12k portable generator for house backup. Question about phasing

[Noltz]

I'll start by saying thanks for reading, and always future-proof your plans.

I recently installed a 14-50 outlet in my garage (using 6ga THHN) for a future EV. I also installed a 30A Generator inlet (14-30P) in a Generac box with 8-3 Romex, a 30A breaker & an interlock plate. Electrician came by and everything passed no problem.

I was looking to purchase a ~8k generator when I found a deal on a 12kw King Canada generator that has 14-50 and 14-30R plugs on it, with a 75A output. Now I'm regretting not going to a 50A inlet.

Without getting into the legalities of it, pretend for a moment I have made a suicide cord for the 14-50 plugs. How can I make sure the phases of the 30A inlet and the 50A backfeed are on the same phases, so that I can take full advantage of the power available?

 

[510ebl]

You would NEVER plug both in at the same time.

ETA: The gene linked does NOT have a compatible 30A plug. It is a 120V only, 30A. Your connection to the house is 240V 30A.

 

[Lassen Forge]

I'd ask the electrician how he'd wire it, and have him or her install that 50 amp inlet. Best way would have a separate male "feed" on your panel box, and it would be set up to feed what you want to. AND you could then feed both sides of the panel without creating a potential disaster.

We did the "backfeed through a house outlet" thing one time - before we had a legal generator installed - it powered half of one side of the house, so we not only had to run another "suicide jumper" to tie both sides of the front half together and a second one to power the back half of the house (where the freezer and washing machine) lives. It was about as flaky as a croissant, destroyed 2 outlets (literally cooked them), and I'd NEVER do it again. And that's not even addressing the issue of the exposed hot prongs on the suicide cords.

 

[Noltz]

You would NEVER plug both in at the same time.

ETA: The gene linked does NOT have a compatible 30A plug. It is a 120V only, 30A. Your connection to the house is 240V 30A.

So I can learn more, can you tell me why I cannot connect both? Assume an off-grid situation like a cabin (which I'm hoping to buy & build in the next 5 years).

I linked the wrong one. Mine is non propane but 100% has the 30A 240 (4 prong, I just physically looked) twistlock connector. Like this one, but no propane setup. It also has the rubber covers which the original one I linked does not have. I think thats why I got a good deal on it. They're supposed to have propane setup but they were built without.

I'd ask the electrician how he'd wire it, and have him or her install that 50 amp inlet. Best way would have a separate male "feed" on your panel box, and it would be set up to feed what you want to. AND you could then feed both sides of the panel without creating a potential disaster.

We did the "backfeed through a house outlet" thing one time - before we had a legal generator installed - it powered half of one side of the house, so we not only had to run another "suicide jumper" to tie both sides of the front half together and a second one to power the back half of the house (where the freezer and washing machine) lives. It was about as flaky as a croissant, destroyed 2 outlets (literally cooked them), and I'd NEVER do it again. And that's not even addressing the issue of the exposed hot prongs on the suicide cords.

Installing the 50A setup would require me tearing out the 30A setup I've never even used yet. This Generac box setup feeds the whole house. It's a genuine Generac inlet box with an interlock plate setup. Mechanically you have to shut the main breaker off, then and only then can you flip a 30A 240 breaker to the on position. This connects a 8/3 feed from the generator inlet (fed by said generator) to both legs of the panel. Obviously you can't run anything large. But since I ended up with a monster generator I'd like to set it up to be able to run the 30A and the 50A in parallel in a longer-then-normal power outage. But only if I can safely determine which poles are on which phase so I don't damage the generator itself.

I need to learn more about generators I think.

 

[510ebl]

Could you link to the gene you actually purchased? The one referenced earlier is 9K with 12k surge. That’s a theoretical 50A surge only, with a run capacity of about 37.5A @240. Assuming a balanced load.

Despite your existing investment, the safest and most reliable option is to start from scratch with a 50A inlet, properly sized wire and breaker, and 50A shore cord. (I know, that hurts!)

Another option is to recycle the “future EV” wire run, move the 50A breaker to the interlocked position, and install a 50A inlet.

As for why not “both”, there is no need to try to pull greater than 50A from the gene at any time. Trying to draw 50A with one load and 30A with another MAY damage the generator by trying to draw more than it is capable of.

Read up on removing the bonding wire as well, for when you are connected to the house. The owners manual should cover how to do this.

 

[wyliesdiesels]

So I can learn more, can you tell me why I cannot connect both? Assume an off-grid situation like a cabin (which I'm hoping to buy & build in the next 5 years).

I linked the wrong one. Mine is non propane but 100% has the 30A 240 (4 prong, I just physically looked) twistlock connector. Like this one, but no propane setup. It also has the rubber covers which the original one I linked does not have. I think thats why I got a good deal on it. They're supposed to have propane setup but they were built without.




Installing the 50A setup would require me tearing out the 30A setup I've never even used yet. This Generac box setup feeds the whole house. It's a genuine Generac inlet box with an interlock plate setup. Mechanically you have to shut the main breaker off, then and only then can you flip a 30A 240 breaker to the on position. This connects a 8/3 feed from the generator inlet (fed by said generator) to both legs of the panel. Obviously you can't run anything large. But since I ended up with a monster generator I'd like to set it up to be able to run the 30A and the 50A in parallel in a longer-then-normal power outage. But only if I can safely determine which poles are on which phase so I don't damage the generator itself.

I need to learn more about generators I think.

you need to look at the running watts which is 9,000. This means you have 37.5a per leg of available current.

If you connect a ~50a load and a ~30a load at the same time you will overload the generator and not even trip the circuit breakers. Even with the surge wattage you would overload it if you pull more than 50a between both outlets.

when sizing a generator, you dont look at the outlets on it, you look at the running watts. This is how youre getting off track.

I would install a 50a inlet with #8 THWN, breaker it at 40a and manage your loads manually.

dont forget to unbond the neutral from the frame...

 

[nadogail]

I have found that puting an excessive load on an electrical generator turns it into a smoke generator.

My advice is guaranteed to be worth exactly what you have paid me for it.

 

[Noltz]

You're all absolutely right. I'm overthinking this and my current setup is likely to be more than sufficient for my very intermittent use.

Thanks!!

 

[Noltz]

you need to look at the running watts which is 9,000. This means you have 37.5a per leg of available current.

If you connect a ~50a load and a ~30a load at the same time you will overload the generator and not even trip the circuit breakers. Even with the surge wattage you would overload it if you pull more than 50a between both outlets.

when sizing a generator, you dont look at the outlets on it, you look at the running watts. This is how youre getting off track.

I would install a 50a inlet with #8 THWN, breaker it at 40a and manage your loads manually.

dont forget to unbond the neutral from the frame...

You're spot on there. So this is my exact generator, although I got it from King directly and it seems to be a HD specific model. It has an external grounding lug.

Two quick questions; Where can I read more about unbonding the neutral? This model has a ground lug and the salesperson said in a home backfeed I should drive a ground rod and ground this lug to it. Secondly I did run 8/3 Romex to the 30A box. If I switch it to a 50A and breaker it at 40, am I still to code?

 

[wyliesdiesels]

You're spot on there. So this is my exact generator, although I got it from King directly and it seems to be a HD specific model. It has an external grounding lug.

Two quick questions; Where can I read more about unbonding the neutral? This model has a ground lug and the salesperson said in a home backfeed I should drive a ground rod and ground this lug to it. Secondly I did run 8/3 Romex to the 30A box. If I switch it to a 50A and breaker it at 40, am I still to code?

you would need to read the manual to see where the neutral bond is. you dont want 2 neutral bonding points on the same system. The main service panel already has the necessary neutral bonding...

as to the advice from the salesperson, it is wrong. a ground rod is for shunting lightning. you dont need a ground rod for a generator and it has nothing to do with the neutral bond... the ground lug would be for connecting to an EGC between it and the inlet or transfer switch. since youre using an outlet, no need as the outlet has an EGC pin on it.

#8 NM-b is good for 40a but your inlet is not, so yes you need to change the inlet.

 

[Noltz]

you would need to read the manual to see where the neutral bond is. you dont want 2 neutral bonding points on the same system. The main service panel already has the necessary neutral bonding...

as to the advice from the salesperson, it is wrong. a ground rod is for shunting lightning. you dont need a ground rod for a generator and it has nothing to do with the neutral bond... the ground lug would be for connecting to an EGC between it and the inlet or transfer switch. since youre using an outlet, no need as the outlet has an EGC pin on it.

#8 NM-b is good for 40a but your inlet is not, so yes you need to change the inlet.

Awesome. I've done a little learning on neutral bonding and this machine is definitely bonded to the frame somewhere. The manual came with a pretty good exploded diagram, and there's a grounding lug on the panel. I'm hoping I can trace that back to the frame and remove it. I appreciate your help.

 

[510ebl]

and there's a grounding lug on the panel. I'm hoping I can trace that back to the frame and remove it. I appreciate your help.

I think you are still off track here...the lug on the panel is not likely related to the neutral bond.

 

[Noltz]

I think you are still off track here...the lug on the panel is not likely related to the neutral bond.

I'm continuing to read and learn about how the systems work together. I'll admit, it's more complicated than I initially thought. I work a lot in automotive electrical systems but it's nearly all DC, so I don't need to worry about phasing or load balancing. That will probably change as we move into electric vehicles, as most of the propulsion motors are AC. And the terminology is quite a bit different. That's a big part of why I ask "why is that?" in most of my posts. Its enough for me to do it if the code requires, but I do want to know WHY it's code.

Tonight I'm reading on bonding, neutrals vs. grounds, and a little bit on GFCI systems. I learned the lug on the panel is only remotely related to the neutral bond on my generator;

https://www.garagejournal.com/forum/showthread.php?t=466583

Perhaps you could do me a favor and have a quick look at this thread? I've located what I believe to be the bonding jumper and removed it. I intend to replace this small harness with one that has a switch so that I can convert between bonded and floating as the situation needs. Your input over there would be greatly appreciated!

 

[theoldwizard1]

How can I make sure the phases of the 30A inlet and the 50A backfeed are on the same phases, so that I can take full advantage of the power available?

First replace the 14-50 outlet with a 14-50 INLET.

Second, this is why the make generator interlocks !

Third, if you have a sub-panel in the garage THERE IS NO SAFE WAY TO "BACKFEED" YOUR HOUSE THROUGH THE SAME WIRES !


BTW - Wher are you going to store 50+ gallons of fuel ? That should last you a couple opf days !

 

[Noltz]

First replace the 14-50 outlet with a 14-50 INLET.

Second, this is why the make generator interlocks !

Third, if you have a sub-panel in the garage THERE IS NO SAFE WAY TO "BACKFEED" YOUR HOUSE THROUGH THE SAME WIRES !


BTW - Wher are you going to store 50+ gallons of fuel ? That should last you a couple opf days !

Thank you for your input!

1) The 14-50 outlet in the garage is an outlet and I won't be changing it. I'll need it there when we move on to an EV. I was simply posing the question to learn more about phasing. The hypothetical situation was if my 30A wasn't cutting it (meaning the interlock plate has blocked the mains already), could a suicide cord be used to supply power on an emergency basis. I already know it can be done. My only question would be how to easily detect which phase each hot leg was on so they're synchronized.
2) I have an interlock plate on the generator feed breaker. That's all done to code & inspected.
3) I do not have a sub panel in my garage, but that's a good point for anyone reading this later. I just an 14-50 outlet and two 120v circuits. Outside wall of the garage has the L14-30R in a proper Generac inlet box. Its wired with 8/3 Romex, 14M long. So it's slightly over spec, but not big enough for a 14-50R inlet outside. I mentioned before that I wasn't hunting for a generator this big. But since I have it... yadda yadda.

Fuel storage is in the shed, away from the house and garage.

 

[theoldwizard1]

2) I have an interlock plate on the generator feed breaker. That's all done to code & inspected.

You making a mountain out of a mole hill ! Just use the 14-30 inlet.

I don't know what you want to run in your house that is going to need that much power anyway !

 

[wyliesdiesels]

Awesome. I've done a little learning on neutral bonding and this machine is definitely bonded to the frame somewhere. The manual came with a pretty good exploded diagram, and there's a grounding lug on the panel. I'm hoping I can trace that back to the frame and remove it. I appreciate your help.

since you have 2 threads going on this, its making it hard for people to follow. best to just have 1 thread but too late now.

I think you are still off track here...the lug on the panel is not likely related to the neutral bond.

yeah the ground lug is not for the neutral bond. it is a grounding lug for bonding to an EGC.

in his other thread, he posted pictures of where he found the neutral lug which is under the alternator wire cover.

 

[wyliesdiesels]

First replace the 14-50 outlet with a 14-50 INLET.

Second, this is why the make generator interlocks !.....

he has an interlock

.....
3) I do not have a subpanel in my garage, but that's a good point for anyone reading this later. I just an 14-50 outlet and two 120v circuits. Outside wall of the garage has the L14-30R in a proper Generac inlet box. Its wired with 8/3 Romex, 14M long. So it's slightly over spec, but not big enough for a 14-50R inlet outside. I mentioned before that I wasn't hunting for a generator this big. But since I have it... yadda yadda.

Fuel storage is in the shed, away from the house and garage.

you are confusing things here by calling the inlet an L14-30R. An inlet is NOT an R, which is a receptacle....

 

[510ebl]

Your input over there would be greatly appreciated!

The best info I have found on GJ regarding your generator questions has come from reading post by guys like wyliesdiesels and a handful of others that not only know HOW, but can explain the WHY of connecting a generator to the house in a particular manner. You won’t go wrong following their advice.

I did look at the other thread, it seems you are doing ok but definitely verify with a meter.

 

[dcg9381]

I have found that puting an excessive load on an electrical generator turns it into a smoke generator.

My advice is guaranteed to be worth exactly what you have paid me for it.

I haven't had the same experience with "small" generators. 3000-5500 watt range.

The 3500 watt generator (Champion), when overloaded, the gas motor loses it's battle pretty quickly.. (which isn't good, things get out of sync and voltage drops)

The 5500 watt brigs, it simply would blow it's circuit breaker - that breaker was like 18 amps of 240V, so the "weak link" in that one was the circuit breaker...

I believe you could smoke one if the internal wiring was the weak link... Course, they shouldn't make 'em like that.

 

[wyliesdiesels]

When the motor slows down and has to work harder, it means the windings are spinning slower, getting hotter and not getting as much air flow. This is how windings can get smoked.

 

[theoldwizard1]

When the motor slows down and has to work harder, it means the windings are spinning slower, getting hotter and not getting as much air flow. This is how windings can get smoked.

Also, on non-inverter generators, when the engine slows down, the output voltage drops and the frequency drops.