I need some help with an AC/DC Inverter issue im having?

D

Devin

Member
I have a 1500WATT continuious, 3000WATT max power inverter in my truck. im trying to power a 710WATT 7.1amp window AC unit but it seems to be more that the Inverter can handle?? i dont understand if thats the case. i know there r wattage spikes with the compressor usage in the AC unit but it starts and runs fine which means that the inverter is handling the CRANKING AMP boost which i would think would be the most it would ever endure... Ive blown two 60 AMP fuses already and i want to be able to use this unit... any suggestions?
Well it will run for about 3 min or so then either the Inverter will shut down or the 60 amp fuse will blow
Well i have 8guage wiring running only about 6ft in length and yes the 60 amp fuse is coming off the positive side of the battery... what can i do to fix it?
ok so assuming there would be a spike in the compressor wattage ... what would be the peak amperage needed (estimate) im thinking ill try a 100 amp fuse today and see how that works?
 
M

MarkG

Member
Fuses work by generating heat to melt (blow) a thin strip of metal inside. There is also an inverse current time relationship on how fats a fuse/circuit breaker will trip. THe more current the fast the fuse will blow, a slight overload will take a little longer to build up the heat and blow the fuse.

A 710 Watt load operated at 12V will draw 59.16Amps your right at the hairy edge at you assume that the fuse was manufactured perfectly to exactly 60 amps.

Since a fuse works on heat any heat that fuse operates helps blow the fuse. So a fuse operating in a warm environment is derated to compensate for this background heat. So if the fuse is operating a a warm engine compartment there is probably enough additional heat to blow the fuse.

Metal gets soft when heated and vibration will cause the hot wire in teh fuse to break


poor electrical connections or overloaded wire will cause a voltage drop. THe reduced voltage will cause an increase in current draw as the connected device attemps to draw the required power.
at 710watts you only need to drop 0.16V to draw 60A

#8 wire is not rated for 60A so you have undersized wire that is probably causing some voltage drop.


At the very least I would use stranded #4 THHN copper wire (Available at Home Depot) which has an ampacity of 95A and a 75amp fuse or circuit breaker.
 
M

MarkG

Member
Fuses work by generating heat to melt (blow) a thin strip of metal inside. There is also an inverse current time relationship on how fats a fuse/circuit breaker will trip. THe more current the fast the fuse will blow, a slight overload will take a little longer to build up the heat and blow the fuse.

A 710 Watt load operated at 12V will draw 59.16Amps your right at the hairy edge at you assume that the fuse was manufactured perfectly to exactly 60 amps.

Since a fuse works on heat any heat that fuse operates helps blow the fuse. So a fuse operating in a warm environment is derated to compensate for this background heat. So if the fuse is operating a a warm engine compartment there is probably enough additional heat to blow the fuse.

Metal gets soft when heated and vibration will cause the hot wire in teh fuse to break


poor electrical connections or overloaded wire will cause a voltage drop. THe reduced voltage will cause an increase in current draw as the connected device attemps to draw the required power.
at 710watts you only need to drop 0.16V to draw 60A

#8 wire is not rated for 60A so you have undersized wire that is probably causing some voltage drop.


At the very least I would use stranded #4 THHN copper wire (Available at Home Depot) which has an ampacity of 95A and a 75amp fuse or circuit breaker.
 
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