Startups of appliances

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Hey guys, maybe some people could help me. I have a 5000 watt Royal Power power inverter. Pure Sine Wave. My batteries are fully charged, 13.33v, 10 x12v.

Is there any magic number to determine startups of things like a microwave? The continuous is 900 watts but everytime I have my fridge/tv/ac/some lights running. when I start the microwave it really isn't working well. It's hard to manage everything and guess startups.

Also, startups don't fall under the peak/surge category? I called in for help and they told me it falls under the continuous since it lasts longer. Anyone have information on that, if it's true or not? Thanks.

• Solar Expert Posts: 1,341 ✭✭✭
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Re: Startups of appliances

It takes a clamp-on meter that can do "inrush" measurement:

http://www.hmcelectronics.com/cgi-bin/scripts/product/3410-0138/Fluke-336

Anything else is just a guess - even though it may be an educated guess, it's still just a guess.
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Re: Startups of appliances

Measure the 12 volt DC connection on the inverter and see what the actual voltage is under load--You could have too much voltage drop from the battery bank (too small of wire or to long of run to inverter).

Realistically, for a 12 volt inverter, you are looking at about 1.0 volts of drop from the battery to the inverter under load. And for a 5kW inverter on 12 volts, there is a lot of current:
• 5,000 watts * 1/10.5 volts inverter cut out * 1/0.85 efficiency = 560 Amps
• Fuse/Wiring rating: 560 amps * 1.25 NEC safety factor = 700 amps
That is a heck of a circuit.

If you have a filament light plugged into the inverter--do you notice significant dimming when the microwave is turned on?

Many microwaves really do not like MSW (modified square/sine wave) inverters and do not operate as efficiently... Does the microwave otherwise work when the other loads are not on the inverter?

What is the total/maximum continuous wattage that you are trying to drive (less than 5kW--your wiring does not have to be as heavy).

It is very difficult to operate inverters much over 1,200-1,500 watts on 12 volts DC because of the very heavy currents and very small allowable voltage drop...

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 168 ✭✭✭✭✭
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Re: Startups of appliances

Microwaves will not run properly on Non Pure Sine Wave Inverters. It will take alot longer to cook anything and it still does not really work correctly from my experience.
• Banned Posts: 17,615 ✭✭✭
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Re: Startups of appliances
RWB wrote: »
Microwaves will not run properly on Non Pure Sine Wave Inverters. It will take alot longer to cook anything and it still does not really work correctly from my experience.

Agreed. Neither do AC induction motors and several other things.

And how many times have I said "never rely on the surge rating of an inverter"?
There are those who disagree, of course, but it's not my nickel.
• Solar Expert Posts: 1,571 ✭✭
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Re: Startups of appliances

The OP said that he's running a Pure Sine Wave inverter.
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Re: Startups of appliances

Sorry, that was my fault--I am used to seeing 5kW (very high power rating) 12 vdc inverters being MSW... I looked all over the web and could not find a 5kW Royal Power inverter....

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 1,571 ✭✭
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Re: Startups of appliances

Found this: http://www.rpeltd.com/product5.html but couldn't find any further tech specs.

Ph33r my g00gle foo
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Re: Startups of appliances

I had found them too... but given that they are out of Lagos, Nigeria--I am not sure that they are really the manufacturer. Just an importer/installer (my guess).

From the way they layout their ratings--I would guess that it is Peak/Surge rating and not continuous power rating (5kW inverter to run a 1 HP motor). But there are no real specs. to speak of.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 257 ✭✭✭
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Re: Startups of appliances

The lack of information on the Royal is disconcerting, I looked on Ebay US and UK, found 1 300 W unit. The fact that the link offers no information is also worrisome.

What size wire and how far are you running to the inverter, as mentioned it takes a large conduit for that amount power.

I have been monitoring some battery issues. As an example, I had my clamp on meter in place when the well pump came on as the 1500 W microwave was running and the coffee maker was on, the washer might have been running, my Trace showed a 40 Amp load AC, this load would not have lasted more than 3 minutes, the timer setting for the microwave, the meter showed some 240/245 Amps @ 24 V, I had a voltage drop of about 1.6 to 1.8 volts, it fell to 23.8 V.

Thats a lot of facts, but the point is under similar loads, you would be pulling 500 +Amps at 12 V, and the volt drop would be even more sever.