A/C with generator Q's

[KTManiac]

Just got off the phone with Dometic and they told me that my A/C unit's "LRA" (Locked Rotor Amps, aka start-up amps) is rated at 60 amps. Whaaaat!!! At 115V that is like 6900 watts!!! OK, let me get this straight, the built in Onan 5500 (which I don't have), is supposedly able to run the A/C that I have, plus another 13.5k btu A/C unit, plus some other stuff to boot? I don't get it. I don't have a 2nd A/C, so that's not really a worry for me. For those that have dual A/C, what are your experiences, and how the heck does that work? Is there some sort of control in the units that does not allow them both to be in a start situation at the same time?

I am leaning toward twin Honda eu2000's hooked together to run my one 15k btu unit. Is this going to work at all??? If they are able to start the A/C I should be OK, as the running amps are rated at 12 amps, which is 1380 watts. Does anyone here use this set-up with any success?


Another thing that I would like to know is:
If they can handle the start-up, will the over-draw/under supply of amperage mess up the A/C's electric motor or the generator's inverters or other circuitry over a period of time. Even if I get twin eu3000's, the math still does not pencil out.

I talked with a tech at an outfit that sells Honda gens, and he said his rule of thumb is to take the running amps and multiply by 3 to figure out the minimum amount of generator that you need to start an A/C. In my case the number is 4140 watts. He said it should work, but just barely with two 2000 watt units.


On a side note:
How can a 30 or 50 amp service at a campground handle a 60 amp LRA unit? Is it just that the draw is so quick that the breaker doesn't heat up enough to react and trip the circuit?

[bsmeaton]

I beleive the start up spike is too short for the circuit breakers to react. Setting the pencil and slide rule down, I can tell you that our 5500 will run both ACs.

Not to confuse the issue, but I did have have to move the front AC to the other master 50A breaker in the panel. The campground feeds two 50A breakers, but the Onan only feeds 30A + 20A. Our original wiring had both ACs on one of the 50A master breakers, so it did fine at a campground, but the Onan couldn't do it on just the 20A. Once I separated them, the Onan did fine and now one runs on the 30A and the other on 20A. Not sure how that will spill out with your two Hondas.

[ole dude]

Good information and words of wisdom from the Wal Mart greeter. HA HA HA I plum smooth couldn't resist.

[bsmeaton]

[Waynem]

I had the Onan 5500 on my 3400RL and never had a problem running both AC's and/or other appliances at the same time. Never did do the math, just turned things on and they worked.

[ARJ]

2 Honda 2000i's. No problem starting and running the AC.

[skypilot]

I agree with ARJ. I have the two - 2KW Honda's and have run them now for 3 seasons. I did find this year that I had to have one running full bore (i.e. have econo-mode turned off) and the other could be on eco mode; last year both running on eco-mode would spool up fast enough to cover that start surge; this year (for some reason) they didn't and the generators would trip off-line; I'd have to shut them off, restart them and then start the AC again. Forgot to ask Honda dealer about that when I turned them in for fall/winter annual service...

By the way, with both running full bore the two handle our 15K AC, the microwave, Refer on Electric, and TV (older tube type still) with not a blink; but again, both have to be running out of econ-mode to handle the Microwave being started up with AC running; without the AC running, both can be on econo-mode and they handle the microwave start up fine.

Sorry for the long post -- guess I'm getting tired and very wordy -- Best to all out there.

[Delaine and Lindy]

We had a Onan 5500 mounted in our Cambridge 358 and it pulled two A/C and the other appliances with no problem. We also have a 50amp Tool box Generator made by Generec and it pulled the 2 A/C also. However when using the Microwave at times would trip the breaker. Don't know why. We don't have a Generator in this 5er but still have the Tool Box generator but we leave it at home base. We just never use the Generators enough to justify the cost. GBY....

[Fjkiss]

your info is not right the LRA is ONLY that: locked rotor (motor will not turn)
start amps are very different. about 3 times run amps for a mill.second
our gen. will work with power to spare.

[KTManiac]

I think perhaps that we may both be a little wrong. The following is from a page that I just found:


AMPS

Full Load Amps
The amount of current the motor can be expected to draw under full load (torque) conditions is called Full Load Amps. It is also known as nameplate amps.

Locked Rotor Amps
Also known as starting inrush, this is the amount of current the motor can be expected to draw under starting conditions when full voltage is applied.

Here is a link to the page >>>

http://www.motorsanddrives.com/cowern/motorterms.html


Also read somewhere else that the LRA rating of the motor is used to determine what guage of wire needs to be used when wiring the unit in. So, in the event that the rotor is prevented from turning(frozen bearings, obstruction, etc.), the wiring to the motor can handle the load until the breaker trips.

Also, from yet another source, evidently, any time the rotor is not turning, it is considered to be in a locked condition, even if it is free to turn. But that kind of sounds like a technicality to me because once it starts turning, the draw would decrease quickly.

Even though it sounds like two 2kw generators are working for some of you, I guess the only real world answer for me is to drag my 5er down to the Honda shop, have them hook up a couple eu2000i demo gennys, and make sure it works on my unit.

[KTManiac]

UPDATE:

Well, a couple weeks ago, I hauled the 5er down to the local Honda Motorcycle dealer and demo'd 2 eu2000i generators hooked up in parallel to see if they would push the 15k BTU air conditioner.


Good news to report:

• With both of them on Eco-mode, the A/C started with no problem.
• With A/C up and running, the microwave worked.
• With A/C up and running, the convection oven worked too.
• I got a great deal on them! (in Honda price comparison terms, anyway)

I bought one eu2000i Companion 30amp* unit, and one regular eu2000i unit. This eliminates the need for buying the $200 30amp parallel box set-up thing that hangs off the front of one of the units. Instead, all that you need is just the $50 cable set, because the Companion unit has the 30amp twist-lock outlet and parallel stuff built into it.
*(30amp is just one of the outlet types on the Companion unit, when used by itself, it still only puts out 2000watts/16.7amps peak and 1600watts/13.3amps continuous. When the units are hooked in parallel, you can get 4000watts/33amps peak and 3200watts/26.6amps continuous.)

I asked the guy what his best deal was, and he came back with some good prices. Just as good as Mayberry's, and I didn't have to wait for them to be shipped halfway across the country either. Camping World wouldn't come down from their price, and besides, they don't carry, nor have they even heard about the Companion model. Other retail outlets near me had sky-high pricing as well.

So, in the end, the Companion unit was $999, the regular unit was $899 (both of them, commissioned, serviced, and tested), the cable kit was $40, and I got 2 hour/tach meters for $30 each. The Honda shop was happy to have my business, and I got a fair deal with no hassles, in my view.

I installed the hour/tach meters last week-end, so now I'm ready to go camping! (if it ever stops raining and snowing here)

[noneck]

Sweet...sounds like your gonna be a "cool" boon docker we can all envy!