120V AC outlet/circuit question

[bigbadwanger]

quick question the other day the gf tried cleaning my vehicle by plugging a 120v 12a vacuum cleaner to the outlet of my sr 5 '16. Obviously the outlet is rated for 400 W and the vacuum cleaner is trying to pull more which i assume is 120v x 12 a. The vacuum worked for like 15 minutes or something and then shut itself off- the vacuum just had lower suction power and made a soft whine noise while using. Vacuum still works in the house afterward.
My question is was there any damage to the truck circuitry? In my mind, the vacuum is trying to draw more current but I assume because the truck is only able to deliver 400W which i assume is 3 A in this case, the vacuum didn't have sufficient power to stay on. I assume the truck wouldn't be damage from this? I'm dont know a much about circuits...was trying to think what happened.

Thanks.

 

[tigger]

quick question the other day the gf tried cleaning my vehicle by plugging a 120v 12a vacuum cleaner to the outlet of my sr 5 '16. Obviously the outlet is rated for 400 W and the vacuum cleaner is trying to pull more which i assume is 120v x 12 a. The vacuum worked for like 15 minutes or something and then shut itself off- the vacuum just had lower suction power and made a soft whine noise while using. Vacuum still works in the house afterward.
My question is was there any damage to the truck circuitry? In my mind, the vacuum is trying to draw more current but I assume because the truck is only able to deliver 400W which i assume is 3 A in this case, the vacuum didn't have sufficient power to stay on. I assume the truck wouldn't be damage from this? I'm dont know a much about circuits...was trying to think what happened.

Thanks.

If you can still plug something in and it works everything is fine. If it doesn't it blew a fuse.

 

[snowboardwcu]

answer is "it depends"

the 12a draw the vacuum has on the inverter is obviously way too much for it to handle. a few things can happen when you do this:

1. you blow a fuse (400w rating ~ 33A inlet / 3.5A outlet). on the inlet side thats a lot of current.
2. the inverter is quality enough that it detects an excess draw above rating, and provides no power (this was not the case)
3. the inverter provides power to the vacuum, but at a degraded level. i'm sure exactly how depends on lots of factors, but basically the transistors can't keep up with converting dc to ac, so you lose both voltage and amperage perhaps even still providing 400w.

number 3 sounds like what happened. the whining of the vac are the tell-tale not enough power was getting to the motor. since it worked in the house after, the motor is fine.

i'm surprised the inverter lasted 15minutes in this condition. i'm much more surprised a fuse didn't blow. inverter was surely super hot :flame:, and possible damage could have occurred.

possible damage:
1. overcurrent in wiring to/from the inverter, leading to melted wires, insulation, degraded connections, etc. visual inspection can determine this, or measuring resistance in these lines can help determine if there are issues.
2. overheating / overdraw in the inverter itself. if it still measures 115v and operates other devices normally then the unit is probably ok, for now. but, you may have burnt it out.
3. possibly nothing. maybe you got lucky.

moral: dont do this again. vehicle inverters aren't meant for high current applications. 400w is a pretty big inverter (is that stock in '16's?). your vacuum would need a 115v * 12a = 1380w without accounting for efficiency, current inrush during startup where amps can be 10times nominal.

 

[m85476585]

If the inverter is properly designed it should be difficult or impossible to damage it by overloading it. It should have an internal circuit breaker that shuts it off if the load is too much, and thermal overload to shut it off if it gets too hot. Plus it is on a fused circuit, so it is unlikely to damage anything on the 12V side.

If the voltage drops the vacuum will run slower than normal. In one house I was in the voltage would drop to around 100V if I plugged a vacuum into the end of a daisy-chained circuit. Some things can be damaged by low voltage if they draw more current to compensate, but I don't think a vacuum is that way.

The inverter puts out modified sine wave power, which is basically chopped square waves instead of a sine wave. That might cause the vacuum to run hotter or make extra noise. Square waves have higher frequency harmonics, which could make a whine sound.

Most inverters are designed to supply more than their rated power for a short time for things like motors starting up. How long they can do that is usually limited by how hot they get. The inverter in a 4runner is probably designed with automotive grade parts good up to 125C, so if it wasn't a hot day it has more room to get hotter from heat dissipation. It's probably designed to run at 400 watts in a 130+ degree vehicle, so it can handle some extra heat on a cooler day. That is why it costs hundreds of dollars when you can get a more powerful one for $30 at a store.

I suspect the vacuum uses less than 1380 watts when it's running, depending on the vacuum. They do put out a lot of heat, but not as much as a space heater for example.

 

[bigbadwanger]

answer is "it depends"

the 12a draw the vacuum has on the inverter is obviously way too much for it to handle. a few things can happen when you do this:

1. you blow a fuse (400w rating ~ 33A inlet / 3.5A outlet). on the inlet side thats a lot of current.
2. the inverter is quality enough that it detects an excess draw above rating, and provides no power (this was not the case)
3. the inverter provides power to the vacuum, but at a degraded level. i'm sure exactly how depends on lots of factors, but basically the transistors can't keep up with converting dc to ac, so you lose both voltage and amperage perhaps even still providing 400w.

number 3 sounds like what happened. the whining of the vac are the tell-tale not enough power was getting to the motor. since it worked in the house after, the motor is fine.

i'm surprised the inverter lasted 15minutes in this condition. i'm much more surprised a fuse didn't blow. inverter was surely super hot :flame:, and possible damage could have occurred.

possible damage:
1. overcurrent in wiring to/from the inverter, leading to melted wires, insulation, degraded connections, etc. visual inspection can determine this, or measuring resistance in these lines can help determine if there are issues.
2. overheating / overdraw in the inverter itself. if it still measures 115v and operates other devices normally then the unit is probably ok, for now. but, you may have burnt it out.
3. possibly nothing. maybe you got lucky.

moral: dont do this again. vehicle inverters aren't meant for high current applications. 400w is a pretty big inverter (is that stock in '16's?). your vacuum would need a 115v * 12a = 1380w without accounting for efficiency, current inrush during startup where amps can be 10times nominal.

thanks much for the response. i did put my iphone charger on it the next day and it charged up, thankfully, so I am guessing that it didn't get burnt out since it's still functional? Definitely a lessons learned.
Yes it is stock. I'm glad a fuse didn't blow.

 

[bigbadwanger]

If the inverter is properly designed it should be difficult or impossible to damage it by overloading it. It should have an internal circuit breaker that shuts it off if the load is too much, and thermal overload to shut it off if it gets too hot. Plus it is on a fused circuit, so it is unlikely to damage anything on the 12V side.

If the voltage drops the vacuum will run slower than normal. In one house I was in the voltage would drop to around 100V if I plugged a vacuum into the end of a daisy-chained circuit. Some things can be damaged by low voltage if they draw more current to compensate, but I don't think a vacuum is that way.

The inverter puts out modified sine wave power, which is basically chopped square waves instead of a sine wave. That might cause the vacuum to run hotter or make extra noise. Square waves have higher frequency harmonics, which could make a whine sound.

Most inverters are designed to supply more than their rated power for a short time for things like motors starting up. How long they can do that is usually limited by how hot they get. The inverter in a 4runner is probably designed with automotive grade parts good up to 125C, so if it wasn't a hot day it has more room to get hotter from heat dissipation. It's probably designed to run at 400 watts in a 130+ degree vehicle, so it can handle some extra heat on a cooler day. That is why it costs hundreds of dollars when you can get a more powerful one for $30 at a store.

I suspect the vacuum uses less than 1380 watts when it's running, depending on the vacuum. They do put out a lot of heat, but not as much as a space heater for example.

it was a cold raining day at around 50 degrees. based on your explanation, if the circuitry was designed correctly and given the limited time i used on it, it probably didn't damage the 4runner circuit much? since i was able to plug my iphone charger and it worked fine powering my iphone the next day.

 

[MeefZah]

The invertor is fine. No damage.