# Inverter generator and transfer switch ?



## Shane Jordan

I am looking to buy a champion 3000 watt inverter generator. I cannot for the life of me figure out what transfer switch to get. Most generators I have seen have 240 same with the switches. The inverters use 120. So where can I find a transfer switch that will work with an inverter generator? If any transfer switch will work what do I do about hooking it up? Anything special I should know? Most transfer switch I see have four prongs and the inverter generator has 3.


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## davefred99

You could use one of the 240 transfer switches but only on one leg of your home panel. Also you would need to wire in an L5-30 inlet plug. The actual reality is that that generator or any other 120 only generator is not intended for direct to home hook ups. It can be made to work somewhat but really intended for RV's and portable use.


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## RonJ

FWIW, I dont feel an Inverter Gen is really suitable for Transfer Switches. If you come up with a viable solution, I believe your cost vs return is not worth the trouble. If it were me, I would run the heavy duty extension cords for refrig and a second to a light or two and some heater/air conditioner that falls within the watts allowed.


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## grouchy-hermit

RonJ said:


> FWIW, I dont feel an Inverter Gen is really suitable for Transfer Switches.


Will you please elaborate on this?


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## Romore

There is no reason a manual transfer switch would not work with any portable generator, it merely switches to standby and back to utility. For your safety and insurance reasons have it installed to code by a licensed electrician.


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## Shane Jordan

So they push inverter generators to be safe for electronics but aren't designed for homes or transfer switches? That's confusing to ignorant people like me. 

So if I can hook it up to a transfer switch of any type then I assume an electrician will know how to do this with 120v. I just keep reading things like it will only power half the circuits on the switch but I am clueless as to why.


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## davefred99

Shane Jordan said:


> So they push inverter generators to be safe for electronics but aren't designed for homes or transfer switches? That's confusing to ignorant people like me.
> 
> _Technically speaking no portable generators are made to connect to homes but it can be done and is popular because standby generators are expensive. There are wiring issues that you must understand, that is why a licensed electrician is recommended to handle it._
> 
> So if I can hook it up to a transfer switch of any type then I assume an electrician will know how to do this with 120v. I just keep reading things like it will only power half the circuits on the switch but I am clueless as to why.


You can only power one leg of your home panel because all modern homes are wired for 240 volts. Basically two separate 120 volt circuits.


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## exmar

IMHO most "home electronics" don't need inverter generators, will do nicely on a regular genset, at least I've never had any problems. When you think about it, the power that comes in from your utility isn't that pure, has spikes, dips, surges, etc. and your "home electronics" get along. 


Not sure what you mean by transfer switch, to me that means something that just transfers from utility power to genset power and prevents backfeed from the genset to the utility lines and vice versa. "Usually," they"re used with a whole house generator powered by natural gas or propane so everything is automatic and are permanently installed and you do nothing when an outage occurs. Agree with Ron J, just run a couple of extension cords IF you want a 3KW inverter unit. To tie a transfer switch to that genset, not sure you could do it legally, you'll certainly end up with some very creative (Xpensive!!) wiring.


What you might consider is getting a 5000-5500W unit, put in a lockout switch and associated 30A breaker to feed your existing load center or breaker box. When an outage occurs, you open the main breaker which disconnects utility power, the "lockout" mechanically then allows you to close the 30A genset breaker, you then start the genset and connect. Obviously, you also have to open up all the "non critical" breakers in the box, leaving only the ones you need, e.g. Frig, Furnace, Freezer, a few lighting circuits. The load center typically would have a 200A main breaker and you're now limited to 30A so a lot of loads would have to go.


By all means, talk to an electrician who's familiar with gensets, lockouts, etc. otherwise you'll buy the wrong thing and have to get something else. There's a lot of info we can't possibly go into in a paragraph or two in a forum. e.g. Grounding, there would be two different schemes depending on running extension cords, vs interlocking a transfer switch.


Good luck,


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## RonJ

When I said that about Inverter types, it is strictly info passed on by a guy a couple miles away. We lose power often; he said he had borrowed a buddies inverter type and it got messed up! He started going into detail, and he seemed knowledgeable and capable of hooking up a gen. He had the TransSwitch for awhile...his old genny just died and his intend was to buy another soon. So, I had a guy have trouble using an Inverter, for whatever reasons could be deduced, I have never heard of anyone having problems with the tried and true generator. I have an Inverter, for camping, but have a regular for house use. I looked at the current situation and it had not been bought, that is why I put FWIW.


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## motormonkey

Just to add to the confusion:

The output of a typical inductive type generator is predominantly sine wave 60 hz AC, closely resembling what the utilities deliver.
The output of an inverter generator is more like square wave 60 hz AC, (having a LOT of harmonics in it... frequencies other than 60 hz). That's what can damage electronics.
Your electronics (and most of your other home electrical equipment) are actually safer on the inductive generator. (Assuming it is in good operating order.)

Agree with Ronj and exmar. If you can't go with a true 120/240 volt generator, forget about installing a transfer switch or lockout.


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## Shane Jordan

davefred99 said:


> You can only power one leg of your home panel because all modern homes are wired for 240 volts. Basically two separate 120 volt circuits.



I actually found a 125v transfer switch. It is branded as Honda but looks like they just had Reliance make/modify it for there inverter generators.

Anyway being ignorant about electricity and how things work is what your saying still true about only being able to power one leg? The install for these switches makes it look like the circuits you tie into are isolated so I am trying to wrap my brain around why this would not work. 

And for those questioning why do this with a 3500w inverter generator? Two fold, I am paranoid about the equipment running clean. The top priority for me is my reef fish tank. So every piece of equipement I use has some sort of computer running it including a controller. The transfer switch is for ease of use. I plan to run my tank, fridge and a few lights. I have two small kids and prefer to just plug this in rather than having 3 to 4 extension cords laying around. Also these inverter generators weigh less and are quiet compared to the traditional ones. 

And yes it's expensive doing this but if you had any idea what the investment of the actual tank is you may understand


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## davefred99

I would defer back to the transfer switch manufacturer. It might well be made by reliance and work just fine. I believe you are correct in that it would isolate the circuits so it would be safe to use if the manufacturer certified it.
So either call Honda or Reliance and talk to them first then hire an electrician to hook it up if you do not feel confident in doing it yourself.


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## Waypoint

I've been using a Honda EU3000is inverter gen with a Reliance 6-circuit transfer switch since 2012, including 12 days on it after hurricane Sandy. The electrician who installed the switch removed the tie bar joining the two center switches into a single 2-phase switch, leaving me 6 individual single-phase switches. The Honda output connector is an L5-30, and I bought an adapter pigtail that converts this to 4-pole (both hot leads tied together internally) which plugs into the Reliant 10ga cord:

30A NEMA L5-30P to L14-30R 30A 125/250V 1.5 Feet Power Adapter PL530L1430 | eBay

This setup powers our fridge, central gas heat, basement, garage, and provides partial power to the kitchen and bedroom plugs. I've found that the Mr. Coffee uses more wattage than the rest of the house combined, which was surprising.

Main decisionmaking factors for me were gasoline consumption and noise. The Honda's 3.5 gallon fuel tank lasts over 12 hours with room to spare, and we can't hear it inside the house. Difficult to accomplish either with a conventional generator.


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## Predator

motormonkey said:


> Just to add to the confusion:
> 
> The output of a typical inductive type generator is predominantly sine wave 60 hz AC, closely resembling what the utilities deliver.
> The output of an inverter generator is more like square wave 60 hz AC, (having a LOT of harmonics in it... frequencies other than 60 hz). That's what can damage electronics.
> Your electronics (and most of your other home electrical equipment) are actually safer on the inductive generator. (Assuming it is in good operating order.)
> 
> Agree with Ronj and exmar. If you can't go with a true 120/240 volt generator, forget about installing a transfer switch or lockout.



You've got it backwards.
The Inverter Generators produce the cleanest pure sine wave output.


Typical non-Inverter generators produce a modified sine wave that is squared and less "clean"

.
.


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## RedOctobyr

It's not always black-and-white. A good inverter generator will have an extremely clean sine output. But, at least considering standalone DC->AC inverters, low-end inverters will be ugly modified sine wave outputs. Better inverters are pure sine output. 

I'd imagine there are inexpensive inverter generators that are modified sine wave outputs. But generally, yes, an inverter generator should have a cleaner electrical output than a typical fixed-RPM ("contractor") generator.


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## exmar

To perhaps save you some $$, rather than use a transfer switch, just go with a generator lockout and L14-30 power inlet box. You'll have to do something like that to get the 120V on both "sides" of your load center unless you want to "redistribute" the critical circuits to only one side. You'll be running wiring whichever way you go. Also, going with the generator lockout, you'll be ready if you decide to get a bigger genset down the road. With the 120V transfer switch, I'm not sure what you'd have to do if you upgrade.

Here's a link where I was asking about doing something similar only I was using a "contractor" 3500W unit. You will have to make up a cable and connectors as described below. Anyway, I did it and it works fine.

https://www.powerequipmentforum.com/forum/9-generator-forum/21992-generac-gp-3250-schematic.html


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## motormonkey

Predator said:


> You've got it backwards.
> The Inverter Generators produce the cleanest pure sine wave output.
> 
> 
> Typical non-Inverter generators produce a modified sine wave that is squared and less "clean"
> 
> .
> .


No, I don't actually have it backwards, but you have a point. Quality is everything. A good induction generator will produce a nice clean sine wave. A cheap induction generator can have a lot of damaging harmonics. So will a cheap inverter. Decent inverters are fairly new on the scene though.


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## FlyFisher

Predator said:


> You've got it backwards.
> The Inverter Generators produce the cleanest pure sine wave output.
> 
> 
> Typical non-Inverter generators produce a modified sine wave that is squared and less "clean"
> 
> .
> .


Predator - I just happened to notice the post dates and you brought this thread back from 2017. That was well over 2 years ago... Just curious what you were searching for when you came across this old thread?


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## johndeerefarmer

From Google search;

One of the problems with more inexpensive generators is that the power isn’t always great. Under load, the sine wave of AC power tends to distort. But the Honda eu7000is is capable of producing a very clean sine wave. The total harmonic distortion is a shocking 4%. For reference, the grid power in New York is commonly rated at 6%. This makes it ideal for anyone who’s trying to wire in a backup generator for a home, or run some kind of high end electronics that require a clean sine wave, the Honda eu7000is is a clear winner.


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## Predator

RedOctobyr said:


> It's not always black-and-white. A good inverter generator will have an extremely clean sine output. But, at least considering standalone DC->AC inverters, low-end inverters will be ugly modified sine wave outputs. Better inverters are pure sine output.
> 
> I'd imagine there are inexpensive inverter generators that are modified sine wave outputs. But generally, yes, an inverter generator should have a cleaner electrical output than a typical fixed-RPM ("contractor") generator.


I have a Hitachi oscilloscope. I have looked at the wave form for my inductor non inverter generator. It was clearly modified sine wave and very blocky. I use that one only for the water heater and AC incandescent lighting. No sensitive electronics. WAG....10-15% THD

Because my leads were misplaced and I just ordered a new set of probes, I haven't checked the waveform from my inverter generators.

Typically, inverter Generators need to have a THD of less than 6% to be considered safe for sensitive electronics. While people say they have "safely" used non inverter generators on sensitive electronics, what they may be unaware of is that accelerated wear (mostly in the form of heat) can occur which can shorten the life of the electronics even though it may not have failed at the time.

It's sort of like driving a car with the tires far out of alignment. You can still drive it, but the wear on the tires will be accelerated.

After I get the waveform output for my inverter generators I'll post the results and pictures of the waveforms.

If ANY of my inverter generators produce more than 6% THD, then the primary benefit would only be fuel efficiency. The large capacitors and electronics are supposed to smooth out the harmonics to below 6%
I have 3 inverter generators. A HarborFreight Predator 3500, a Pulsar PG2000is and a Honda eu2000i. I'll be checking the waveforms from all 3.
I expect all three to have fairly nice sinusoidal waveforms compared to the non inverter generator. 

That said, When I CALLED Pulsar and spoke to someone in their cust serv dept, they said their inverter generators produce 5% THD at 50% load and as much as 8% THD at full load. BUT....in the Owners Manual under SPECS, it says Less than or equal to 3% THD. I think the technician was looking at NON Inverter specs. But as others have pointed out, the simple fact that you have an inverter generator is not a guarantee that the output is "clean". 

HarborFreight Claims their Predator 3500 Inverter Generator to have only 2% THD (load unspecified). That seems to be an odd claim.
The Honda eu2000i is said to have only about 1% THD.

While I won't have the precise THD, it will be fairly self evident from the waveform the quality of the power output. Well, to some degree.


What might be of most value from all this is that even cheap inverter Gensets today have THD that is very acceptable for sensitive electronics.....provided they are being honest in their published THD numbers. Anything below 6% THD is generally considered safe for all electronics.

.
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.


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## RedOctobyr

Cool, it will be interesting to hear what you find! I have an old LeCcroy DSO, but I sold my "conventional" generator, so I can't look at its output. I could check my EU2000i, but I expect it wouldn't be very interesting (hopefully just a nice sine wave).


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## Predator

RedOctobyr said:


> Cool, it will be interesting to hear what you find! I have an old LeCcroy DSO, but I sold my "conventional" generator, so I can't look at its output. I could check my EU2000i, but I expect it wouldn't be very interesting (hopefully just a nice sine wave).



Probably almost a pure sine wave. You get what you pay for. Honda says 1% THD for their eu series Inverter Gensets and I tend to believe it.


I have some doubts about HF's claim of 2% THD on the $700 Predator 3500 Inverter genset.
If that's actually true, I may buy another.


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