Microwave question?

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ChopperBill

Well-known member

• Jul 24, 2006

• #1

My 3000 watt inverter wont run the 900 watt Sylvania microwave. It will run it a half power but you can tell it ain't to happy about it. The inverter will run a 1800 watt hair dryer with no problem. While on our last trip the only way my 3000 watt generator would run the microwave is if I made sure every thing else was off. I even ran the 15.000 BTU A/C with the generator at 9100 feet so I am pretty sure it is up to snuff. The microwave runs on shore power OK. I thought a read a post about the Sylvania's having a problem or two. Anyone?

 

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jbeletti

Well-known member

• Jul 24, 2006

• #2

Bill,

Is your Xantrex a pure sine wave type? Perhaps the microwave requires it.

Jim

 

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ChopperBill

Well-known member

• Jul 24, 2006

• #3

Jim its a modified. Hype sheep from Xantrex claims it will run " Household appliances, microwave ovens , bread makers, food processors...........
Not a real problem if we don't have a micro, but over buying an inverter I would expect it to power all that is claimed. Also figured if it would run an 1800 watt hair drier it should run the 900 watt microwave, especially when it claims a 5000 watt surge capacity! Hence thinking the micro is screwed up somewhere.

 

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dieselengineer

Charter Member

• Jul 24, 2006

• #4

Microwaves have a high in rush the sometimes causes a problem also. However, most likely the inverter is not a pure sine wave. Some of the inverters are square wave output and this really smokes electronic equipment. Things like the the converter or anything that has a rectifier in it. I always isolate all this type of equipment, before I energize my inverter. I learned the hard way, I smoked a microware a number of years back.

 

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dieselengineer

Charter Member

• Jul 24, 2006

• #5

Bill
The modified sine wave is not a pure sine wave. A real good inverter will have a pure sine wave and state the total percent of distortion (THD). This should be as low as possible if the power is going to be the same as utility power. Modified sine wave is far from pure and okay for non electronic equipment.

 

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ChopperBill

Well-known member

• Jul 24, 2006

• #6

Thanks for your input DE! Guess I figure that when they tell me it will run a Microwave I believe them. I really have to learn not to believe all that the manufactures print. Having a micro is no biggy but I guess I could have got a long with a smaller, cheaper inverter. As long as Renee can do the hair drier thing while mistakingly leaving the coffee pot plugged we will all be happy!

On a p.s. I think I will take my 800 watt portable microwave out to the camper and plug 'er in. If it works I am going to ask that they check the Sylvania out.

 

jpmorgan37

Well-known member

• Jul 24, 2006

• #7

Bill;
I ran my microwave in the Sea Breeze with a 1800 Xantrex with no problem. I don't believe that the inverter is the problem. JMHO.

John

 

DennisZ

Well-known member

• Jul 24, 2006

• #8

Bill
How large is the wire going to the inverter, for a 3K inverter located as far from the battery as your unit is, the wires should be on the order of 4/0 for the current draw.

For a 3K inverter.
For a run up to 7 feet one way, use 4/0 wire
"Note: Never use a cable longer than 7 feet."

If you have a smaller cable than that installed, you will most likely get enough voltage drop to cause the inverter to get a low voltage cutout.

BTW... 4/0 wire is really big, a standard battery cable on a car is 4 ga, about 1/8 the capacity of 4/0.

With your micro running on low power, see what the voltage is at the input to the inverter, that will give you a good idea what's happening.

 

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dieselengineer

Charter Member

• Jul 24, 2006

• #9

I agree DennisZ you have a good point. I mounted my inverter as close to the golf cart batterys as I could. Keep the low voltage cables real short. The easy cable to route is the 120 volt. To make it easy, I just made a shore cord that only energized the one leg (neutal to one hot side). Then a moved all the equipment and loads that I did not want on the inverter ( like the converter, microwave, etc) to the other leg at the CB panel. So it is easy at setup time, if the camp site does not have utility power then I just plug into the inverter.

 

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ChopperBill

Well-known member

• Jul 24, 2006

• #10

Inverter is less than 2 feet away from the batteries. 4/0 cable is used. Dealer put a skimpy 100 amp fuse between the two. Going to replace it with a 500 or so amp circuit breaker. Some resistance maybe with the 100 amp fuse? From what I have been hearing the 100 amp fuse could be the weak link even if it doesn't blow.

 

DennisZ

Well-known member

• Jul 24, 2006

• #11

Bill
That 100 A fuse is way to small, a 1200 watt load will draw over 100 amps, figuring the efficiency factor of the inverter, with a full load, it will draw about almost 300 amps! The 500 amp breaker is a good idea, but might be hard to find.

 

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ChopperBill

Well-known member

• Jul 24, 2006

• #12

Yes the Xantrex factory rep told me the same thing. But did say the inverter was probably defective and have the dealer replace it. I informed the dealer of my factory findings and they are going to replace the fuse with a more tolerable circuit breaker. That is when I hope they do the Timk "swelling belly bar'' mod.

 

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dieselengineer

Charter Member

• Jul 25, 2006

• #13

Bill
The other issue on high amp loads, battery have an internal impedance. In another words there will be a voltage drop during high amp loads within the battery. Just increasing the CB size does nothing to improve this internal voltage drop. Place a good Volt meter across the battery terminals and take a reading with no load and a reading with the inverter under high load (200 amp plus). If your voltage drops lower then the inverter can handle then there is not an issue with the inverter, It is an issue that there is not enough battery. Normally to improve the system impedance, you will need to add an additional set the batteries.

 

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ChopperBill

Well-known member

• Jul 25, 2006

• #14

I sure am learning a lot of stuff! Thanks! Didn't give a second thought that my 2 6v's may not be enough battery! Now that I think about it that probably is the problem. Will have to do without an inverter powered microwave. Not putting anymore batteries in the BH. Have enough to contend with. I still am going to try my portable microwave and see if it powers it just for fun. Wife really is not much of a micro fan anyway. Refuses to let me bring the portable into the truck camper.

 

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dieselengineer

Charter Member

• Jul 25, 2006

• #15

Bill
Give it a try, If you can get the microwave started on the inverter (place a load in the oven like a big cup of water) take a reading on the voltage at the battery terminals. I would like to know what your voltage drop down to. I have two golf cart batteries (6 volt) and they have fairly low impedance.

 

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ChopperBill

Well-known member

• Jul 25, 2006

• #16

Tried the portable 600w micro. Battery was at 12.9 v but I had just taken it off the charge wizard but it had only be on a few minutes Normally it stabilizes at 12.6-12.7. Ran it with no problem. Checked the voltage while it was running. 12.05 v's. The Sylvania is 900w output. Tried it again. Inverter didn't even try. Shut down then right back on. The 900w is overkill (kind of like my 3000 watt inverter ) so is there any way to de-watt the Sylvania?

 

timk

Well-known member

• Aug 18, 2006

• #17

ChopperBill,

We have a 2000w Xantrex with 4 6v bats and 4/0. When we run the microwave, it really sucks the juice out. Something like 80+ amps. We regularly get error messages from the inverter that the batteries are gone, while I know they are not.

I would also suspect that you don't have enough battery.

TimK