Ron Goldstein Rongold
I had a 70431 22 KW unit installed 2 years ago. We had a small outage this past winter, and it ran fine, but my 2 central AC units were not involved then. The hurricane that hit the east coast on Tuesday knocked out power in my entire town @ 1:30 PM on Tuesday, and the power came back on @ 7:30 PM tonight (Thursday), for a total outage of 54 hours. I have a 3 ton A/C unit and a 5 ton unit. They are both 30 years old. The 3 ton has an LRA of 66.0 amps and an RLA of 14.2 amps. The 5 ton unit has an LRA of 99.5 amps and an RLA of 21.5 amps. Neither one has a soft start, and I was expecting problems. I flipped on the 3 ton unit, and the generator rpm dropped slightly and lasted for about 1/10 of a second--no problem. I turned it off, and went and turned on the 5 ton unit--again, a slight rpm drop for about 1/10 of a second--no problem. Now the big test---I turned on the 3 ton unit and then, reluctantly turned on the 5 ton unit----surprisingly, the rpm's dropped for only about 2/10 of a second, and the generator handled both units being on without any problems, along with the rest of the house---well pump, electric stove, pool pump--hot water heater---really surprised me. 

I turned off the generator twice at 24 hour intervals to check the oil, and it used only a total of about 2 ounces for the whole 54 hour run. I have three 120 gallon propane tanks, and they went from about 70% down to about 50%. I estimate that I used about 70 gallons of fuel in those 54 hours---not too bad. My electric supplier (NYSEG) is very reasonably priced. I guess generating your own power IS NOT very cost effective.

RON
Quote
BillM
You have bigger nuggets than I do.  I would not have tried both but super happy it turned out ok for you.  There are some really inexpensive home automation products that you could easily program to prioritize your AC units and run only one at a time.  You can prioritize based on temperature or a priority like after 7pm the unit supplying the bedroom(s) gets priority.  Then again, based on your post it seems running both at the same time is viable.  I don't have the expertise to know or chug the numbers if you are within specs but my concern is if you are not, them starting at the same time will beat up your generator too much and that's why I was thinking home automation.  I did something similar 2 years ago for different reasons but used home automation coupled with a relay in line with the AC Compressor control wires.  The house could call all it wanted for 'cold' but only one compressor would run at a time based on logic I set.  The furnace running, fan on, thinking it was cooling wasn't harming anything and I always believed running the fan all the time is not a bad thing.
Quote
Peddler
I think if you went from 70% (84 gallons) to 50% (60 gallons)  x 3 should be about 72 gallons averaging about 1.33 gallons per hour.  Presuming they are 120 gallon tanks which hold 100 gallons when full at 80%.  That fuel and oil consumption is right in line with what see with these units.
Quote
Ron Goldstein Rongold
One other thing I forgot to mention is that the power came back on while I had the generator turned off to check the oil and let it rest for a while. Even though it wasn't running, it sensed that the utility power came back on and switched the transfer switch back to the utility position. I noticed this when I went back into the house to go into the garage and get some oil---The night light in the basement was on. Evidently, the switch had transferred while I wasn't paying attention, although I did hear that that one of my neighbor's generator had turned itself off. I thought that maybe he was giving his unit a rest too.
Quote
Ron Goldstein Rongold
BillM wrote:
  I don't have the expertise to know or chug the numbers if you are within specs but my concern is if you are not, them starting at the same time will beat up your generator too much and that's why I was thinking home automation.


After this experience, that bothers me too. It doesn't happen often, but once in a great while, I have heard both of them starting at the same time. 
Quote
murphy
Install Hyper Engineering Sure Starts on both and it won't be a problem.  My 3 ton went from making the generator sound like it was going to stall to not being detectable.
Quote
grsthegreat
what murphy says. i installed the hyper sure start last week on mine. while using clamp on meter prior to install up to 97 amp short load. after sure start...22 amps.
Quote
Geoff Z
They really do stay true to their spec and provide 60%-70% drop in LRA. The technology is really quite amazing. We sell a lot of them. Their failure rate is almost nonexistent. 
Quote