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30AMP Service
We may have to utilize 30AMP service on some of our HH builds. In looking at the manual to switch over the Inverters to 30AMP service, it says to adjust both Inverters under the “Set shore cord” from 50AMP to 15AMP. My question is why is it not 30AMP since both of them are set at a default of 50AMP for 50AMP shore cord power? If using just 15AMP on each circuit, we would only be able to run a minimal number of devices at one time before blowing a breaker. Or, we’ll need to use the generator if we need to run more than one or two of the cruiseairs at one time.
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12 Replies
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The manual is correct. The 50A service is really 2x50A since it uses the 240V split phase. The 30A is really only 30A. With the 50A plug you can draw 240Vx50A=12000W; with the 30A plug you can draw only 30Ax120V=3,600W.
On a 30A plug both inverters have to share 30A.
Gerald
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Tim,
50 amp plugs have a 50 amp service on each leg, or each side of the plug, which means you have two hots, one ground, and one common.
On a 30 amp plug, you have 3 lugs, only one of them is the hot, which is 30 amp total. Then you have a ground, the round terminal, and the other is common. So your inverters have to share the one 30 amp, 15 each.
Hope that helps.
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I believe it is a “best practice” to set the limit slightly below the breaker rating.
(i.e. on 50amp service, set each “leg” at 46 or 47, approx 5% below max) Breakers can degrade and not hold their rated limit. If you try to pull the full rating, you will likey overheat and/or trip the breaker.
ALSO – on 30 amp service, as stated above, the inverters are “sharing” the total 30 amps. When in storage, you should set the total (inverter 1 plus inverter 2) slightly less than 30amps for the same reason as above.
That said, when in storage when I am plugged in at 30 amps, I set my inverters at 17 and 11. WHY? My inverter one drives the circuits that include my salon AC and salon toe-kick heater. Setting that leg higher allow the inverter to provide the current to those devices to help keep the bus cool or warm. The 2nd inverter (when in storage) is supplying only the refirgerator and float charging on the batteries.
I am sure there are many ways to “solve” the shore power limits but the above is what has worked for me.
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The phrase “energy management” is always going to come into play regarding our coaches and how we use them.
We have options that give us choices regarding whether we want to live large and make use of all the assets our coaches have to offer, or we can opt to live with the energy that is available from shore power. Dry camping doesn’t provide much choice. We either opt to run off batteries and charge the batteries as required, or we just start the generator and use anything we want on the coach.
When we plan on relying on shore power we have to know how much is being provided, and then operate within the limits of that shore power. To begin as has been pointed out above it is important to understand 50 amp is really 100 amps total, but only 50 amps per leg. That means even if we believe we have 100 amps available, it doesn’t mean one leg can be loaded with 60 amps and the other leg 40 amps. The 60 amp leg is overloaded so the breaker will trip.
When we are connected to 20 or 30 amps that is our total available power and it is shared by both legs. No matter how each leg is loaded, the total current draw for both legs cannot exceed 20 or 30 amps.
While it is possible to draw the full rated amps it should be recognized the breakers in the shore power boxes were never designed to be on-off switches, which is exactly how they are being used. As a result it is more probable you will trip a breaker than no if you draw more than 80% of the rating. In other words a maximum of 40 amps per leg on a 50 amp service or 16 or 24 amps total on 20 or 30 amp service.
The difficult thing to remember on our coaches is we have uncontrolled devices whose on-off cycles can occur without input or warning. Refrigerators, water pumps, water heaters, inverter chargers, etc. We all also have phantom loads from such things as clocks, alarm systems, power to TVs and radios to retain memory, power to some operating systems, automatic lights such as when we open a bay door, etc. All of these will draw from the batteries which in turn will engage the charging portion of the inverters.
Everyone should learn the current draw from all devices in their coach, and when on limited power supplies, or when it is necessary to run heavy loads like all A/C units only those items essential to the coach should be turned on. It might require some staggered use of devices such as letting water heat up before turning on the water pump to take a shower, turning each device off when not absolutely required. If you have a coach that runs everything through inverters energy management is still required because you cannot draw more power from the batteries than the inverters when charging are capable of restoring.
After a while all energy management becomes intuitive.
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How many amps do we have on each leg when we use a 30 to 50 amp adapter? For example we carry a “Y” adapter where the short legs of the “Y” have 30 amp male ends that plug into two shore power receptacles and the long leg of the “Y” adapter has a female 50 amp end into which we plug our normal shore power cord.
correction: the adapter is actually “V” shaped, not “Y” with the 50 amp female at the bottom and the two 30 amp males at the top. I presume that gives us 30 amps on each leg.
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30 amps is 30 amps. You still have 30 in. The controlling factor is the circuit breaker in the shore power box. If it is a single you get only the total amps shown. If it is a double like the 50 amp breaker is, you get 50 per leg.
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Do others set their shore cord to “46-47” like Roy when using 50AMP service?
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Yes that the way to set your inverters slightly lower then the supply breaker.
I camp at festivals where 20 amp circuits are all thats available so I set my inverters at 18, keeps my batteries up but thats about all.
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Just so folks who are relatively new owners do not get confused it should be noted that coach electrical systems as they relate to the inverters and shore power vary to a great extent.
Not all inverters can be set to limit current draw from shore power. Some can be programmed for lower charge rates. Some have a myriad of features. Some are very basic and changes of a limited nature can only be accomplished by DIP switches on the rear of a remote.
What is important for owners to understand is your best information is going to come from the inverter owner’s manul or the converter. Converters often make running improvements in their designs and systems and it is entirely possible that two owners of the same conversion only a few build numbers apart could have two completely different operating systems as relates to the inverters.
Sharing information is good as long as everyone recognizes it has to be verified as to being valid for a specific coach.
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I love stumbling across these types of posts. The collective knowedge is pretty impressive.
Mike
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Before my recent move to a house that also has room for the bus, used a dryer feed from my house to supply power while loading for trips. Had my electrician wire the dryer with a 50 amp recepticle giving me two legs of 30 to the bus. After rebalanceing the pannel in the bus, was able to run all 4 roof airs on a double feed of 30.
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Dan and Barb, if your two 30 amp to one 50 amp adapter is a “cheater box” as I suspect, and you plug each 30 amp end into a unique 30 amp supply, then YES you do have 30 amps available on each leg of your 50 amp outlet end of the cheater box.
As has been discussed you can have 60 amps total, but only 30 amps per Line 1 and Line 2. On a true 50 amp/240 volt shore power connection, that total is 100 amps but again only a max of 50 amps on Line 1 and 50 amps on Line 2.
You need to be aware that if you have 240 volt appliances (dryer and possibly electric cook top), plugging in to two discrete 30 amp connections may or may not (most likely not) provide 240 volts to those appliances. To verify you would need to use a VOM to check the voltage between Line 2 and Line 2.
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