Paralleling Yamaha 4500W and Honda 2000W

Sorry that I haven't responded until now. The Yamaha is 4000W with 4500W surge. Fivers with two a/c's come with a 5500W generator. Looking at the specs on some air conditioners a 15k unit takes 3500W to start up and 1500W to run. A 13.5k unit takes 2750W to start and 1250W to run.
Total start power= 6250W Total run = 2750W
Starting is the problem. My best bet to run both with the Yamaha would be to start one up and then the other and make sure that both could never try to start at the same time as this is when damage to the compressor would occur. I guess leave the thermostat in the bedroom as low as possible so that it never shuts off and let the other unit cycle. Then come night, shut off the living room a/c completely.
If this is too much trouble then I guess the safest bet would be to wire in a separate plug for the bedroom a/c and run it off of the Hondas. It's gonna be a real pain carrying around 3 generators though.

I may have to end up getting a Yamaha 5500W which is 6300W surge. It also has the advantage of having both 120V and 240V which is convenient as that is what my water well pump runs off of.

EDIT: I see now you've got 2 hondas. Manual transfer switch, parallel the hondas, you're off to the races!

If you haven't tried running both off the Yammie, try it just to see. Do your best to make sure the batteries are fully charged so that the converter draw is taken out of the equation. Because I'm sitting here scratching my head as to why a 4500 won't run two ACs.

If it really won't, then I would get fancy with a manual transfer switch to separate out one of the ACs to an aux inlet fed by a second gennie. Then, you can parallel or go separate, as you choose.

Wayne Dohnal wrote:

LittleBill wrote:


why was the lights changing? was the voltage all over the place?


i would think when they sync, voltage and hertz would sync


i personally think it will either work, or go into overload and protect the inverter.

Naturally the voltage would have to be changing for the lights to vary in brightness. The Outback inverter was running off of battery and can change its contribution to the output instantly. The Honda has a ramp-up/ramp-down delay. I'm "assuming" the two devices were in a slow oscillation loop trading off which one carried most of the load. The Outback's output is around 122 volts steady, the Honda's is 128 volts under lighter loads, ramping down to 120 as the load gets heavy. When the Outback inverter sees a higher voltage than it's producing its bi-directional H-bridge turns into an unregulated battery charger. When I realized I had the outputs cross-connected, I broke the connection without any investigation. A couple of factors here aren't present with generators only.

makes sense. pretty cool

LittleBill wrote:


why was the lights changing? was the voltage all over the place?


i would think when they sync, voltage and hertz would sync


i personally think it will either work, or go into overload and protect the inverter.

Naturally the voltage would have to be changing for the lights to vary in brightness. The Outback inverter was running off of battery and can change its contribution to the output instantly. The Honda has a ramp-up/ramp-down delay. I'm "assuming" the two devices were in a slow oscillation loop trading off which one carried most of the load. The Outback's output is around 122 volts steady, the Honda's is 128 volts under lighter loads, ramping down to 120 as the load gets heavy. When the Outback inverter sees a higher voltage than it's producing its bi-directional H-bridge turns into an unregulated battery charger. When I realized I had the outputs cross-connected, I broke the connection without any investigation. A couple of factors here aren't present with generators only.

I searched YouTube pretty good and didn't find any vids on the subject.

In my world if it hasn't been posted on YouTube I ain't doing it.

Wayne Dohnal wrote:
My best hopefully educated guess, taking absolutely no responsibility if anything is damaged:

1. They will sync.

2. Because of the different design voltages, the Honda will carry all of the load, up to and possibly past its rated continuous load, before the Yamaha begins picking up any of the load.

I wouldn't try it myself unless the value of knowing what happens is more that the cost of at least one new inverter.

As a comment, I have accidentally paralleled my eu2000i with an Outback inverter (during a power outage). Nothing broke, and it took me a while of watching the lights in the house changing brightness until I figured out what was happening.

why was the lights changing? was the voltage all over the place?


i would think when they sync, voltage and hertz would sync


i personally think it will either work, or go into overload and protect the inverter.

Do you really NEED both AC's while running off the generators??? The few times that we boondock, the twin EU2000's are fine to run my 15k AC and all the lights I need... Sometimes you just have to rough it a little :B:B

My best hopefully educated guess, taking absolutely no responsibility if anything is damaged:

1. They will sync.

2. Because of the different design voltages, the Honda will carry all of the load, up to and possibly past its rated continuous load, before the Yamaha begins picking up any of the load.

I wouldn't try it myself unless the value of knowing what happens is more that the cost of at least one new inverter.

As a comment, I have accidentally paralleled my eu2000i with an Outback inverter (during a power outage). Nothing broke, and it took me a while of watching the lights in the house changing brightness until I figured out what was happening.

First give it a go with the Yamaha and Hondas not in parallel.
Some report running two air conditioners on 30 amp service and with new units I believe it has some possibility with 4000 or 4500 surge watts.
Make sure the batteries are charged and everything else is off.

Assuming it fails, break out one air conditioner to run on a separate power source.
Just need a transfer switch, inlet and some romex.