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Old 07-26-2009, 05:26 AM   #1
elwood
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Before hooking up 50 amp service?

Hey Folks, I am going out next weekend for the first time with our new Monty and this is also the first time I have ever used 50 amp service. Is there anything I should know before plugging in? Do I need anything special to check the power from the campground prior to plugging in? I am a mechanic and not an electrician so any help would be appreciated. Elwood
 
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Old 07-26-2009, 06:11 AM   #2
richfaa
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We have a PT 50 surge protector and let that check the power at the pole BEFORE allowing power to the camper. It would be a good idea to invest in a "good" protective device. At any rate turn the power at the power pole off, plug in the camper then turn it on. Look for anything unusual like burn or scorch marks around the plug. I assume you do not have a volt meter to check the volts on legs of the 50 amp service. That is so a good investment. Good protection is not cheap.

http://www.progressiveindustries.net/ems_pt50c.htm
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Old 07-26-2009, 09:52 AM   #3
NCFischers
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Jerry,
A good multimeter and a little instruction on it's use and you'll be able to check campground power before you plug in. Do you have any surge protection on your rig? If not, that would be a smart first mod. It might be a bit late to do anything about it before next weekend but I'd look into it pretty soon.
Jim
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Old 07-26-2009, 10:00 AM   #4
KTManiac
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Jim,

Speaking of using a Multi-meter to check the pedestal, could you give us a little tutorial on how to check a 30amp and 50amp receptacle with one? Which holes to put the probes in, and what the proper readings we should be getting for each, ...and perhaps, things to look out for so I don't get curly, smoking hair while doing so!

Would be much appreciated!

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Old 07-26-2009, 11:41 AM   #5
BB_TX
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Here is a web site for 50 amp service and another for 30 amp service.
These show the pins on each connector and describe what should be connected to each.
The 50 amp has two hot legs. Each of those should read approx 115-120 VAC relative to neutral. And they should read (approx) 230-240 VAC relative to each other.
The 30 amp has only one hot leg and should read approx 115-120 VAC relative to neutral.
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Old 07-26-2009, 12:11 PM   #6
NCFischers
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These guide lines are to help you understand the testing of a power pedestal. If you have any problems or concerns making these tests please contact me or a professional electrician. Your safety is most important.

Testing the pedestal is pretty easy and foolproof. I hope that I can explain this so it's understood. First, take a piece of paper and draw two separate circles. These will look like your 30 and 50 amp pedestal outlets. The 30 amp will have 3 slots that are at 2 o’clock (hot)/slanted 10 o’clock (neutral) /slanted and 6 o'clock (ground)/round hole.
The 50 amp will have four slots with three blades at 9 o'clock (hot), 12 o'clock (neutral), 3 o'clock (hot) and a round hole at 6 o'clock (ground ).

Basic meter usage and Safety:
The Multi-meter has many functions. We are only going to use the AC (Alternating Current) function. Because the highest reading should be under 250 Volts AC I recommend setting the AC number above 300 for elimination of any errors. Remember DO NOT TOUCH the metal contacts when taking reading because it will BITE you. Always keep your fingers on the non-metalic portions of the leads.

First the 30 amp pedestal.
Set the Multi-meter selector to the AC voltage setting with the number higher than 300 volts AC (some meters will set themselves automatically/some meters require DC or AC selection). Take the two test leads from your meter which are color coded black and red. Put one lead in the 10 o'clock slot and one in the 2 o'clock slot of the outlet, it makes no difference which lead (red or black) is inserted into either slot. The meter should read about 110 to 126 volts. Now take the 10 o'clock lead and insert it in the 6 o'clock slot leaving the 2 o’clock lead where it is. The reading should again read between 110 to 126 volts. If it is, you have good power.


Now the 50 amp. First step of test:
Set the Multi-meter selector to the AC voltage setting with the number higher than 300 volts AC (some meters will set themselves automatically/some require DC or AC selection). Take the two test leads from your meter which are color coded black and red. Put one lead in the 12 o'clock slot and one in the 9 o'clock slot of the outlet, it makes no difference which lead (red or black) is inserted into either slot. The meter should read about 110 to 126 volts. Now take the 9 o'clock lead and insert it in the 3 o'clock slot leaving the 12 o’clock lead where it is. The reading should again read between 110 to 126 volts. This has tested the hot legs with the neutral.

Second step of test:
Put one lead in the 6 o'clock slot and one in the 9 o'clock slot of the outlet. The meter should read about 110 to 126 volts. Now take the 9 o'clock lead and insert it in the 3 o'clock slot leaving the 6 o’clock lead where it is. The reading should again read between 110 to 126 volts. This has tested the hot legs with the ground.

Third step of test:
Put one lead in the 9 o’clock slot and one lead in the 3 o’clock slot. The meter should read about 228 to 242 volts AC. This is a final test, but does not indicate your trailer is wired for 220 volts AC.

Fourth step of test:
Put one lead in the 12 oclock slot and one lead in the 6 oclock slot. You should get no voltage reading.

This test will only tell you if you have good power at the pedestal. Some sort of surge protection is still highly recommended. I hope this is clear enough. If not, please feel free to let me know and I'll try to clarify.

When you buy a meter, it doesn't have to be expensive but the metal tips on the leads should be the longest ones you can find. Sometimes, the 30 and 50 amp outlet contacts are set back in the plastic and are a little hard to make contact with. You might have to wiggle the leads a bit to make contact. If the readings you get are a couple of volts higher or lower it's not a big deal.


Jim
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Old 07-26-2009, 12:19 PM   #7
elwood
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You Folks are the best. This is some really good info for us non-electrical types. I will take you advice and invest in a surge protector asap. Thanks, Elwood
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Old 07-26-2009, 02:07 PM   #8
dsprik
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Awesome, Jim! Thanks a bunch.
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Old 07-26-2009, 02:14 PM   #9
NCFischers
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Hey guys,
Check my edit. I made a correction on the 30 amp diagram.
Jim
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Old 07-26-2009, 02:28 PM   #10
dsprik
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Got it! Thanks again, Jim. I saw the edit when I went to print this off...
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Old 07-26-2009, 03:12 PM   #11
Waynem
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All the answers above are correct, but one has to remember that in an electrical circuit, things can change, and change fast. I also have a PT-50C, and on more than one occasions it has, what I think, saved me. Once, it shut it self off because the frequency went to high. At least that is the indicator I got. It has also shut down because of low voltage. Both of these conditions happened after I had been plugged in for awhile. I'm glad it wasn't a hot day, but I do have an on-board generator, and I had one in the 3400RL.

This time of year there is a high demand for electricity to power air conditioners. Depending on the wiring of the CG, this can cause the voltage to drop (think brown out) to a limit that can cause problems in your equipment. So, not only should you measure the power (as the PT-50C does) but also monitor it for conditions that are not favorable to your RV.

That is why I have the PT-50C.

You will find many on here that do not have protection and have never had a problem. I just think of it as a one time insurance purchase.
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Old 07-27-2009, 08:57 AM   #12
sreigle
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I use an inexpensive (less than $5) tester to check power at the pole before I plug in the rig. It checks for ground faults, reversed polarity, etc. I bought it at Walmart in the electrical section. It has a 110v 3-prong plug that I just use with adapters to plug into 30 or 50 amp receptacles, whichever we are going to use. Twice it has detected ground faults and we moved to a different site. The tester is yellow and has three lights and a diagram showing what each light means. It does not replace a surge protecter. It is only for testing the power before plugging in the rig.
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Old 07-27-2009, 09:27 AM   #13
NCFischers
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Steve,
That tester will work on 120 volt outlets but how does it test a 50 amp 140 outlet? If it is only designed to test 120 volt circuits, it is only testing one hot leg of a 240 volt circuit.
Jim
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Old 07-27-2009, 11:49 AM   #14
Tom S.
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Quote:
quote:Originally posted by NCFischers

Steve,
That tester will work on 120 volt outlets but how does it test a 50 amp 140 outlet? If it is only designed to test 120 volt circuits, it is only testing one hot leg of a 240 volt circuit.
Jim
It doesn't, it can only check 110. A meter can test both sides of 220 connection (one at a time, of course!) and give the voltage readout. A meter is a good thing to have when you travel as it can help you diagnose all kinds of power problems - both 12DC and 110/220AC. I'm a little hesitant to recommend one of those $10 'made in China' specials at Harbour Freight though. We are, after all, talking about serious voltage/amperage.
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Old 07-27-2009, 11:53 AM   #15
NCFischers
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I agree about the Harbor Freight "Chinese" meters. Get one from Lowes, Home Depot, Sears or someplace else. They will be a lot more reliable and you will want reliability. It's cheap insurance.
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Old 07-27-2009, 02:31 PM   #16
sreigle
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Quote:
quote:Originally posted by NCFischers

Steve,
That tester will work on 120 volt outlets but how does it test a 50 amp 140 outlet? If it is only designed to test 120 volt circuits, it is only testing one hot leg of a 240 volt circuit.
Jim
Well, darn, Jim. Now you went and made me think about it. You are correct. I'm ok on 30 amp but on 50 amp with an adapter to the 3 prong 110v configuration it's only bringing through one leg.

Can you or anyone with more electrical knowledge than me (which means darn near everyone on this forum) tell me if a ground fault might show up on only one leg and not the other? Or am I at least adequatelly testing for that situation? Or is it going to cost me more money for a tester than can handle both legs of a 50 amp supply? Thanks.
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Old 07-27-2009, 03:28 PM   #17
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Steve - That tester is still a good test. Although it only tests one hot leg, it does show that the polarity on that leg is correct, i.e. hot pin is hot and neutral pin is neutral. And then if you use a meter on both legs at the 50 amp connector, and both legs show 120 VAC to the neutral pin, then the other leg must also be the correct polarity.
And if you show no ground fault, then you are probably OK there also. A ground fault indication will typically be on the neutral line. A ground fault on a hot line will almost surely trip the breaker or prevent it from being reset.
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Old 07-28-2009, 02:31 AM   #18
sreigle
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OK, that makes me feel better. Polarity and ground fault are the reasons I use that tester. Actually, I have the tester plugged into one of those super duper Camping World voltage/amperage testers a good friend gave me. That's still only going to check one leg of 50amp for voltage. That, in turn, is plugged into the adapters for 30 and 50 amp. The CW tester I use also to determine amperage draw of our various appliances, like fans, electric heaters, toaster, coffee pot, etc., so I know about what they draw. However, I lost my notes so need to do it again someday.

I also have a VOM but don't normally use it to test the park power. I use that CW unit instead. I also have a voltage meter on an outlet in the rig where I can see it from my chair.
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Old 08-10-2009, 07:32 AM   #19
garyka
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After all that testing I always turn the breakers off at the pedestal before I plug in my shore power plug,then flip the breakers on after the plugs are in.
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Old 08-10-2009, 09:25 AM   #20
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Thanks Jim,
This whole topic kinda makes you wonder why RV parks don't test each site before they allow you on the grid. Steve
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