Community Forums

JMonroe · 08-24-2015, 10:30 AM

We're contemplating the purchase of a new coach and one of the options is to upgrade from the standard 10kw gen set to a 12.5 - both Onan. Our current coach has a 10kw generator and I've noted that we get more amps when using it than we have when plugged into the 50 amp shore power.

My question is: Is there any benefit to upgrading to the 12.5kw generator? The cost is not very high for doing so (just over $400).

Sky_Boss · 08-24-2015, 10:49 AM

Obviously you can run all 3 AC units and freeze your butts off while running you coffee maker to warm up. LOL

I would look at a couple things to decide...

1. Fuel burn at equivalent power output. In other words, will the 12.5KW unit use the same or less fuel at 50W as the 10KW unit?

2. How much more weight will it add to the front axle? I'm very conscious of that factor since I'm running at the limit but that might not be so close in the newer units like yours.

One other thought. If the 10KW unit wil meet your realistic needs it will be easier to get it up to 50% power output for monthly exercising it. Not a big deal but something to consider.

Steve Ownby · 08-24-2015, 10:58 AM

Quote:

Originally Posted by JMonroe

We're contemplating the purchase of a new coach and one of the options is to upgrade from the standard 10kw gen set to a 12.5 - both Onan. Our current coach has a 10kw generator and I've noted that we get more amps when using it than we have when plugged into the 50 amp shore power.

My question is: Is there any benefit to upgrading to the 12.5kw generator? The cost is not very high for doing so (just over $400).

50 amp shore power provides approx 12,000 watts. The 12.5kw generator essentially duplicates that power, so 100 amps is available. The 10k unit provided 83 amps.

My 12.5kw Onan has been trouble free with over 2000 hours on the clock. Of course mine is powered by a Isuzu diesel and the current units use a Kubota diesel. Both the 10 and 12.5kw units are true 120/240 generators that operate at a constant rpm.

Since the cost is minimal, I would up grade to the 12.5kw. The 12.5 weighs 20 pounds more and to run at 50% load will burn about .20 GPH more than the 10kw.

Steve Ownby
Full time since '07

CapuTech · 08-24-2015, 11:08 AM

I would upgrade given the minimal cost. One other consideration is that both models will loose a portion of their power rating with elevation. It may not mean much unless you regularly need it at high elevation. However, to illustrate the point, the 10kW becomes only 7kW in Breckenridge, CO while the 12.5kW becomes around 8.7kW...

See the respective user manuals for the elevation related ratings.

Sky_Boss · 08-24-2015, 02:00 PM

Quote:

Originally Posted by Steve Ownby

...
Since the cost is minimal, I would up grade to the 12.5kw. The 12.5 weighs 20 pounds more and to run at 50% load will burn about .20 GPH more than the 10kw....

Personally...I would go with the larger one for the reasons you gave.

Of course, in my previous post I meant 50 AMPS not 50 WATTS. LOL That will teach me to type on an iPad and eat lunch at the same time.

I only suggested the 50 AMPS comparison because that is about 50% of the 12.5 KW output and 60% of the 10 KW output. I also find that TYPICALLY I seldom exceed 40 amps in my coach with a residential refer & 2800W PSW inverter. I just kinda guesstimated that 50 amps would be a fair estimate of average demand for an all electric coach. I'm just kinda anal retentive on figuring this stuff out.

(It's a curse.

)

At 20# more than the smaller generator (thanks for tossing that out there!) I would probably say...NO BRAINER! Go big or go home. I just thought I would suggest a couple factors to consider since he asked.

mrschwarz · 08-24-2015, 07:47 PM

Technally, what is the difference between the two generators, other than the circuit breakers? I know the engines are the same. What about the generator part?

SteveLevin · 08-24-2015, 08:01 PM

You can never have too much power!

And if the upgrade causes a weight issue, well, that ain't right.

Steve

Mr_D · 08-24-2015, 08:12 PM

My whole post just went away due to a "database error"!
Are the new Onan 10's a constant speed? I know the 7.5's were variable.
In the '02 DSDP we had the PowerTech 8.0 which was a constant speed Kubota and used only about a half gallon per hour on 50% output which was less than the 7.5 Onan's used.
Never had a problem with the PT but then we only had two 13.5 heat pumps. I specifically ordered the 13.5's so I could run both on 30 amps.

JMonroe · 08-25-2015, 07:01 AM

Looked up the specs on the Cummins site. Both the 10.0 and the 12.5 are pure sine wave and constant speed.

Also, shows only a 5lb weight difference between the two, .43 gal per hour at half power for the 10kw, .48 for the 12.5. At full power, 1.01 gallon per hour vs 1.2.

TQ60 · 08-25-2015, 08:32 PM

Go big?

At same "worst case" load with all ac running on hot day the smaller one is running fine but getting a workout.

The larger one will be wondering when you are going to turn something on.

The small difference in fuel consumption at 1/2 load indicates overhead close to same so full load difference could indicate if engine converts energy well.

Other factor in fuel use is smaller one operating at say 1/2 capacity load would mean larger one operating at 3/8 capacity.

So to be apples to apples ask for chart showing consumption by watts and they likely will be close

The larger one will make less noise and less vibration due to it not working very hard.

Playtime III · 08-26-2015, 05:43 PM

I believe the OP is from SC so this would not apply often.
When it is really cold outside, my 10kv is hard to turn over as there is no pre-heat option like on the main cummins engine (pre-heat via aqua hot or via 110v block heater). It also runs rough until the oil warms up which cant be good on the genny. Does the 12.5kv have a pre-heat ability?

Steve Ownby · 08-26-2015, 06:00 PM

Quote:

Originally Posted by Playtime III

I believe the OP is from SC so this would not apply often.
When it is really cold outside, my 10kv is hard to turn over as there is no pre-heat option like on the main cummins engine (pre-heat via aqua hot or via 110v block heater). It also runs rough until the oil warms up which cant be good on the genny. Does the 12.5kv have a pre-heat ability?

My 12.5kw has an Isuzu diesel and it has Glo plugs to provide some pre heat. I don't know about the later and I believe current Kubota diesel.

Steve Ownby
Full time since '07

CampDaven · 08-26-2015, 06:54 PM

I have a 10K with pre-heat on an 42 foot 09 with all the then available trimmings that I have not been able to even challenge with all systems lit up and running at Bryce Canyon (8200 ft).
So.....

MtnTrek · 08-31-2015, 09:43 PM

Product Details: 10.0 HDKCA11506 10KW 16HP Onan

Product Details: 12.5 HDKCB11506 12KW 23HP Kabota

<$1k difference, Go big or go home !! Same dimensions, nearly same weight.

They can put an 110v heat on the oil pan if you're worried about keeping that Rotella syn. warm on those arctic nights.

"Model Notes: Models tested to start and run from -20° F (29° C) to 120° F (49° C). Diesel models will lift fuel 3' (914mm)."