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Inverter Amps vs Shore/Gen
Here’s a question for the electrical experts…
On inverter, my microwave shows about 14 amps and my Mach 5 shows about 7 amps.
On shore/gen, my microwave shows about 28 amps and the Mach 5 shows about 15 amps.
So it just about doubles on shore/gen. What am I missing here?
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19 Replies
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Don’t have clue but on mine the microwave pulls the same amps on gen or shore power same with a/cs and everything else.
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something an’t right
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Tom, the first thing to do is determine which reading is correct. My gut feel is there is no way a microwave draws 28 amps. BTW, I’m surprised to see AC amp meters on the output of the inverters. The amp reading that’s important when on inverter power is DC amperage wich will be about 10 times the AC load. Unless you have Trace 4000s wired like Vantare does, you must have two sets of AC amp meters. One set of meters for inverter only loads and one for all loads. That too would seem a bit unusual.
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Nope, one set of digitial meters for amp and volts per leg and 1 transformer per leg.
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Hmmm, one amp meter. That means that it is either before or after the inverter output, likely before. If it’s before the inverter then it will tell you the coach’s total draw, but in this location it can’t tell you the draw while on inverter power without a selector switch to read from two different pickups, one before and one after the inverter. Maybe you have such a switch given you are reading current while on just inverter power or when on commercial/generator power.
Did you check the microwave’s rating?
I don’t think Liberty supplies a basic wiring schematic. If they do, can you determine how you are getting two readings from the one meter? If so, you may want to check the connections on the pickups. They will look like donuts with the AC wire to be measured passing through them.
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On a Liberty, and perhaps some other conversions, the inverter powered circuits are on a separate section of the busbar in the electric circuit breaker panel. The circuit brealer switches are all lined up and every breaker looks like it would be fed from the common bus bars but that is not the case.
When on inverters only, the only circuits (circuit breakers) that carry power are those fed by inverter 120 volt output. All others are dead.
When the coach is connected to shore power or generator the transfer switch supplies power to the legs not served by the inverter only. On those busbar legs are the circuit breakers that provide power to the inverters. So at that point the inverters “recognize” the availability of shore power and switch to battery chargers as well as sending the incoming shore power back to the inverter powered bus bars to supply power to anything on those inverter powered circuits.
The amp meters are measuring the total load on the circuit breaker panel so they not only measure the power drawn from the device on the inverter bus bars, they are measuring the power going to the inverters from shore power so it is being measured twice.
I hope that made sense. Bottom line is the amp reading on inverter is correct.
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No switch and the transformers are just fine.
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Tom,
You must have a relay that deenergizes the pickup loop on the inverter output when it senses commercial or generator power. That relay is not working correct and that’s why you have twice the reading you should on commercial power. There really isn’t any other logic that comes to mind that can explain your readings. You have two pickups, when on inverter power the reading is correct as the commercial/generator power pickup has nothing to read, when on commercial/generator power the reading is twice what it should be when the only loads are those that run through the inverters because both pickups are supplying the meter.
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We may have cross posted. There is nothing wrong in terms of devices that do not work. It is just the way the amp meters read current.
I think all Libertys are the same in how the amp meters measure current.
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That makes sense Jon, there in is the reason I can see 50+ amps at times without any breaker problems when on shore power.
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Guys, measuring the inverter supported loads twice when on comm/gen power is senseless. What is your load when on comm/gen power? The answer is you would have no idea. Call Troy.
I bet most conversions don’t display AC amps when on inverters unless they have 2 AC amp meters.
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Tom.
I know mine is different from yours, but, when on Gen or Shore, my inverters use up to 15 amps each more as a battery charger, until in float mode. When just inverting, they are not charging, so less amps are used by not charging. I can force the inverters to go to float, which gives me more amps for other things if needed.
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Jerry, This issue is strictly one in which the real current draw on any device on the inverter circuits is being doubled when on shore or generator power as displayed on the amp digital readout. If our understanding of what is happening is correct then all we have to do is ignore the false readings and mentally adjust them to reflect the correct value.
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I have seen some Prevost converters put both the inverter output cable AND the transfer switch output cable (the common “shore/gen” feed wire to the load center) through the same current “donut” before, which would account for the “summation” or doubling of the actual load current, if that IS in fact what Liberty or someone else did on your coach. I was thinking that Liberty put the current transformers (donuts) in the automatic transfer switch enclosure though. Jon, do you recollect where they are?
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Ben,
I wish you wouldn’t have asked. I saw them on my 97 and now I am driving myself nuts trying to remember where they were. I haven’t had my present coach apart enough to see them.
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