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Old 07-30-2014, 06:22 PM   #15
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Originally Posted by Dr4Film View Post
For those RVer's that own a Portable EMS unit from either Progressive Industries (model EMS PT-50C) or from TRC (model 34750), purchasing another tester is a waste of money.

However, for those RVer's who have hardwired EMS units mounted inside your RV, then having a portable Power/Pedestal Tester is a good time saver. It will tell you in less than a minute whether the power is acceptable at your assigned site or whether you have to go back to the office and ask for another site.

Whether you build it yourself or have one built which I have done for people it's totally up to you. The Power Pal is an OK device, fairly expensive @ $169 BUT its biggest downfall is that it doesn't check for a "Fake 50 AMP" pedestal.

In my book not worth the money.

Here are a few photos of the one that I use.

Dr4Film ----- Richard
What is a 'fake 50amp' pedestal?
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Old 07-30-2014, 07:43 PM   #16
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Vince,

A pedestal that is wired correctly for 50 amp service will have two Hot legs, one Neutral leg and one Ground leg. The HOT legs will be out of phase from each other.

A Fake 50 amp pedestal will most likely be found at an older campground or RV Park. Essentially, when they did their "upgrade" they took shortcuts and simply wired another hot leg from the one already there over to the other hot leg. Therefore they are from the same phase and will only provide 120 VAC and not 240 VAC.

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Old 07-30-2014, 08:41 PM   #17
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Fake Pedestal--new term???? Since nothing on most coaches actually requires 220/240 [like elect stoves or resid A/C, I am not sure why in or out of phase matters? Curious -- does having both legs off the same 120 phase cause a problem? For spreading amp load, its nice if each leg of a 50 amp plug is a separate 50 amp circuit [for 100 amps total], but not phased--what am I missing?
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Old 07-30-2014, 10:24 PM   #18
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Old Scout,

Here is a simple explanation of Single Phase, Split Phase and Three Phase Electrical Supply.

Explanation of 120v single phase, 240v Split Phase, and 208v 3-phase - The Samurai Appliance Repair Forums

Two excerpts from the article.

120V: First off, the standard household voltage in North America is 120V AC, 60Hz. Most appliances are designed for this. There can be some variations in the voltage depending on the load and condition of the network. The step-down transformer has its primary winding wired between two of the three transmission wires.

240V or split phase: For small residential buildings, the usual method is to rig up a 240V stepdown transformer (instead of 120V) in which the secondary winding is split into two 120V windings (hence the name "split phase"). The center tap is then grounded and fed to the house as if it was the neutral wire of the old 120V system, and each end is wired as a separate 120V live wire. Their waveforms have a half-cycle offset, or 180 degrees, when measured against the neutral wire. The normal 120V designed machinery does not care which live wire you use for them as long as you connect them between a live and neutral wire. Appliances in the home can be distributed on either live wire to maintain balanced loading, and when heating requires high power, the concerned appliance can be connected to both live wires to operate the heating element, providing 240V for it.


There are many other sources on the Internet that explain the differences between Single Phase 120 VAC and Split Phase 240 VAC. Google is your "Friend".

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Old 07-30-2014, 10:43 PM   #19
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Interesting but for most coaches, all applications are 120v only. Perhaps some luxury coaches or those with special hi-voltage equip, but the avearge coach-- I dont think so. Unlike a kitchen range or perhaps central heat or A/C in a residential home; there is no time in a motor coach where both legs are connected at the same time to produce 208/220/240 volts. Its important to have 2 separate 50 amp circuits [total of 100 amps], one for each leg, but phasing shouldnt be an issue....
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Old 07-31-2014, 02:22 AM   #20
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Quote:
Originally Posted by Dr4Film View Post
For those RVer's that own a Portable EMS unit from either Progressive Industries (model EMS PT-50C) or from TRC (model 34750), purchasing another tester is a waste of money.

However, for those RVer's who have hardwired EMS units mounted inside your RV, then having a portable Power/Pedestal Tester is a good time saver. It will tell you in less than a minute whether the power is acceptable at your assigned site or whether you have to go back to the office and ask for another site.

Whether you build it yourself or have one built which I have done for people it's totally up to you. The Power Pal is an OK device, fairly expensive @ $169 BUT its biggest downfall is that it doesn't check for a "Fake 50 AMP" pedestal.

In my book not worth the money.

Here are a few photos of the one that I use.

Dr4Film ----- Richard
Richard,
Given the questionable pedestals we encountered on our last trip I really like your idea for a separate "tool" to check the power before connecting the coach to the pedestal. And I particularly like the design illustrated in your pictures. (I am fairly handy with electricity and think I could make one of these.)

Is there any chance you can share the diagram (or explanation) of how you wire your "tester" so that it can show true values for power at the post? (I have already located the Polarity Checker you use.) I am missing how you wire your tester so it would identify a "false" 50-amp post.

Thanks,
Bob
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Old 07-31-2014, 06:21 AM   #21
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I keep my multimeter in a compartment right over the driver seat (cables connected) all ready to go. It take seconds to check all legs of the socket I am go into to plug into. Am I missing something, if you already own a meter does the tester tell you something that the meter doesn't?
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Old 07-31-2014, 07:32 AM   #22
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Phasing on multi-leg circuits will come into play on the current returned on the neutral. If phased properly, and both legs are at max of 50 amps, the current returned on the neutral should be close to 0. If both are the same phase, the current returned could be close to 100 amps.
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Old 07-31-2014, 08:38 AM   #23
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Quote:
Originally Posted by MandG-Fun View Post

I keep my multimeter in a compartment right over the driver seat (cables connected) all ready to go. It take seconds to check all legs of the socket I am go into to plug into. Am I missing something, if you already own a meter does the tester tell you something that the meter doesn't?
Glenn,

No, do not worry, you are not missing anything. If you have and use a good multi-meter that will accomplish the same task.


Quote:
Originally Posted by Bob&AnnaMari View Post

Richard,
Given the questionable pedestals we encountered on our last trip I really like your idea for a separate "tool" to check the power before connecting the coach to the pedestal. And I particularly like the design illustrated in your pictures. (I am fairly handy with electricity and think I could make one of these.)

Is there any chance you can share the diagram (or explanation) of how you wire your "tester" so that it can show true values for power at the post? (I have already located the Polarity Checker you use.) I am missing how you wire your tester so it would identify a "false" 50-amp post.

Thanks,
Bob
Bob,

The basic wiring is found at THIS web site. I substituted a 3-way switch for one duplex allowing to switch between Leg #1 & #2.

If you are adept in electricity & electrical connections, you can figure it out easily.

If you would like one built for you, please PM me.


Quote:
Originally Posted by 4x4dually View Post

Phasing on multi-leg circuits will come into play on the current returned on the neutral. If phased properly, and both legs are at max of 50 amps, the current returned on the neutral should be close to 0. If both are the same phase, the current returned could be close to 100 amps.
4X4 Dually,

A good simple post and explanation of "Phase".

There are many RVer's who don't understand 50 amp RV service nor do they want to. All they want is to plug in and enjoy. Unfortunately, there are many ways to destroy hundreds if not thousands of dollars worth of electrical items inside an RV.

I always HIGHLY recommend those RVer's who are inept in regards to RV 120/240 VAC power that they read and bookmark THIS website.

Hopefully, after reviewing it they will be a little more knowledgeable about their RV's.

Thanks for posting.

Dr4Film ----- Richard
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Old 07-31-2014, 08:46 AM   #24
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I always HIGHLY recommend those RVer's who are inept in regards to RV 120/240 VAC power that they read and bookmark THIS website.
Thanks for that link. That is some good info. No telling how many times I've typed crap like that out. From now on....my buddies are getting that link and I'm not answering the phone again until they read it all.

It is sad that we even have to test the pedestals. We went to Lake Oolagah a few weeks ago. I plugged an electric skillet into the auxiliary recept provided on the ped. When the A/C in the camper kicked on, the 30A main would trip in the ped, but not the single 20A breaker the skillet was plugged into. It was apparent that the 20A breaker was somehow connected to the load side of the 30A main. Apparently an unsupervised apprentice was wiring ped's that day.
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Old 07-31-2014, 08:53 AM   #25
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Cant resist--so what are the chances that an RV owner of let us say, "average ignorance," could build their own test meter? Would a "store-bought" test meter detect phasing issues and if so, how?--curious minds with otherwise limited capacity need to know....
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Old 07-31-2014, 08:58 AM   #26
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The difference between (2) 50 amp 120vac circuits (4 load carrying conductors) and a single 50 amp 240vac circuit (3 load carrying conductors) is the neutral (grounded conductor). In the 240vac 3 wire circuit the neutral carries the unbalanced current. Exanple: Line A current = 30 amp; Line B current = 12 amp; neutral current will be 18 amps.
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Old 07-31-2014, 08:59 AM   #27
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Off the shelf phase detection meters are not cost effective. I imagine a person could put a test load on each leg and use an LED to illuminate if the net current on the neutral was less than 1 VAC or what ever the upper limit would be. It wouldn't be too complicated to design one and build with some elec knowledge. I'll think about it and ask a few of the older 'experts' around here what they think. I'm sure the old farts will have some words of wisdom on why my idea wouldn't work. LOL
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Old 07-31-2014, 09:00 AM   #28
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Phasing on multi-leg circuits will come into play on the current returned on the neutral. If phased properly, and both legs are at max of 50 amps, the current returned on the neutral should be close to 0. If both are the same phase, the current returned could be close to 100 amps.

Correct. And since the neutral wire is not sized to carry that much current, bad things happen.
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