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Old 02-09-2016, 03:09 PM   #15
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Originally Posted by photopilot View Post
OK, here goes.

I'm not an electrician, but I did play one on a former job, so please correct me if I'm wrong.

50 amp service for an RV is based on the current carrying capacity of each conductor. Each conductor should be rated to carry 50 amps current. I don't have the chart in front of me, but I believe it is 6 gauge. A 50 amp RV plug has 4 wires- two hot, a neutral and a ground. The hot wires carry 120 volts each, 180 degrees out of phase such that if you put a meter across both, you would get 240 volts. However, everything in the RV runs on 120 volts, so they keep the two 120V wires separate, and run each to the neutral.

When you connect a 120V 15/20 or 30 amp adapter to a 50 amp plug, they actually connect the one hot lead to the two hot leads in the RV, so the electrical power is shared between the two legs in the RV. The 50 amp supply provides a LOT more power. 50 amp x 120V x 2 legs = 12,000 watts. Using a 30 amp service, you get 30 amp x 120V = 3,600 watts. (Only one hot lead in a 3-wire 30 A plug). Even less with 15 amps- 1800 watts.

Now, if I understand the OP's question, I suppose you could wire a custom junction box to two different 15 or 20 amp circuits and use a 50 amp receptacle and feed the two hot wires into the RV, giving you twice the power. Not something I would try, but theoretically it might work. It would not work with a 30 amp plug as there is only one hot lead.

I'm not sure how the load manager distributes the power once inside the RV, so I don't know how it would handle the reduced power on each leg. It would be smart to see what devices are on each leg.

If I'm all wet, let me know!

Photopilot
Agree on the 50 amp service.

Agree it will NOT work on 30 amp unless both feeds are from one leg.
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Old 02-09-2016, 03:16 PM   #16
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I guess no one posting on this thread has ever seen a cheater cord before? I have a cheater into which I can plug my 50A cord and then plug the cheater into two 30A receptacles. If the two 30A outlets are separate circuit breakers and are on the same leg of the circuit the net result is to provide ~60A of power capability (that has to be compared to the 100A that is provided by a so-called 50A RV power connection).

There's nothing particularly unusual about being able to do this. Electrically, it's no different than connecting a couple of batteries in parallel. The current is split and half goes into each leg.

Similarly, instead of plugging the two outputs of the cheater into 30A outlets you could use a 30A/15A adapter and plug them into two 15A outlets which would provide you a true 30A of power. Unfortunately, such cheaters won't work with outlets that are protected by GFCI devices and the 115V outlets on all modern RV pedestals have GFCIs. So I don't get much use out of the cheater these days, but it does come in handy every once in a while.

Here's a link to a cheater for sale: http://www.amazon.com/Cordtec-Power-.../dp/B00760FG2E
If you plus your little cheater cord into 2 legs of 120 volt 15 amp outlets you get a 240 volts short.
You can not combine 2 hot legs down to 1 wire.

Remember a 30 amp service only had 1 hot wire, it is not split like 50 amp.

30 amp to 50 amp works because 50 amp has 2 hot lines into the RV.
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Old 02-09-2016, 03:28 PM   #17
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Firefighters run the hose to a pumper truck that increases the pressure.
How would 2 or more hoses from a hydrant create more pressure from the hydrant ?

Actually as you flow more GPM, the hydrant pressure drops, due to friction loss in the underground pipes. We would routinely call the water authority to increse the pressure during large working fire scene.

Double lay or large diameter hose was used to increses GPM to the fire engine. The pump creates more pressure to send the water to the nozzle.
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Old 02-09-2016, 04:06 PM   #18
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This is how I have been doing it for years, 1st pic is my plug inside the garage and 2nd one is outside. The outside is a regular campground plug. The plug inside was made with a 50 amp stove type female receptacle which accepts my RV 50 amp plug.

As you can see I can plug into two 15 amp circuits, thus feeding 15 amps to each Leg or each side of my RV electric panel.

In my garage I am using a split plug which means a split breaker which also implies two 15s out of phase. This way each side gets 15 max, (not 30). It is up to 30 total for both.

If you plug into a receptacle that is connected to only one breaker then you get 15 amps total going in so each Leg or each side of the RV panel can still take up to 15 as long as the total from both does not exceed 15. (ie 7.5amps on each side).

And yes I know the 50 A receptacle should be boxed up for safety... Don't shoot me!
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Old 02-09-2016, 04:17 PM   #19
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Originally Posted by docj View Post
I guess no one posting on this thread has ever seen a cheater cord before? I have a cheater into which I can plug my 50A cord and then plug the cheater into two 30A receptacles. If the two 30A outlets are separate circuit breakers and are on the same leg of the circuit the net result is to provide ~60A of power capability (that has to be compared to the 100A that is provided by a so-called 50A RV power connection).

There's nothing particularly unusual about being able to do this. Electrically, it's no different than connecting a couple of batteries in parallel. The current is split and half goes into each leg.

Similarly, instead of plugging the two outputs of the cheater into 30A outlets you could use a 30A/15A adapter and plug them into two 15A outlets which would provide you a true 30A of power. Unfortunately, such cheaters won't work with outlets that are protected by GFCI devices and the 115V outlets on all modern RV pedestals have GFCIs. So I don't get much use out of the cheater these days, but it does come in handy every once in a while.

Here's a link to a cheater for sale: Robot Check
A 'cheater cord' that links two 30 amp or a 30 amp and a 15 amp outlet together for a 50 amp RV is a different idea than what the OP wants. In your cheater cord, each outlet is fed to a different leg of the 50 amp RV. If the power outlets aren't in sync phase wise, it won't be a big deal as the most that could be sent down the neutral wire would be 45 amps, less than the 50 amps it's rated for. In the two 15 amp outlets, if in phase, they would create the 30 amps wanted. If out of phase, they would create a short at the neutral connection and trip a breaker.

By the way, with Docj's cheater cord on two 30 amp circuits, if they were in phase, the neutral could be exposed to 60 amps if both legs were using all 30 amps available to them, an unlikely occurrence. It would work best if the two 30 amp outlets were 180 out of phase.
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Old 02-09-2016, 07:03 PM   #20
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Well.. One of my titles is "Certified Electroinc Technician" (Kellogg Community College, Battle Creek, MI, back in the 1970s)

The answer to the question "Why not" is: IT might.. or might not, but odds are it will not

Here is why

How many places are wired
..15 amp branch-----Outelt 1-----outlet 2----outlet 3

Now as you can easily see one 15 amp breaker feeds all 3 (NOTE RV's are wired like this too) Often #1 is a GFCI, but in this case you could plug into 1, 2 or all 3 and it would still be a 15 amp feed. Clearly you can not draw 30 amps through that single breaker.

Or you could have this.

L-1----15 amp----Outlet--(possible additional outlets)

L-2----15 amp----Outlet--(possible additional outlets)

Now if you plugged into each of those, and parallelled you would have a lovely 240 volt SHORT CIRCUIT and zero amps. Cause the breakers trip.

Finally we have this mess Both on the same leg

15 amp breaker----Outelt
15 amp breaker-----Very long wire----Outelt

Now here in theory you can draw 30 amps but what happens is the shorter wire to the top outelt has less resistance so if you are drawying say 25 amps it may well be pushign 17 of them to the other wire's 8.. Only when that happens the breaker trips, now the other breaker tries to carry the load, for about 0.10 second and then it trips.

So as you can see it does not work

What does help though is one of the devices called a Power Maximizer, Sold as a Genrator to RV adapter it is a solid plastic block (or hollow one) with a 30 amp outlet on one side and TWO 15 amp plugs on the other, Designed to plug into a standard duplex outlet. This unit can easily handle 20 amps (if the outelt is a 20 amp feed) and will have a lower overall resistance than a single 15-30 adapter.

Two places I park the 15/20 duplex is actually fed with 30 amp.. Sadly I left my maximizer at one of 'em.. Looking for a replacement.(Found it online but have not yet purchased).
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Old 02-09-2016, 09:09 PM   #21
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Very good points and some not so much...

Combining 2 15 amp circuits can be done to get 30 amps total at 120 vac or 15 amps total at 240 vac and if this is confusing do not think about trying anything.

The STANDARD outlet is rated for 15 amps with a we amp optional unit.

Many folks myself included wire as 20 amp to give better performance but the outlet is limited and with current quality maybe not 15 amp but that is another story.

The rv has a SINGLE buss inside so having 2 plugs to connect could have a live male plug when one is plugged in.

Side note...One could build an interlock with switches and or contactor/relay to only connect a cord to the rv when the cord is plugged into a live outlet.

If one is using more than one outlet on SAME circuit then they are limited to the breaker feeding it.

If one was to use two outlets with one each on seperate circuits then one could have the combined capacity of both circuits but then one would need to be certian BOTH outlets are on the SAME phase.

Secondary issue there is the circuits now being in parallel have the combined amperage which now is greater than the rating of the wiring or devices.

So yes it is possible to do what you ask it would require extensive work and hardware to allow it to be used safely without having a live plug on the unit the house or source side would be made dangerous via the connecting circuits together.

So, option 1 is to upgrade an outlet to a 20 amp outlet and be sure it is valid 20 amp all the way to the panel including the breaker and also if you have a removable shore cord make a home one by modifying a 12 X 3 extension cord by adding the rv end so you avoid using an adaptor as they are maybe rated for 15 amps on a good day.

Option 2 is best...Just install correct outlet.
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Old 02-09-2016, 09:19 PM   #22
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Originally Posted by HHIDan View Post
This is how I have been doing it for years, 1st pic is my plug inside the garage and 2nd one is outside. The outside is a regular campground plug. The plug inside was made with a 50 amp stove type female receptacle which accepts my RV 50 amp plug.

As you can see I can plug into two 15 amp circuits, thus feeding 15 amps to each Leg or each side of my RV electric panel.

In my garage I am using a split plug which means a split breaker which also implies two 15s out of phase. This way each side gets 15 max, (not 30). It is up to 30 total for both.

If you plug into a receptacle that is connected to only one breaker then you get 15 amps total going in so each Leg or each side of the RV panel can still take up to 15 as long as the total from both does not exceed 15. (ie 7.5amps on each side).

And yes I know the 50 A receptacle should be boxed up for safety... Don't shoot me!
You are stating 1/2 amps per side...?

Each leg is capable of 15 amps current flow due to the 15 amp breaker.

The current flow is 15 amps at 240 vac since both are in series and 180 out of phase.

Also 15 amps either leg at 120 vac out of balance.

The neutral carries out of balance loads meaning if one ac is on and it is on L1 and nothing else is on the current flow is L1 to AC to Neutral.

L2 has no current in this example.

Your photo is not real clear as it looks like the front most post has no wire.

Can you supply photo from directly in the rear?

Your hookup is clever...being it plugs in it is an extension cord and the inspector cannot say boo.

As long as your connection goes it sounds like you have a properly wired outlet close so these plugs go there so less chance of plugging both into same phase which could cause too much current in neutral.
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Old 02-09-2016, 09:28 PM   #23
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Two Honda eu2000i generators can be combined with a special parallel cable to produce 30 amps......seems like a special box could be built to do the same thing from two 15 amp shore power cords

😃
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Old 02-10-2016, 12:04 AM   #24
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Two Honda eu2000i generators can be combined with a special parallel cable to produce 30 amps......seems like a special box could be built to do the same thing from two 15 amp shore power cords

😃
Now we're talkin'...

My knowledge of electricity is limited, you flip the switch up and the light comes on, hence my original 30 AMP question. I just thought that in this computerized age that a combiner box could be made to combine and regulate 2 15amp cords in to 30amps. I now see that 50amp in a different animal and that's why you can do a 20amp and a 30amp to get 50.
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Old 02-10-2016, 12:28 AM   #25
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Now we're talkin'...

My knowledge of electricity is limited, you flip the switch up and the light comes on, hence my original 30 AMP question. I just thought that in this computerized age that a combiner box could be made to combine and regulate 2 15amp cords in to 30amps. I now see that 50amp in a different animal and that's why you can do a 20amp and a 30amp to get 50.
Actually 50 amp RV service is made up of two 'legs' of 50 amps, 180 out of phase. It gives a total of 100 amps of power, 12,000 watts. 30 amp only yields 3,600 watts, just a little less than 1/3 of the potential of 50 amp service. 30 amp and 20 amp together only gives 6,000 watts, or half of 50 amp RV service.
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Old 02-10-2016, 01:28 AM   #26
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FWIW I think the split phase 240 VAC is a diversion. If I understand what he wants it is 120 VAC single phase 30 A to match his plug. The problem is basic physics. As someone said, it can be done by choosing two outlets on separate breakers but the same phase. The problem is load balancing. The resistance of the two legs will set the balance of the currents into the summing junction of the plug. The only problem is a lot of messing around to find two otherwise not loaded 15 amp circuits to tap and running the cords. Draw out the circuit if it seems confusing.
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Old 02-10-2016, 04:54 AM   #27
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Wow - some OP really blew this thread beyond the question. the question of 50 amps was never asked but many of the answers are very informative. Northermark is the most accurate response especially about finding two outlets in the same area wired back to the distribution panel on separate circuits and same phase.

Yes two 15 amp = 30 amps. Think of it this way - two D size 1.5 volt batteries side by side have an output of 1.5 volt but twice the current as just one battery. Three batteries in parallel will also still be 1.5 volt but three times as much current output as one battery.

so it goes for two 15 amp outlets from two distinct breakers on the same side of the power distribution panel (in phase). No need for a computer to do it. If your wrong it will be like the 4th of July. They don't call Electricians Sparky for nothin.
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Old 02-10-2016, 06:55 AM   #28
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How come there isn't a converter that I could plug two 15A power cords into and get 30A capability out the other side? Seems like with computerization these days, some one would sell a box that I could make 30A for my motorhome at home from two 15A extension cords coming from two different outlets.

Just wondering, I know there is a reason.

F4Gary
If you have "50A coach" you can plug your 50A power cord into 2 different"out of phase", "non GFCI protected", 15A receptacles and get 30A to your coach through two 15A extension cords.

To do that you need a Camco RV PowerGrip Power Maximizer Adapter, (or a similar "RV cheater box"), and a 30A female to 15A male adapter plug: Aleko Rv30M15Fa 30A Male To 15A Female Adapter Plug - Walmart.com






However if yours is a "30A coach" it CAN'T be done because a "30A coach" uses only 1 hot wire, (NOT 2 like a "50A coach").

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