RV 30A and 50A Shorepower Explained.

when it comes to 30 and 50 amp Shore power for RVs there are a few misconceptions and hopefully this video will provide some clarity on this topic two common questions are of ears often have are what do I tell the electrician if I want to have RV service wired at my home and is 50 amps 120 or 240 volts ac we will start with an explanation of 50 amp service as that seems to be the most confusing and everything else will make sense once we have that concept understood so what does 50 amp service actually called unfortunately nobody can even decide that if you're a historian you may call it an Edison system or if you're an electrical engineer you may refer to it a split phase or an electrician may call it three poles four wire and even the National Electrical Code section 551 which deals with RVs and RV parks refers to 50 amp service as both 3 wire and 3 pole for wire given this variation the alerted person will recognize all these terms as equivalent and interchangeable the next difficulty our viewers have is 50 amp is that 120 volts ac or is it 240 volts ac and even RV manufacturers manuals such as this one calls a 50 amp 120 volts well in reality it is actually 50 amp 240 volts however we can wire the electrical panel in such a way as to obtain 120 volts ac service and that is where the confusion is and to demonstrate that we're going to disconnect our power cable and we're going to measure voltage if we go from leg to leg in there we go 243 volts so this is a 240 volt system from leg 1 to leg to so how do we get a 120 volts from this system if we go from neutral to one leg we measure 121 volts and then if we go from neutral to the other leg we also measure hundred twenty-one volts [Applause] and if we measure the two legs on our panel we're measuring 240 volts from leg 1 to Lake 2 so we have 240 volts on this panel and then of course if we go from the neutral to one leg we have 120 volts and neutral to the other leg we also have 120 volts so you see we have 240 volts coming in here to the main breakers but then we have two legs that go down to these breakers and these breakers are all using half of the 240 volts and it's kind of easier to explain this on a piece of paper because I think you'll find a couple things that are interesting so let's visualize a generic 120 volt AC circuit n with a 60 watt bulb a half an amp should flow through the light bulb but then what if we change the voltage on this circuit to 240 volts ac well we know that would not work too much current would flow through the light bulb and damage it but here's an idea what if we put those light bulbs in series then you'd have two light bulbs that would drop 120 volts across each one everything would work fine and this is the very principle behind the 120 240 50 amp service if you can understand this simple concept you will understand how everything works when we tie it all together unfortunately this is not a very practical circuit because say we put a switch on one light bulb we turn the switch on and off both light bulbs are going to turn on and off so we cannot switch the bulbs on and off independently the second issue is if we have unbalanced loads in this example we have a hundred twenty watt bulb and a 60 watt bulb and as you can see here the voltage on the 60 watt bulb is going to be 160 volts the voltage on 120 watt bulb is going to be 80 volts so we have a voltage imbalance so for this scheme to work the loads have to be exactly the same which is not practical fortunately there is a solution that will work but to understand that we have to know how we get 240 volts to begin with typically the every park or your residence is fed by a much higher voltage than 240 volts depending on your location this could be anywhere from 480 volts to over 12,000 volts it goes through a step-down transformer that's located on a power pole or in the vault adjacent to the property and it's dropped down to 240 volts the transformer secondary contains a center tab the center tab essentially divides the voltage in half we still have 240 volts across the entire secondary but now we have a hundred 20 volts on each side of the center tab and the center tap technique is commonly called split phase so now we have our series circuit but with a center tap reference in the center so how does that help us with two different sized light bulbs well as you may know all remaining current means that the current goes one direction for half the cycle then the other direction for the other half so in the first half cycle 1 amp flows out of the top of the transformer and through the 120 watt light bulb supplying the 1 amp that it needs however the lower light bulb being a 60 watt bulb only needs half nap so half an amp is returned to the transformer via the center tap and the other half amp continues through the lower light bulb back through the bottom part of the transformer and that way it gives us the 1 amp for the 120 watt bulb and the half amp for the 60 watt bulb and in the second half cycle it reverses half an amp goes out of the transformer through the 60 watt bulb another half amp is through the center tap and both of them combined go through the 120 watt bulb which provides one amp and then one amp is returned to the transformer and if we put a switch on one of the light bulbs the same thing happens if the switch is opened for the one ant bulb then one day if amp goes from the transformer through the lower bulb and back to the center tab so the center tap always carries the differential current that is the current that is different between one leg and the other so this is how we can get a 240 volt circuit to supply a hundred twenty volts to two loads and yet they're independent and it should be noted that if both loads were identical we wouldn't need the center tab so the center tap is only there for loads that are not the same and from a historical perspective a hundred years ago Thomas Edison was having trouble with trying to get the loads balanced on his system he came up with this solution and that's why it's also called an Edison system and when we put it into our IV terms we simply put a 14 - 50 R receptacle on the power pole that's why sometimes this is called a three wire system and if we want it to label the wires the two ends of the transformer are known as l1 and l2 or leg one and leg - the centre tap is called the neutral further their neutral is usually grounded to ground so this is how the term three pole four wire came about and in fact other than the connector this is pretty much identical to the system that you have in your home we could also connect ATT 30 our 30 amp connector to each leg that would give us two independent 30 amp circuits at 120 volts ac this would typically power two RVs with 30 amp service neither RV would ever have 240 volts in their electrical panel and another variation maybe a 20 amp receptacle in place of one of the 30 amp receptacles and it will provide 120 volt service as well and then finally it's not uncommon to have a pedestal that has all three that is 50 amp service 30 amp service and 20 amp service and of course the 50 amp service will provide 120 or 240 volts while the 30 and 20 amp service will provide 120 volts only please understand these are just conceptual drawings they don't include everything that you need such as breakers surge suppressors or any other thing that is in the panel so do not use these schematics to do any wiring in your and if you go to my website at RV - project comm and I'll provide the link in the upper right hand corner here I do show all the various kinds of specialized connectors that you may find in your RV so what have we learned so far the regulatory authority for RV campground wiring is the NFPA publication 70 commonly known as the National Electrical Code and while the NFPA is not a government agency federal and state governments as well as virtually all local governments have adopted these as regulations so they are law further the RV industry Association has also adopted these standards for their minimum requirements for manufacturers to follow so when in doubt consult the National Electrical Code section 551 which covers RV parks and RV wiring so the answer to the first question what do I ask for when contracting with an electrician to provide either 30 or 50 amp service at my house for my RV well if you haven't figured it out yet simply ask them to provide 30 amp or 50 amp service in accordance with the National Electrical Code section 551 any competent electricians should know what that contains and if you get the deer-in-the-headlight look find another electrician you should also know that 30 amp service is 120 volts and 50 amp service is 240 volts at 50 amps in fact maybe the high-end RVs such as the multi-million dollar motor homes have appliances such as water heaters or dryers that do require 240 volts however most of us that have 50 amp service in our RVs have electrical panels that are wired that only give us two legs of 120 volt service even though it is actually fed by 240 volts so in reality we have a hundred amp service because we can get 50 amps from each leg and finally 50 services known as split-phase Edison three wire or three pole four wire depending on your background the goal of this video is to provide some history background and familiarize ation of how RV electrical systems are wired this is not a guide for instructions for the do-it-yourselfer to work on his electrical equipment please refer any electrical wiring issues to a qualified electrician

Channel: RVProject

Views: 65,506

Keywords: rv, recreational, vehicle, motorhome, camper, camping, fifth, wheel, 5th, travel, trailer, 5er, project, campsite, campground, dyi

Id: v8oB4QE1r3o

Length: 12min 25sec (745 seconds)

Published: Thu Feb 13 2020