Connect 120v Gen to 50Amp ATS?

wa8yxm wrote:

DryCamper11 wrote:
How is a 120v only generator connected to the gen input of an automatic transfer switch in a 50 amp coach? Is the hot lead from the 120v gen simply connected to (and shorted across) both the L1 and L2 hot leads of the ATS?

Depepends on the generator but basically... YES

Now my ONAN is a 120 volt generator, but it has two 30 amp outputs. one goes to L-1, one to L-2 They are "in phase" though so I can not get 240 V out of it (Well I can but I cheat). According to "Sources" the unit can not be rewired for normal feed.

But one breaker goes to L-1, one to L-2 that simple.

Internal to the generator they are shorted together.

Others.. Well if I had a single 50 amp feed, then it would be shorted to L-1 L-2 as you describe.

If they are internally shorted, then they could be externally shorted as well, correct? You might blow a 30 amp fuse on one leg, if you draw more than 30 amps and the current doesnt flow equally through tbe two legs due to some imbalance.

If you don't do that, then you are limited to 30 amps on any one leg from a generator rated for over 60 amps when supplying a leg in the coach rated for 50 amps.


In other words, if you independently connect L1 and L2 to the two 30A outputs of the gen and you put a 40A load on the L1 input leg, the gen will be unable to meet that need even though it is capable of supplying 60+ amps.

Is it possible to cross connect L1 and L2 safely.? If you do, wouldn't you be able to meet that 40A need?
(provided the gen outputs remain balanced and feed current roughly equally through both breakers.) Even if current doesnt flow equally, at worst, thone of the 30A gen breakers will blow, I would think.

I wasn't sure if an HKAK with two 120 v outputs could have both outputs connected.

I know there is still the issue of the ATS which is usually 30A rated for switching.

It would have been nice that the OP stated what he was dealing with!

DryCamper11 wrote:
How is a 120v only generator connected to the gen input of an automatic transfer switch in a 50 amp coach? Is the hot lead from the 120v gen simply connected to (and shorted across) both the L1 and L2 hot leads of the ATS?

Depepends on the generator but basically... YES

Now my ONAN is a 120 volt generator, but it has two 30 amp outputs. one goes to L-1, one to L-2 They are "in phase" though so I can not get 240 V out of it (Well I can but I cheat). According to "Sources" the unit can not be rewired for normal feed.

But one breaker goes to L-1, one to L-2 that simple.

Internal to the generator they are shorted together.

Others.. Well if I had a single 50 amp feed, then it would be shorted to L-1 L-2 as you describe.

DryCamper11 wrote:
I'm interested in the electrical connection, not the mechanical plug/socket connection.

You can't really talk about one without the other, or shouldn't, because the physical type of plug/socket MEANS something about the configuration and capacity.

IF your gen has only one 120 output, then it probably doesn't have the capacity to run both legs of your 120 service in the RV.

You might be able to get away with it by severely restricting your usage inside......but it really isn't a good idea.

It is perfectly OK, however, to feed ONE leg off the generator.

time2roll wrote:
The manual I read has two 30 or 35 amp breakers so while it is single phase each pole may get connected to each side.

Yes! I suspect that's exactly what I will find. I was thinking about the 4.0CCK Onan 120 v gen in our first coach when I asked the Q. I had forgotten that I'd read in the HKAK manual that although it was single phase 120v, it had a split output. The CCK would be bridged across L1 L2 in that application (it has only a single output and no breaker).

That means that one could only pull a max of 33 A on each of the 50A branches even though the HKAK gen is rated at 66A. One couldn't pull a full 50 A on either branch if one needed to.

The 2800 watt inverter in the all-electric design would probably be bridged across L1 L2, since it isn't a split output.

Thanks to all for the comments.

The manual I read has two 30 or 35 amp breakers so while it is single phase each pole may get connected to each side.

MrWizard wrote:
are you 'wondering' about the built in generator is wired in a 50 amp coach ?

that generator has two outputs, and is wired to the genset input exactly like the
50amp shore cord is wired on its set of inputs

NO,, there is no shorting or connecting the two hot wires

that only occurs in a 50a female to 30a male dog bone adapter for shore power use

most RV generators have two 120v outputs
even a 4kw genny in an RV with a 30amp shore cord and breakers

one input will go directly to the house circuits
the other will handle the A/C unit and maybe minor bedroom or bath
so the house circuit can handle the kitchen, MW , fridge etc

I was wondering about generators like an Onan HKAK 8KW. It is inverter based and produces single phase 120v power. It doesn't matter how many physical outlets or receptacles it has, electrically, it has only one hot lead. My older Onan which produces 240v has L1 and L2 connected to the matching leads on the ATS.

time2roll wrote:
if the generator has a single output then yes generator input L1 & L2 will be bonded on the TS.

X2
Generator HOT goes to 'gen input L1' with a jumper from 'gen input L1 to L2'


When generator is source of AC Power.....both L1 & L2 are energized so Main Panel is hot on both busses.

Otherwise only 1/2 of main panel would be hot when on gen.

are you 'wondering' about the built in generator is wired in a 50 amp coach ?

that generator has two outputs, and is wired to the genset input exactly like the
50amp shore cord is wired on its set of inputs

NO,, there is no shorting or connecting the two hot wires

that only occurs in a 50a female to 30a male dog bone adapter for shore power use

most RV generators have two 120v outputs
even a 4kw genny in an RV with a 30amp shore cord and breakers

one input will go directly to the house circuits
the other will handle the A/C unit and maybe minor bedroom or bath
so the house circuit can handle the kitchen, MW , fridge etc

You would need to get the correct adapter to go from the three wire 120 output to go to the rig's 50 amp 120/240 connector. Yes L1 and L2 are connected together.