I have a commercial convection oven that is 240 volt, 3 phase. My question is: Power to the building is 3 phase with a 208 high leg. Can this operate the oven being the oven has no neutral? Thanks...

 

Sure. None of the legs should have any loads connected between them and the ground.

 

I don't see why not.

I am a little puzzled by your reference to 208V 3 phase with a high leg. That would not be code compliant in the U.S.

 

Frank... the answer is yes, but there are two concerns:

1) If the source is comprised of a single 3-phase transformer or three single-phase transformers (closed delta-connection), then make sure the source capacity (in kVA or Amps)exceeds that of the Oven's requirement (in kVA or Amps)

2) If the source is comprised of just two single-phase transformers (open-delta connection), then make sure their total kVA exceeds sqrt(3) x oven capacity!

Regards, Phil Corso

 

Frank,

I don't know if it's legal for new installations today or not but there's plenty of it around. Besides, it's not 208 with a high leg, it's 240 Delta with a high leg (208 to ground).

 

> I don't know if it's legal for new installations today or not but there's plenty of it around.

> Besides, it's not 208 with a high leg, it's 240 Delta with a high leg (208 to ground). <

This is not what the OP said.

240V delta with a CT between 2 of the legs is pretty common, but it is not 208V / 3phase, which is virtually always in a wye configuration.

If what he has is a 240V delta power system, I don't get what his question is about.

 

> This is not what the OP said.

You're right. He said "3-phase with <b>A</b> 208 high leg". Still, I can't think what else he could mean other than 240 Delta with a center tapped winding.

 

Gentlemen... the 3-Ph, 4-Wire, delta, provides 240/120V connection. Also known as known as the "high leg" or "red-leg" or "stinger leg", etc, has one phase center-tapped. The center-tap is the grounED phase.

Furthermore, it is covered by the NEC!

Regards, Phil Corso

 

We've had this discussion before... remember the "Hermits In A Cave Story!"

See Control.Com Thread # 1026198752!

Regards, Phil Corso

 

208 phase to phase, 120 phase to neutral, 3 phase 4 wire system.

 

>208 phase to phase, 120 phase to
>neutral, 3 phase 4 wire system.

Should have said that in the first place! ;-)

OK, the fact that the oven has no neutral is fine. You can serve 208 single phase and 208 three phase loads from that service.

The only thing you have to check is if the nominal 240 volt oven will work at 208. A lot of times things will work OK but the variation is over 10% so you should check with the OEM.

 

Frank... if you would like a drawing depicting the exact situation you described, then contact me off-forum!

Phil Corso (cepsicon [at] aol [dot] com)