Electrical Management Systems questions

Ed Gee,

Start with a hybrid (load support) inverter/charger.

Use the remote control to limit input amperage to what ever number works for you. Mine can be set as low as 5 amps.

If the voltage is low, it is possible to use load support to increase it by turning on the feature and then "trimming" the input amperage lower and lower. I do not recommend this--just that it is possible to do so.

Since I purchased an autoformer I have no need to "force" load support to do something it was not intended to do.

pianotuna wrote:
Hi Bobbo,

<< snipped>>

I do have a way to limit my demand to 80% of what is available, so on 15 I limit to 12, 30 to 24, and 50 to 30.
.

I would be interested to learn how you limit current consumption as outlined above....

In my 40 years of RVing, I have NEVER heard of a generator failing in a way that could harm the electronics in an RV. On the other hand, I have personally heard of hundreds of RVers who experienced damage from flawed shore power. EMS protection is aimed primarily at the statistically high chance that you may encounter bad shore power in your travels. If one is paranoid about the extremely unlikely chance a generator could somehow fail in a damaging way, have at it and wire your EMS to include it, as outline in the many responses above.

Hi Bobbo,

I can see a use for EMS with 50 amp. With 30 amp--not so much.

I have superior surge compared to what is available and use an Autoformer (boost and buck) to take care of low voltage.

I do have a way to limit my demand to 80% of what is available, so on 15 I limit to 12, 30 to 24, and 50 to 30.

An EMS to me would simply be another potential failure point.

I always check voltage under load and polarity before plugging into an unknown source.

dryfly wrote:

cavie wrote:

road-runner wrote:
There is no issue with using an inverter generator. The issue is with the generator having a floating output as opposed to a bonded neutral. Some non-inverter small generators also have a floating output. When the EMS senses a lack of continunity between the ground and neutral wires, it mis-diagnoses the situation as an open ground. The plug-in outlet testers make the same incorrect diagnosis.

One slight correction. It is diagnosing the situation exactly correct. Open ground. In a main service panel the ground and neutral are bonded together. Every panel after that is a sub-panel and the neutral and grounds are kept separate.

The generator is the Power Company and is the place that the neutral and grounds are bonded. Since the generator is not bonded, the ground is not connected. Think OPEN. Hence the OPEN GROUND indicator. Someday Gen manufacturers are gonna wake up.

This is kinda getting off subject but would you explain why sub-panels should not be bonded? I ran into this issue a couple of years ago when I was installing my whole house generator with automatic transfer switch. I'm obviously not a trained electrician and I'm still having trouble (after a lot of reading and research) in understanding this.

NEC code states that the ground/neutral shall not be bonded downstream of the main panel. It's a safety issue. Also if ground/neutral are bonded downstream of a GFI protector the GFI will trip.

Ground and neutral are NOT the same. one is a return path for the current flowing in the circuit, one is a safety path to earth reference.

Unless there is a fault, no current flows in the ground wire. If ground and neutral are bonded, the current will always flow in the ground wire when something is drawing power. The amount will be shared between the neutral and ground paths.

So in a properly wired trailer ground and neutral should never be bonded since the trailer is intended to be plugged into a pedestal wired to a main panel.

I have used the PI EMS 3A system for a decade. Almost always when running on a generator I dig out my bonding plug. On occasion I've left it somewhere else, in which case I put the PI in the bypass mode.

In reality, the PI and a generator the only likely fault is going to be low or high voltage. not swapped hot/neutral etc.

pianotuna wrote:
I don't see the reason to use an EMS downstream from the generator. You already know the voltage from the generator. The generator would stall out before voltage became too low.

There is also my pet peeve about EMS. The low voltage disconnect is far too low. I'm not comfortable with running the roof air below 107 volts.

Because generators, being made by man, can and do fail. I don't want the electronics in my RV subject to the generator failing in a GOOD way. Murphy's law says that would not happen for me. It is too easy to let the EMS protect from a generator too.

As far as the generator stalling out before the voltage becomes too low, you are betting your electronics on that. I am not. What if the generator fails by providing voltage that is too high? What if the generator fails by providing power that is not 60Hz +/-?

I don't see the reason to use an EMS downstream from the generator. You already know the voltage from the generator. The generator would stall out before voltage became too low.

There is also my pet peeve about EMS. The low voltage disconnect is far too low. I'm not comfortable with running the roof air below 107 volts.

SoundGuy wrote:

Bobbo wrote:
Build a bonding plug.

Instead of building a bonding plug build a bonding dongle that will allow you to make full use of both 120 vac receptacles on your Honda EU2000i. First buy a 30 amp RV female pigtail like this ...

... and a contractor grade 15 amp male plug like this ...

Wire the 15 amp plug to the pigtail and when doing so wire the plug's neutral to ground pin as shown in Bobbo's picture above.

Plug the dongle into one of your EU2000i's receptacles and your trailer's 30 amp main service cable into the dongle - your genset is now bonded but you can also plug another device into the genset's second receptacle, even a fan to help cool the genset as I used to do when my genset was sitting in the back of my truck.

That's an interesting concept. Make your own BONDED 15a to 30a adapter.

Dryfly, you asked Planning if he routinely used his bonding plug. I am not Planning, but I use my bonding plug every time my RV is plugged in to the generator. I do not use the bonding plug if using the generator for anything else.

Bobbo wrote:
Build a bonding plug.

Instead of building a bonding plug build a bonding dongle that will allow you to make full use of both 120 vac receptacles on your Honda EU2000i. First buy a 30 amp RV female pigtail like this ...



... and a contractor grade 15 amp male plug like this ...



Wire the 15 amp plug to the pigtail and when doing so wire the plug's neutral to ground pin as shown in Bobbo's picture above.

Plug the dongle into one of your EU2000i's receptacles and your trailer's 30 amp main service cable into the dongle - your genset is now bonded but you can also plug another device into the genset's second receptacle, even a fan to help cool the genset as I used to do when my genset was sitting in the back of my truck.

cavie wrote:

road-runner wrote:
There is no issue with using an inverter generator. The issue is with the generator having a floating output as opposed to a bonded neutral. Some non-inverter small generators also have a floating output. When the EMS senses a lack of continunity between the ground and neutral wires, it mis-diagnoses the situation as an open ground. The plug-in outlet testers make the same incorrect diagnosis.

One slight correction. It is diagnosing the situation exactly correct. Open ground. In a main service panel the ground and neutral are bonded together. Every panel after that is a sub-panel and the neutral and grounds are kept separate.

The generator is the Power Company and is the place that the neutral and grounds are bonded. Since the generator is not bonded, the ground is not connected. Think OPEN. Hence the OPEN GROUND indicator. Someday Gen manufacturers are gonna wake up.

This is kinda getting off subject but would you explain why sub-panels should not be bonded? I ran into this issue a couple of years ago when I was installing my whole house generator with automatic transfer switch. I'm obviously not a trained electrician and I'm still having trouble (after a lot of reading and research) in understanding this.