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Old 07-30-2011, 10:47 AM   #15
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I wasn't trying to "cause" a problem for the CG owners, but PREVENT a problem for the M/H owners... Isn't that who this site is about??
That is exactly what this site is about and why I post this situation. We should be aware of these situations so we can take whatever measures necessary to protect ourselves, which involves taking voltage readings at the pedestal so we know the type and condition of the electrical system before we plug into it.

As stated previously, unless you have 240 volt appliances or systems you will not be effected and even 240 volt systems that use resistive heating elements will only experience efficiency problems. The only real problem may exists with those all electric coaches or high end coaches and only if they use 240 volt motors.

As another poster has mentioned, there are parks that have upgraded their electric service by simply tapping off the existing 30 amp live conductor to supply a second live conductor to the coach and can be verified by a 0 volt reading line to line.
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Old 07-31-2011, 08:58 AM   #16
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It all just brings up an issue that has bothered me for years. I am an industrial electrician and have worked on everything from electronic boards to 13.8 Kv substations but have never understood why we don't have more closely regulated voltage standards?? 110, 115, and 120 are all common "names" for household electricity. Then you have 208, 220, 230, or 240 and in the mills you'll hear 440, 460 or 480. Seems it really should be one number for each level and a tolerance set where it should be regulated at. THEN you have single phase, two phase and three phase power or in some campgrounds two lines of the same phase called 50 amp that is actually 100 amp service?? I do understand that some of this is just what transformer is used, but why is there no more closely regulated standard?? I've spent most of my life in this field but just don't get this aspect of it... Not meaning to hijack here...
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Old 08-01-2011, 12:02 AM   #17
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Without going into a lot of detail a 120/208 volt service is not a short cut. This is the voltage that is used in most commercial installations including schools, hospitals, restaurants, large stores, etc. There are advantages to using a 120/208 volt 3 phase system as opposed to a 120/240 volt 3 phase system, the main one being that the amperage can be balanced on all three lines of the 208 volt system. On a 240 volt 3 phase system one line will have a reading of approximately 200 volts between hot and neutral, therefore that line would be unusable in an RV and all the load would only be on the other two lines.
480 volts 3 phase is an industrial/commercial voltage, they are not taking the cheap way out but are doing it the proper way.
I don't know how this works with the RV surge suppressors but I suspect, as was mentioned, that they read the line(s) to neutral. I also suspect that most loads in an RV are 120 volts. If there is a 240 volt heater on 208 volts the heat output will be decreased by approximately 25%.

I hope my reply answers some questions, I meant to keep it short but when I get going.......sorry.
Thanks for the explanation. We stayed at an RV park in Douglas, WY last year that had this configuration. The owner was proudly explaining how reliable it was, and expensive, at check-in. When we parked in our site, I checked the 50A recepacle with my VOM_ and it was dead. You should have seen the expression on his face when I told him, he was mortified. He gave us a free night (different site of course) for our trouble.
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Old 08-01-2011, 12:45 PM   #18
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I just heard back from Progressive Industries concerning whether their Surge Protector checks for phase to phase voltages. It seems they presently do not check for this condition but are working on a software upgrade to check for a true 50 amp service. A true 50 amp service is two live legs each measuring 120 volts to neutral and 240 volts between each live leg. They are not sure if a software change is possible but they are looking into it and will do it if they can.


I also confirmed that the 220 volt test published in their literature is to check for a 220 volt phase to ground condition on 30 amp services.
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Old 08-10-2011, 01:51 AM   #19
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I'm sure a lot of you will jump all over me for this, but i'm goona throw it out there anyway

As Nuge pointed out, there are alot of different voltages out there, and it is confusing at the best of times (here in Canada, a lot of our industrial facilities and even some commercial have 600/347V feeds) For those who want to know the voltage relationships, take your phase to phase (line to line) voltage and divide by the square root of three or 1.732 to get the line to ground voltage.

The important thing to note is that these voltages all fall into a 'range'. Your RV is rated at 240V, but will not suffer from a slight undervoltage. If it does, I would take it back, since there is no way to guarentee you will always have 240V. They will typically rate equipment at the top end of the acceptable voltage 'range' (An exception to this that I see alot is 600V motors, the nameplates always state 575V, but they run perfectly for years at 600V) As long as the line to line voltage is between 208V and 240V, you shouldn't experience anything more than a slight inefficiency in some systems like hot water heaters. (I believe, this was mentioned by the OP)

As a last note, even if a CG measures 240V at the transformer, line losses due to distances can greatly reduce this voltage, never mind if the wiring is old or even undersized. And then there is total load on the system... i'll stop now.

Ok, let me have it!
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Old 08-10-2011, 02:04 AM   #20
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I believe that may be appropriate in situations where all loads are 120 or specifically designed for 3-phase. Residential systems (which RVs count as), are designed for 240v split phases (aka 120/240), not 3 phase, and can be damaged by that installation. Sounds like someone did a major screw up on this one.

joe
What the heck, i'll throw in on this one too, for those that are interested. Everything A/C starts out as 3 phase, including residential. For simplicity sake, a 3 phase 480V system means that you will get 480V between any two of the three phases, and 277V from any one of the three phases to ground. The transformer that steps it down to 120/240V can be either three phase, or single phase. Your house, or your RV connects to two of the three available phases and the neutral.

I hope this all makes a semblance of sense to anyone who bothers to read it, it's kind of late here... cheers!
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Old 08-11-2011, 06:52 AM   #21
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haha, the pasrt that makes little sense is that 220v single phase residential power is actually 2 phases!!!

We run into this a lot at work, including in my own office. Some of the equipment we sell/service is 220 volt single phase stuff. It wants 208-240 between the hot legs, and is happy in that range. BUT, the darn things have a Power supply inside that only connects to 1 phase. It creates the 5, 12, and 24 volt DC power for various controls in the system.

Many industrial properties, including my own office, have 3 phase power, and many if not most have a "High Leg" that measures 180 volts to neutral. We have to be very careful, as do the electricians wiring the offices spaces in these buildings. 3 phase motors on heavy equipment love this stuff. Plug a computer, or even a 110 volt electric light into the "high leg" and watch the show!

My breaker box in my office is a "use 2, skip one" all the way down. The only 3 phase device I own is the battery charger for the forklift.

If, as was said, the 208 volt system actually has 110-120 between each of the 3 phases and neutral, that would by much preferable.
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Old 08-11-2011, 07:52 AM   #22
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3ph 120/208v is a wye transformer (Usually a single transformer with three windings on a common core) hook-up and each phase is 120v to the grounded conductor(nuetral) and 208v to the other phase conductors. 3ph 120/240v is a delta transformer (usually three single winding transformers) hookup and each phase-to-phase voltage is 240v. The 120v comes from a grounded conductor that is center-tapped to one of the windings and is ONLY between the grounded conductor and the two phase conductors common to that winding. The other phase conductor to the grounded conductor varies with the loads on the individual windings and is often in the 195v range. The delta hook-up is rarely seen today other than in industrial usage where it is usually 480v without the grounded "nuetral" conductor.

240v(aka 220v) single phase is a single winding, center tapped transformer. 240v across the winding and 120 from either end to the center tap.

2ph 240v is an archaic 5 wire hook-up of 4 windings with 4 "hot" conductors and a grounded "nuetral". In my 53 years in the electrical field I have never seen a 2 phase system.
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Old 08-11-2011, 08:24 AM   #23
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I worked for a Electric Utility for 45 years. If a customer applies for service on a residential or commercial rate the standard voltage @ 3 phase is 480Y/277V or 208Y/120V. If you are a residential customer and wanting a single phase service the standard is 120/240 volts. back in the early days (1920's-1950's) the single phase residential service voltage was 110/220 and the 3 phase was 440 delta connected. Another point of fact (as I remember it) electric motor voltage ratings are 115V, 230V and 460V. The are all supposed to have a + or - %10 voltage tolerance (NEMA standards-National Electric Manufacturers Association) above and below the rating levels. In effect a 230V motor will work on a 208V system...however on a hot day when the voltage get supressed due to a large demand, the voltage can dip below the 208 volt level and the motor will over heat due to its attempt to supply the rated HP/torque (The current will rise). If the protective devices are properly sized the motor will just trip off line, if not...the motor will release some or all of its built in smoke .

In my travels with the Utility I came upon the situation many times where the customer installed 240V air conditioning and never thought about their system voltage being 208V until the motors released thier built in smoke. Of course...they blamed the Utility for giving them low voltage.. With the Utility I worked for, they published the voltage levels that they were resposible for. The base voltage is 120V, the high is 126 volts with a low of 114 volts. Outside of the high and low limits the Utility is legally responsible for damage to the customers equipment.....that said, proving that the Utility is responsible is another story.
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Old 08-11-2011, 11:06 AM   #24
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It all just brings up an issue that has bothered me for years. I am an industrial electrician and have worked on everything from electronic boards to 13.8 Kv substations but have never understood why we don't have more closely regulated voltage standards?? 110, 115, and 120 are all common "names" for household electricity. Then you have 208, 220, 230, or 240 and in the mills you'll hear 440, 460 or 480. Seems it really should be one number for each level and a tolerance set where it should be regulated at. THEN you have single phase, two phase and three phase power or in some campgrounds two lines of the same phase called 50 amp that is actually 100 amp service?? I do understand that some of this is just what transformer is used, but why is there no more closely regulated standard?? I've spent most of my life in this field but just don't get this aspect of it... Not meaning to hijack here...
You're an industrial electrician and you have to ask?
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Old 08-11-2011, 11:34 AM   #25
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The standard 50A RV service is essentially two independent 120v services sharing a common neutral. Each one operates independently of the other and couldn't care less if the other is 120 degrees out of phase with the other. This is why CGs can use 120/208 services. The only time a 120/208v becomes a problem is when a manufacturer or owner installs 240v appliances. As long as the 208 is at 208 or more, one can get away with it but let the voltage drop any, then there could be problems. Resistive loads, such as ranges, etc. will be alright although output will be reduced. Anything with a motor could be affected, however. Some appliances that use a motor use only the 120v and will be fine as long as the voltage drop isn't too much. Those that use 220v for the motor will suffer a somewhat shorter life at 208v (some motors are dual rated for 208v or 240v but don't count on it) but when the voltage drops below that, motor life will be dramatically reduced (as in fast failure).

In a nutshell, if you have no 240v appliances, everything, including surge arrestors and EMS units will work just fine on a 120/208v service. In fact, many RVs have are dual rated for 120/240v services. If you have 240v appliances, then you will have to determine if the appliance is capable of running on the 208v or move to a CG that has 120/240v services.
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Old 08-11-2011, 08:24 PM   #26
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You're an industrial electrician and you have to ask?
Yes I did!! When a motor burns up I replaced it with the same frame number and HP, voltage and amps. When a transformer released it's "blue smoke", I tried to put a little bigger one in but wired it the same as the one I took out. I've been taught to work safely on high powered RF circuits and 13.8 KV substation switch gear and 250 VDC overhead cranes. I'm a technician, a repair guy NOT an engineer!! I can also fix TVs and computers and most other household appliances, but I can't DESIGN them. I am now an RV technician in training...
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Old 08-12-2011, 10:37 AM   #27
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Just a point here.My 2011 5th wheel is rated for input of 208/120 or 240/120.
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Old 08-12-2011, 11:09 AM   #28
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Just a point here.My 2011 5th wheel is rated for input of 208/120 or 240/120.
That's very interesting. What do you have that requires 208 or 240 volts and do you have to do anything so you can use one or the other.

I've been trying to research the new all electric RV's to see what voltage requirements they have but the specifics are hard to find. I did find a reference to air conditioning motors being 240 volts which on the 208 volt system would not work or would be damaged.
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