Onan 5.5 HGJAB Wiring Question

[campincaptain]

I have a on-board Onan 5.5HGJAB - 6755k Gen. I need to know if this can be wired to push out a true 240v. Right now if I use a multimeter L1 to N=120v and L2 to N = 120v but L1 to L2 =0. From looking at the wiring diagrams the black wire is split off to go to L1 and L2 on the transfer switch. I know that true 120v/240v split phase I should get 240v when testing between L1 and L2 just like when connected to shore power. Why do I need this, well we have an inverter/charger that outputs 240v. When shore power is connected it runs through the inverter (transfer switch) to power to RV and charge the batteries. When we start the Gen the inverter does not recognize the gen power and does not switch to charging mode because of the L1 and L2 reading 0. Thanks.

[franktafl]

The power in your RV is composed of two single phase 120 volt legs not 240 v. the transfer switch makes the neutral come to the generator because there is no neutral tie in because the trailer park's power supplies that.

further explanation will be along shortly.

[wildwest450]

Originally Posted by franktafl

further explanation will be along shortly.

Cue a 4 paragraph dissertation in 3-2-1

[sundancer 87]

Originally Posted by wildwest450

Cue a 4 paragraph dissertation in 3-2-1

Waiting, waiting, waiting...................

[KN5DX]

Look at a previous post by me that answers this specific question.
Dutchmen News / "Change ONAN Voltage", it was a moment ago still top post in that category. Sorry I don't know how to link it directly. The short answer is no easy way to do this.

[KN5DX]

Hi. I see several different questions asked and some partial answers.

To the OP: Dutchmen wired this way due to industry standards. ONAN is the gen manufacturer, they wired the internal windings to produce 2 separate 120v phases 120 degrees apart from each other. Much like a 3 phase motor produces 3 separate phases each 120 degrees apart.

There basically ends up being dead / hidden phase. More common in the EU as it relates to getting a motor to rotate the proper direction. It is done for emergencies on HV transmission and distribution lines in an open delta config here in the US. Usually 1/3 transformers down, no replacement.

The RV distribution side is really 2 independent 120v services to load balance. There is no "240v" (line to line) equipment installed. A typical home is 2 separate 120v service with ability to wire line to line for 240v equipment.

An RV transfer switch does not connect L1/L2 internally to genset. It switches both like a motor across the line starter.

While you can have ONAN re-configure the windings the downside is you will lose around 15% (maybe more) of your capacity. Basically derating your genset drastically.

My personal solution is : house power out, I fire RV UP and wait.

[KN5DX]

I re-read your original post. The inverter/charger should be outputting 12vdc. Why are you saying its outputting 240vac? I have personally worked on large switchgear equipment that had inverters to produce 240 vac (EU style voltage). This was an aircraft hanger. This was very specialized (expensive) equipment. It may not be working the way you think it should, the first place I would look is at transfer switch control circuit side. That charger might be getting "cut-out" of circuit when on gen set. Will need more information to help troubleshoot.

[persistent]

Yes, what they said...
Your shore power and generator power are configure the same as most other RV's. Your transfer switch or inverter/charger may not be.

Bottom line: TT's and RV's are usually wired for two separate 115 volt legs, but are rigged to accept two out of phase 115 volt legs (230 volts with a neutral wire) or one 30 amp or more leg.
The better systems have a transfer switch that manages the source power to keep the two legs separate, but still power all 115 volt appliances.

A high end inverter charger is usually rigged to work under all these conditions. The Onan can be wired either way but are usually supplied for RV use as one leg with high amps because it provides more usable power. If it were wired for 230 volts, you could have one leg using no power and the other leg over loaded. This would be effectively half the rated output of the generator.

Transfer switch, inverter, and charger may be all in one box or in separate boxes. But, something is connected or configured wrong. You may be able to fix it by configuring the unit or changing the wire connections or jumper wires. Look for installation or operators manuals to explain your unit or units.

[larrypride]

I called Onan and you can do it.

[larrypride]

I don’t understand why one leg should carry more than the other. If the loads are balanced ? I have two A/C’s I can put one one each leg and that should balance the lead if the draw is the same for each,.

[persistent]

Of course you are correct.
If you have a 30 amp 115 volt Onan and rewire it for 230 volts, it will be at 15 amps each leg. You can run one A/C on each leg with a little to spare on each leg. However, the small amps remaining on each leg can not be combined to run one device because they would be "out of phase".

If each leg had 3 amps remaining, you could not run a 5 amp battery charger.

The numbers used above are hypothetical. You would have to recalculate using your actual numbers.

[KN5DX]

Yes you can re-wire GENSET. Download Installation Manual and page 76 has wiring diagrams for 3 different voltage setting. The real question is WHY would you do this? Without a full understanding of WHY, you will damage installed equipment and likely burn camper to the ground. I'm retired Military; specialty was electrical and power generation.

[larrypride]

It would be nice to have 230 available. So I could connect it directly to my house or welder or other equipment. I don't see why it would damage my trailer I connect to 230 every time I plug into 50 amp service.

[KN5DX]

Originally Posted by larrypride

It would be nice to have 230 available. So I could connect it directly to my house or welder or other equipment. I don't see why it would damage my trailer I connect to 230 every time I plug into 50 amp service.

Correction: There are 2 different voltage settings on page 76, the 3rd one shows all possible voltages and internal windings. You can set it to whatever suits your needs. The genset will be derated for capacity by approx 15%. The reason for "fire" comment was if done incorrectly it will cause serious problems. I've seen it. Melted transfer switches for a RAPCON facility (no air traffic control for 2 hours), gensets wired wrong- entire compound of A/C units smoked, etc,etc. I'm retired Military and specialty was electrical / power generation. If you choose 240v, I would recommend you drive dedicated ground rod ever time you use genset. I don't really know how to convey thousands of hours of education and hands on knowledge into 2 paragraphs. Plugging into pedestal is and is not the same thing. The upstream 3 phase transformer center leg is tied to a min #6 ground ran down pole and made into a coil. As well the distribution panel that services the pedestal is grounded locally. A GENSET wired for 240v sitting in a camper has to "float" that residual current somewhere (think frame). As wired for dual 120v, that return path is feed back onto itself canceling itself out. Can you wire for 240v, yes. But why derate your capacity and add extra work (driving a ground rod)? When we set a generator, the #1 thing was establish a ground first. These GENSETS do produce lethal currents. Now an ideal situation would be remove generator from camper, re-wire for 240v, ground it permanently, load balance based on derating, then operate as needed. Just because you can doesn't mean you should.

[larrypride]

I don’t use a ground rod now when I use the gen. Why would it be different if I change the internal connections of the gen?

[KN5DX]

Originally Posted by larrypride

I don’t use a ground rod now when I use the gen. Why would it be different if I change the internal connections of the gen?

My assumptions for answering the question: The Generator will now be used to power external connected loads (welder, house- per forum post), and/or changing voltage output of onboard generator. A ground rod is required. If no changes or use(s) to factory installation a ground rod is not required.

NEC (2014 Handbook hardcopy) Art. 250.34 Portable and Vehicle-Mounted Generators (B) Vehicle-Mounted Generators. The frame of a vehicle shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by a generator located on this vehicle under the following conditions
(1) The frame of the generator is bonded to the vehicle frame AND
(2) The generator supplies only equipment located on the vehicle or cord-and-plug equipment through receptacles mounted on vehicle, or both equipment located on the vehicle and cord-and-plug-connected equipment through receptacles mounted on the vehicle or on the generator, AND
(3) The normally non-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.
{Explaination notes NEC Handbook}
Vehicle-mounted generators that provide a neutral conductor and are installed as separately derived systems supplying equipment and receptacles on the vehicle are required to have the neutral conductor bonded to the generator frame and to the vehicle frame. The non-current carrying parts of the equipment must be bonded to the generator frame.

Paragraph C also applies if voltage is changed to a single-phase 240/120v system. I'm not typing it out.

[franktafl]

Originally Posted by KN5DX

My assumptions for answering the question: The Generator will now be used to power external connected loads (welder, house- per forum post), and/or changing voltage output of onboard generator. A ground rod is required. If no changes or use(s) to factory installation a ground rod is not required.

NEC (2014 Handbook hardcopy) Art. 250.34 Portable and Vehicle-Mounted Generators (B) Vehicle-Mounted Generators. The frame of a vehicle shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by a generator located on this vehicle under the following conditions
(1) The frame of the generator is bonded to the vehicle frame AND
(2) The generator supplies only equipment located on the vehicle or cord-and-plug equipment through receptacles mounted on vehicle, or both equipment located on the vehicle and cord-and-plug-connected equipment through receptacles mounted on the vehicle or on the generator, AND
(3) The normally non-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.
{Explaination notes NEC Handbook}
Vehicle-mounted generators that provide a neutral conductor and are installed as separately derived systems supplying equipment and receptacles on the vehicle are required to have the neutral conductor bonded to the generator frame and to the vehicle frame. The non-current carrying parts of the equipment must be bonded to the generator frame.

Paragraph C also applies if voltage is changed to a single-phase 240/120v system. I'm not typing it out.

that's why I love the CD version (and it's searchable)!

[KN5DX]

Yes CD or subscription service is nice. I had subscription service until I retired. But I always kept hardcopies to hand carry to a controversial job site meeting.

[KN5DX]

Other factors related to why a generator is "derated" for capacity when "uses" change. Assumption is changing voltage to 240v output and operating a welder will increase the internal heat load of generator stator. By derating the available load you can stay within the operations limits of the machine.

What follows is copied in part from https://www.chainsawjournal.com/how-...enerator-work/

What's total harmonic distortion?

The black line in the above picture is a complex sine wave which is just a composite of multiple waveforms called harmonics. Total harmonic distortion (THD) is the sum of all harmonic waves of the voltage or current waveform compared to a pure sine wave. The harmonic distortions of the sine wave have been with us since they delivered the first utility power. They were negligible at first because of the lack of non-linear loads before the 1960s. Since then non-linear loads became more prevalent. These loads include electronic ballasts, computer power supplies, Industrial welders, and variable frequency drives.

The current flowing in power systems can increase when unwanted harmonic distortions are present that causes higher operating temperatures. In motors the higher frequency harmonics increases core loss, resulting in excessive heating of the rotor core. These higher order harmonics can also affect communication transmission. If left unchecked it raises the temperature of electronic components. The harmonic interference can shorten the life of electronic equipment and cause damage to power systems.

No national standard dictates total harmonic distortion limits, but IEEE Std. 519 recommends values for acceptable harmonic distortion. From this recommendation, they set voluntary restrictions on voltage harmonics at 5% THD and 3% for any single harmonic.

[franktafl]

VFD's are fun to work with when searching out harmonics. People don't usually use the proper cable.