Question for electricians

[grsthegreat]

I made my own output box for my shop generator. Box cost $9.30 and another $13 for two ct and meter combo units plus $8 for manual start switch. And as stated elsewheres…theres no such thing as 9 gauge wire.

 

[alexinPA]

Electric water heaters and ranges are usually fed with 10/2 or 10/3 romex and a 30 amp fuse - however if you look at the wires inside the appliance they're usually 12AWG. Those wires are short runs so it works. The Amazon amp meter with its 10 AWG wiring is a short run and should be OK. If you're like me you'll monitor the amp meter and see which appliances you can run simultaneously and then once you know the meter will come off and sit in a drawer. The generator will sit outside, as will the meter. Worse case scenario, in the unlikely chance the meter wires or gauge overheats, it's outside anyway. The Amazon amp meter is really unique, I did a quick search and couldn't find anything else that would let you monitor 50 amps without tapping into or separating the two 120V legs. It's inexpensive too.
Your generator should have breakers on the 240 output, if you exceed the breaker rating the breaker will open. Keep in mind that anything with a motor has a momentary heavier draw than the normal operation (AC, Freezer, Refrigerators, water or sewage pumps) so if you're running close to the output of 9KW (37.5 amps), the starting factor of motors should be considered.
I'm no electrician but I'd use the Amazon meter and get a feel for what you can run simultaneously and then put the meter away. 9KV will require careful use of electric in the home to avoid tripping the generator breaker.
Generators can have some really odd outlets for 240, they vary by amperage and aren't interchangeable. I'd suggest taking a close look at the Amazon meter's plugs to make sure they'll fit the generator's outlet and whatever you're connecting the house with.
Hope this helps.

You read my mind ! That is exactly what I want to do. Thank you.

 

[alexinPA]

In theory, it would probably work…..but….. I would not purchase it unless it is “approved “ by UL or a similar standards agency.

Spec says UL approved

 

[grsthegreat]

Also, as a side note. That amazon device is NOT designed to be placed outdoors. Theres no NEMA3R Protection on that device. Also, i dont see how that could ever receive a UL rating.

As a note, i AM an electrical contractor.

If you placed it in some kind of weatherproof enclosure that would change things. As it stands, the electronics are not shielded from water intrusion.

 

[alexinPA]

And what is gauge of cable you are connecting generator to transfer switch.....

Bottom line with 30 or 50 amp generator ( maybe 10KW) you need to cut back on what is turned on in house....... IF you were to have 20-25KW generator you could turn everything on....

Generator cable is 6 awg. I know things like electric water heater is no go

 

[grsthegreat]

Spec says UL approved

I honestly dont see how.UL would have required 50 amp rated cord when used with 50amp rated outlet. The only time they ever vary this are for items like welders that only peak at 50 amp during strike off, and run significantly lower amps while operating.

 

[alexinPA]

Also, as a side note. That amazon device is NOT designed to be placed outdoors. Theres no NEMA3R Protection on that device. Also, i dont see how that could ever receive a UL rating.

As a note, i AM an electrical contractor.

If you placed it in some kind of weatherproof enclosure that would change things. As it stands, the electronics are not shielded from water intrusion.

Yes, my plan is to use an enclosure. But still worry about 10 awg cable. And I didn't like seller reply about short length/low resistance good for 50A

 

[grsthegreat]

Legally the wire is undersized, as there is no discount for short wire length. There is a thing called 6 foot tap rule, but that would not apply here.

Would this work for a 9 kw generator….more than likely. #10 copper can legally carry 40 amps, but is derated to 30 amps by code. The generator only provides 37.5 amps.

If it were mine, i would not risk it. But thats only because ive repaired alot of buildings with melted, overloaded wires over the years. If generator was only used to power lights and refer/freezers i wouldnt worry about it. Its when you add things like water heaters to the load that it's an issue.

Most 9 kw generators ive seen over the years will peak out around 11 kw for starting loads. This is where the overloaded wire comes into effect.

 

[WinterDeere]

...50 amp cable so the whole house will be supplied during power outage...
The problem is 10 awg cable. 10 awg supposed to support 30 Amp.

Don't confuse the NEC's "Small Conductor Rule" (SCR), with actual ampacities for wires and cabling. The SCR only applies to site wiring, not appliances, which are rated individually by their manufacturer.

As @Camofurever1 showed in that nice chart (first one, not the second), the current-carrying capacity of a wire is dependent on its insulation type and configuration, such as the number of current-carrying conductors in a bundle and the temperature ratings of the terminals at either end of the wire. It is the manufacturer's responsibility to figure this out for their wire type and configuration, and the UL or CE approval (although often self-declared) is your assurance that this was done.

Bottom line, you don't have the information required to make an absolute determination on your own, but you can at least see if the rating is in the realm of reasonability by comparison to tables such as the one posted by @Camofurever1. In this case, it appears it is not, as even if high-temperature insulation was used, the terminals at either end (your mating cables) are likely not rated above 90C.

Sent txt to the seller and his answer:

"The short distance (1.3 ft) means that the resistance is low and the cable is resistant to high temp., so it can pass 50 A current".

I find it hard to believe. Any opinions? Are there other similar gadgets? Don't want to overload the generator.

The reality is that yes, a short conductor will allow higher current for the same temperature rise, under the assumption that either end is connected to a large conductor. In fact, I do this every day in my business, cooling smaller conductors by connection at either end to larger conductors... but what I'm building is installed in military test sites and not your home. I've never seen anyone ever operate a mains voltage circuit for consumer appliances on wiring beyond its standard temperature current rating, on the bet that it will be cooled by connected devices... it's just not commonly done. If legal, I don't know, but it's terrible practice.

I would personally not use this device on a 50A breaker, but you haven't stated what size breaker you're operating this circuit on.

I'm an MSEE, so I can give you all the theory in the world, and reasoning behind various conventions and the NEC. But I don't have the NEC memorized, like any good commercial electrician should, so their conclusions would overrule mine. I work on very high power industrial and military electronics, not residential or consumer products.

 

[WranglerX]

Maybe I missed something, but all comments are about a 9KW generator, BUT what is max size of circuit breaker on output....