120V Single Phase Panelboard

[JDBrown]

This question just came up at work:

Does anyone make a 100 Amp, 120 Volt, single-phase panelboard? Not 120/240V, not 208Y/120V, just single-phase 120V.

I've heard of these in some older residential systems, but apparently this is what somebody has specified for a new subpanel in a commercial building. As far as I know, nobody makes these anymore, but I've been wrong in the past.

Anybody know of a manufacturer who makes this animal? Or is this designer just full of it?

 

[qcroanoke]

This question just came up at work:

Does anyone make a 100 Amp, 120 Volt, single-phase panelboard? Not 120/240V, not 208Y/120V, just single-phase 120V.

I've heard of these in some older residential systems, but apparently this is what somebody has specified for a new subpanel in a commercial building. As far as I know, nobody makes these anymore, but I've been wrong in the past.

Anybody know of a manufacturer who makes this animal? Or is this designer just full of it?

After a quick search I found none.
Although you may find one built into a UPS with only 120 volt output.

 

[templdl]

This question just came up at work:

Does anyone make a 100 Amp, 120 Volt, single-phase panelboard? Not 120/240V, not 208Y/120V, just single-phase 120V.

I've heard of these in some older residential systems, but apparently this is what somebody has specified for a new subpanel in a commercial building. As far as I know, nobody makes these anymore, but I've been wrong in the past.

Anybody know of a manufacturer who makes this animal? Or is this designer just full of it?

Personally, I believe the individual requesting it is misinformed. What you are actually looking for is a 1ph2w 120v panel which I,m not aware that there are any. If you get backed into a corner could use a 120/240v 1ph3w panel which you could feed with 1ph2w by simply connecting the single 120v line to both bus. As such you eould have 120v from each bus to the grounded conductor but would have zero volts between the bus. It is of my opinion is a very poor design.

 

[SceneryDriver]

Please protect this "designer" from himself. It may be a case of a simple nomenclature mistake in how the desired panel is described in the spec, but if it's not, do everyone else down the line a favor and pull that second phase. I just demo'ed an installation where a small 120/240v panel had both of its phase buses tied together; no wonder the feeder breaker was tripping. It appeared, until a close inspection, that there was twice as much power available at the subpanel than there actually was. Any cost savings in copper wire will be more than spent on a specialized one-phase-bus panel, if they even exist.



SceneryDriver

 

[GeorgeB]

If you get backed into a corner could use a 120/240v 1ph3w panel which you could feed with 1ph2w by simply connecting the single 120v line to both bus. As such you would have 120v from each bus to the grounded conductor but would have zero volts between the bus. It is of my opinion is a very poor design.

If for no other reason that the grounded conductor would carry the sum of all circuit currents instead of the difference between the 2 with 120/240 1ph3w. The bus is not likely sized for it.

 

[templdl]

If for no other reason that the grounded conductor would carry the sum of all circuit currents instead of the difference between the 2 with 120/240 1ph3w. The bus is not likely sized for it.

Good point.

 

[JDBrown]

Thanks, guys.

Yes, templdl, the "designer" (and I use that term because I don't know if he's a PE, a contractor, or something else entirely) is asking for 120V, 1 phase, 2 wire. Strange, I know.

This isn't something I'm going to install -- I'm an engineer, not an electrician. But we've been asked to review someone else's plans, and didn't want to tell the client, "Well, this is wrong because this type of panelboard doesn't exist" if that wasn't the case. Of course, even if it does exist it's still poor design practice, except maybe in some very special circumstances.

Thanks again for the input.

 

[GoldDigger]

This question just came up at work:

Does anyone make a 100 Amp, 120 Volt, single-phase panelboard? Not 120/240V, not 208Y/120V, just single-phase 120V.

I've heard of these in some older residential systems, but apparently this is what somebody has specified for a new subpanel in a commercial building. As far as I know, nobody makes these anymore, but I've been wrong in the past.

Anybody know of a manufacturer who makes this animal? Or is this designer just full of it?

The cheapest solution that may mollify the designer is to take a 120/240 3-wire panel and leave the L2 terminal disconnected and covered. Then make sure to install blank plates over all of the L2-fed breaker positions and add a prominent label stating that 240V is not available at the panel.
You can, without fear of contradiction, tell him (or her) that would cost less than a 120V 2-wire panel. (If you could find one.)

 

[JDBrown]

Update:

I just got off the phone with my local Square D rep and, surprisingly, Square D makes a 120V, single phase, 2 wire load center. It's on page 1-10 of the Square D Digest. Learn something new every day, I guess.

I'm still telling them it's not a good design, though.

Again, thanks for the input, everybody.

 

[Dennis Alwon]

I wonder if they are starting to make the 120v panels for solar installs.

 

[GoldDigger]

I wonder if they are starting to make the 120v panels for solar installs.

Possible, but by far the majority of GTIs are going to require a 240V two and a half wire or 208V three and a half wire connection. (The "half" refers to the need for a neutral for voltage balance verification even when it will not be carrying any generated power.)
For off-grid use with a 120V inverter, maybe, but that does not seem like a very big market.

 

[petersonra]

I have seen them before, but not recently. Call your local supply house and put them to work on it.

 

[templdl]

Update:

I just got off the phone with my local Square D rep and, surprisingly, Square D makes a 120V, single phase, 2 wire load center. It's on page 1-10 of the Square D Digest. Learn something new every day, I guess.

I'm still telling them it's not a good design, though.

Again, thanks for the input, everybody.

Very smart.

 

[Jraef]

Update:

I just got off the phone with my local Square D rep and, surprisingly, Square D makes a 120V, single phase, 2 wire load center. It's on page 1-10 of the Square D Digest. Learn something new every day, I guess.

I'm still telling them it's not a good design, though.

Again, thanks for the input, everybody.

Those have been around forever. We used to call those "Woodshed Panels" because they were used a lot in small outbuildings where all you had were lights and maybe one outlet, so you didn't want to run 3 wire +G cable to it.

But read it CAREFULLY. For 120V only, you are limited to 50A and 4 1" breaker slots, or 5 slots, but 30A. That's because basically, it's just one bus out of a 100A 120/240 panel. That's not what he wanted, he wanted 100A. When you get to the 100A version, its back to the same deal of 120/240, 2 side-x-side busses.

I don't understand the insistence though. Is he thinking he is saving $$ by not having to run another wire? Because that's false economy; to get 100A from 1 wire, it will be twice as big. Actually, BIGGER because the VD would be worse!

 

[Smart $]

... Does anyone make a 100 Amp, 120 Volt, single-phase panelboard? ...

... surprisingly, Square D makes a 120V, single phase, 2 wire load center. ...

Actually, if you look for what's known as column-type panelboard, you'll find several manufacturers make a 1? 2W version. Narrow in width and only one column of breakers.

 

[masterinbama]

I have seen them used on small UPS installs.

 

[masterinbama]

I have also seen 120/240 3W panels wired to the 120V output of an isolation transformer where the output was not intentionally grounded and left to float. They wired the 120 to both busses and used 2 pole breakers for all circuits.


This was in an old electronics lab at Marshall Space Flight Center and was a holdover from the Apollo days.

 

[GoldDigger]

I have also seen 120/240 3W panels wired to the 120V output of an isolation transformer where the output was not intentionally grounded and left to float. They wired the 120 to both busses and used 2 pole breakers for all circuits.


This was in an old electronics lab at Marshall Space Flight Center and was a holdover from the Apollo days.

With the addition of a hard or resistance grounded center tap on the secondary, you would have a balanced circuit, as described in NEC.