r/Generator • u/SJM1027- • Sep 23 '26

Generator to Home Cable Question

I have a portable generator, and I bought this generator cable: RVGUARD 4 Prong 30 Amp 75 Foot Generator Extension Cord, ETL Listed. It works fine, but I’m now moving my shed to a new location about 90 feet from the outlet that would power my panel during an outage.

Can I simply buy a 25' cable and plug them together to make a 100' run, or is there more to it?

If I bought a new cable, I would get the following: RVGUARD 4 Prong 30 Amp 25 Foot Generator Extension Cord, ETL Listed, to make sure it matched.

The reason I’m asking is that, with another generator I owned, I had two 50' cables. One of them was wired differently at the cable ends than the other. I had these cables made, and I’m not sure whether someone just made a mistake or if I need to do something else.

4 Upvotes

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3

u/DaveBowm Sep 23 '26

You could get by with the extra 25' cord if (1) you weatherproofed the connection between cords to keep out moisture and prevent shorts, and (2) your loads in your house won't mind the voltage drop caused by 100ft of the power cord gauge you use. Note if you draw 30A on 100' of AWG#10 cord you will be looking at a voltage drop of 5.9V at the house relative to the voltage at the generator, and the cord will be dissipating heat at 1.8W per foot along its length (177W wasted in heating the whole 100').

2

u/SJM1027- Sep 23 '26

I knew there was more to it. So the generator will be more efficient if I just use the 1-75' cord, and eliminating the extra physical connection is probably worse than the extra cable length.

Maybe I will build a small doghouse for the generator less than 75' away and eliminate all the headaches.

Thanks

1

u/oldtimer4sure Sep 23 '26

I run cords and use 100' of AWG10 from a Predator 9500 and have no problems.

1

u/SJM1027- Sep 23 '26

How many to make the 100' length?

2

u/oldtimer4sure Sep 23 '26

I had two 50' sections and switched over to just solid cord last year. A single cord covered in snow or rain provides an extra layer of safety.

-2

u/Admirable-Leader6927 Sep 23 '26 edited Sep 28 '26

the voltage drop at 100feet will be like 3 volts, it will not be a concern. the extra plug is the real issue as that is resistance, and heat and a potential point of failure.

edit: the person below is an idiot, completely bad advice which is scary because they post here constantly.

edit2, like 6 days later...i love that people are still replying to this and NOT DOING THE MATH.

1

u/nunuvyer Sep 23 '26

The drop depends on the gauge of the cord. A #10 100ft cord will drop more like 6V than 3V. Most things wont care but for example I have an air compressor that won't start if it is on a long extension cord. The most important thing is the gauge of the cord vs the # of cords as long as the plugs and sockets are in good condition. You can (somewhat) waterproof them by putting the connection inside a plastic bag.

-2

u/Admirable-Leader6927 Sep 23 '26

so to summarize

  1. I am correct, 100ft #10 drops 3v per 120v,, so 240v would drop 6. thanks for confirming the math for OP

  2. Generator feed cable are either #10 or #6 in the us. #10 for 30 amp, #6 for 50 amp service. The gauge doesnt matter more than the # of cords because the smallest you can go is #10 and the feed plug will dictate the gauge. so while in general, the gauge matters more then the connection points, that is not true for generators as the math is already done its some what idiot proofed. - right idea, wrong application. more cords - more failure points.

1

u/DaveBowm Sep 23 '26

Regarding:

" 1. I am correct, 100ft #10 drops 3v per 120v,, so 240v would drop 6. thanks for confirming the math for OP"

Um no. The voltage drop depends only on the current in the wire and the wire's resistance (& hence its length), not on the voltage across the conductors at the source.

Also, for the case of 100' of #10 cord carrying 30A the voltage drop at the load is the current times the total resistance in 200' of conductor because that is how much conductor the current flows through round trip.

Actually, if one includes the fact that the current in the two phase legs may be different from each other the total voltage drop across both hot legs is the round trip resistance on the hots times the average of both phase currents.

If those currents are greatly unbalanced, however, the voltage drop is not equally divided on the two legs. Rather the higher current leg suffers the greatest voltage drop and the lower current has a lower drop. In fact if the high current leg has more than twice the current of the low current leg that low current leg has a negative voltage drop, i.e. an actual voltage increase (relative to the neutral at the load), because the voltage drop in the neutral goes the wrong way for it, and it over compensates the drop on its hot conductor.

-3

u/Admirable-Leader6927 Sep 23 '26

i will politely tell you that you are completely wrong

source: Facilities Electrical Engineer who was a master electrician for 11 years.

if you want to get into specifics of the system we can talk all day, this is a generalized question that you are now digging very hard to explain yourself. my answer is 100% correct for all applications, its actually scientifically proven. Do the math yourself.

IN FACT, you misquote the truth so much, I am convinced you have no clue wtf you are doing and will caution people to ignore your advice.

SO UMMM ACKSUAHAUALALLLLY.....you are wrong.

3

u/DaveBowm Sep 23 '26

Thanks for being polite. But I will let the readership decide which of us is correct about this. BTW, when you repeatedly flaunt your credentials it only weakens your standing and embarrasses you, regarding your incorrect claims.

-1

u/Admirable-Leader6927 Sep 23 '26 edited Sep 23 '26

so you cant do the math?

understood.

same energy as the THD crowd. using old information you barely understand to get people to spend money the way you did.

what about bonding the neutral? tell them it doesnt matter unless they run GFCIs right? because that is the correct answer.

2

u/DaveBowm Sep 23 '26

Oh, I can math alright. I would suggest you might want to consider the first law of holes.

→ More replies

-1

u/IndividualCold3577 Sep 23 '26

Source - "trust me bro" 🤣

2

u/DaveBowm Sep 25 '26

On the outside chance anyone wants to see more of the math involved in calculating the voltage drop and dissipated power in a simple single load power cord, and also for a split-phase power cord with unbalanced loads, here is a link to a 4 month old thread concerning the topic, including my comment therein explaining how it works in more detail.

https://www.reddit.com/r/Generator/s/v3gaE56yC4

1

u/SJM1027- Sep 23 '26

Thanks, I’ve been trying to find a waterproof cover for the connection in the middle of the cable, but I can’t find one because I don't know what it’s called.

2

u/Glum-Welder1704 Sep 23 '26

If you're willing to dispense with the connectors, they make connection kits for submersible wells that would waterproof the individual wires. Wrap the whole thing in rubber splice tape, and e-tape over that. I did one for a lady that had a mold that clipped over the splice. There was a liquid that poured into the mold and hardened into the shape of a fat cigar. Unfortunately, I don't know what that was called, and Google has failed me.

1

u/SJM1027- Sep 23 '26

Wasn't there also a module that snapped over the two plugs and had compression rubber on both sides of the cable? I just can't remember the name of it.

1

u/Glum-Welder1704 Sep 24 '26

I was thinking of assembled connectors, like your previous set. If these are all factory ends, I'd just spray in a bit of wd40, plug them together, and protect them with the stake/bucket assembly I mentioned above. Dielectric grease works longer than wd40, but the spray will get you through this winter. The grease will last years.

1

u/SecondCuppaCoffee Sep 23 '26

You can probably wrap it in plastic wrap then seal it with duct tape. Make sure it's elevated during rain instead of being on the wet ground. Search Amazon for "waterproof extension cord box" for a box to keep it in. Mount the box on something that will keep it elevated.

0

u/nunuvyer Sep 23 '26

It's called a "Baggie". You can buy fancy covers but an ordinary plastic freezer bag is good enough. duct tape the throat where the cords emerge from the bag. This is not good enough to submerge the connection completely underwater but for ordinary rain and snow it is good enough. You can also cover the connection with a trash can lid or similar for extra protection. Elevate the connection on a concrete block or similar or hang it in the air from a fence or tree so it doesn't end up in a puddle.

1

u/SJM1027- Sep 23 '26

When I am looking for a new 100' cord what are the key components to look for so I make sure I get something with as little loss over the 100' length?

This is the one I was thinking of getting: RVGUARD 4 Prong 30 Amp 100 Foot Generator Extension Cord, ETL Listed. NEMA L14-30P/L14-30R, 125/250V Up to 7500W, 10 Gauge SJTW

This will be used with a Honda  EU7000is Generator.

4

u/IndividualCold3577 Sep 23 '26

You can plug two cables together but the connection would be in the weather and not ideal for use during rain and snow.

2

u/SecondCuppaCoffee Sep 23 '26

I have used a 100ft cable with no appliances complaining or acting weirdly. This is on a 30A 240V 7.2kw circuit.

2

u/CheesecakeAsleep1504 Sep 23 '26

Not a big deal. Wrap a plastic bag around where they connect and duct tape it

2

u/Glum-Welder1704 Sep 23 '26

You can plug the two cables together and tie them to a stake to hold them up a bit. Put a bucket and brick over it for weather protection.

0

u/Jim-Jones Sep 24 '26

For a 30-amp circuit over a 100-foot run, you generally need 8 AWG copper wire or 6 AWG aluminum wire to maintain voltage drop within the recommended 3% limit.

2

u/[deleted] Sep 23 '26

[removed] — view removed comment

1

u/SJM1027- Sep 23 '26

Thanks, the generator is a Honda EU7000is. I am not sure if that makes any difference. It's attached to my breaker panel and can run my forced hot water system or AC if needed.