Is there 3 pole 240V?

Status
Not open for further replies.
C

Cudal81

Member
Location
Islip, NY
Occupation
Design Engineer
Our surveyor forgot to measure voltage between phases/neutral. this is my first time to encounter this kind of Service Panel. Main OCPD says 3 Pole 240V AC. I thought it's 3 phase 208V. Anyone has idea on this. Thank you


orig_image_1.jpgorig_image_1 (1).jpg
 
That panel could be 240 high leg, but if it is the marking tape is wrong. ( not convention, reg leg in middle)
Could be 208.
need to measure voltage.
by the marking tape I’m betting 208
 
There is a 240/120V 3Ø system. It is a high leg Delta which consists of 3 ph legs of 240V L-L, 120V L-N. However, one leg to neutral is around 208V. It is also a center tapped Delta, very common in industrial and commercial.
 
Hv&Lv said:
That panel could be 240 high leg, but if it is the marking tape is wrong. ( not convention, reg leg in middle)
Could be 208.
need to measure voltage.
by the marking tape I’m betting 208
Click to expand...
I bet you're right in it being 208V. I see a SP breaker on "B" phase. Unless high leg isn't on "B".
 
This is an artifact of the "keep it simple stupid" (K.I.S.S.) principle of engineering.

It is not worth the effort of a manufacturer to make a special version of the same breaker for both 240V and 208V. The 240V breaker is "backwards-compatible" with 208V by design, and needs no special components to make it work with 208V. Any marginal benefit you'd get with building a special version for slightly less voltage, is not going to justify the burden of doubling the variants of products you need to manufacture. For this reason, the exact same product is used for both 208V systems and 240V systems, and it will carry a 240V rating to be applicable to both voltage systems.
 
Carultch said:
This is an artifact of the "keep it simple stupid" (K.I.S.S.) principle of engineering.

It is not worth the effort of a manufacturer to make a special version of the same breaker for both 240V and 208V. The 240V breaker is "backwards-compatible" with 208V by design, and needs no special components to make it work with 208V. Any marginal benefit you'd get with building a special version for slightly less voltage, is not going to justify the burden of doubling the variants of products you need to manufacture. For this reason, the exact same product is used for both 208V systems and 240V systems, and it will carry a 240V rating to be applicable to both voltage systems.
Click to expand...
Well maybe. Check with your wholesale house as to the availability and price of a 240 volt breaker vs slash rated
A straight rated breaker, as shown is far more expensive than a slash rated breaker 120/208, and most wholesale houses don't carry the straight rated breaker, esp around here as there are very few high leg services left. The 240 breakers at Platt Electric don't even show a price...
Its very easy to tell a high leg service if its overhead, its a big transformer and a little transformer, and typically fed from open delta primary. The other way to tell if its a high leg is there are two breakers and a space....the space being the 208 volt leg.
 
Look super close and they're all 120/240 rated minis. You can't do that on the high leg, so my guess is 208Y/120.
 
tom baker said:
Well maybe. Check with your wholesale house as to the availability and price of a 240 volt breaker vs slash rated
A straight rated breaker, as shown is far more expensive than a slash rated breaker 120/208, and most wholesale houses don't carry the straight rated breaker, esp around here as there are very few high leg services left. The 240 breakers at Platt Electric don't even show a price...
Its very easy to tell a high leg service if its overhead, its a big transformer and a little transformer, and typically fed from open delta primary. The other way to tell if its a high leg is there are two breakers and a space....the space being the 208 volt leg.
Click to expand...

That's a good point too. I'm well aware of that issue of straight vs slash-rated breakers. I would guess that because slash-rated breakers and applications that permit them are the most common, there simply isn't enough demand to justify discontinuing them and standardizing on straight-rated breakers. I wouldn't be surprised if this were a common oversight that people get wrong regularly, because you really have to know how to read the fine print and know what you are looking for. It isn't like the datasheets elaborate on the meaning of this rating in English, so it is as clear as possible. Like "maximum voltage is 240V between poles, and shall not exceed 120V to ground".

My point still stands that for the line-to-line rated voltage, the manufacturers "bin" the breakers into the same category for 208V and 240V. I've never seen a fuse, a disconnect, or a breaker that spells out a rating of 208V. From what I've seen, breakers in the US/Canada market are binned into the categories of 240V, 480V, and 600V, some of which are slash-rated and some of which are straight-rated. It is also common that the same breaker is rated for all three of the above voltages, but with significantly less KAIC rating at higher voltages.
 
Carultch said:
My point still stands that for the line-to-line rated voltage, the manufacturers "bin" the breakers into the same category for 208V and 240V. I've never seen a fuse, a disconnect, or a breaker that spells out a rating of 208V. From what I've seen, breakers in the US/Canada market are binned into the categories of 240V, 480V, and 600V, some of which are slash-rated and some of which are straight-rated. It is also common that the same breaker is rated for all three of the above voltages, but with significantly less KAIC rating at higher voltages.
Click to expand...
Yes that is possible. I used to work on motorola portable radios, the only difference between the 16 and 32 channel was the knob. to get the internal speaker to work, a jumper had to be cut, they were all the same, but you paid extra for the speaker. I think one of mods discussed this issue of breakers and perhaps he can add to this.
 
Status
Not open for further replies.
Top