240V 3 phase

[desert designs]

Hello, it's me, desert designs. greetings MHF people! so, I inherited a jack in the box project in Stockton, CA. The previous designer is showing 240V 3ph service, 400A. On his panel schedules, single phase power is using A & B legs only, and 3 phase power is using A, B & C....Is this right? I've never seen this situation.

 

[augie47]

You would need to find out from POCO the characteristics of the supply.
240/120 3 phase 4 wire high leg delta would lead to that arrangement.
(other than the 120v loads would be on A&C, 3 phase on A,B,C)

 

[desert designs]

Thanks augie. this job is so screwed up I thought the guy might have been out of his mind. "240/120 3 phase 4 wire high leg delta" imagine that. so 208/230 3phase hvac equipment will work. I'd use √3 * 240 * amps = VA.

 

[augie47]

Thanks augie. this job is so screwed up I thought the guy might have been out of his mind. "240/120 3 phase 4 wire high leg delta" imagine that. so 208/230 3phase hvac equipment will work. I'd use √3 * 240 * amps = VA.

If the system is actually 240 volt and the HVAC equipment is actually 208v, the install would be a violation of 110.4

 

[desert designs]

208/230 means it will run on either voltage correct ?

 

[desert designs]

is that a no? hahaha, oops sorry, charlie

 

[broadgage]

A pedant could argue that equipment listed for 230 volt operation should not be used on a 240 volt supply.
Likewise it could be argued that dual rated equipment listed for 200/230 or for 208/230 should not be used on a 240 volt supply.

In practice though, in the USA it is normal practice that motors intended for 240 volt circuits are described as "230 volt"
Those intended for 208 volt circuits are often described as "200 volt"

 

[desert designs]

york air conditioning says yes. 208/230V 3ph hvac equipment will work within a range of 1 hundred some odd V - 250V

 

[kwired]

Hello, it's me, desert designs. greetings MHF people! so, I inherited a jack in the box project in Stockton, CA. The previous designer is showing 240V 3ph service, 400A. On his panel schedules, single phase power is using A & B legs only, and 3 phase power is using A, B & C....Is this right? I've never seen this situation.

If it is 240 volts three phase and there is 120 volt loads connected also it can't be anything but a delta with mid point of one phase grounded, that system will have a "high leg" that is 208 volts to ground - there is no getting around that outside of using a different system like a 120/208 wye - but then you will not have 240 volts.

Code says the higher voltage to ground lead should be the center position in switchgear and panels. If for some reason it is not - you still have 208 to ground on that leg and you have to deal with it, Ignoring that fact will make smoke come out of things that get connected to the high leg instead of to a 120 volt leg.

208/230 means it will run on either voltage correct ?

correct. It will draw less current at the higher voltage if doing same amount of work.