Unusual Question - Powering a single phase panel with 120 Volts

[sheldonrf]

I have a design I am completing which will be installed in various locations around the US for the Federal Government. The installation will be at radio station tower locations.

There is a 30 amp 120 volt feed and I need two 20 amp 120 volt circuits powered through this feed. The 30 amp circuit is capable of handling the loads as they are minimal wattage for each item. (1200 watts for one and 600 watts for the other)

I need a means of disconnect and the items are both required to be on a 20 amp max disconnect per the manufacturer. I have two thoughts for how to do this (other than in-line fuses which I don't like and do not want to use)

1 - Install a single phase panel and power only one leg of the panel
2 - I have seen some din rail mounted circuit breakers that could be placed in a Hoffman enclosure, but I do not think they are code compliant due to the fact that the Hoffman enclosure is not UL listed for that purpose and the cover must be removed to access the breakers

So, does anyone know if I can power a single phase panel with 120 volts? or am I mistaken about the Hoffman enclosure? Thank you in advance for your help.

 

[petersonra]

I would get a small 240/120 panelboard and just jump the incoming terminals on the main together and feed it with 120V.

 

[greenspark1]

I've looked at powering 1 phase of a panel before but it seem like it gets messy and would need lots of labeling.
You could use 2x enclosed circuit breakers tapped to the feeder. Or even a 2 pole 240V/20A with both poles tied to the same hot.
For 1800W of load you would only need 1x20A circuit which is even simpler.

 

[jap]

There is a 30 amp 120 volt feed and I need two 20 amp 120 volt circuits powered through this feed.

Why cant you just replace the 30 amp 120v feed with (2) 20 amp 120v feeds from the panel that the 30 amp feed is coming from already ?


JAP>

 

[sheldonrf]

Why cant you just replace the 30 amp 120v feed with (2) 20 amp 120v feeds from the panel that the 30 amp feed is coming from already ?


JAP>

It is complicated, but it is what must be because the power is an output from a "black box" so to speak.

 

[jap]

It is complicated, but it is what must be because the power is an output from a "black box" so to speak.

Almost sounds like a 20 amp circuit would handle both of those small loads.

Change the 30 amp CB out to a 20 amp, and rock and roll with the new 20 amp branch circuit.


JAP>

 

[JFletcher]

Run your 30 amp feed to a 6 breaker sub panel. Power one side of the bus. Install 2 20 amp Breakers that are powered from that bus. Done.

You can use three phase panels for single-phase applications, and you can use a split phase panel with just 120. No special labeling required unless perhaps you put a jumper across from A to B, which is unnecessary here anyway

 

[jap]

Run your 30 amp feed to a 6 breaker sub panel. Power one side of the bus. Install 2 20 amp Breakers that are powered from that bus. Done.

You can use three phase panels for single-phase applications, and you can use a split phase panel with just 120. No special labeling required unless perhaps you put a jumper across from A to B, which is unnecessary here anyway

There's a special brand name for the panels used in this type of installs.

They're called Whodoneits.


Jap>

 

[tortuga]

There is a 30 amp 120 volt feed and I need two 20 amp 120 volt circuits powered through this feed. The 30 amp circuit is capable of handling the loads as they are minimal wattage for each item. (1200 watts for one and 600 watts for the other)

I have seen this exact setup a few times. Its NEC compliant. A 30A 120V feeder going to a two circuit loadcenter, hots jumped together on the main lugs. These had a 1 pole 20A and a 1 pole 10A. I remember thinking it was odd every time and looking it up. When we demoed one out I kept the 10A plug in circuit breaker because I had not seen one before. It is now in my odd breaker collection.

 

[macmikeman]

I have seen this exact setup a few times. Its NEC compliant. A 30A 120V feeder going to a two circuit loadcenter, hots jumped together on the main lugs. These had a 1 pole 20A and a 1 pole 10A. I remember thinking it was odd every time and looking it up. When we demoed one out I kept the 10A plug in circuit breaker because I had not seen one before. It is now in my odd breaker collection.

Siemens 10 amp single pole breaker. SQ-D 10 amp single pole breaker. Both under $5 at wholesaler's.

 

[jap]

I have seen this exact setup a few times. Its NEC compliant. A 30A 120V feeder going to a two circuit loadcenter, hots jumped together on the main lugs. These had a 1 pole 20A and a 1 pole 10A. I remember thinking it was odd every time and looking it up. When we demoed one out I kept the 10A plug in circuit breaker because I had not seen one before. It is now in my odd breaker collection.

No that is not NEC compliant.

JAP>

 

[Besoeker]

Maybe it's just my Brit way of thinking but I don't quite see the complexity. A lot of the control circuitry in our panels was 110Vac.
Simple. A 400V/110V single phase transformer. Job done.

What am I missing?

 

[sheldonrf]

No that is not NEC compliant.

JAP>

What is the code article that says this is not compliant?

 

[ptonsparky]

What is the code article that says this is not compliant?

I'm curious too.

I've seen it done and on occasion done it myself.

 

[jap]

Think about how that jumper from one phase to the other on the main lugs is usually made and the violation will become evident.


JAP>

 

[ptonsparky]

Think about how that jumper from one phase to the other on the main lugs is usually made and the violation will become evident.


JAP>

A #10 wire spliced via Scotchlock to two other #10s then to the lugs is prohibited?

 

[Jraef]

I wouldn’t bother with the load center at all for that little bit. You can by “panel mount” single pole breakers that have lugs on both sides and tabs to screw them to a back pan in an enclosure (or even use DIN rail now). Sq D calls them “QOU” breakers, the others offer them too, I just don’t have the names handy.

 

[tortuga]

Think about how that jumper from one phase to the other on the main lugs is usually made and the violation will become evident.
JAP>

I thought you were going to speculate if there is a 15A duplex receptacle on the 10A circuit breaker.
110.14(A) A valid concern. The lug should be identified for two #10's in a way acceptable to the AJH. See UL whitebook ZMVV.
Most manufacturers offer a double lug that can be field installed.
Note the (2017) NEC 110.14(A) does not use the word 'listed' it uses 'identified'. That opens up some flexibility.
I know the different agencies such as the forest service act as their own AHJ and adopt the NEC by safety rule.
Keeping with easy to get breakers may be an advantage if they need to replace one at rural site on short notice.

 

[sheldonrf]

I wouldn’t bother with the load center at all for that little bit. You can by “panel mount” single pole breakers that have lugs on both sides and tabs to screw them to a back pan in an enclosure (or even use DIN rail now). Sq D calls them “QOU” breakers, the others offer them too, I just don’t have the names handy.
View attachment 20130

I have seen the QOU breakers, and I spoke with Schneider but they do not have any rated enclosures for these breakers and I do not think I can install these in something like a Hoffman enclosure because the enclosure is not UL listed, and the cover would require the screws to be removed. I can install a switch as a means of disconnect, but I was thinking that the UL listing, or lack thereof would be an issue.

 

[jap]

A #10 wire spliced via Scotchlock to two other #10s then to the lugs is prohibited?

Go read post #9 again carefully.

Then you can take the question mark and the smiley face of the end of your sentence above.

JAP>