480V, 3 phase delta to 240V with high leg question

[xformer]

Actually no, ranges and dryers are 120/240, so a misplaced B phase will fry them, but compressors and water heaters (240 volt) would be ok. But all of those will work on 120/208

Only the controls.

 

[hillbilly1]

Only the controls.

Sorry, but not only the controls, they can easily be manufactured 240 volt. On dryers they use cheap motors, so they are not rated 208/240, so they use 120 volt motors because the manufacturer does not want to make two different models.

 

[LarryFine]

Hillbilly,
This is important remark! will the oven need 120V power if it's rated 240V with single point connection? If it does need 120V, wouldn't the transformation be done internally within the over?

You tell us. Look at the appliance connections and see whether there is a neutral terminal or wire.

 

[Jraef]

We have 3 phase 480V. We will also have 208Y/120V 3phase for building loads but for the apartment units, the above is what he wrote. Of course I didn't want to seem like I dont know what that is, hence my question in this post.
I did my calculations and everything based on 208Y/120 for the apartment before he asked me to change it.

HE doesn't know what he is talking about!
You CANNOT get 240Y120, the math doesn't work.
If you have 240 3 phase 4 wire "high leg", you only have 120/240 on two of the phases to the center point of one leg, so you have a LIMITED amount of single phase 120V capacity relative to the size (and cost) of the transformer, plus you will end up with an inherently unbalanced system with respect to the 3 phase source. COULD it be done? Sure, with a lot of careful attention to which floors get which legs, and a lot of extra money (compared to just going with 208Y120).

 

[tortuga]

Yes. My calculations at 120/208 give 139a to 141 amp per unit. So I told the team 150a minimum, 175A recommended for each dwelling.
I had a discussion with the architect and contractor late evening yesterday, the contractor's goal is to cap each dwelling at 125A. I guess it makes a difference when you have 5 floors with 7 units each. He may have a point, but I want to make sure nothing gets fried due to wrong connection being made in the field.

Yeah there is a pretty big penalty for 208 when it launches you up past 125A panels.

 

[augie47]

but I want to make sure nothing gets fried due to wrong connection being made in the field.

If that is your goal you better stick to 208Y/120 or single phase 240/120 transformers.