Used my "Line switcher adapter" today

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SargeW

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While RVing 2 years ago in the New York area we stayed at Liberty Harbor in New Jersey. Convenient to NYC, but a horrible little jammed in park. A parking lot with hook ups really, and over priced to boot. We were there in the summer and the everyone's AC's were cranked up. We weren't there 15 minutes when I discovered that our PI Surge Guard was taking us off line due to low voltage on line 1. We wound up running a generator the first day just to be able to keep the AC on. 

A volt meter showed that line 1 was running about 100 volts, but line 2 was about 118 volts.  At that time I  decided to build a short 18" adapter with 50 amp male and female ends on it. While wiring it, I switched the black wire and the red wire from one end to the other.

The idea was to change the park pedestal's hot lines from 1 to 2, and 2 to 1.  I reasoned that if I could run off of line 2 that was much higher voltage from not having as many rigs all pulling from the same line, that maybe I  could still be hooked to shore power.  But I didn't get a chance to test it after I built it. 

Until today. We pulled into a KOA in Desert Hot Springs, just outside of Joshua Tree National Park. There were lots of rigs here, and it was about 85 degrees when we pulled in. I plugged in while setting up, and when Diane turned on the AC, it made it about 5 seconds before shutting down.  I checked the PI and it was showing line one at 102 volts, and when my neighbor's AC started,  my line one voltage dropped to 90 volts. All the while line 2 was showing 119 -124 volts. 

It also seems that some parks will wire their 30 amp pedestal's to draw off of line 1 as well. My pedestal only has a 50 amp breaker and plug.

I plugged the "switcher adapter" into the pedestal and verified that line 1 was now showing 120 volts, while line 2 hovered around 111 volts. When the PI put power through to the rig, we were able to turn on the front AC, which runs on line 1. Diane was also able to start the washer, which runs on our line 2. The washer didn't pull near the amps that the AC units do. 

I bought the necessary plugs on Amazon for under $40 and picked up the wire cheap at a hardware store, only "18 long.  So far, it looks like it was a good investment.   
 
What an interesting little tool to have in the toolbox. Thanks for sharing Marty
 
Yeah... very interesting idea Marty. I've often wondered if I should build such a switch for the same reasons. Thanks for sharing that.

Kev
 
Great deduction from observation, and a genius way to fix it. Thanks for the great tip! :))
 
I'm going with "brilliant" also Marty. Whenever someone creates a fix that I don't understand for a problem I don't understand I place it in that category!
 
Good job, Marty! I have a similar "adapter" I made by accident. A few years ago I found a damaged 50 amp extension cord that someone left by a park dumpster. I decided to cut it back and make a 10' extension cord for those times I didn't need the whole 25' extension. After I wired it and metered the ends, I noticed I had reversed L1 and L2 since it was a 50/50 shot. Normally it makes no difference when both legs have good voltage. But in situations like Marty described, it does help, and I've used it for that purpose on a couple of occasions now. Back in our 30 amp RV days, I also had a pair of 50/30 adapters, one that used L1 and the other L2.
 
A few related thoughts: 

1) If you use the "switcher" but the low voltage doesn't switch legs, or if it moves between legs at different times, then the problem is likely to be a poor quality neutral rather than excess loading on one leg. The switcher can't fix that, plus a bad neutral is potentially dangerous.

2) It's not unusual to have shared power in older parks that have been half-ass upgraded to provide some 50A sites. The presence of a 50A outlet doesn't necessarily mean you can actually draw 50A on each leg.

3) The 30A outlet on a pedestal that also provides 50A will always be powered from one or the other of the 50A legs. And if that 50A source is shared (daisy-chained) with other sites, there may be multiple rigs sharing it.  Even if the other sites also have 50A rigs, the load is probably dis-proportionally on L1 because most rigs have imbalanced loads on the two legs.

4) Even well-designed, professionally wired systems can come up short. Standard practice is to plan for 80% normal load, e.g. five 50A sites sharing one 200A source. If they all try to get the full 50A on L1, either a breaker will trip on the source power panel (not the pedestal breaker) or voltage will fall due to a poor connection somewhere on the loop.
 
Marty, nice fix.  When I first started reading I understood right away at the 1st paragraph that you were switching legs, but the engineer in me immediately went into 'complicated mode', imagining a hardwired switch in your coach somewhere for the same purpose, or even an auto relay switch to do the same function.  Reading on....I love your approach, simple and cheap.  KISS principal wins!! 

So how did that feel when you saved the day?

Gary RV_Wizard said:
Probably more than most people wanted to know, though! Sometimes the professor in me cannot be suppressed and I just have to lecture!  ;D

Gary, what is/was your profession, were you a professor?
 
Brad,
While I have given some professional training classes, I was never employed as a professor.  Professionally I was a computer systems software engineer,  a system designer/architect, and a product development manager for IBM.  One of my strong points was the ability to explain the ever-changing technology advances to the executives at both IBM and its customers, in terms they could understand.  8)
 
ah, I figured it was a technical background of some sort!  I'm a mechanical engineer by schooling....  I always enjoy learning and you do a great job!
 
Gary RV_Wizard said:
A few related thoughts: 

1) If you use the "switcher" but the low voltage doesn't switch legs, or if it moves between legs at different times, then the problem is likely to be a poor quality neutral rather than excess loading on one leg. The switcher can't fix that, plus a bad neutral is potentially dangerous.

2) It's not unusual to have shared power in older parks that have been half-ass upgraded to provide some 50A sites. The presence of a 50A outlet doesn't necessarily mean you can actually draw 50A on each leg.

3) The 30A outlet on a pedestal that also provides 50A will always be powered from one or the other of the 50A legs. And if that 50A source is shared (daisy-chained) with other sites, there may be multiple rigs sharing it.  Even if the other sites also have 50A rigs, the load is probably dis-proportionally on L1 because most rigs have imbalanced loads on the two legs.

4) Even well-designed, professionally wired systems can come up short. Standard practice is to plan for 80% normal load, e.g. five 50A sites sharing one 200A source. If they all try to get the full 50A on L1, either a breaker will trip on the source power panel (not the pedestal breaker) or voltage will fall due to a poor connection somewhere on the loop.

Thanks Gary, I depend on you to keep me out of trouble!  I too am always impressed with the depth of Gary's knowledge and his willingness to share it.  Gary was one of the guys I ran this idea past a few years ago, and he provided the insight then. 

blw2 said:
Marty, nice fix.  When I first started reading I understood right away at the 1st paragraph that you were switching legs, but the engineer in me immediately went into 'complicated mode', imagining a hardwired switch in your coach somewhere for the same purpose, or even an auto relay switch to do the same function.  Reading on....I love your approach, simple and cheap.  KISS principal wins!! 

So how did that feel when you saved the day?

Gary, what is/was your profession, were you a professor?

I got a big ol' hug from the wife Brad! And that always makes it worth it!
 
Well done, Marty. I'm definitely going to make one of these up even we only use 30A so I can choose either leg when a 50A outlet is available and there are voltage level issues.

Thanks for the great idea!
 
 
Whenever we were working on job sites the power was usually wired from sketchy Temp. power poles.... and it was not uncommon to find faulty/ damaged neutrals or horribly imbalanced 110 legs. 

Sometimes we would just find a good 110 leg measured to ground,  then we would pound a ground rod into the ground,  connect a wire to it and use it as the neutral.

(just gotta watch out for the wild leg of 3 phase service ;D)
 
There is one other main issue about this post. I didn't mention it at first, but the real issue is that you really should have a surge guard that protects your coach against low voltage in RV parks.  Low voltage is much  more common in RV parks than spikes, especially in the summer months  when a parks electrical grid is pushed to the max. 

A low voltage condition may not be noticed right away, but the damage inflicted on your 120 volt electrical motors is cumulative. One day your AC or refer just quits for seemingly no good reason.  A really expensive lesson to be sure. 

TonyDtorch said:
 
Whenever we were working on job sites the power was usually wired from sketchy Temp. power poles.... and it was not uncommon to find faulty/ damaged neutrals or horribly imbalanced 110 legs. 

Sometimes we would just find a good 110 leg measured to ground,  then we would pound a ground rod into the ground,  connect a wire to it and use it as the neutral.

(just gotta watch out for the wild leg of 3 phase service ;D)

You are definitely braver than I Tony! I worked around a lot of temp power poles when I was a concrete guy in my earlier years. Some of the poles were a bit scary to plug into, fortunately we were usually only running a worm drive Skill saw. They could withstand the occasional  240 volt burst of electricity.......
 
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