Generator Conductor to House Panel Question

[Isaac-1]

#8 and #6 as well as larger conductors are already stranded. The only exception in SOLID bare ground wire.

I thought most conductors in NM-B are now rated 90deg. C . THHN and THWN are 90 degree wire. You are supposed to use THWN wire in wet locations. (outdoors)

Most tend to be stranded, however Aluminum stranded or not, are much more prone to cracking than copper, it is a ductility thing.

Ike

 

[baxter]

Dont forget to derate to 80%. I use 4-4 SO cord and coil it up on the gen set then when the power goes out i just drag it over plug it in and throw the lever on the transfer switch, that way im still portable. My gen is abot 65 ft away.

 

[mistaken1]

Here is a great explanation and diagrams of a generator hookup.

From this site:
Generator Grounding

 

[storeman]

thanks fellas. i'm back to square one on my 5kw so since i'm using the 10k as a parts source, i may give up on the higher capacity and stay with 5kw, #8.
jerry

 

[trukhead]

Mep-002A, Can I...

Can I hook up a 4 conductor, female twist lock connector for running a 3 phase machine from the appropriate L-ought-1-2-3 while still also hooking up an appropriate 3 conductor twist lock connector to go to the transfer switch to run the home circuit breaker for 240-110 single phase from the appropriate lugs as indicated on the panel and other threads here on steel soldiers.

what are the appropriate grounding circuits? I have seen the previous poster's diagram.

My intent is to have dual cords simultaneously hooked up power cords for dual use and just turn the switch for appropriate phase and power use.

I figure to use the generator to run 3 phase machines I have yet to aquire and keep it ready to go for emergency use to keep the house snuggly and cozy.

Why is the nuetral hooked up to the ground in the non-sepperately derived system? I see it goes through the genset means of disconnect but doesn't the return juice still look for return path of least resistance.

 

[Isaac-1]

There is way too little information here to answer your question, and you really should start your own thread instead of reviving a year old thread.

As to answering your question, I would say it does not sound very safe on the surface, instead consider getting a pin and sleeve female connector and a pair of matching male connectors. Wire one up to supply your future 3 phase grounded with neutral bonded distribution panel, and the other to feed to a common solid neutral transfer switch at your house when in 120/240V split single phase mode. Either way leaves the generator frame grounded only and the neutral bond jumper removed.

This way you can leave the generator set for 120/240 1 phase and the house cable plugged in for normal standby, and when you want to use your 3 phase equipment, simply unplug the house, flip the connection switch to 120/208 3 phase and plug in the 3 phase distribution panel, then unplug and flip the switch back to 120/240 1 phase for standby mode.

Ike

p.s. I would not use a common 120/240 twist lock like an L14-30 for this as people will expect it to always be 120/240 with standard wiring, a pin and sleeve industrial connector will make most people stop and think before plugging in.

 

[quickfarms]

If you have to ask you should hire an electrician. That is my advice. I do not understand 3 phase power enough to play with it. A wise man knows his limitations.

 

[PeterD]

Can I hook up a 4 conductor, female twist lock connector for running a 3 phase machine ...

Technically no. You need a five conductor cable and connectors, three phases, neutral and ground.

... 3 conductor twist lock connector to go to the transfer switch to run the home circuit breaker for 240-110 single phase ...

Again, technically no. You need a four conductor cable, and connectors. Two hot, neutral and ground.

...
what are the appropriate grounding circuits? I have seen the previous poster's diagram.

My intent is to have dual cords simultaneously hooked up power cords for dual use and just turn the switch for appropriate phase and power use.

Appropriate grounding circuit consists of a conductor from the generator's frame to the building's ground. Any other configuration leaves the specter of a generator with voltage on the frame. That is why you need five conductors for three phase, and four for single phase.

Basically you can have two connectors however if they are not the same connector you run the (serious) risk that the wrong connector will be used at the wrong time. I have two connectors on my MEP-004A, however they are identical so that it doesn't matter what they are connected to. (I have both dual transfer panels in the house, and dual breakout boxes when running mobile.) And, yes, my cables and connectors are five conductor/five pin.

For single phase you need something like a NEMA 14-30 (or any 14-xx of sufficient current carrying capacity, as the 30 is amperage.) For three phase you would probably use a NEMA L21-30P, or any L21-xx where xx is the current capacity of the connector. (I use two NEMA L21-30 connectors...)

 

[goldneagle]

You have to size the supply wire run for the biggest generator you anticipate feeding on the wire. 10 KW at 240V is 42 amps. #8 UF won't get you there. It's 60C rating means that 40 amps is about all it can handle, and that's assuming a 30C ambient temperature, which is a little optimistic.

So if you size the run for the MEP-003A, you're going to need #6 or #4 wire. They do make copper #6 UF, but it isn't cheap. A cheaper way to get the same result would be to run #6 or #4 aluminum USE in the conduit.

Also, remember to pull some 14/2 UF through the conduit as well to a socket powered from the house to run the battery charger and light the generator shelter when the power isn't out...

Most NM-B now days are rated 90 degrees C. NM in the old days was 60 degrees or 75?

 

[Isaac-1]

While the wire is often rated at 90 degrees C, the terminals they connect to are usually at 60 or 75 degrees so become the limiting factor.

Ike

 

[SCSG-G4]

Derate capacity by 20 percent for four to six live conductors according to the NEMA codes I've read (IE, ground does not count). So the OP could use two separate runs (more than a six inch gap between the wires except where they are hooked into the lugs) and not get into trouble, even though it would be better to use the heavier wire in a single run.

But them, I'm the guy that only buys 10 and 12 ga extension cords, and won't touch 14 and (gasp) 16 ga ones even for light bulbs.

 

[trukhead]

Here is a great explanation and diagrams of a generator hookup.

From this site:
Generator Grounding

I saw this, printed it off and am studying it.

There is way too little information here to answer your question, and you really should start your own thread instead of reviving a year old thread.

As to answering your question, I would say it does not sound very safe on the surface, instead consider getting a pin and sleeve female connector and a pair of matching male connectors. Wire one up to supply your future 3 phase grounded with neutral bonded distribution panel, and the other to feed to a common solid neutral transfer switch at your house when in 120/240V split single phase mode. Either way leaves the generator frame grounded only and the neutral bond jumper removed.

This way you can leave the generator set for 120/240 1 phase and the house cable plugged in for normal standby, and when you want to use your 3 phase equipment, simply unplug the house, flip the connection switch to 120/208 3 phase and plug in the 3 phase distribution panel, then unplug and flip the switch back to 120/240 1 phase for standby mode.

Ike

p.s. I would not use a common 120/240 twist lock like an L14-30 for this as people will expect it to always be 120/240 with standard wiring, a pin and sleeve industrial connector will make most people stop and think before plugging in.

thanks for The Idea. I will invest in the appropriate, safe connectors capable of handling the current and correct number of conductors. I am thinking and pondering your explanation and am researching connectors and conductors. THaniks for your help!

If you have to ask you should hire an electrician. That is my advice. I do not understand 3 phase power enough to play with it. A wise man knows his limitations.

Definitely, Of course I will have a Master Electrician do the transfer switch and cabling. It is just that I want to be skooled up on this and get what I want and not sold stuff I don't need while I'm paying sparky $80.00 an hour.

I worked maintenance for a resort and pros installed a 3 phase well sump pump and it would only pump 5 feet out of a 3 inch pipe. I told them it had 2 legs wired backwards ant hey told me I didn't know S%*T. After a day of limited water supply during demand of the resort, sparky came back and switched 2 of the legs and shazam, water squirted 50 feet. Pump was runnin backwards. I learned you can reverse direction of a motor by reversing legs but it will burn them out and could have spun the impeller off. But the efficiency is low and it will burn the motor out.

I ask because there are people who know and I like to find out.

So why does 3 phase act like the pump example?

Inquiring minds want to know.

I just asked so I know what to look for

Technically no. You need a five conductor cable and connectors, three phases, neutral and ground.



Again, technically no. You need a four conductor cable, and connectors. Two hot, neutral and ground.




Appropriate grounding circuit consists of a conductor from the generator's frame to the building's ground. Any other configuration leaves the specter of a generator with voltage on the frame. That is why you need five conductors for three phase, and four for single phase.

Basically you can have two connectors however if they are not the same connector you run the (serious) risk that the wrong connector will be used at the wrong time. I have two connectors on my MEP-004A, however they are identical so that it doesn't matter what they are connected to. (I have both dual transfer panels in the house, and dual breakout boxes when running mobile.) And, yes, my cables and connectors are five conductor/five pin.

For single phase you need something like a NEMA 14-30 (or any 14-xx of sufficient current carrying capacity, as the 30 is amperage.) For three phase you would probably use a NEMA L21-30P, or any L21-xx where xx is the current capacity of the connector. (I use two NEMA L21-30 connectors...)

Thankyou, Thankyou for the explanation. The grounding is of utmost critical importance as well as the proper installation of the transfer switch to isolate the generator and it's power from the utility poles. again, thanks

I also want an "extension cord" approach to plugging in 3 phase machinery and the proper 5 conductor looks to be an appropriate way to do it. but the 3 phase machine will have the chassis grounded through the 5 conductor as well as a copper rod driven into the ground for the genset and another for the 3 phase machine.

I see for my single phase transfer switch installation the 4 conductor will have a chassis ground through the 4rth conductor but I will still install a copper rod for the genset and I presume the house has a copper some where as well.

I have not even started the genset yet but it is a 2007 rebuild and has 6 hours on it so I'm optimistically sure it will work. I am saying that I am patient and want it done right and safe.

I just want the wiring proper so everybody is safe and not doing this .

Thanks all

Dennis

 

[Isaac-1]

Ok, we seem to be rambling around a bit here, but here goes:

3 phase vs 1 phase motors - think of 3 phase motors as motors that get 3 nudges around each rotation, reverse the order of the nudges and it spins the other way, if you were to build a single phase motor the same way with 1 nudge per rotation it would randomly start up going the wrong way, so single phase motors use run/start capacitors or some other means to induce a preference for direction on startup, this is also why you sometimes find single phase motors (such as on air conditioner fans) running backwards when the capacitors go out.

The thing I don't like about many of the online transfer switch installation instructions is that they tend to refer to 3 phase installations then don't clearly describe the difference between the 2 types under the NEC.

As an example when dealing with 3 phase power you would use a 3 pole transfer switch for a solid neutral non-separately derived source, and 4 pole transfer switch for a broken neutral separately derived source, then they go on to say something like a 3 pole switch must be used for a non-separately derived source, however in single phase 120/240V world, a 3 pole switch is used for a separately derived source, and a 2 pole switch is used for a non-separately derived source.

On the topic of transfer switches many experts feel a solid neutral transfer switch is safer, as they have concerns that the broken neutral design may have higher risk of a broken neutral during normal operation and therefore wildly swinging voltages, etc. Also is the concern that when switching into a live load that due to flexure and wear in the switch it may make or break neutral at a slightly different time than the line connection again resulting in wild voltage swings during the transfer.

Ike

 

[trukhead]

Ok, we seem to be rambling around a bit here, but here goes:

3 phase vs 1 phase motors - think of 3 phase motors as motors that get 3 nudges around each rotation, reverse the order of the nudges and it spins the other way, if you were to build a single phase motor the same way with 1 nudge per rotation it would randomly start up going the wrong way, so single phase motors use run/start capacitors or some other means to induce a preference for direction on startup, this is also why you sometimes find single phase motors (such as on air conditioner fans) running backwards when the capacitors go out.

The thing I don't like about many of the online transfer switch installation instructions is that they tend to refer to 3 phase installations then don't clearly describe the difference between the 2 types under the NEC.

As an example when dealing with 3 phase power you would use a 3 pole transfer switch for a solid neutral non-separately derived source, and 4 pole transfer switch for a broken neutral separately derived source, then they go on to say something like a 3 pole switch must be used for a non-separately derived source, however in single phase 120/240V world, a 3 pole switch is used for a separately derived source, and a 2 pole switch is used for a non-separately derived source.

On the topic of transfer switches many experts feel a solid neutral transfer switch is safer, as they have concerns that the broken neutral design may have higher risk of a broken neutral during normal operation and therefore wildly swinging voltages, etc. Also is the concern that when switching into a live load that due to flexure and wear in the switch it may make or break neutral at a slightly different time than the line connection again resulting in wild voltage swings during the transfer.

Ike

Thanks for taking the time to explain this subject. Along with the above ground diagram and your explanation, I am seeing very important distinctions in the grounding and neutral circuit.

I believe the solid neutral is the way to go for the single phase transfer switch for the home use.

I think if were to use the extension cord approach to attaching the legs of the generator to a 3 phase machine for usage, a separately derived neutral would be ok as long as the machine is in the off position and the genset has the breakers off and not supplying power. Of course a neutral and a chassis ground would go through the 5 conductor wire of the extension cord. A copper ground rod will still be installed to the proposed 3 phase machine and to the genset as well.

Thanks to all for your patience and explanations.

And of course a certified electrician will be consulted and hired prior to me taking any steps to connect the genset to any thing.

I have really enjoyed this conversation on this subject and I hope it has helped others with their gensets as well to use them in a proper and safe manner.

Thanks again

Dennis

 

[n1oty]

Most NM-B now days are rated 90 degrees C. NM in the old days was 60 degrees or 75?

You better double-check the code book. I believe that any NM-B with a 90 C rating can only use that for de-rating purposes.

John