I live in South Florida an as such need to have generators for hurricanes.

I have 2 Generators, a small 3300 Watt Inverter and a big loud 9000 Watt generators.

Edit: My plan is to use only 1 generator at a time. My 2 Generators are: Small Generator Larger Generator. I am looking for a solution that will allow me to use the smaller quieter Genset overnight and the more powerful one during the day. Not looking to use both at once.

The small inverter is what I use overnight to power the necessities, such as Aquarium Equipment, small window AC, Fridge and freezer. It works great, is very quiet and efficient and runs through the night. However I would like the option to power some of my bigger stuff during the day off the big generator and some 240 stuff such as Pool pump, stove, etc..

I am planning on having a generator tie in installed in my electrical panel. along with a disconnect so I do not back feed the grid.

240 power is basically 2 120 circuits out of phase. What I would like to know is can I consider each leg independent? Can I connect my 120v Generator to 1 leg and just make sure my 'crucial lines' are powered by this leg. Over night I would ensure all my 240v Breakers are off.

When I want to power my 240V stuff during the day I could disconnect the small inverter and connect my bigger generator, then in my panel choose my desired 240 loads and activate the breakers for the 240 loads I want to run?

How would I achieve this... My Small generator has a TT-30R Outlet. I would get a cable and connect that to a L14-30 Connector, but only to one side. The big Generator has native outlet of L14-30 so I could use the same generator tie in for that at full 240V.

I know there is the potential for my load to be unbalanced. However I would not run the AC during the day and the running amps of the Fridge, Freezer and Aquarium are pretty low. so in the grand scheme of things I think it would end fairly balanced. I am not looking to do this DIY, I am gauging the feasibility before I try to hire an electrician. Additionally I find it helpful to understand things somewhat before I hire someone. Not all Tradesmen are equal and I what they do needs to make sense to me before they do it.

  • \$\begingroup\$ You should ask this in the DIY stackexchange - lots of questions on house wiring and AC power stuff there. \$\endgroup\$ Nov 2, 2018 at 16:27
  • \$\begingroup\$ Thanks was not taking this on as a DIY project! Was looking for the feasibility before I tried to hire an electrician. \$\endgroup\$
    – V Britt
    Nov 2, 2018 at 20:56
  • \$\begingroup\$ I'm not necessarily suggesting you do it yourself, but that there are people in the DIY group who are familiar with this sort of thing so can advise you, discuss feasability, discuss electrical code requirements, etc. This group tends more towards electronics than power wiring. \$\endgroup\$ Nov 2, 2018 at 21:27

4 Answers 4


Sorry to do this, but I'm going to have to come down on this.


This is one of those, "If you have to ask, you can't afford it," type questions. Only in this case, it's "If you have to ask, somebody's going to get hurt."

Do this right. Hire an electrician and get a transfer switch installed. If you do this yourself, there's a decent chance you'll do something wrong. If so, in the best case you will be killed or seriously injured. Note that this is the best case - auto-Darwinism is, by its nature, self-limiting. Much worse is the possibility that you'll kill a power company worker when you forget to disconnect.

Sorry to be harsh, but you clearly don't know enough to know what to avoid. Don't mess around with this stuff unless you have experience or a mentor who does.


Assuming both machines are 120V I don't see this ending well. The problem is that they will not likely run at exactly the same frequency or in an exact 180 degree phase relationship which you need to obtain 240V from two 120V sources. I would also worry about the possibility of one or both machines having one side of their output tied to frame ground (This tends to be a bit of variable with small generators).

Obtain a proper split phase machine and appropriate switchgear if you want to do this.

  • \$\begingroup\$ I edited my original post, but I am not looking to use both machines at once. I want to use my small machine to power 1 leg. Then my big machine to power both when needed/desired. \$\endgroup\$
    – V Britt
    Nov 2, 2018 at 21:13

If you get two 120 V lines in your house making 240 V together, then don't worry about balancing the two. Your neighbours might take care of that and that system is designed to have (some) unbalance.

Yes, I think you can treat each leg independently. But Simon Richter commented that your question must have been about the off-grid situation. That situation however is not clearly described.

You say: "I have 2 Generators, a small 3300 Watt Inverter and a big loud 9000 Watt generators." But this sentence doesn't make clear what exactly you have. Do you have a small 3300 Watt Inverter and consider it as a generator? And do you really have 'a big loud 9000 Watt generators' (in plural)? Maybe you could rephrase that part of your question to make it more clear. At the moment I take it looks as if you have one 3.3 kW generator (and call it an inverter) and a 9 kW noisy generator. Is that correct?

I have no idea about US connectors and their codings so maybe someone else might be able to help you with that.

About the grid tie in. WhatRoughBeast answered that you could 'forget' to disconnect the grid and kill yourself or a power company worker in the process, although the law of Darwinism also applies to those people who don't properly ground a power line that they work on. But to make 'forgetting to disconnect' a non-topic I advise to use a double-throw switch, so that the grid is automatically uncoupled when you connect a generator. Implement this consequently for every generator/inverter you connect.

  • \$\begingroup\$ This is specifically not about grid power. \$\endgroup\$ Nov 2, 2018 at 15:43
  • \$\begingroup\$ He was saying that he needs the inverter and generator for hurricanes. I read that as for hurricanes only and that this implied he has 2 120 V lines coming from the grid to power both his 120 V and 240 V loads. This in my defense. But you are right. His balancing question must be about the off-grid situation. \$\endgroup\$ Nov 2, 2018 at 16:17
  • \$\begingroup\$ I assume that the "inverter" is really an inverter-type generator. \$\endgroup\$ Nov 2, 2018 at 16:26
  • \$\begingroup\$ I have no idea what an 'inverter-type generator' is. \$\endgroup\$ Nov 2, 2018 at 16:30
  • \$\begingroup\$ I googled it, now I see what it is. A variable speed generator with an inverter that gives off a fixed-frequency sinusoidal voltage. Nice. \$\endgroup\$ Nov 2, 2018 at 16:36

These projects are all about safety.
If the hassle of using extension cords to power main equipment during power outage is too much, or you have too many power outages. Why not invest in a permanent backup generator?

Can I connect my 120v Generator to 1 leg and just make sure my 'crucial lines' are powered by this leg. Over night I would ensure all my 240v Breakers are off.

Looking at the schematics, you could use the large generator to power your house. You will need a transfer switch.
However, note the 30A circuit breakers in B and R, these trip independent. Meaning when one of them trips due to a 120V overload, one leg of your 240V system might still be live, creating all sorts of funny business phantom powering equipment.
As it is built right now, I would deem this generator unsuitable to power a house.

Although it might be possible to use voltage monitors to guard for such situation, I'm sure it's not according to local code.

Using the 120V inverter would be a lot more complicated, this would require a secondary transfer switch to make sure all 240V loads are disconnected.
You saying I would ensure all my 240v Breakers are off, is a problem, since your wife, son or helping neighbour might not.

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