On Saturday, May 24, 2014 at 9:11:09 AM UTC-6, trader_4 wrote:
On Saturday, May 24, 2014 10:53:29 AM UTC-4, sms wrote:
On 5/22/2014 4:54 AM, DerbyDad03 wrote:

I bought this inverter at you-know-where. I will be calling the tech

support number given in the manual, but I thought I'd run my questions by

you folks also.

Keep in mind there are two sides(so to speak) of the inverter: 1. the 12 volt side and 2. the 120 volt side. The 12 volt side needs 10 times the amps to provide the same watts as what you see on the 120 volt side. Watts = volts X amps or if you do a little algebra Amps = watts/volts. So, if you are wanting to run a 120 volt electrical device, say a single 100-watt lightbulb, that pulls 100 watts at 120 volts then on the 120 volt side you have 100 watts/120 volts = 0.83 amps ON THE 120 VOLT SIDE...but on the 12 volt side that same 100 watts is pulling 100 watts/ 12 volts = 8.3 amps! So your 1.0 amp air mattress at 120 volts is pulling 10 amps from the 12 volt side. If you are going to run a hand drill that pulls 7 amps of 120 volt juice then it will pull 70 amps of 12volt juice. For a 1000 watt inverter measured on the 120 volt side you have to wire the 12 volt side with a wire size that will carry 1000 watts/12 volts = 83.3 amps!! To run 80 amps 10 feet you need an absolute minimum of 4 guage wire. And I say minimum because the calculations above do not provide any safety factor, just the minimum mathematical value. Wire guage capacity tables at given voltages are all over the internet.

http://t.harborfreight.com/1000-watt...oogle.co m%2F



1 -When I power it on, the fan starts, runs for about a second and then

stops. Is this normal? Will the fan start again if required?



2 - When I plug in a lamp with a 72W bulb, it works fine. When I plug in a

air mattress pump (120V, 1.0A) the pump may or may not start and the

inverter chirps its alarm. Sometimes the pump seems to run fine, other

times, not so much. The chirping is more evident and consistent when the

pump is running at what appears to be full speed.



Shouldn't even a cheap 1000W inverter be able to handle the pump without

breaking a sweat?



(I'd return it and try another inverter, but both of my local stores are

out of stock right now.)



You could try another one, but it sounds like HF just rated the inverter

way too high. Or else you're not using sufficiently thick gauge wire.

The motor may be drawing more current when using a modified sine wave

that the inverter puts out. Allowing for losses in the conversion you

should use about 10AWG wire and connect directly to the battery. For

higher loads look at 4AWG wire, i.e.

http://www.amazon.com/dp/B007L6DYVS or 2AWG i.e.

http://www.harborfreight.com/automotive-motorcycle/power-inverters/300amp-6ft-inverter-cable-set-69537.html.



You may need the proper gauge wire even when you're operating the

inverter with a load that is far lower than it's capacity.



Why would that be? Where would all the wasted power
be going? Makes no sense to me that you need the same
wire for 100W that you'd need for 1000W.