Delta/Delta AC circuit

[billsims]

This year I've ran into two examples of where a delta connected service feed is feed into a single phase distribution panel. In the first panel I assumed that it was totaly in violation of the code since it had two separate breakers feeding the AC unit 3 phase. They had placed a two pole breaker in panel to feed two phases and mounted a single pole breaker to the side of panel to feed the high leg. (This I found in a water utility plant) I refused to replace the breaker since I did not think it was safe.

Yesterday I was called to a Post Office branch and found that the feed was delta and they had used a single phase panel, but here there was a three pole breaker with a common trip, one pole of the breaker had a side terminal where the high leg fed into. The breaker is clearly marked as a Bryant breaker, but I can find no record of Bryant ever making a breaker like this.
Is this in violation of code? I know that today I would use a three phase panel and identify high leg, but how to fix this easily without high cost of rewiring. High leg is only used for AC unit.

iss@charter.net

 

[bennie]

Re: Delta/Delta AC circuit

bill: The first situation is a Rube Goldberg delta breaker. The second situation is a delta breaker.

There is not many of these around anymore. They were legal in the 50's. I installed them.

 

[bennie]

Re: Delta/Delta AC circuit

bill: This installation was likely legal at the time of original construction.

Other than the material being old, this is a safe procedure. At least no one can put a 120 volt breaker on the high leg.

Delta breakers are legal only for replacement purposes. I highly doubt one can be located, except from used breaker dealers.

It does not seem logical that manufacturers are still tooled up for making the delta breakers.

 

[roger deas]

Re: Delta/Delta AC circuit

Bennie, I don't think they are allowed even for replacement any longer. 408.16(E)

The last one I installed (out of three total) was in the late 70's and seems I remember " For Replacement Only" on the packaging even back then.

I may be wrong, (won't be the first time ) but I think this was also worded in the 75 and 78 codes.

I remember it was a SQ D.

Roger

[ May 09, 2003, 02:37 PM: Message edited by: roger deas ]

 

[tom baker]

Re: Delta/Delta AC circuit

Sq D makes a delta breaker rated 240 volts 3 phase.

 

[don_resqcapt19]

Re: Delta/Delta AC circuit

Tom,
They still make a real "delta" breaker? One that has 3 poles, but only two bus connections?
Don

 

[tom baker]

Re: Delta/Delta AC circuit

Ok we are talking about two different delta breakers. the one I mentioned is for mid point grounded delta services.

 

[bennie]

Re: Delta/Delta AC circuit

The delta breaker originated in the 1930's during the REA program to electrify farms.

240/120 services were installed at the farms. Single phase water well pumps did not perform very good. Companies started making 3 phase motors for the pumps.

Adding one additional transformer, sized for the pump motor load, connecting open wye to open delta, and using two phase conductors plus the MGN made the three phase system.

The delta breaker originated for connecting the third phase in a single phase panel.

 

[bennie]

Re: Delta/Delta AC circuit

Orange was the color selected, for the stinger leg, due to the single phase panel.

Delta breakers worked very well. 240 volts was much better than 208. Three phase panels were not necessary for one circuit.
The demise, of the delta breaker, was by efforts of the loadcenter manufacturers. The electricians in the trenches had no problem with them.

The substantiation was for safety reasons. The cure was, a three phase panel with "B" phase the stinger leg, so a 120 volt breaker would cause all kinds of smoke and phone calls.

 

[bennie]

Re: Delta/Delta AC circuit

The best date I can determine for delta breakers not being permitted in single phase panels is 1978.
384.16(e). There is no exception "for replacement only", but I think that is an automatic consent due to the breaker being legal at time of original installation.

The delta breaker should still be approved for replacement only.

 

[definitive]

Re: Delta/Delta AC circuit

Isnt this just a corner grounded delta?

 

[bennie]

Re: Delta/Delta AC circuit

When this configuration is added to a 240/120 single phase service it is an open wye/open delta. A to C phase is center tapped for MGN connection. B phase is the high leg.

The derived neutral is solidly connected to the system MGN.

This system is only for 240/120 volts, 3 phase.

Only two single bushing transformers are required.