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pianotuna
Hi all,

This protocol was suggested by mexbungalows whom I have the greatest respect for:

TEST: Shore power versus, alternative power. Put glass of water in microwave and start, if voltage drops to 109 vac or less at same outlet as microwave is plugged into, end of test. Energy source is inadequate.

Stage 2 Same glass of water, start at room temperature with oven thermometer. Set timer for one minute high. Remove glass measure temperature on shore power

Stage 3 Do the same with alternative power source and compare temperature difference to test above.

If there is a large temperature difference, then your microwave is going to unlove you trying to suffer through inadequate voltage or waveform.

--------------------------------------------

My personal results:

122.6 voltage, no load; shore power
112.4 voltage, 1591 watt Dometic microwave; shore power

112.1 voltage, no load; Cobra 2550
111.1 voltage, 1591 watt Dometic microwave; Cobra 2550

111 seconds of shore power raised one cup of water to 72 C.
111 seconds of Cobra 2550 raised one cup of water to 71 C.

The batteries were fully charged before this test was performed. No other devices were being powered.
John Blue
Don,

I do not understand the problem here. We have a 2000 watt Heart Interface 3 stage unit. The two house batteries are AGM new 8D with more amps that the Heart could use. Output voltage is 109 to 110 AC. Unit will run microwave, two TV's, Sat Dish, Uline ice machine, our two PC's, plus all the AC and DC lights with no problem. We can cook anything we like and not start up the generator. Never had a problem yet.
pianotuna
Hi John,

The problem is that all inverters are not created equal. Some may cause serious damage to a microwave. There is also a myth that modified sine wave inverters are not suitable for use with a microwave.

This allows folks to do a test before they end up with a bill for replacing their (often built in) microwaves, from either underpowered or very poor wave form inverters.

Some folks (me for example) have beer budgets smile.gif
Denali
Although I have never heard the myth that an inverter can damage a microwave, I know that in both motor homes we have had the microwaves have run at about half power when running off the inverters. These were Xantrex 1500-2000 watt MSW inverters. This has been the widely reported experience of others with MSW whole-house inverters.

I don't understand how you were able to get essentially the same heating performance from your microwave with both shore power and MSW power. A better inverter? Superior Canadian sunshine charging your batteries? Or is it just clean living and a clear conscience?
pianotuna
Hi Denali,

I agree that MSW usually may cause lower output from a microwave. My Cobra is specifically designed to be able to run microwaves. Until I did the test I thought that might be "salesman speak". But I guess for once--it is really true that the Cobra design allows a microwave to work and essentially at full power.

The inverter is also 2500 watts, which might be part of the answer? All I know is I'm very happy with the results. Not bad for a $200.00 NIB inverter!
pianotuna
Hi John,

I forgot to mention that I, too, can run anything in my rv from my inverter and battery bank. (air conditioner and microwave at the same time)

I think your bank is a somewhat larger, but I forget if you have solar to assist it.
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