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Small Cabin Forum / Off-Grid Living / Wiring to generator
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mattd
Member
# Posted: 16 Mar 2018 17:52
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I know this topic has been discussed many times, but I’m having a hard time getting my head wrapped around it. I don’t even get as far as the 240v twist-lock male outlet before getting confused. Is there a wiring to genny for dummies, or any other reading on the basics you guys can suggest.

Borrego
Member
# Posted: 16 Mar 2018 20:20
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Yeah, it's one of those head things...I couldn't get it until I did it and then it was easy....
You can find a lot of posts here about it...

http://www.small-cabin.com/forum/3_7359_0.html

mattd
Member
# Posted: 16 Mar 2018 23:00
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Thanks. Your other post refers to transfer switches, which sound like the solution when you have main power, but need to run a few things when the power goes out.

My thought was to run the 30a plug from my gen to a 6 space breaker box, $20 plus breakers and $20 on RV 4 pin male outlet to plug gen into outside of cabin. 1 15a circuit for outlets, 1 15a for lights and ceiling fan, 1 20a for window ac and microwave.

The 2 hot wires coming from the gen would wire into the 2 hot terminals in the box, neutral to neutral and then ground. As long as gen is running and plugged in the box is hot, but there’d be breakers for any issues w circuits inside.

Am I way off?

DaveBell
Member
# Posted: 17 Mar 2018 01:45 - Edited by: DaveBell
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Quoting: mattd
Your other post refers to transfer switches, which sound like the solution when you have main power, but need to run a few things when the power goes out.


Matt, you're not making any sense. "You need to run a few things when the power goes out." So you have main power?

If you have main power, you need a transfer switch.

mattd
Member
# Posted: 17 Mar 2018 10:00
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You have a transfer switch so when main power goes out you can safely get off the grid, power a few circuits w the gen, then get back on the grid when power returns. Is that not how it works?

I don’t have any main power at the cabin. So I believe the functionality of a transfer switch would be wasted. Nothing to transfer between. That’s why I was thinking I could use a normal breaker box.

Borrego
Member
# Posted: 17 Mar 2018 12:38
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I didn't mean a transfer switch, sorry....I don't have Grid power either. I used one of these to use my Generator to power the cabin. It goes in between the genny and main panel.....you wire the panel as usual and run #10 wire from this box to the input of the panel box. You may need to use a jumper wire to hot up both side of your panel....

https://www.northerntool.com/shop/tools/product_200220924_200220924?cm_mmc=Google-pla &utm_source=Google_PLA&utm_medium=Generators%20%3E%20Generator%20Accessories%20%3E%20 Generator%20Transfer%20Switches&utm_campaign=Reliance&utm_content=100029&gclid=CjwKCA jw-bLVBRBMEiwAmKSB89-4SkrehXtUG4hlPG8VtKhteNAOy1NRI6ICkxVeNsXU0Rtmut2jkRoCaPgQAvD_BwE

Steve_S
Member
# Posted: 17 Mar 2018 13:27
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I think Mattd needs to clarify a bit... not sure but I think he wants to use the 240V coming from the genny and split it in the panel box using one hot for one buss bar and the other for the 2nd buss bar.

If running 120v/30a from genny to a mini panel then a single bus with 4 breakers @ 15a each would be fine. Yes that is beyond the capacity but the "main" in this instance would be the gennies breaker for that outlet.
The important point it that the max load, regardless of how many breakers is still 30A which is all the genny can give.

Each breaker can support 10 devices (plugs, switches, lights) per circuit (12 is max but 10 is safe margin measure) if that circuit exceeds 15a, that breaker will trip.

Quick KISS math formulas to know when trying to figure Amps & Watts.
120volts X 15amps = 1800 watts max load
1800watts ÷ 120volts = 15A

Clarity is important because the wrong tip could be, well a shockingly bad experience one might say.

ICC
Member
# Posted: 17 Mar 2018 15:11
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It has been stated the generator has 240 VAC output. Is there anything you need the 240 VAC for, such as a well pump, big welder, etc?

This is maybe simple stuff to some but bear with me. A 240 VAC generator has two hot leads and one neutral. Some 240 VAC generators also have 120 VAC outlets.

Hot leads are either both black or a black and a red. Neutral is white or gray. 240 VAC is obtained, of course by using both hot wires to feed the circuit. 120 VAC is obtained by using one hot wire and the neutral. So in effect, there are two "sides" to a 240 VAC generator; like two sets of windings.

IF all the 120 VAC loads are run off one side the generator is running in what is called an unbalanced state. It is possible that prolonged running like that may damage the generator.

It might be best to wire the 240 VAC to a panel that is manufactured as a 240 panel. The 240 inputs are connected just like the power company does in a grid setup. The odd numbered breaker spaces connect to one leg of the 240 and the even numbered breaker spaces connect to the other incoming hot. The neutral connects to a common buss and serves both of the 120 VAC circuits. Then you do your best to separate loads in the panel connections so when in use most often the power used is split to both the 120 sides.

Or a balancing autotransformer can be used to make only 120 VAC output from the 240 VAC. Those are fitted between the generator and the panel.


Quoting: Steve_S
Each breaker can support 10 devices (plugs, switches, lights) per circuit (12 is max but 10 is safe margin measure) if that circuit exceeds 15a,


In the USA the NEC is the bible for residential and commercial electrical systems. There is no section in the NEC that limits the number of devices on a 120 volt circuit. Local regulations may specify a limit but that number can and will likely vary between governing bodies.

To me, placing limits on the number of devices certainly does not make sense in this modern day world. It used to be that TV's, table lamps, etc. all used much more current than today. So maybe device limits made some sense as it reduced the possibility of connecting too many lamps or whatever on a single 15 amp breaker and the wires.

I reasoned, a polite form of arguing, with the electrical inspectors here when I did the wiring in the new place. I wanted to double up on the number of receptacles I placed around the room walls. Most of my boxes are doubles, providing 4 plugins instead of the normal two. Most of those are for ease of connecting today's low wattage devices. It seems I have more devices that might be connected to the mains than I did as a kid, but the total energy used is a fraction of what it was a couple of decades ago.

So the entire point of this last part is to say, first check the local regulations. Talk to them if like me you want to vary from the book.

Steve_S
Member
# Posted: 17 Mar 2018 19:21
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I only go by our code here, I am Canadian.

ICC
Member
# Posted: 17 Mar 2018 19:51 - Edited by: ICC
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Quoting: Steve_S
I only go by our code here, I am Canadian.


Great, and remember to advise others to do the same. Matt is somewhere in the USA; NEC rules

Steve_S
Member
# Posted: 18 Mar 2018 10:34 - Edited by: Steve_S
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Quoting: ICC
Great, and remember to advise others to do the same. Matt is somewhere in the USA; NEC rules
NEC Rules are almost identical to ours and STOP being so difficult ICC, it's tedious and not helpful to anyone.

[quote= Always the big question, how many lights on one breaker
I’m ask so many times how many outlets and or lights can I put on a 15 amp or 20 amp breaker. Well NEC code does not have it listed that way. By rule of thumb you would stick with 8 to 10 outlets and or lights per breaker. Now this is of course they are 120 volts 60mhz (USA or Canada).[/quote]

REF https://www.askmediy.com/how-many-lights-and-or-outlets-can-go-on-15a-or-20a-breaker/

NUMEROUS sites in USA including Bob Villa's and the like tell the same story.

GENERAL WIRING RULES FOR HOUSES USA PDF File
http://www.wirapids.org/egov/docs/1231176047_156250.pdf
All basic guidelines in straight terms per basic US codes.
*#11 "11. It is recommended that not more than 10 bedroom or living room receptacles go on a 15 amp circuit"

210.24 Branch Circuit Requirements see para 1 bottom
https://www.jadelearning.com/jadecc/courses/UNIVERSAL/NEC05.php?imDif=2190.1

TO Original Poster: Always verify information received with local codes & requirements to ensure you are complying or using best practices for your own and everyone else's safety & wellbeing. Never make assumptions and always check & verify for yourself.

toyota_mdt_tech
Member
# Posted: 18 Mar 2018 11:05 - Edited by: toyota_mdt_tech
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What I was told was about 10 outlets on a typical 15 amp circuit. I do try to keep lighting seperate, so its not dark when a outlet pops.

I was also told if its a 20 amp circuit, ie 20A breaker and 12AWG, you can add about 3 more as long as you only use 15A outlets. The outlet is the limiting factor. I have always went less than the 10 outlets, but this is just a reference I use. I try to keep rooms separate too, ie bedrooms, garages, kitchen and I like to see freezers and fridges on their own circuits or at least a freezer isolated. A fridge with no power would be noticed quickly. A freezer in the corner of a garage, not so till the smell of rotting flesh...

I have also added surge protection outlets on my home on any appliance with a computer which is most new appliances, ie washer, fridge. Computers, I just use a surge strip. If I was building a new home, I would add a surge protector at the panel to include the entire home.
Reading Steves link, I picked up more info.

Steve_S
Member
# Posted: 18 Mar 2018 11:19
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@TMT You can do whole house surge protection but it ain't cheap ! But for things like CGFI it's more prudent to use a CGFI Breaker now than the plugs, especially for thing like bathrooms with a plug, switch, lights which should all be CGFI protected for most safety.

If your on Grid Power, using a UPS for computer is wise as it conditions & filters lines, takes surges and brownouts and always keeps the 120v clean power there... besides, nothing worse than working on the computer and having a power blink cause you to lose your work & potential damage the computer.

Borrego
Member
# Posted: 18 Mar 2018 12:21
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mattd - Did you ever get your original question answered?
Seems like it got a bit off topic, happens around here........

I think what you want is the Generator Input Box....

toyota_mdt_tech
Member
# Posted: 18 Mar 2018 15:55
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Quoting: Borrego
I think what you want is the Generator Input Box....



Inlet such as Borrego did, if you hooked to grid, an interlock kit (manual) or auto transfer switch

https://www.interlockkit.com/

mattd
Member
# Posted: 19 Mar 2018 09:21
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Quoting: Steve_S
I think Mattd needs to clarify a bit... not sure but I think he wants to use the 240V coming from the genny and split it in the panel box using one hot for one buss bar and the other for the 2nd buss bar.


That was my plan! Unless you guys tell me I'm way off base. Really I plan on 3 circuits, 4 outlets on 1, 2 ceiling fans and 3 lights on another, and window ac unit and microwave on another. The outlets wouldn't be used much. The lights and fan would get the most usage, along w ac in the summer.

Two questions i still have, if the above plan works, is the generator grounding all that's needed? I doubt i'll be able to get a grounding rod 8' in the rocky ground, and burying horizontally will be a pain as well.

There's nothing in between the gen and the outlets that will level out the power and let me charge my phone from an outlet right?

Thanks,

mattd
Member
# Posted: 19 Mar 2018 09:28
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Quoting: ICC
IF all the 120 VAC loads are run off one side the generator is running in what is called an unbalanced state. It is possible that prolonged running like that may damage the generator.

Or a balancing autotransformer can be used to make only 120 VAC output from the 240 VAC. Those are fitted between the generator and the panel.


My gen actually has a switch that can flip that outlet between 120 and 240. I could go with the 6 breaker box, and with my 3 breakers just run off the one hot 120 side in 120v mode. right? would that be balanced then?

ICC
Member
# Posted: 19 Mar 2018 10:05
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Quoting: mattd
just run off the one hot 120 side in 120v mode. right? would that be balanced then?


Depends, on whether or not the generator is made to combine the 120's into a single or if the 120 output is simply 2 legs that are separate. Ask the manufacturer, check the internal wiring if you have a schematic. Hearing there is a switch that flips between 120 & 240 doesn't mean much without knowing more of what that actually does.

Steve_S
Member
# Posted: 19 Mar 2018 10:55
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Mattd, please post Make & Model # of you Generator. That will let us look it up, (unless you have a link to manufacturer & model info) which would help a lot more.

I run only 120V as I do not have an EV and otherwise no use for 240v. My heavy gear like compressor & mig get power from my large genny when needed.

Your configuration and what you can do is limited by the circuit breakers / fuses on your genny. You can indeed use you small box with ONE BUS @ 120V and plug your breakers into that which then feed to your 3 circuits. The total load across all of it cannot exceed the breaker on the Generator else it will trip. The sum total of your maximum draw is limited to that which means that even if the breakers do not trip in your panel the gennies will. The only time the break in panel would trip is IF that particular circuit exceeds 15A load.

Unless the generator is an Inverter Type, which is safe for electronics and motors, you may have some issues with certain devices. Inverter Generators put out Pure Sine Waves (which costs more to produce) versus regular industrial type generators which are most commonly Square Wave which is hard on motors and terrible for "fine electronics" like cell phones & computers.

Your panel will have to be grounded, this is not something you want to consider not doing, so a ground plate or rod is in your future.

mattd
Member
# Posted: 19 Mar 2018 11:01
Reply 


It's this one...http://www.wenproducts.com/store/wen-3500-watt-generator-56352

Quoting: Steve_S
Square Wave which is hard on motors

compressor motors? the luxury goal is ac!! i knew it was bad for electronics but could deal with that.

Quoting: Steve_S
Your panel will have to be grounded

notice i have a grounding terminal on the generator, right next to the 30a outlet. so ground both the gen and the panel?

Steve_S
Member
# Posted: 19 Mar 2018 12:17
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If your panel is properly grounded the plug will be as well and so no issues. That ground lug is intended for "field use" where the circuits running from genny are not grounded.

Manual is not terribly great BUT the diagram is helpful. 120/240 switch will allow you to go 120V @ 30A using the one plug.

ICC
Member
# Posted: 19 Mar 2018 19:52 - Edited by: ICC
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Mattd, Re the voltage selector switch. I’m not the best when it comes to understanding that diagram. I’m not clear on what the switch is switching. I DO know that the 120/240 Hondas I have, actually switch how the alternator windings connect to produce either only 120 or make 240/120 volts available. The instructions on one Honda state the selector should only be switched when the engine is off. The older one does not; no idea why the difference. When set to provide 120 volts only the two windings are coupled to remove the problem of running unbalanced as everything the generator can put out is funneled into the 120 volt outlets. The limit then becomes the rated capacity of the outlets and cords used.

I believe that generator probably works the same; the windings are switched or re-configured between being in parallel or in series. Or something like that.

The specs state the rated amps are 25 on 120 volts, not 30. 30 is the surge ability. The three prong outlets appear to be 20 amp rated types. Probably not a big deal but if one outlet/cord was used to draw the full rated 25 amps that would be overloading the generator outlet and possibly the wire internal gauge. Some Hondas and others provide a 120 volt 30 amp outlet for full capacity use through one outlet or cord. Not a criticism as much as simply a note.


There is an AVR “box” included in the schematic. (AVR = automatic voltage regulation) As long as it is of good quality the power output should be regulated well.

ICC
Member
# Posted: 19 Mar 2018 20:17 - Edited by: ICC
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… Square Wave which is hard on motors …

While that is a true statement, the statement is more applicable to using AC power from a modified sine wave or square wave inverter, not a generator. Common inverters (using battery power to produce AC power) produce square or modified sine wave power. Those are bad for just about anything that is not just a simple heating element. Square or modified sine wave power cause motors to run hotter and heat is what kills most motors.

A conventional generator has a motor spinning an alternator to produce a sinuous waveform output. Same as the power company but on a different scale. Some traditional generators may have poorly designed speed controls and if the engine speed varies so does the frequency. That is supposed to be 60 Hz in the US and Canada, but if the engine drops speed the Hz falls and that can be bad for electronics. The alternator spins at 3600 RPM in most alternators to produce the 60 Hz. Unsteady engine speed can also cause a voltage fluctuation, also detrimental. The waveform may also be not as smooth as it should be, but in most cases will be much better than any mod sine wave battery powered inverter. Not as good as grid power or power from an inverter-generator, but better then low cost battery inverter power.

Generator output can also be influenced negatively by harmonic distortions which seem to be the product of poor design. I don’t even pretend to understand what that it all about.



As an aside, a comment….
I think a simple test of a generator or a battery powered inverter power output is to see how well a microwave oven operates off it. Microwave ovens are fussy beasts. Microwave ovens make a lot of loud humming noises, almost seem to be vibrating, when run off a modified sine wave inverter (the battery powered thing, not an inverter-generator). Microwave ovens also don’t heat very well when off square or modified wave inverters. I’ve tried some on modified sine wave inverters that barely warmed a cup of water in the time it would usually take to produce a too hot to drink cup full.

However, the microwaves I have tried over many years have all worked fine on grid power, or on any inverter-generator and any construction grade generator. I never put a meter on them or tested to see if a conventional generator powered m-wave heated any worse than when operated on an inverter-generator, but they both seemed to work as well as when powered by the grid.

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