks, those adapters (below) are pretty easy to come by.

However, you would be far less likely to find a 120/240V 30A receptacle (typical dryer receptacle) in a campground, so a commercial 120/240V 30A to 120V 30A adapter might be harder to find.

Further confounding this issue is that older 120/240V receptacles had holes for only three prongs, making them strikingly similar to a modern 120V receptacle. This is where things go south fast if you are trying to wire up your own adapter without understanding how electricity is distributed in a typical residential (or campground) system.

Residential wiring isn't particularly difficult, but you had better know exactly what you are doing--and why--before attempting it.

This oughta work with newer dryer receptables:

ScottG

JEB said:

This oughta work with newer dryer receptables:
...

Yep, I think that would do the trick!

northwestinatab

Hi again everyone,

I am a "newbie" of course, so learning a lot, but glad I can turn to you guys.  Good to know I can use my 15-30 amp adapter to plug the Tab into my sister's garage with the regular plug and 20 amp circuit.  I'll definitely be using the surge protector -- always.

On the household dryer-type outlet in friend's garage:  
a) I still don't understand why I can't just use a 220-110 voltage adapter, but it sounds like it is because you think that must also be a 50amp circuit and so I need not only to control voltage, but also amps?
b) since the voltage adapter is not an option, i need a dogbone that adapts 50amps to 30amps and because of the way it is plugged in, only accesses 110volts so i need no further adapters?  I think you can see I'm still kind of confused, and installing a special outlet for the tab is not an option there...

I would appreciate any further information you can give me on this last point.  Thanks for your help!
nwinatab

JEB

northwestinatab said:

Hi again everyone,

I am a "newbie" of course, so learning a lot, but glad I can turn to you guys.  Good to know I can use my 15-30 amp adapter to plug the Tab into my sister's garage with the regular plug and 20 amp circuit.  I'll definitely be using the surge protector -- always.

On the household dryer-type outlet in friend's garage:  
a) I still don't understand why I can't just use a 220-110 voltage adapter, but it sounds like it is because you think that must also be a 50amp circuit and so I need not only to control voltage, but also amps?
b) since the voltage adapter is not an option, i need a dogbone that adapts 50amps to 30amps and because of the way it is plugged in, only accesses 110volts so i need no further adapters?  I think you can see I'm still kind of confused, and installing a special outlet for the tab is not an option there...

I would appreciate any further information you can give me on this last point.  Thanks for your help!
nwinatab

No.  It's not about the amps.  If you're planning to plug into a dryer receptacle, you don't need to worry about amps.  The house circuit is 30 amps, and your trailer is 30 amps.  So, you're good.  And it will do you no harm to plug into a circuit that provides more amps than you need.  In fact, that's a good thing because you won't pop the house breaker.

What you do need to worry about is voltage.   Totally different animal.  You tap into too many volts and bad things will happen.  Unless you love the smell of burning insulation and trips to the dealer. The dryer receptacle is 220-240 volts.  Fortunately, the adapter I posted above should take care of the voltage issue.  The reason--highly simplified--is that the receptacle has two hot legs but the adapter taps into only one of them, effectively cutting the volts in half to a safe 120 volts but still giving you all the amperage you'll need.  You would need a voltage adapter/step down transformer only if you had no way to tap into just one of the hot legs of the receptacle.  And you can't just use any old 220-110 voltage adapter like you were going to England and you wanted to run your electric razor.  To provide enough amperage, the transformer would have to be rated at 3000-4000 watts minimum and would weigh about 50 pounds.  Assuming you could use it at all with a dryer outlet.

ScottG

+1 what JEB said.

@northwestinatab, let's back up a bit...

Are you wanting to plug your T@B into something other than a regular household outlet?

If so, can you provide a photo of the outlet you want to use and describe what it is currently used for?

There are a dizzying array of electrical outlets, each specific to the voltage, amperage, and plug type they are designed to accommodate. You are asking good questions, but they suggest you don't have much knowledge of electrical wiring or basic electrical principles. I'm not saying that to insult you, but because I don't want you to destroy your T@B, burn your house down, or electrocute yourself. Before offering any specific advice, I need a better handle on exactly what it is you want to do! 

Sharon_is_SAM

@northwestinatab, it would help if you had a picture of the outlet with the 220 voltage.

northwestinatab

Hi everyone,

Thanks again for the help!  I don't have a picture of the outlet -- it is at a friend's house -- and my plan unless I'm certain about what I'm doing with the dryer outlet, is to skip it and to use the regular household outlets they also have in the same place.  I just want to be sure that when they start talking to me about what they do, I don't get sucked into trying something that isn't safe for me to do.  So this is helpful.  I'm going to probably wait until I get out there and get a picture of the outlet itself to be sure the dogbone adapter above (thanks JEB!), will work.  If so, I'll get one and try that (checking the voltage with the surge protector before I plug in).  I am definitely not familiar with electricity, but I do understand better now why the 220-110 voltage adapter won't work, and also why the dogbone will.  If I'm still uncertain, I'm going to plug my 15-30 adapter, heavy duty 10 gauge cord, surge protector and finally Tab into the regular (not the dryer!) household outlets that I know are 110 volts.  Right?  You guys are very patient! THANK YOU.  

Sharon_is_SAM

You got it!  Now, one last question...did your friends call it a dryer outlet?

JEB

If you decide to proceed with a hookup, at a bare minimum look at the socket very carefully.  If it has FOUR slots and looks like the pattern in my dogbone post above labeled "14-30P," that's a newer style dryer receptacle and you will probably be ok with a dogbone.  If it looks like anything else--particularly if it has only THREE slots--I'd avoid using it entirely.  Since it's in a garage, it's most likely a receptacle for a welder or an older style dryer.  Both carry all 240 volts on one hot leg, if I recall correctly.  You don't want to mess with those.  Stick with the standard 110v residential receptacle.

ScottG

To add...

@northwestinatab, you've referred to both a "50 amp" hookup and a "dryer outlet"--these are not the same and will require different adapters. If it is in fact an outlet for a welder, that will be different again. Further confounding matters (as JEB suggested) is that older 120/240V outlets may have only three slots. An outlet with three slots can be 120V or 240V or 120/240V, so you can see how this gets confusing quickly.

Fortunately, most plugs are unique to their application, so if you use a commercially made adapter and everything fits with out forcing, you'll probably be okay, assuming the house is wired correctly. I still suggest reporting back here with a photo of the outlet in question and a report of any markings on the face of the outlet.

I'll also add that depending on what you want to run while you T@B is parked, you may not need 20 (or even 15) amp. In that case, there's no advantage to plugging up to anything larger that a standard receptacle.

Keep the details and the questions coming!  :-)

ScottG

JEB said:

...

If it looks like anything else--particularly if it has only THREE slots--I'd avoid using it entirely.  Since it's in a garage, it's most likely a receptacle for a welder or an older style dryer.  Both carry all 240 volts on one hot leg, if I recall correctly.

...

Not quite. Any 240 volt receptacle will have two "hot" legs each carrying 120V. Each connects to one of the hot bus bars in your panel, which in turn connect to the two hot lines from the grid. Drawing off both legs simultaneously provides 240V.

The difference between the new (4-prong) and old (3-prong) 120/240V receptacles is that the new ones separate the operating ground (white wire--commonly but incorrectly called the "neutral") and the safety ground (green or bare wire). Ultimately, both of these are combined and grounded at your service entrance, but they are kept separate downstream from that.

As I implied in my previous post this is where it gets confusing when there are only three slots (regardless of the amperage)...

• A 120V receptacle will have one hot, one operating ground, and one safety ground.
• A 240V receptacle will have two hots and one safety ground.
• An older 120/240V receptacle will have two hots and one combined operating and safety ground.
  

JEB

ScottG said:

JEB said:

...

If it looks like anything else--particularly if it has only THREE slots--I'd avoid using it entirely.  Since it's in a garage, it's most likely a receptacle for a welder or an older style dryer.  Both carry all 240 volts on one hot leg, if I recall correctly.

...

Not quite. Any 240 volt receptacle will have two "hot" legs each carrying 120V. Each connects to one of the hot bus bars in your panel, which in turn connect to the two hot lines from the grid.

The difference between the new (4-prong) and old (3-prong) 120/240V receptacles is that the new ones separate the operating ground (white wire--commonly but incorrectly called the "neutral") and the safety ground (green or bare wire). Ultimately, both of these are grounded at your service entrance, but they are kept separate downstream from that.

As I implied in my previous post this is where it gets confusing when there are only three slots (regardless of the amperage)...

• A 120V receptacle will have one hot, one operating ground, and one safety ground.
• A 240V receptacle will have two hots and one safety ground.
• An older 120/240V receptacle will have two hots and one combined operating and safety ground.
  

Got it.  Then theoretically, you should be able to hook up to a welder receptacle (e.g. NEMA 6-50) if you could find an appropriate dogbone with one dead hot leg.  I haven't seen any of those that can go directly from 6-50 to TT-30R.  You'd need another intermediate adapter, which I don't like the idea of.

EDIT:  Scratch that.  I don't think this can be done because I don't see where you're going to get the "neutral"/operating ground from a 6-50.  Two hot legs and a safety ground on a 6-50, right?

ScottG

Sorry, nope. The NEMA 6-50 looks like a dedicated 240V receptacle. That means it has a safety ground but no operating ground linking back to the panel.

In order to have 120V service, one hot leg and one operating ground are required to complete the circuit.

Now, I know what you're thinking...  :-)

Since the operating ground and the safety ground ultimately come together anyway, why not just use the safety ground to complete the circuit? After all, that is what they used to do with those old three prong 120/240V outlets, right? While that would probably work electrically speaking, but I'll bet more than a nickel it would be a serious violation of the current NEC (National Electrical Code). And that is probably why you can't find an adapter for this specific application...

I'll admit the reasoning for the separation of the operating and safety grounds in modern 120V circuits is a little out of my pay grade. Even master electricians I have asked have not provided a real clear answer.

JEB

ScottG said:

Sorry, nope. The NEMA 6-50 looks like a dedicated 240V receptacle. That means it has a safety ground but no operating ground linking back to the panel.

In order to have 120V service, one hot leg and one operating ground are required to complete the circuit.

Now, I know what you're thinking...  :-)

Since the operating ground and the safety ground ultimately come together anyway, why not just use the safety ground to complete the circuit? After all, that is what they used to do with those old three prong 120/240V outlets, right? While that would probably work electrically speaking, but I'll bet more than a nickel it would be a serious violation of the current NEC (National Electrical Code). And that is probably why you can't find an adapter for this specific application...

I'll admit the reasoning for the separation of the operating and safety grounds in modern 120V circuits is a little out of my pay grade. Even master electricians I have asked have not provided a real clear answer.

I agree with you.  See my edit.  I don't think this can be done safely when I thought about it a little more.

ScottG

You got it.

A little contemplation (and a quick Google search) also revealed why the operating and safety grounds should not be connected until the service entrance. This is what is commonly referred to as a "bootleg ground" and it's done when the circuit lacks a safety ground wire back to the panel (as in those old dryer receptacles). In those cases, the safety ground from the equipment is jumpered to the operating ground at the receptacle. It works, but creates a potentially dangerous situation of energizing the safety ground, and possibly the equipment plugged into it. (Now we are getting into why calling the operating ground a "neutral" is technically incorrect.)

In the situation we are discussing, you would effectively be doing the opposite by jumping the operating ground to the safety ground. Electrically the effect is the same, but now you've compounded the issue because a bare (or green) wire is NEVER expected to be carrying current. Colors mean something in wiring, and this situation would be deceptive to someone working on the circuit at a later time.

If you absolutely wanted to use a 240V welder circuit for your camper, you probably could do it safely and within code, but it would involve rearranging (and recoding) the conductors in your panel, AND swapping the receptacle for a correct 120V version with the proper slot configuration and surface markings so as to leave no doubt as to how the circuit was wired.

Phew. Thanks for indulging me; I do like talking about wiring even more than plumbing. Hopefully we haven't completely frightened off northwestinatab at this point!  ;-)

JEB

To paraphrase a sage contributor, if an extended discussion keeps him--or anyone else--from destroying his T@B, burning his house down or electrocuting himself, it's a discussion worth having.

northwestinatab

Hello again,

I have to say again that this is all very helpful.  My friends did use the term "dryer" outlet (220volts) exactly.  It is, however in a garage that was using heavy-duty equipment for car reno, etc. and so I'm thinking all of it, based on what you guys are saying, is probably something I don't want to mess with until I'm absolutely certain. I don't know if it is an older or newer outlet, and I don't know if it was really used for a dryer or for welding equipment.  So the regular household outlets is what I'll use.  I might take a picture of the "dryer" outlet once I'm there and then see if it is safe to use with the right adapter, but that won't be until June.  For now, I'm going with the plan I outlined above and say thank you again for sharing all of this knowledge with me.  I'm so glad I bought a Tab!

klenger

Share a picture of the outlet when you can and we should be able to help.  As you can see from this discussion, without that, everything is speculation.  Running on a T@B 320 with 15-20 amp household outlet will run most everything except the Alde with both 120 VAC heating elements on, and you can avoid that by using only 1 element and/or LP.  

northwestinatab

northwestinatab

Hi everyone,

I am so glad you all responded with all the good information and that I re-read again today after finally getting a picture of the receptacle from my friends.  I am not there yet -- tomorrow -- but looked this up and it is an Eaton 50 amp power receptacle NEMA 6-50.  It is in a large garage used by someone who worked on automobiles, so as suspected, it appears to have been used for welding.  Based on everything you guys said, I need to stay away from it entirely.  So instead, while at my friends' house, I'm going to use the regular household outlet (15 amp) for the Tab 320S.

I've been at my sister's for two weeks using a 20 amp outlet and have had no electrical problems.  I run the Alde on 1 only (no 2), and when it was hot, I was running the AC with the Alde off.  I try to make sure I'm only using the Fridge, and either Alde or AC (depending on weather), and often one other electronic device (charging PC or phone or tablet) only.  As soon as things are charged -- including the computer, I unplug, and I don't have a microwave or any other electronics.  Do you think all of that should work equally well on the 15 amp?

THANK YOU!
northwestinatab

northwestinatab

sorry, it is a leviton, not an eaton...  

Sharon_is_SAM

Generally, most contemporary regular, household outlets are on a 20 amp supply circuit.  Just check the breaker box in the house to know for sure.  You’ll be fine on your regular 15 amp household outlet.

Edited -thank you @WilliamA!

davel4wa

Actually I have done this when at a relative's home and needed to have air conditioning available. They had a gas dryer so the 30A 240 circuit was available. I used an RV style 30A extension cord, cut off the male plug and replaced it with a dryer plug. Only one side of the 120/120 (240) line is used along with the neutral and ground.

davel4wa

One thing to remember in all of this, is that A/C electrical connectors come in different shapes and sizes for a reason. The primary reason is safety. By having different plug patterns you are prevented from connecting in a way that could be dangerous. That being said, as long as YOU know the purpose of a cord with mismatched connectors and understand the purpose of the cord you will be safe. Others may not have that understanding so best to keep the cord for your use only. Just sayin'.

WilliamA

This thread is starting to sound like a Clark Griswald Christmas tree light how-to. I had no idea that hooking my trailer to house power was so complicated.  

Determine maximum amperage potential. If it's more than 15 amps, then put in a 30 amp 110V outlet. If you don't know how, hire it done.  A 20 amp outlet is not the same as a 15 amp outlet. There is more to it than breaker size. The outlet is different. 
Stay away from 220 volt power. Period. 
WilliamA 

ScottG

@northwestinatab, thanks for the followup! That is a 50A, 240V receptacle. If it is wired as intended, it would NOT be suitable for plugging in your T@B. While it looks deceptively similar to a regular household outlet, a strictly 240V receptacle has two "hot" wires but no operating ground (often incorrectly called a "neutral").

Your T@B is designed to run on 120V, which requires one hot and an operating ground. There is no simple adapter that would make this receptacle work for a T@B.

If this all sounds like Greek, don't worry--just do what you are doing and stick with a regular household outlet. A 15A circuit is sufficient for the level of use you describe! 

ScottG

Sharon_is_SAM said:

Generally, most contemporary regular, household outlets are on a 20 amp supply circuit.  Just check the breaker box in the house to know for sure.  The 15 amp and 20 amp outlets are essentially interchangeable.

...

WilliamA said:

...

A 20 amp outlet is not the same as a 15 amp outlet. There is more to it than breaker size. The outlet is different. 
...

Electricity is dangerous stuff, so in the event that someone is reading this closely, let's clarify these two mostly correct statements.

Disclaimer: What I say here assumes all receptacles and devices are properly wired according to code. This may not always be the case.

There are 15A receptacles (left), 15/20A receptacles (middle), and 20A receptacles (right). The 15A version is the typical household outlet, and virtually every household appliance or device has a matching 15A plug. 15A receptacles can be (and often are) attached to a 20A circuit. In fact, code requires this in certain locations such as kitchens.

15/20A and 20A receptacles must be wired to a 20A circuit, as they are designed to accept the different plug of a device requiring 20A. Such devices are unusual in a residential setting, however.

In summary:

• Yes, the breaker will tell you the capacity of the circuit. A 15A receptacle may be able to provide 20A if on a 20A circuit.
• No, the outlets are not interchangeable. Putting an outlet that will accept a 20A plug on a 15A circuit is a no-no.
• Yes, 15A and 20A receptacles are different, but this is confounded by the NEMA 5-20R T slot version which may be found on a household circuit and is designed to accept either a 15A or 20A plug.