7KW Onan instead of 5.5KW?

[pitman44]

My wife and I recently bought a new 397TH. It came generator prepped, but no generator. In looking around for the rare as a unicorn horn generator, I found Onan makes a 7KW RV generator that has the same physical dimensions and weighs less than 20# more than the 5.5KW. Is there any reason to not go to the 7KW unit? Or is some place I could check? TIA

[matt & correen]

I have the 5.5Kw in my Momentum. Works great and will support 2 A/Cs, but I will say fuel consumption when dry camping you want to monitor if you want to use for longer stretches without moving the rig or transporting in fuel. I’ve burned through the 60 gallons on a long weekend at the tracks a few times. Looking at the spec sheets although higher power it’s hard to tell if you have higher fuel consumption for equal power. The top end of the 5.5kw is 0.9 gal/hour and 7kw is 1.2 gal per hour. At no load they are rated 0.3 vs 0.4 gal/hour. Maybe something to consider. But I typically buy more capacity when shopping, can’t beat having more power than needed.


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[pitman44]

I have the 5.5Kw in my Momentum. Works great and will support 2 A/Cs, but I will say fuel consumption when dry camping you want to monitor if you want to use for longer stretches without moving the rig or transporting in fuel. I’ve burned through the 60 gallons on a long weekend at the tracks a few times. Looking at the spec sheets although higher power it’s hard to tell if you have higher fuel consumption for equal power. The top end of the 5.5kw is 0.9 gal/hour and 7kw is 1.2 gal per hour. At no load they are rated 0.3 vs 0.4 gal/hour. Maybe something to consider. But I typically buy more capacity when shopping, can’t beat having more power than needed.


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Thanks for the reply. I agree with you that more available power is a good thing. Sort of like you can't have too much truck.

[Overtaxed]

I'd also consider the EFI (fuel injected) version if you're going to put your own in. People have had plenty of carb problems in, well, everything since gas became gas + corn. The EFI isn't much more and, doing it again, I'd absolutely get that vs the carb version that come stock from GD.

[pitman44]

I'd also consider the EFI (fuel injected) version if you're going to put your own in. People have had plenty of carb problems in, well, everything since gas became gas + corn. The EFI isn't much more and, doing it again, I'd absolutely get that vs the carb version that come stock from GD.

Definitely. EFI is pretty much a no brainer anymore.

[SolarPoweredRV]

You need to check that the generator output does not overload the wires that Grand Design pre-installed in your coach.

It doesn't matter if your coach can't use the extra 2kw, it only matters that the Generator can produce the full 7kw and the wires could be "Over Powered" by that extra energy. Additionally, your coach is rated for 50 amps and 50 amps is the Maximum amperage it should be fed.

Be extremely cautious with this "Buy Bigger" strategy when it comes to installing your Generator. You need to ensure that someone who is very qualified (Not the Salesman) does the Electrical calculations to ensure your safety.

[CX500T]

7KW is only 30A at 230V.

Your standard 50A park connection is 50A at 230V, or the way the RV uses it, 2 50A at 115V lines.

7KW won't overpower your RV.

The concern for input wires is legitimate. The wires that run from my gen to transfer switch are sized for 30A, and 30A is the output breaker on my 5.5kW.

(Starting loads are a bit more than the 5.5k that's the continuous rating)

As long as your gen to transfer switch wiring is of sufficient gage for the output breaker on the genset, you are fine.

If they are too small (say sized for 30A and it has a 50A breaker) you have two choices.

1- Put a breaker that trips before the ampacity of the installed wires.

2- Replace the Genset to Transfer switch wires with something that matches your breaker.

I would do #2. On my 397, its maybe $100 of wire and not too far or hard to run them.

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[Hoopy Frood]

Amperage isn't "fed", amperage is the current draw by the particular item using the electricity. A larger generator won't hurt anything.

[pitman44]

Amperage isn't "fed", amperage is the current draw by the particular item using the electricity. A larger generator won't hurt anything.

I think you're correct in that a larger generator by itself won't hurt anything. However a larger generator allows for the possibility of drawing more amperage than the wiring from the generator to the rig is designed for. CX500T's response is exactly what I need to check on. I was in that bay last weekend and my recollection is the wires into and out of the transfer switch were the same size, but I didn't check the label on the wire which I will do now.

[pitman44]

7KW is only 30A at 230V.

Your standard 50A park connection is 50A at 230V, or the way the RV uses it, 2 50A at 115V lines.

7KW won't overpower your RV.

The concern for input wires is legitimate. The wires that run from my gen to transfer switch are sized for 30A, and 30A is the output breaker on my 5.5kW.

(Starting loads are a bit more than the 5.5k that's the continuous rating)

As long as your gen to transfer switch wiring is of sufficient gage for the output breaker on the genset, you are fine.

If they are too small (say sized for 30A and it has a 50A breaker) you have two choices.

1- Put a breaker that trips before the ampacity of the installed wires.

2- Replace the Genset to Transfer switch wires with something that matches your breaker.

I would do #2 . On my 397, its maybe $100 of wire and not too far or hard to run them.

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Thank you for spelling that out for me. I've recently retired as an owner of a residential HVAC business, but we never installed generators or transfer switches so this is a bit different for me. I appreciate the guidance.