Cummins Onan Diesel

Wattless · March 2011

I'm getting close to adding my permanent generator on my offgrid system, and at this point I'm investigating the Cummins Onan 7.5 KW diesel. I'm looking at the model 7.5HDKAL for the 120/240 option not available on thier QD series.

I'll be charging three strings of Trojans L-16s wired for 24 volt. If I remember the math right that should be running the genset at about one half load.

I still need to find out if the AGS on the Outback system will interface with the Cummins.

Any comments from people having gone through this process already would be helpful.
Thanks,
Wattless

blackswan555 · March 2011

Re: Cummins Onan Diesel

Which outback system ? how many inverters ? how many ah bat`s ?

The AGS is "two wire start" ,The FX Aux gives a 12v, you would usually use that to power a relay giving your a 2 wire start system, contacts close, gen runs,, Contacts open , gen stops,

have a good one
Tim

Schmidt · March 2011

Re: Cummins Onan Diesel

Wattless wrote: »

I'm getting close to adding my permanent generator on my offgrid system, and at this point I'm investigating the Cummins Onan 7.5 KW diesel. I'm looking at the model 7.5HDKAL for the 120/240 option not available on thier QD series.

I'll be charging three strings of Trojans L-16s wired for 24 volt. If I remember the math right that should be running the genset at about one half load.

I still need to find out if the AGS on the Outback system will interface with the Cummins.

Any comments from people having gone through this process already would be helpful.
Thanks,
Wattless

I have been fortunate to work with a tremendous amount of off grid systems utilizing solar PV with battery based inverters systems and generators. For installations ranging from industrial to off grid homes, we have had the best results with Northern Lights Generators. Click for more information. These generators can be equiped with the GSC300 Auto Start, so they can be easily integrated with the "2 wire" Start/Stop functionality found on the Outback inverters.

With many of the industrial sites where we install a PV/Generator hybrid system (replacing generator only), we have seen the large majority of Northern Lights Generators run up to 20,000-25,000 with only regular maintenance.

Our experience with Cummins Onan generators is that they don't provide the realibilty and longevity of the Northern Lights, with proper installation and maintenance, they can still offer a descent service life. However, you will need a third party start module for this generator, as the "2 wire" start/stop function of the Outback will not start the Onan.

peterako · March 2011

Re: Cummins Onan Diesel

Hi there running a diesel gen set on half load is not good for it life time.
They like to work special if you think that a 1800 RPM gen is running slow as engine it easyly can run on 2500 RPM but as gen it is fixed on 1800 RPM and based on that it can not clean it self so easy from carbon built ups.
That is why it is best to have them run between 70 & 80 % load.

See if you can run also other load at the same time.

Also keep in mind that at the end from your charge cycle you are not putting 50% load in your batterys bud more like 5 - 10% so that means you are running on very low loading this time and that can be 30min. to 2 Hours based on the settings that you use.

Greetings from Greece 8)

techntrek · March 2011

Re: Cummins Onan Diesel

I agree, if you won't normally be running them well above 50% load you need a smaller genset. Or switch to another fuel.

Chuck46 · March 2011

Re: Cummins Onan Diesel

Well that specific generator is a 2 wire remote start variable speed, based on load and is rated for operation from 50% to 100% load. This engine is also low sulfer and quite clean for a diesel gen set. My thought is go fo it if you can afford the cost of fuel.:D

Chuck

BB. · March 2011

Re: Cummins Onan Diesel

Regarding Diesel and minimum loads... I have been recommending 50% minimum for any genset as the least amount of load that any generator can supply in a fuel efficient manner.

Some of the Honda euX000i and other Inverter Generator AC generators can run fairly efficiently down to ~25% load (depends on model and vendor) because they can throttle back with light loads.

For Diesels, it appears the general recommendation is 60% minimum load to reduce chances of wet stack, glazed cylinders, carbon / coke deposits, etc... Although I have seen 40% to 70+% recommended minimums too.

You have some alternatives besides finding a smaller genset... Running optional loads when the genset is running (water heater, pumping, vacuuming, washers, etc.).

As well as something called LP Fumigation (also may work with natural gas). The link I provided talks about automotive diesels, but the information should be helpful for diesel gensets too.

As always, do your own research. Adding LP Gas to a intake on a genset is always fraught with risk.

-Bill

oil pan 4 · April 2011

Re: Cummins Onan Diesel

The little 4 pole diesel generator sets I work on run at 40%, no more no less load for many thousands of hours and I dont have any problems from them.

Saying diesel engine fumigation "also may work with natural gas" is an understatement. Natural gas is the original diesel engine fumigating gas. Its been done since at least the 1930s.

jauguston · April 2011

Re: Cummins Onan Diesel

FWIW the engine in the 7500w Cummins Onan is a three cylinder Kubota. I have one in my motorhome. They are a inverter type generator like the Honda EU series portables. Engine RPM varies with load. They are very quiet.

Jim

Cummins Onan Diesel

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