Problem running 2nd a.c on generator

[ctwebb]

Hi all, I have a Onan 5.5 LP gen in my 2014 HC, I have had problems running both air conditioners at the same time. It started out tripping a breaker on the gen set. I found out both ac, units was on the same leg in the panel box. I have moved the breakers to where the ac units are on two different legs. No more tripping breakers . But now it sounds like the transfer switch is opening when starting the second unit. This only happens when running the generator , Everything works fine when connected to shore power.

[uhftx]

Just throwing this out there. Remember this is 120/240Volt circuit when connected to the utility power. Your gen set may be different. I'm not giving you advice on how to correct this. Without knowing your knowledge of AC circuits. You will have to consult a qualified licensed electrician and have them make a few measurements.

http://www.forestriverforums.com/att...0d73c8bef4.gif

Much more information here:

http://readingrat.net/wiring-diagram...nd-rv-about-2/


The transfer switch may trip if your hot leg and neutral leg are reversed on your second AC unit. Another possibility is the Ground and Neutral are not independent or may be crossed at the AC unit or the ground is developing a voltage from the second AC unit and causing the transfer switch to fault out.
Out of curiosity I looked up the specs here and the generator set is only 120V at 45.8Amps.

http://power.cummins.com/content/rv-qg-5500-lp

So you only have one leg of power. You should be able to run both AC units with that power. There could be an internal problem with your second AC unit causing the neutral voltage to rise.

Don't play with live voltages. Resistance measurements with all power disconnected and ohms law will allow you to do some calculations. If you have a clamp on amp meter for Alternating current you can investigate further and perform more calculations to identify the problem.

If you know of a retired electrician or electrical engineer they will be of further assistance. Probably not what you want to hear but better to be safe than sorry.

[ctwebb]

Thank you for the information, I will have a electrician look at this to figure out what it needs

[jameswbarton]

I have a 7500Watt Generator which can barely handle the two AC's on the same leg. Now You will have the Water heater and one AC on the same leg which is almost as power consuming. If your Water Heater is on electric. In my setup the two AC on one leg and the Water heater and Microwave on the same leg balanced.

[Snoopy]

A few years ago, my brand new onan gen was shipped without the second breaker installed. it was only putting out 1/2 the power need to run our second ac unite.
Snoopy

[TELECOOL]

Hi there I just read your post was wondering if you have been able to find a solution to your problem about running both a/c units with your generator.If not I may have a solution for you

Thanks Johnny

[ctwebb]

have not had a chance to get a electrician to look at it, It has not been fixed.

[TELECOOL]

Originally Posted by ctwebb

have not had a chance to get a electrician to look at it, It has not been fixed.

It sounds like your start up amps could be the problem the units are drawing too much current when they first start up thus dragging down your generator causing it to trip.

Also you may want to check in to installing an Easy Start 364 from Micro-Air soft start on each of your a/c units then you will be able to run two a/c units on a 30 amp campsite hookup plus if you need to run your generator it will help the generator operate at a lower start up load.This is not only better on your a/c units but also is better on the life of your generator.
I have (3) 13,500btu units on my 2017 3811MS and they are working great.Plus it about cuts the start up amps in half. I'm a air conditioning contractor been doing this business for over 30 years and this product works great.

[ctwebb]

Thank you Telecool

[Rondo]

Question for TELECOOL: Can these Easy Start 364's by Micro Air be installed by us common folk or do we need to have an A/C specialist or RV tech install these? Can you also tell me what the approximate cost of each unit is? Sounds like a good thing to have especially if we plan on doing any boondocking. Will they help to run even one of the A/Cs if we have two of the Honda 2000's hooked up also?

[jeff_banning]

I am confused on the statement of "same leg" in the panel box? A 50A unit with two A/C's should have one A/C installed in the breaker box on each leg of the 50A 120V/240V 50A feed.

I also just looked up specs of the Onans 5500 and 7500 and both are 120V only so this means much like when you go to a 30A campsite, all appliances are combined to a single leg no matter where they are in the breaker box.

I will also assume the transfer switch on the ONAN is just dumping this power to the breaker box one leg.

I do see the Onan 5500 lists 45A but most gen sets this size (residential) I have dealt with still only have one 30A 120V output and one 15A receptical. On our bowfishing boats we use both the 30A and 15A to keep from popping just the 30 under full load..

My question is, much like splitting 30A and 15A camping site legs to two legs (Camco makes this splitter), does the Onan 5500 need to be wired/rewired to have both feeds so you can have full 45A of power?

[uhftx]

I am unsure if the onan 5500 or 7500 LP models have the internal windings on the stator/communtator to generate a 120/240 V. By specifications from cummins/onan it is 120V only and that is all I have to go on.

In order to get 240V you have to double and have separate windings on the commutator.
This is why the RV 30 Amp plug comes into play. Most home generators have a 30 Amp twist lock connection. The 30 home vs RV are differrent so you can not screw it up. RV 30 is single leg of 30/120V. Home is 4 wire 30 Amp/leg 240V between both legs or 120V each leg to Neutral.
With that being said. The RV generators only run at 1800 rpm. To increase the windings and spacing for a 240 circuit and maintain a compact space. The generator would have to operate at 3600 rpm. Double what the RV gen set operates and much louder. Go to a nascar race and you can do the comparison and contrast for noise. Most tracks limit the operational hours for generators just for this reason.

You can get the 240V at 1800 rpm by increasing the size of the # winding's which results in a larger physical size or 1/2 the current rating / leg for the same physical size.

If there is a service outlet, normal duplex outlet at the gen set which only supplies 120V then it is on the same leg anyway and the splitter you mention is redundant. Where this device comes in handy is if you are connected to the 30 plug @ at a campground and need more power. Because they are separate in the CG circuit breaker box but you can not tell if they were wired to the same leg or not.
So you could still fry your electronics if miss wired unless you just use an extension cord from that duplex outlet. Safe or sorry. I would not go that route.
In my unit. The 50 only supplies the Washer Dryer closet and if I had a second AC Unit. I've only used it for convenience or to plug in a space heater in the bed shower area into electrical socket closet because I have the the not equiped W/D.

If you have 2 honda's with a parallel kit and connect via the 30Amp plug it still is only 33 Amps @ max load.

Air conditioner soft start units. The original ones were nothing more than a larger capacitor to supply surge current upon start up. Newer ones may use a charge pump / limited current boost, circuit to perform the same or similar function.
They have been around for at least 30 yrs and we have used them on difficult problematic ac unit compressors. Wiring is pretty straight forward if you are comfortable with this type of work. Amazon has them also, otherwise if not online. Then it is off to an electrical distributor FYI: may require a license for purchase.
https://www.google.com/search?q=soft...w=1622&bih=854

I just checked this is a home depot item now. Maybe be order only or on the shelves.

http://www.homedepot.com/p/SUPCO-120...SPP6/203566183

Chris

[h2ojocky]

I got an email from Matteo at Micro Air. This is what he said:Yes, the EasyStart 364 will allow you to start and run your 15kBTU A/C on a single Honda EU2000i generator. Hundreds of our customers have met with this same exact success. Please realize though that a 15kBTU A/C can consume upwards to 1800W and even more on extremely hot days, so there will not be much headroom left for auxiliary loads in your trailer. Some fairly strict power management is therefore required. Typically, both your hot water heater and refrigerator need to be operating on propane to eliminate their AC power loads, and also the battery charger/converter might need to be turned off at its circuit breaker so it is no longer fed AC power either. Many converters can draw up to 1000W (!) when there are in bulk (rapid) charging mode, or if a lot of 12V loads are being used (e.g. lights and fans). Please keep this in mind since generator overloads can still occur, even with EasyStart installed, and it won't be the fault of the EasyStart or the A/C directly.

If you have any further technical questions about EasyStart, please visit our new EasyStart™ Knowledge Bank , recently added to our website. There you will find helpful information, installation guides, and a library of wiring diagrams for various rooftop makes and models.

Thank you again for your interest in our EasyStart products.

Matteo Giovanetti
Electrical & Controls System Engineer
matteo@microair.net

Micro-Air, Inc.
124 Route 526
Allentown, NJ 08501
609-259-2636
www.microair.net

[Ironbrow]

Originally Posted by TELECOOL

It sounds like your start up amps could be the problem the units are drawing too much current when they first start up thus dragging down your generator causing it to trip.

Also you may want to check in to installing an Easy Start 364 from Micro-Air soft start on each of your a/c units then you will be able to run two a/c units on a 30 amp campsite hookup plus if you need to run your generator it will help the generator operate at a lower start up load.This is not only better on your a/c units but also is better on the life of your generator.
I have (3) 13,500btu units on my 2017 3811MS and they are working great.Plus it about cuts the start up amps in half. I'm a air conditioning contractor been doing this business for over 30 years and this product works great.

Absolutely! We had a micro-air soft start on our old KZ 5th wheel and we ran our 15k AC on a Honda 2000. We just bought a 2018 Montana 3790RD and the first thing we did was get two micro-air soft start cards. I wouldn't own any RV with out it.

[Dam Worker]

Jeff if you look carefully at the Onan 5500 you will see it has two legs going into the RV panel. Neither is 30 amps, I can verify that as Keystone did a crappy job of wiring my 5500 at the junction box and I had all the wire nuts melt. A bit of cussing out Keystone and some rewiring on my part and it now never has a burning plastic smell. Two legs 27.5 amps through each leg if I remember correctly. That is also why you will see the metal junction box rated for 30 amps or less. If it had only one leg I think it would be 55 amps and it would need a different box. Also if you look and start counting wire you will see a bunch and they are all rated for 30 amps in theory.

My generator now runs both just fine but the living room one does not put out much air. More of Keystones work to be redone.

Tom Marty

[Mudchief]

We have the 7500 gas and it puts out 58 amps at 240 volts. I have turned on everything for a test and it runs everything.

[Wheelhouse]

We were dry camping and found only one hot leg of the gen transfer switchgear was wired. I placed a black jumper wire on the gen switchgear side top lugs, BLACK TO BLACK. Switchgear transfer on left side is Shorepower, on right side is Generator transfer switchgear. This now feeds all my outlets and conveniences with no lags. Hope this helps.