ECN Forum Forums General Topics of the Trade General Discussion Area 30 amp sp breakers

Just ask the guy who works in the electrical department, he'll tell you exactly how/where to install one. HAHAHAHAHAHA

But seriously, the main uses I can see are wall hand dryers (most have a 120v/20a rating), the already mentioned ac/heat units and and RV (travel trailer) receptacles(125v/30a).

Just for the sake of novelty, NEMA does list a “5-50” plug and receptacle—rated 125V/50A 2-pole 3-wire wiring devices. {However rare I guess it wouldn't be impossible to genuinely need a 50-amp 1-pole breaker.} The only use I can remember for 120V 50A circuits was for stage arc lights…”follow spots.”

Bjarney I did a job where I needed a 1 pole 50 amp breaker.

This was for the National Weather Service at Logan airport, they had a Ford Aerospace Computer (It even had a big blue Ford oval) that needed 50 amps @ 120 volts.

This was about 1983 and the computer looked to me like it was from the 1960s.

I ended up using 1 pole of a 2 pole 50 as all the supply houses claimed no such thing as a single pole 50.

Bob

I was able to find some photos of this equipment, it was a dinasour when we where relocating this equipment in 1983, I would hope they modernized since then.

Ford Terminal

Ford Equipment rack (notice the blue)

quote from the page I got these images

I wonder what "huge" would mean as compared to the PCs we are sitting at.

http://www.atarimagazines.com/v5n5/whereweathercomesfrom.html for more info if anyone finds this old equipment interesting.

Sorry for the threadjack.

Bob

For awhile brand-X was particularly adept at insisting on dedicated circuits for their photocopiers. Their means of “assurance” of this was to insist on using only (their “approved” parts-inventory house-branded) NEMA 5-30R receptacles. I think it was a guise, for peak machine load always measured well below 20 amperes. They seemed to be famous at automatic fingerpointing when any of their machines screwed up—getting flat-out snippy about demanding week-long power-quality printouts if there were any complaints about their equipment acting up.

Back when they had a bunch of sole-source lease agreements with my employer, their maintenance group was consistently most uncooperative at responding to anything that remotely appeared to be the slightest possibility of a power-quality problem. You know—the fat-headed ‘guilty-by-defective-branch-circuit until proven innocent’ mindset.




[This message has been edited by Bjarney (edited 10-08-2003).]

I've got a friend who was sent to a house where the complaint was that every time they changed the thermostat setting on their stove, the lights in the kitchen dimmed. It turned out that there was an airconditioning unit fed with a single pole 30 amp breaker which had blown one of the phases in the house. backfeeding through the element of the stove.
Whoever invented the SP 30 amp breaker....

Sparked,

Besides from the already mentioned uses, I've seen 30 and 50 Amp single poles breakers used for larger computers or UPS loads. The UPS output can either be hard wired to devices or have eight to sixteen outlets on the back. (Four outlets per 20Amp breaker)

Typically they are in data centers and have been wired correctly but I've seen plenty of smaller shops chop of the twist-lock and install a 15Amp plug on the end.

Eric

Square D lists a single pole 70 amp QO in their catalog.

They also list a single pole 100 amp in the QOU and FAL styles.