Newbie here. Try not to freak out if this question is waaay off base.
Can I tie two 750 watt inverters together to form a 1500 watt inverter?
I guess it would be like tying a 110/15amp line from 1 house to a 110/15amp line from another house and splicing them together to a single outlet. Would it just short out would I theoretically now have a 110/30amp outlet with both houses splitting the load?

Hello & Welcome:

It depends on the design of the inverters in question.

Some types can be run in parallel, but they will need to be synchronized so that the AC sinewaves are in phase. This generally involves one inverter being "slaved" to the other, so that the outputs are locked together.

The inverters also need to be of a type which will not have their voltage regulation upset by being paralleled in this way.

By the way, trying to tie different branches from different houses together is not a good idea. One problem is that houses on different transformers may well take their high-voltage feed from different phases, so the "hot" lines will be out of phase. There are many other safety concerns as well, so I wouldn't advise anyone to try it.

https://www.electrical-contractor.net/ubb/Forum7/HTML/000113.html

Cross-posting in multiple categories is quite unnecessary and even annoying.


[This message has been edited by Dspark (edited 09-13-2001).]

Paul,
These are your basic hardware store inverters they are made by Vector. Not sure if Vector means anything to you but they tend to supply ambulances/fire rescue etc. with inverters. Good quality stuff. Would there be any way I could tell if I could paralell them from the packaging. Any key signs to look for?. The 3000watt inverters go for $700+. The 1500watt for $300+. The 750 watt goes for $80. I'd like to tie at least Two 750's together to share the amp load and power spike at startup of a 1 1/2 horse 110v 20amp motor on a tile cutting saw. I don't have a problem with the hook up, just the initial purchase price.

I think I can tell from the pricing that they cannot paralleled without modification.

You should splurge and get the 1500 W model.

Just curious, what would you be connecting these up to? And how?

Bill

dspark,
thats pretty much where i'm going, thanks

Bill,
I was going to hook them into a stardard electrical box w/4 outlets. If you mean as far as the battery power, 12v 1500 CCA semi size battery with a 24hr reserve at 25amp draw. That battery would be directly fed off a 160amp alternator and also tied with 2 1000CCA batteries, for a total of about 3500 CCA and 48 hr reserve at 25amp draw. The inverters would only be used periodically during power down times on the jobsite or repeated overloads from wimpy 50amp breakers when there are 6+ trades on the job trying to pull from one temp pole.
Shawn

I doubt that even the 3000 watt inverter would be able to start a 1 1/2hp 120 volt motor. The start current would be 120 to 150+ amps.
Don(resqcapt19)

Shawn,

Yes, I did mean the Battery. Just checking to see if you were going to try this with a standard car/van Battery. You seem to be aware of what you need in that aspect.


Bill

I assume he is also pedaling to keep it going. 1500 W won't keep a 20 A load running even if it could start it with a pull string.

dspark,
Thats why I wanted to paralell them. I'm aware that 1500watts won't even come close to maintaining the load.

resqcapt 19. I would be carrying a surge of about 4500-5000 watts. I think thats probably enough to get it rolling. I wouldn't want to operate the motor everday off the inverters but for an occasional use I think it will be allright.

Tilesetter,
The start current will be a minimum of 5 times the motor full load current. This would be 100 amps and 11,200 watts.
Don(resqcapt19)

Shawn,

Well, I think everybody else has pretty much covered it by now. I'm in England, so by the time they post their messages in the evening I'm already asleep!

I'll just echo the problem with the start-up surge. The rating of some inverters is pretty much the absolute maximum you can get, while some of the more upmarket models will actually deliver a transient of two or three times their nominal maximum. Even so, you'll still need more than that for motor starting.

I've not seen the Vector brand inverters in the U.K., but even allowing for your lower prices in the States, I would expect models with sync/slave operation to be quite a bit more expensive than the figures you quote.

Another point to consider: Many cheap inverters have an almost square-wave output which isn't all that good for running motors.