1920's wiring....

[gfretwell]

"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.

[bud--]

A picture is worth a thousand words.

Where do you get the wire with the neon insulation? (nice touch)

Another nice pic. 2 transformers means open delta. Notice the right transformer has 3 connections - the center one is the neutral. Left transformer only has 2 connections.

I have never seen an installation with a delta breaker. Catalog pictures what I remember is a delta breaker has 2 bus stabs and a wire. The wire goes to the neutral bar? Is this the only way delta breakers are used?

[bud--]

Interesting.

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.

[gfretwell]

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.