3phase 120/208y service generator install.

[ctaylo360860]

I have a 400a mpd that feeds 3 separate individual 200a breakers and panels. They want a generator installed on one of the panels so they can run there point of sale and server. They’re looking st getting a 10kw 120/240 portable generator. I was going to add a 1ph 200a double throw after the service disconnect and before the 200a panel, but then realized the service is 120/208y 3phase and the generator is only 1 phase... does anyone see that being an issue besides the third phase not having power during an outage or any other concerns? There are no 3 phase loads in the panel being used. All that will be needed during an outages are 7 20amp 1ph 120v circuits 4 for point of sale computers that were pulling 1amp each, and three for servers that were pulling 1.3a, 1.3a, and .9a and three 120v 1 ph 20amp circuits. Any and all help is appreciate! Thanks in advance!

 

[Nuber]

I would never in a million years feed a 3 phase panel with a single phase power source. That would be a violation of the listing of the panelboard at a minimum and thus would violate 110.3(B) of the NEC.

I would suggest installing a 120/208V single phase sub panel, then installing a transfer switch to feed that panel. Normal is your existing panel via a feeder, emergency is your portable generator via an inlet. Do some load and feeder calculations, move your new emergency circuits over to the new sub-panel, and you are done.

Otherwise get a 3 phase generator...

 

[zbang]

For those loads (no lights or hvac?), unless they want hours of runtime, a few decent UPSs will be both cheaper and easier. (It's all about the run-time.)

 

[ctaylo360860]

I would never in a million years feed a 3 phase panel with a single phase power source. That would be a violation of the listing of the panelboard at a minimum and thus would violate 110.3(B) of the NEC.

I would suggest installing a 120/208V single phase sub panel, then installing a transfer switch to feed that panel. Normal is your existing panel via a feeder, emergency is your portable generator via an inlet. Do some load and feeder calculations, move your new emergency circuits over to the new sub-panel, and you are done.

Otherwise get a 3 phase generator...

I would never in a million years feed a 3 phase panel with a single phase power source. That would be a violation of the listing of the panelboard at a minimum and thus would violate 110.3(B) of the NEC.

I would suggest installing a 120/208V single phase sub panel, then installing a transfer switch to feed that panel. Normal is your existing panel via a feeder, emergency is your portable generator via an inlet. Do some load and feeder calculations, move your new emergency circuits over to the new sub-panel, and you are done.

Otherwise get a 3 phase generator...

I agree with that, not something I was willing to install, I was just trying to make sense of what the previous electrician did.... I was told he brought down portable genset which has a 30a 240v twist lock and hard wired it into the panel. Only way to prevent it backfeeding is authorized personnel turning off a 200a main on the outside and locking it out... transformer says 120/208y I was getting 126volts to ground and neutral, and 220volts between phases.... I’m guessing the transformer tap is turned up? Okay my new plan is to add a 100a 1ph double throw. Line side of double throw will be protected from a 100a 2 pole breaker in the 120/208y pane. I will then feed an 12 space square d 1ph 120/240v 125a main lug from the load side of the double throw. I’ll interrupt the circuits I need in case of an outage and land them in the new 100a sub panel. I then will add a recessed 50a plug on the emergency or genset side of the 100amp double throw. Start up should be as follows Turn off all the breakers in the new sub panel. Plug genset 50a chord into reccesed plug at 100a double throw. Put double throw in genset position. Start the genset let it warm up. Go inside Then slowly turn on each individual breaker inside the new sub panel.

Sorry corrections made... I should use a switched neutral double throw it will be considered a separately derived system and I will need to make sure grounded conductor snd egc at the genset frame are bonded and isolated at sub panel and double throw?

 

[ctaylo360860]

For those loads (no lights or hvac?), unless they want hours of runtime, a few decent UPSs will be both cheaper and easier. (It's all about the run-time.)

Are upcs like a battery back up? The power goes out frequently because horrible sub station and high winds... they were out for 4 hours yesterday. Still planing out my install, the guy I spoke to said he’s just wanting to run server and point of sale. Lights and hvac would be nice I’ll need to figure out a demand load and see if the genset he has is large enough...

 

[petersonra]

I have a 400a mpd that feeds 3 separate individual 200a breakers and panels. They want a generator installed on one of the panels so they can run there point of sale and server. They’re looking st getting a 10kw 120/240 portable generator. I was going to add a 1ph 200a double throw after the service disconnect and before the 200a panel, but then realized the service is 120/208y 3phase and the generator is only 1 phase... does anyone see that being an issue besides the third phase not having power during an outage or any other concerns? There are no 3 phase loads in the panel being used. All that will be needed during an outages are 7 20amp 1ph 120v circuits 4 for point of sale computers that were pulling 1amp each, and three for servers that were pulling 1.3a, 1.3a, and .9a and three 120v 1 ph 20amp circuits. Any and all help is appreciate! Thanks in advance!

I don't have a major problem with it as long as the transfer switch opens up all three lines to the existing panel.

You might have an issue with the listing on the panel though. It might not be listed for use with a 240V source. If this is the case no reason you can't run 120V to the panel through the transfer switch and just jumper the two phase together.

 

[oldsparky52]

Are upcs like a battery back up? The power goes out frequently because horrible sub station and high winds... they were out for 4 hours yesterday. Still planing out my install, the guy I spoke to said he’s just wanting to run server and point of sale. Lights and hvac would be nice I’ll need to figure out a demand load and see if the genset he has is large enough...

Yes, battery power. They don't all work the same, personally I would want the ones that are always supply power from the battery and inverter and using the AC to keep the battery charged.

 

[ctaylo360860]

Yes, battery power. They don't all work the same, personally I would want the ones that are always supply power from the battery and inverter and using the AC to keep the battery charged.

I believe that’s what they have currently, but power was out so long they died....

 

[synchro]

You might have an issue with the listing on the panel though. It might not be listed for use with a 240V source. If this is the case no reason you can't run 120V to the panel through the transfer switch and just jumper the two phase together.

If the loads are on MWBCs then jumpering the two phases would make the currents add in the neutral conductor instead of subtracting.

Yes, battery power. They don't all work the same, personally I would want the ones that are always supply power from the battery and inverter and using the AC to keep the battery charged.

Yes, having "on-line" UPS's would be desirable. Obviously if you also have a generator then that could charge the UPS batteries and extend how long the UPS will be working.

 

[Todd0x1]

What is this 10kw portable generator? Hopefully theyre not powering POS terminals and servers with a cheapo construction generator.

How long do they need to be able to run for? With those light loads might just be able to do it with batteries. I have 4.5kwh of batteries on the office UPS, its kept 2 servers, network, surveillance, and phones up all day during an outage.

 

[Nuber]

I agree with that, not something I was willing to install, I was just trying to make sense of what the previous electrician did.... I was told he brought down portable genset which has a 30a 240v twist lock and hard wired it into the panel. Only way to prevent it backfeeding is authorized personnel turning off a 200a main on the outside and locking it out... transformer says 120/208y I was getting 126volts to ground and neutral, and 220volts between phases.... I’m guessing the transformer tap is turned up? Okay my new plan is to add a 100a 1ph double throw. Line side of double throw will be protected from a 100a 2 pole breaker in the 120/208y pane. I will then feed an 12 space square d 1ph 120/240v 125a main lug from the load side of the double throw. I’ll interrupt the circuits I need in case of an outage and land them in the new 100a sub panel. I then will add a recessed 50a plug on the emergency or genset side of the 100amp double throw. Start up should be as follows Turn off all the breakers in the new sub panel. Plug genset 50a chord into reccesed plug at 100a double throw. Put double throw in genset position. Start the genset let it warm up. Go inside Then slowly turn on each individual breaker inside the new sub panel.

Sorry corrections made... I should use a switched neutral double throw it will be considered a separately derived system and I will need to make sure grounded conductor snd egc at the genset frame are bonded and isolated at sub panel and double throw?

What a mess. What some people will do to try and save money. One misstep and you are paralleling a 10KW generator with utility power. Nothing like watching a generator make fireballs...

 

[ctaylo360860]

What is this 10kw portable generator? Hopefully theyre not powering POS terminals and servers with a cheapo construction generator.

How long do they need to be able to run for? With those light loads might just be able to do it with batteries. I have 4.5kwh of batteries on the office UPS, its kept 2 servers, network, surveillance, and phones up all day during an outage.

So the genset they were looking at getting is a pulsar 10,000 kw genset [pg10000] specs said genset is good for 67amps@120v (83 peak amps) 33amps@240v (42 peak amps) that’s exactly what they are trying to do.... before they were using a suncore generator with 30a 1ph twist lock that’s used for portable lighting.... so I believe they currently have apc by Schnieder bat backups and they said after three or four hours they shut down... power goes out quite frequent because of horrible sub station. it just depends on what needs fixed by the poco... could be three hours the worst I’ve dealt with was days. In this scenario couple of hours max to keep them running until closing time....

 

[ctaylo360860]

What a mess. What some people will do to try and save money. One misstep and you are paralleling a 10KW generator with utility power. Nothing like watching a generator make fireballs...

Yeah I thought the same thing... also thought it was strange to feed a 120/208y 3ph system with a 120/240v single phase genset....

 

[ctaylo360860]

If the loads are on MWBCs then jumpering the two phases would make the currents add in the neutral conductor instead of subtracting.

Yes, having "on-line" UPS's would be desirable. Obviously if you also have a generator then that could charge the UPS batteries and extend how long the UPS will be working.

So far the circuits i am planing on moving are all single pole breakers and should have individual neutrals.... but if they want any type of lighting they are on 2 pole breakers I’m guessing with an individual neutral... have to check that out...
would this be a case of triplen harmonics? I Haven’t had a chance yet to read into this, but looking forward to learning something new!

 

[ctaylo360860]

200a 3ph breaker feeds panel inside with five wires isolating grounded and grounding conductors.

50a recessed genset plug feed genset side of 100a switched neutral double throw with four wires is

 

[ctaylo360860]

200a 120/208y subpanel feeds line side of 100a switches neutral double throw with 4 wires on a 100a 2 pole breaker isolating grounded and grounding conductors

Load side of 100a switched neutral double throw feeds 125a 120/240v 1ph 24 spice main lug sub panel with 4 wires isolating grounded and grounding conductors.

Outside 50a recessed genset plug feeds genset side of 100a switched neutral double throw isolating grounds and neutrals.

This is a separately derived system and the genset frame/ grounding conductor needs to be bonded with groundEd conductor...

 

[hillbilly1]

Keep in mind the normal source is 208, while the alternate source is 240. If the lights are two pole, they most likely are 208. If they are old fashion magnetic ballast, they are not going to like 240 volt for a long period of time.

 

[oldsparky52]

It sounds like forcing a solution when it may not cost much more to get a 3-phase generator in lieu of that single phase generator.

 

[ctaylo360860]

It sounds like forcing a solution when it may not cost much more to get a 3-phase generator in lieu of that single phase generator.

I agree, I’m currently working on a 500,000 bushel grain bin, and don’t have much time to Invest in this issue... it’s not a pressing matter in my opinion since power goes out once a month maybe... This genset is only 900.00 and is something they had. I haven’t looked into pricing anything for a 3 phase system... just trying to make sense of what previous electrician did and make sure it’s a safe install..

 

[ctaylo360860]

Keep in mind the normal source is 208, while the alternate source is 240. If the lights are two pole, they most likely are 208. If they are old fashion magnetic ballast, they are not going to like 240 volt for a long period of time.

Yeah they are new led lights and I’m guessing they have multi voltage drivers, but will have to make sure. Really what they were worried most about is servers and pos...