# Connecting generator at full load to transfer switch



## Bad Irene (Oct 31, 2014)

Hi,

I'm considering buying a Honda EB6500 in order to power house loads via a transfer switch in the event of power outages. It seems like the more I look into getting this done, the more questions I have.

Rated load for this generator is 5500W. At 110V, this means if I intend to load the generator fully, it will be outputting about 50 amps. Problem is, the most that one single receptacle can handle is 30 amps, and the most that the generator can output total from ALL receptacles is 45.8 amps (this is per the Receptacle Selection documentation for the EB6500).

Firstly, I'm confused why the unit can't handle maximum rated loading at common household voltages (only able to output 45.8 amps when 50 amps is expected at full rated load). This seems like poor design, although I'm sure I'm overlooking something because Honda.

Secondly, how can I get the full 50 amps of juice to flow into the one connection leading to the transfer switch if the most that the four receptacles can handle is 30/20/20/30 amps? Can I just plug cords into each receptacle and then run them through a 4-to-1? (all appropriately sized, of course), and does this necessarily mean that the current is balanced across all four? (assuming the 120v/240v switch is in the 120v ONLY position).

It seems like most of my neighbors just plug whatever extension cords they have lying around into whichever receptacle that fits and then call it a day, and they don't seem to have any trouble. But when I run these numbers, I feel like they should at least be overloading the cord they're using.

Thanks in advance for any help given. There's a ton of knowledge in this forum, so I really appreciate it.


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## aandpdan (Oct 8, 2012)

Hi,

It helps if you stop thinking amps and just think in terms of watts. 30 amps at 240 volts is 7200 watts for example.

The 45.8 amps is easy. It's rated at 120 volts, not 110. 5500/120 is 45.8. 5500/110 is 50. 120 volts is consider "normal" in the US.

Only 240 volt loads are balanced not 120 volt loads. You'll have to do that yourself.

You DO NOT want to run it at full load anyways. Not only will it use a lot of fuel but it will get very hot, the engine and the generator portion. I wouldn't load it more than 50%, conservatively. Remember these are for emergency use. You don't need to run everything in the house.

It connects to the house with a 30 amp 240 volt receptacle. That connection could handle up to 7200 watts. You can not connect all the receptacles together to get any more than the 5500 watts anyways and the one receptacle is capable of handling that.

Look into an interlock or transfer panel for your house. You can set them up so that certain loads are balanced on both legs. It makes management really easy. You can also get wattmeters to help you monitor your loads.

I get by comfortably with a 3000 watt generator. I have used a 900 watt generator for an extended period too. It's all how you manage your loads and what your needs really are.

Start with a good load calculation then determine how big a generator you need. Do you have a well pump for example? Do you need a/c? What do you use for heat, etc?


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## Robert Coats (Nov 10, 2011)

A few thoughts...

Honda EB-series models are designed for construction use. All receptacles are GFCI protected, and the neutral is bonded to the frame. You would need to remove the neutral bond when connecting an EB model to a transfer switch. (It is easy to do). 

You might want to consider a Honda EM-series model. They are designed for home back-up power. They are electric start, and have a DC outlet for charging a car battery (EB models lack these features). The difference in list price is about $170 more for the EM6500.

Unless you have a well pump or other high-load needs, you could probably do just fine with a 3,000 watt generator. It can run a couple of refrigerators, lights, microwave, flat-screen, router/wi-fi, etc. 

The is also the Honda EG-series, which are no-frills models. You get a lot of Honda power for not a lot of money. 

If noise is an issue, consider a Honda EU-series. These are fully-enclosed and exceptionally quiet. They make power using an inverter, and can run at lower engine speeds and get excellent fuel consumption. The EU3000is has electric start, hums at only 49 dB, and will run almost 20 hours on a tank of fuel. 

Finally, starting today, Honda is offering a $200 rebate on select models, including the EG4000 and EM4000. 

Honda Power Equipment: Honda Generators, Lawn Mowers, Snow blowers, Tillers


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## Chuck (Feb 11, 2014)

What would happen if an EB-series model was connected to a transfer switch without the neutral bond being removed?


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## aandpdan (Oct 8, 2012)

The GFCI would trip.

Honda has a service bulleting, Generator #20 out about this. You can read it here: 

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB4QFjAA&url=http%3A%2F%2Fwww.mayberrys.com%2Fgfci%2FEB-GFCI.pdf&ei=VDhzVPjaA4SkNu-RgZgF&usg=AFQjCNGFvxEAjS6qbKbqLnau6Yd8_a070A&bvm=bv.80185997,d.eXY&cad=rja


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## Chuck (Feb 11, 2014)

Got it. Thanks again, aandpdan!

I do wish I had some electrical knowledge. Like, what is the purpose of a neutral bond? How does it effect the flow of electrical current?


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## aandpdan (Oct 8, 2012)

The neutral bond provides a fault path in the event of a wiring fault. 

The reason the GFCI would trip is that it would detect a difference in current between the neutral and the hot leads. Some of the neutral current would flow on the ground wire and it only takes about 5ma to trip a GFCI.


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## Chuck (Feb 11, 2014)

Ok. What happens if there is a wiring fault while connected to a transfer switch with the neutral bond removed? Would it make any difference if the generator is grounded to the same grounding rod as the house panel?


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## aandpdan (Oct 8, 2012)

A couple of thing with grounding first.

There is a Grounding Electrode Conductor (GEC) and a Equipment Grounding Conductor (EGC).

The ground rod at your house is the grounding electrode conductor. It is primarily for lightning protection. The neutral conductor from the utility is bonded to the GEC at the first point of disconnect.

An equipment grounding conductor is the 3rd wire in a cord, the "ground." Or, it is the wire that attaches to the frame of a piece of equipment such as a washer/dryer/furnace, etc. 

It depends upon the wiring fault to answer your question.

With the neutral NOT bonded - Using a portable 3 wire drill as an example: if there is a fault from hot to ground (the case) the breaker will not trip but the case on the drill will be electrified (hot) and the drill will keep operating. 

A ground rod alone will not cause the breaker to trip. It has too high an impedance.

In the situation above, the case is hot now and the drill is still working. If there is an additional fault, say a bare spot on the neutral wire, and you touch it then you will be electrocuted. The EGC is electrified (hot) but does nothing.

With the neutral bonded: you are using the drill and a fault develops from hot to ground (the case of the drill). Current passes through the EGC. The breaker will trip, the drill will stop.

Somewhere Chuck you need to have a neutral-ground bond in place. It can be at the generator or at the panel. It's more important than the ground rod.

In both cases above, a GFCI would detect an imbalance on the current between the hot and neutral and trip, cutting power.


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## PeteCress (Feb 9, 2014)

Bad Irene said:


> I'm considering buying a Honda EB6500 in order to power house loads via a transfer switch in the event of power outages. It seems like the more I look into getting this done, the more questions I have.


If you have a well pump, sewage pump, or some other necessary high-draw load this post is probably moot.

Having said that...

When I was going through the process you are now, somebody made what I thought was a useful distinction: "Cruise Ship vs Lifeboat".

I opted for the "Lifeboat" approach partially because I had watched a neighbor drive all over the place trying to find gas to feed his Home Depot monster during a week-long outage last year.

Our house cruises on 800-1200 watts (depending on how hard the furnace blower is working) and a 2KW generator working through a smart transfer switch seems to do keep the refrigerators/freezers/computers/TVs running and give us plenty of light.

No toasters, hair driers, coffee makers or other high-draw appliances with just 2KW. We use little 16-ounce propane bottles with a burner on top for heating food/coffee and have a mini-propane stove on the back porch for cooking.

I chose six circuits to be served by the transfer switch and if one circuit momentarily needs more than what's available (as when a certain old refrigerator starts up) the transfer switch will shut down another circuit for a few minutes to allow extra for the demanding circuit.

We wound up getting a second 2KW generator that can be run in parallel with the first - mainly for redundancy in case the first one decides to fail during an outage. But the obvious secondary benefit is that now we can run a high-draw appliance like coffee maker, toaster, or full-size microwave if both gennies are on line.


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## Dqalex (Nov 25, 2012)

Fuel efficiency in mind inverter generators really shine. Also they are quiet. They use only the RPM's needed for the load. But they come at a price. After Sandy 95% of my community were living back in the 1800's. We had heat lights stove hot water microwave. Everything but cable TV Thanks to my Honda EU6500. I started out the day before Sandy unprepared with only 10 gallons of gas and an old 5000 watt screaming Generac. The day of Sandy before the power went out I called an ordered a Honda EU6500. It came in three days after sandy. Going from that old Generac to the Honda was like going from a model T Ford to a Mercedes Benz. The fuel efficiency of the Honda is outstanding. Where I live we're on city water and natural gas. An Interlock made more sense for me than a transfer switch. Another plus is all Honda EU generators have floating
neutrals and are setup for home backup.


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## aandpdan (Oct 8, 2012)

Dqalex said:


> Fuel efficiency in mind inverter generators really shine. Also they are quiet. They use only the RPM's needed for the load. But they come at a price.


The thing with ANY generator is that many people oversize, thinking they need to run the whole house and then when they realize the amount of fuel they need they understand why smaller may be the way to go. I don't have an inverter generator. My 41 year old 3000 watt Generac can power almost everything in the house (gas boiler and stove). It uses less than 1/2 a gallon per hour and averages a 1000-1500 watt load (fridge, boiler, a couple of lights).

It is noisy though.

The other thing to consider is repairs. All I've had to do is replace a set of brushes because a spring failed, less than $10. Not bad for 41 years. It'll be interesting to see what happens when these inverters start getting older.

No fancy AVR here either, it's transformer controlled. It produces a VERY nice waveform on an oscilloscope and the voltage only varies by about 2 volts from a 100 watt to a 3000 watt load.

My two cents.


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## Dqalex (Nov 25, 2012)

aandpdan said:


> The thing with ANY generator is that many people oversize, thinking they need to run the whole house and then when they realize the amount of fuel they need they understand why smaller may be the way to go. I don't have an inverter generator. My 41 year old 3000 watt Generac can power almost everything in the house (gas boiler and stove). It uses less than 1/2 a gallon per hour and averages a 1000-1500 watt load (fridge, boiler, a couple of lights).
> 
> It is noisy though.
> 
> ...


I agree we have no idea the cost of the inverters long term. They just haven't been around long enough. Oversize generators for home backup is a waste of fuel. Everyone's needs are different. I have two forced air heating systems one upstairs and one downstairs, and a spare chest freezer in the garage. The 5,000 watt range works best for me. I try not to run them up to full power. A Honda EB 10,000 I would consider that to be overkill and a waste of fuel for my application. The EB 10,000 is a nice looking unit, and well built but I just don't have a use for it. I have a Troy-bilt 7500 that I used for my Dairy Queen before I got a standby unit put in. Thats a powerful generator, very well built but it drinks fuel.


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