Generator question

[Evergreen]

Hello, we are new owners of a Montana 380th and new members to MOC. We just returned from our first 3k mile shakedown cruise. found and repaired a factory pin plug on a front level jack that was causing various Errors however I havent had an issue since.
Question:
Our new rig is pre prepped for an Onan 5.5 kw Genset. I want to size an Onan generator to handle a full load requiring both AC units while other appliances are running. I am looking at a little larger Onan QG 6.5 Propane unit. it has the same footprint and roughly the same weight as the spec'd 5.5. my question to those who have an Onan 5.5 LP today, does the 5.5 propane unit handle both A/C units and other appliances (Microwave/TV etc.) with ease as it states on their (Onan) website? and, at what altitudes have you ran your generator? we live at 8100 ft and typically camp at 6,000 ft to 10,000 ft. knowing significant KW loss is going to take place (more so with LP gas) at said altitudes, I want to be sure I am not under sized. (I am aware that a vented retrofit will be required to support two (forklift style) horizontal tanks.)
thanks in advance for your input.

[mlh]

Each 1000 feet of elevation reduces power output 3.6%. At 10,000 feet you are down 36%. That goes for any naturally aspirated engine.
Lynwood

[dieselguy]

Get ready to burn some propane ... but you said you're ready for that.

[scottz]

I can't say that I have tried to run all of those things at the same time; I know my 5.5Kw will handle both AC units. We frequently camp at 11k; the last time we used the generator and ran one AC unit and the mircowave; did not try the second AC.

[Evergreen]

Originally Posted by scottz

I can't say that I have tried to run all of those things at the same time; I know my 5.5Kw will handle both AC units. We frequently camp at 11k; the last time we used the generator and ran one AC unit and the mircowave; did not try the second AC.

Good to hear the 5.5 can handle both AC's at higher elevations.maybe I'm over thinking it. Is your Onan a propane unit? if so, is it connected to the existing LP circuit or do you have a supplemental tank dedicated to the generator?

[scottz]

I can't say for sure if it can handle both AC's at 11k; I did not try. However, the elevation at my house is 7400; it will run both of them here.

Mine is LP connected to the existing tanks. I don't have a lot of data, but I think it will run 6+ hours on one tank.

[Evergreen]

All very helpful data Scottz, thank you very much for sharing. one last question, do you know if your Montana has 1- 15000 BTU AC/Heat Pump and 1- 13000 BTU AC or is your set up different?

[Evergreen]

Just noticed your pups picture, we have a 6 year old chocolate lab. best dog we have ever had in our family.

[Kenw]

If you decide to purchase the larger gen set please assure that the wire size from the generator to the box is big enough to handle the additional amps. Please also make sure that the transfer switch is also large enough.

[Evergreen]

Originally Posted by Kenw

If you decide to purchase the larger gen set please assure that the wire size from the generator to the box is big enough to handle the additional amps. Please also make sure that the transfer switch is also large enough.

Will do and thank you Kenw for the heads up. I will plan to take the 5th wheel straight to the Onan Generator service/supplier here in Denver and have them check wire gauge, compatibility with the prepped start/stop panel/harnes located in the coach. didn't think about the transfer switch...
great advice!

[Evergreen]

Funny, just spoke with the Onan provider here in Denver, when I asked him about the transfer switch he paused and said I was the transfer switch. apparently they have moved away from an automatic transfer internally, simply installing a plug at the generator to run the shore power cord up to the generator. makes sense, less components to fail. no different than plugging into a 50 amp service at an RV site.

[Kenw]

I had that set-up with my Fleetwood C class that I sold earlier this year, It works just great.

[mlh]

I don't think you are over thinking this. Onan says a 5.5 will handle 2, 13500 ACs with 1100 wats left over. The gas model has 12.9 HP the LP has 10.7 HP but at 10000 feet it's down to 7 HP and I think you have a 15000 and a 13500 AC. I don't know if it will handle both at once. I would call Onan to see what they say or just go to the 6.5 and be safe.
Lynwood

[mhs4771]

Our 5.5 Onan will run our dual 15K AC with power left over, but didn't use it in any high altitudes.

[PNW Fireguy]

We have the 6.5 light commercial lp Onan. I have run both AC (15k &13.5k) units, Wingard Trav'ler, two tv's (lcd) and the microwave at the same time. However we are basically at sea level. Haven't had an opportunity to run the genset at high altitude as we have always had full hookups in those areas.

[twindman]

I would doubt you need 2 A/Cs at 11000 feet. More likely to need the furnace.

[Dam Worker]

You might check the specs of both units to see what each leg is actually putting out. The junction box on all the units with a 5500 is rated for 30 amps. There is a post of mine on the forum that gives the exact rating per leg for a 5500 which is less than thirty amps there for allowing Keystone to use the 30 amp rated junction box and 10awg wire. The 6500 might require bigger wire and a better box. Can't tell you much about the transfer switch other than mine hums quite loudly when plugged into shore power. As stated before it is supposed to be able to run both AC units with some extra left over. Better look at upgrading your tanks to at least 40's as the tanks go dry quite quickly. My connection from the generator to the 10awqpg in the junction box nearly caught fire. All the tape was burnt off and or melted along with the wire nuts. Could have been real ugly, lucky it was a metal box and it was so hot you couldn't touch it with your bare hands. Be careful whichever way you go and it wouldn't hurt to double check the installation.

Tom Marty

[mlh]

Originally Posted by twindman

I would doubt you need 2 A/Cs at 11000 feet. More likely to need the furnace.

That has been my experience to. I've camped at 9200 feet in Wy in July and had frost every morning and a blizzard in September.
My Onan does have a high altitude setting on the carburetor.
Lynwood

[scottz]

Originally Posted by Evergreen

All very helpful data Scottz, thank you very much for sharing. one last question, do you know if your Montana has 1- 15000 BTU AC/Heat Pump and 1- 13000 BTU AC or is your set up different?

I think both of mine are 15k BTU. Here is a shot from the build sheet:

[Evergreen]

Originally Posted by PNW Fireguy

We have the 6.5 light commercial lp Onan. I have run both AC (15k &13.5k) units, Wingard Trav'ler, two tv's (lcd) and the microwave at the same time. However we are basically at sea level. Haven't had an opportunity to run the genset at high altitude as we have always had full hookups in those areas.

Great data, thank you! Im assuming your Montana had the pre packaged control panel in coach and harness's into the genset cabinet? or did they install the generator at the dealer/factory, or, did you have it done after market?