"Delta" breakers are really only telling you they have higher line to
ground ratings. The normal breaker you see in 120/240 is really only
rated 120v nominal to ground. In a delta you always have at least one
leg above 200v to ground. In corner delta you have 2 at 240v above
ground. The place you are likely to see corner delta is in a sewer
lift station where the only load is the pump and a control panel that
runs l/l at 240v. That will usually be open delta too.
The panel will look like a single pole (2 hots and a grounded leg)
unit but the tip off is 240v to ground and 3 p loads. That is really
the one you have to look for "delta" breakers in. All 3p breakers I
have ever seen are rated that way.
Although a corner delta panel looks exactly like a 120/240 panel, it
still needs to be listed for delta (higher voltage). I suspect it may
only be the label ;-)
An example would be to compare a QO230H "delta" breaker $200
with a QO230 120/240 breaker (the one on your water heater) $67
That is list price, you will beat that by up to 60% on the regular
breaker but you might not on the delta breaker.
A few posts back I mentioned a "delta breaker" then you mentioned "delta
rated breakers". My last post confused the distinction. I looked in the
SquareD catalog and your delta ratings are easy to find. They are
supposed to have a catalog for corner grounded delta but I haven't
searched for it yet. Should reinforce the info you provided above.
I looked in an my old electrician's handbook and it shows a "delta
breaker" as a 3-phase breaker except it only has 2 bus connections. The
third connection comes out to an additional lug. In use, you have high
leg delta service entrance wires but a single phase panel. The delta
breaker plugs into the panel and picks up the 120V legs. The service
high leg connects directly to the additional lug on the breaker. The
only 3-phase available is on the load side of the delta breaker - to
equipment or a subpanel. Everything else in the service panel is single
phase. I suspect they were used to add some 3-phase load to a single
phase panel - you just add 3-phase service wires and meter to the
existing single phase panel. To be safe you also add a 3-phase common
trip circuit breaker as a separate service disconnect. They could also
be used as one of the service disconnects in a split bus panel.
I looked on google (Holt) and delta breakers have not been allowed in
panelboards since 1978 (408.36). I sure have never seen one. But I
remembered seeing them in the NEC which is why I was interested.
Perhaps it is really just confusion about the term "delta breaker". I
prefer to just talk about the voltage rating, because that is the
distinction. If you look up that QO230H you will see it is referenced
to as going on corner delta systems.
The SqD site is pretty informative and the "breaker selector" will get
you to the right breaker fairly easily.
On 10/26/2009 12:47 PM Existential Angst spake thus:
I don't think this is true if a proper wire-nutted connection is made:
the threads of the nut should bite into the wires, and with enough of a
twist inside the nut, there's a plenty large enough contact area.
Soldered connections are, of course, better (assuming they're properly
made), but this isn't something I envision us going back to. (Although
who know, after the Apocalypse and a return to primitivism ...)
Well, while I don't necessarily want to fan the embers of the
back-stabbing argument, I think the consensus of opinion is that wire
nut connections are far superior to backstabbed ones.
Found--the gene that causes belief in genetic determinism
Many European countries have gone to lead free solder in their electronics.
Give the electronics a few years and they grow what is called tin whiskers.
This shorts out the circuits.
You have to use the lead free solder to do a good repair on them.
A pediatrician I know (doctor for children) tells me that
lead poisoning in kids is still a very real problem. Lead
free paint and plumbing is a very real advantage.
I figure that circuit boards are not likely to be eaten, or
much exposure to people. As such, that's plenty safe for my
It's funny, we started with copper, went to tinned copper, went back to
copper, slid further back to effing aluminum (goodgawd), learned from that
mistake and went back to copper again. Altho power companies use aluminum
in parts of their service -- and steel!
Also, there are different grades of copper, wire supposedly being
"electrical grade", which is among the higher grades, iiuc. Electrical
grade copper commands a substantially higher scrap value than copper pipe,
altho I don't know how a dealer would tell, if it were copper bar.
I wouldn't be surprised if wire is now a crappy grade of copper. Proly
could tell by comparing the resistance of an old 500 ft spool to a new
one -- if one could find an old spool.
As several people have said, steel is not used as a conductor.
Aluminum is rather widely used inside buildings for larger sized wire.
It is very common to use aluminum wire for the service wires from the
utility connection to the meter to the service panel. The problems were
with 15 and 20A branch circuits. Aluminum can still be used for them
too, but not likely any time soon.
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