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Old 02-09-2016, 12:34 PM   #1
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Why can't 15A + 15A = 30A?

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.

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Old 02-09-2016, 12:50 PM   #2
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As long as you divide your 30 amp load into two 15 amp circuits
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Old 02-09-2016, 12:54 PM   #3
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with a meter check the two hot wires from the two outlets. If you have 220v you could combine them into a 220v 30 amp service similar to a 50amp. Not sure if its worth it.
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Old 02-09-2016, 01:11 PM   #4
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You would need to find 2, 15 amp circuits on different breakers, but on the same leg of your home panel.

If you find two different legs, I would think a shower of sparks would be coming out of the adaptor. At least until one of the breaker poped. You are creating a 240 volt short.

Do it wrong and 240 volts goes to your 30 amp 120 volt MH. That's bad !!!
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Old 02-09-2016, 01:13 PM   #5
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Originally Posted by jporietis View Post
with a meter check the two hot wires from the two outlets. If you have 220v you could combine them into a 220v 30 amp service similar to a 50amp. Not sure if its worth it.
If the OP has 30 amp service it is 120 volt only.

Not the same as 50 amp 120/240 volt service.
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Old 02-09-2016, 01:24 PM   #6
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Originally Posted by F4Gary View Post
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.

how about thinking of it this way;
2 water hoses, each has 15 psi of pressure.
run both hoses to a bucket, it fills up fast.
now connect the 2 hoses to a y adapter, you still only have 15psi of pressure. you gain nothing.
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Old 02-09-2016, 01:28 PM   #7
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how about thinking of it this way;
2 water hoses, each has 15 psi of pressure.
run both hoses to a bucket, it fills up fast.
now connect the 2 hoses to a y adapter, you still only have 15psi of pressure. you gain nothing.
Now that makes sense.
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Old 02-09-2016, 01:40 PM   #8
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how about thinking of it this way;
2 water hoses, each has 15 psi of pressure.
run both hoses to a bucket, it fills up fast.
now connect the 2 hoses to a y adapter, you still only have 15psi of pressure. you gain nothing.
Not completely true. If the Y is near the bucket, you still get 15 psi pressure but the gallons per minute will go up, just like the Amps would in 2 cords.

PSI is like volts.
GPM is like Amps.

Firefighters use parallel fire hoses to get more GPM from the same pressure hydrant. There is some loss in the Y but not near half.
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Old 02-09-2016, 02:01 PM   #9
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Alternating Current, AC, travels in sine waves. If the two outlets are from the same leg of the power panel, they would be in sync. If opposite legs of the panel, you would create a dead short. The 15 amp wiring is not sized to carry 30 amps, its illegal to wire it as proposed. I wouldn't do it.
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Old 02-09-2016, 02:02 PM   #10
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Not completely true. If the Y is near the bucket, you still get 15 psi pressure but the gallons per minute will go up, just like the Amps would in 2 cords.

PSI is like volts.
GPM is like Amps.

Firefighters use parallel fire hoses to get more GPM from the same pressure hydrant. There is some loss in the Y but not near half.
Firefighters run the hose to a pumper truck that increases the pressure.
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Old 02-09-2016, 02:12 PM   #11
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Not completely true. If the Y is near the bucket, you still get 15 psi pressure but the gallons per minute will go up, just like the Amps would in 2 cords.
There is some loss in the Y but not near half.
This is not a true analogy of what would happen with a "Y", unless the output orifice of the "Y" was twice the size of either input.
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Old 02-09-2016, 02:23 PM   #12
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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
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Old 02-09-2016, 02:45 PM   #13
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Quote:
Originally Posted by F4Gary View Post
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.

Try one of these. You will have to insure that the electrical outlets that you plug into are on different circuit breakers and you will need 2 of the adaptors from 30 amp to 110. If your coach is 30 amp you will also need an adaptor from 50 amp to 30 amp.

50 Amp 125/250V RV Female - (2) 30 Amp RV Male Plugs Y-Adapter with Powersmart LED's - Furrion F5431RY-SB - Electrical Adapters - Camping World

http://tweetys.com/rv-50-amp-cheater...FQyHaQodWn8HHg

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Old 02-09-2016, 02:50 PM   #14
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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!

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