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ranchn2 · 01-18-2014, 04:42 PM

Help, we have a new fifth wheel and have added a generator to the truck. The trailer has 50amp cord going to generator. I'm good with that but we are thinking of adding a 30amp cord (lighter weight) and I do not understand the difference of the 3 prong and 4 prong plugins. We have an adapter for the 4 prong plugin to use with the 50amp cord but do I need a 3 or 4 prong for the 30amp cord? Even though the 3 prong says L5-30 the manual says it is 20 amp. The shape of the plugin is that of the L5-30 which to me says it is 30amp. What am I missing? Any input would be helpful. Thanks PJ

jesilvas · 01-18-2014, 05:10 PM

50A means you have TWO hot lines of 50A each.
30A is ONE line of 30A.

BFlinn181 · 01-18-2014, 05:11 PM

How big is your generator?
An RV 50 amp service is actually 2 50 amp cords, 180º out of phase. The cord has 2 50 amp hot leads, 1 neutral (since power is 180º out of phase, the neutral never exceeds 50 amps) and 1 ground connection. This provides 100 amps of power to the RV 120v X 100 amps = 12,000 watts.
A 30 amp service is just that, 1 hot, 1 neutral, and 1 ground. 120 v X 30 amps = 3,600 watts

A huge difference it how much electricity can be delivered to your RV. I'd keep the 50 amp cord and use a 30 amp dogleg if that's all the generator can supply. Also the dogleg can be used when you know you don't need 50 amp service and can use a 30 amp campsite for less money.

RV Electrical Systems

smiller · 01-18-2014, 05:35 PM

In the RV world 4-conductors usually mean split-phase 240 volts (same as is supplied to your house.) The wires are ground, neutral, leg 1, and leg 2 (each leg is at 120 volts so you can reference each to neutral and have two 120 volt-circuits or you can reference the two legs to each other and have one 240-volt circuit.) A three-conductor circuit (in the RV context) means you have hot, neutral, and ground, and these will provide one 120-volt circuit (hot referenced against neutral.) The 240-volt connections at RV parks usually can supply 50 amps per leg or 12kw total. The 120-volts connections supply 30 amps or 3.6 kw.

Regarding connectors, the number on the connector only indicates the maximum amount of current the connector is capable of carrying, it has nothing to do with the amount of current available from the source (generator or whatever), which can be anything up to the maximum.

You can adapt a 120-volt generator to an RV 240-volt supply with the proper wiring, although you will be limited to the maximum amount of current available from the source (and you won't have 240-volts available, but normally that won't be a problem since most RVs do not have 240-volt appliances.)

Lastly, if none of the above makes sense to you then I'd really suggest getting someone knowledgeable to do the wiring. One mistake and you have ruined a lot of equipment at best and electrocuted yourself at worst. Not a good candidate to 'learn by doing' because the lessons can be very expensive.

NeilV · 01-18-2014, 08:12 PM

What size generator did you get for the truck? Generally you would be using a 5.5 killowatt generator and put a plug on in matching the 50 amp cord on your RV. You can get by using a 30 amp adapter however you do so with limitations afterwards such as don't run the water heater on electric while running an electric coffee maker or toaster if somone might be turning on a vacuume cleaner or hair dryer.

caissiel · 01-18-2014, 09:34 PM

Quote:

Originally Posted by NeilV

What size generator did you get for the truck? Generally you would be using a 5.5 killowatt generator and put a plug on in matching the 50 amp cord on your RV. You can get by using a 30 amp adapter however you do so with limitations afterwards such as don't run the water heater on electric while running an electric coffee maker or toaster if somone might be turning on a vacuume cleaner or hair dryer.

I have a 25 ft 30amp cord that I use most of the time due to the ease of storing and handling. It has the 4 prong trailer end connection. I just carry a 30ft extension that I had for the previous unit.
Right now the washing machine is working while using 120V water heater. Later the fireplace will be switched on.
The CG post has both 30 and 50 amp circuit.
Bought my cord on EBay but RV stores have them for much more.
If generator is 120 volts a twist type male plug must be used. I have one extension for my 3000watt genny.

NeilV · 01-19-2014, 05:09 AM

Quote:

Originally Posted by caissiel

I have a 25 ft 30amp cord that I use most of the time due to the ease of storing and handling. It has the 4 prong trailer end connection. I just carry a 30ft extension that I had for the previous unit.
Right now the washing machine is working while using 120V water heater. Later the fireplace will be switched on.
The CG post has both 30 and 50 amp circuit.
Bought my cord on EBay but RV stores have them for much more.
If generator is 120 volts a twist type male plug must be used. I have one extension for my 3000watt genny.

With just a 3,000 watt generator I would forget any extenson cords to minimize line loss and just get an adaptor that will allow the 50 amp cord to plug into the generator. Every extension you add just increases the line loss and your chances of damage to the swich gear and electrical devices in your coach from low voltage. The twist type recepticle on most generators I have seen is 220 volts however most I use are 5,000 or 5,500 watts so be carefull and verify that before proceeding. My generator has four 110 volt recepticles and one 220 volt twist lock for powering a transfer switch or distribution center.

I looked over a few PowerMate 3,000 watt generators and see that some have both a 120 and 220 locking recepticle. On those I would make up and adaptor to plug in the 50 amp cord to balance the load on both sides of the generator which would give you the greatest capacity running each half of the 50 amp service on each side of the generators fields while just hooking into a 120 volt recepticle would only load up 1/2 the generator and be an imbalanced load.

3,000 watts should work out to 25 amps per leg which would be a little light on only one leg if you are running the AC or electric heat as you indicated with the electric fireplace which could use up 15 of those amps of itself leaving you only 10 amps to power the rest of the coach.

ranchn2 · 01-19-2014, 07:39 AM

Thanks so much for the information. The generator is a Pacific 8500M. Since it is just the two of us for convience we thought the 30 amp would be easier to use for the most part. (Lighter weight) We don't want to always rely on a campground. We have been out of the camping circut for some time. Bought the Crusader and was hoping to get back into it. Still have the very slightly usedmotorhome. Will try to sell it in the spring. In the meantime we are trying to think of everything we could or would need to start traveling. Again thanks so much for the replies I think we finally have the generator figured out.

________
the Ryan's

Rockwood27 · 01-19-2014, 08:11 AM

Quote:

Originally Posted by ranchn2

The generator is a Pacific 8500M.
the Ryan's

I just researched the 8500M generator. Very expensive (> $3,000) for a 5500 watt continuous duty, loud, commercial generator!! I stated 5500W because it has an 11 HP engine. I normally figure 500 continuous watts per HP for these types of generators. It looks as if you can use it in 120 or 240 volt mode. The loudness of it may alienate your neighbors within a 300 foot radius. I've been to several National parks with RV'ers using this type of generator and the long-term noise was annoying.

Fran

smiller · 01-19-2014, 09:23 AM

Yes, if you haven't used a 'contractor style' generator before in a campground you might find out that after all your efforts the thing is near useless because of the noise level. Even the higher-quality 'quiet' Onan and Honda/Yamaha inverter generators don't seem so quiet in a quiet area, and the inexpensive models are pretty terrible in that regard. There will be a big difference in how the thing sounds to you in your driveway vs. a campground, believe me.

NeilV · 01-20-2014, 04:28 AM

Some will get it quieter by putting an automotive muffler on them but they are still mechanically much noisier than the correct sized Onan 5,500 watt generator and not as electrically clean.

The Pacific 8500M which is claimed to be 8,500 watts will probably use quite a bit more fuel than the better sized 5,500 watt generator too and with the M suffix I believe that makes it a manual recoil pull start so no AutoStart/Energy Command option to automatically run the generator only when the AC/Heat is calling or the batteries are getting low.

No quiet enclosure to mitigate noise or protect it from the weather either.

On the original question use the 50 amp cord and have whatever adapter is required made up to get a matching 50 amp socket at the generator that taps into both fields on the generator to balance the load. Generators don't really like imbalanced loads favoring only one side for extended periods of time.

ranchn2 · 01-21-2014, 06:36 AM

You are very much correct. It is noisy. The reason we started out with this gen. is because it was basically "free". Later when we decide how much we will actually travel we will probably purchase something quieter and more effecient. For now this is what it is. I appreciate all your information. I have the cord ends ordered. When (if) we decide to change out to a better generator what would you recommend?

the Ryan's