Connect two AC power sources to get more power

[andymlende]

Hi,

I have two AC power supplies that provide about the same 230V but are not on same phase (one is 120° off) and provide different max current. Is there a way to connect these two sources so I can get an output of  230 V and the combined current from both sources, therefore to have more power at the same voltage? Thanks 🤗

[Teken]

If this question was about how to achieve redundancy the answer would be to use a ATS (Automatic Transfer Switch). But, that isn't your real question and can't be done as you have asked & stated. A device will only draw what it needs in terms of current (amps) as required to operate. If you currently have 20 amps and want 30 amps available you would have the correct wiring, outlet, and breaker installed.

You can't draw down 30 amps off a 20 amp outlet / wiring without burning down your house / building. You also can't have out of phase voltage which could be -120 vs +120 without knowing the connected load and hardware is designed to do so.

Hire a certified electrician  . . . ☝️

[dpierce4776]

@Teken is correct and to add to that. All UPSs, PDUs, and the like can only use a max amperage. Which is also protected against over amperage by the plug type (L5-30, L6-20, L6-30) the number after the dash is the max amperage the device can handle.

So even if you could connect to power sources to get more amperage/power the devices themselves could not handle it. My suggestion to you is that if you need to handle more load get a bigger UPS or device.

[andymlende]

These two power sources that I have are two 3Kw grid tied inverters. Each inverter gets it's signal from different live line, therefore each one feeding the grid with different voltage and current if the load of my house is covered. What I want to achieve is not feed the grid when the load of my house requires more power, but put the two sources together to cover the maximum power available and feed just the excess to grid. I am not able to do any changes to the inverters setup as they are provided by government incentive program.

[andymlende]

The power sources I have are two 3kw grid tied inverters, each getting it's signal from a different live line, therefore feeding the grid if the load on the circuit is covered. What I want to achieve is cover the need of my entire house from both inverters and just the excess to feed the grid. Right now I am using inverters to feed 2 separate circuits in my house, one inverter to each circuit. Most of the time the inverters will not cover the need for each circuit, so I have to draw current from the grid.

[Teken]

I’m sure there’s a little bit of a language barrier in intent and translation going on here. So I’m going to try to ask and state some basics. A typical grid tied PV (Solar) system is connected to the homes AC mains. This power is sent back to the grid to offset what the consumer would owe per month. Some POCO’s may also offer the consumer incentives for generating the same during peak periods etc. The ideal is to be Net Zero or better yet Net Positive where you receive a credit from the utility. 👍

A typical grid tied system only operates when the grid is working. Should there be a black out the solar PV will turn off. This is done to protect the linesmen from being electrocuted from the solar PV back feeding.

Those who want to have the ability to power their homes during a grid down event would have a hybrid inverter system in place. That requires a bank of batteries that the inverter can tap power from and also engage its transfer switch to remove itself from the grid. 

If your inverter doesn’t have the ability to transfer and charge batteries. You’ll need to replace the current inverter or add in a third party inverter / charger system. Along with a bank of batteries so you can draw on it whenever you want. It should be made clear many other solar inverter companies have the ability to define when and how much power is fed to the grid vs consuming excess power within the home.

Anyway you cut it it’s going to cost you time and finances . Hence why it’s important to know what the long term goals are and to purchase hardware to meet those needs.

[dpierce4776]

And while that may be those inverters could be in phase rotation of each other or not. If they are not then tying them together would result in a large BOOM.

I understand what you want to do. But the reality is that without the proper equipment to match phase rotations of the two inverters or to only feed what you do not use or are not using at the time there sadly is no real way to do this. The only other thing you could do is, if as you say you have two circuits on your home then if you can move some devices to balance the loads between the two inverters. That way your home is using all it needs or can. As you said sometimes the inverters can not handle the load but unless I miss my guess you more than likely have more load on one than the other.

This usually happens as circuits in the home are daisy chained and if you have say large appliances on the same side of the home they are on the same inverter. Usually the front of the home is one one circuit and the back of the home on the other. So if your say HVAC and Electric hot water heater on on a back/rear wall they are pulling all from one feeder. You might need an electrician to extend one of those to the other circuit.      

[andymlende]

Thanks for the details provided on how the grid tied inverts work. In my case I just want to cover as much as possible for my house load from both inverters without adding any battery to the system. Looks like there is no easy way to do that with the setup I have.