480 to 240volt or 208volt

[AC\DC]

Hvac installer put in a 208/240 3/0 unit. I have 480/277 3/0.
Wed a transformer. Seems since they’re no neutral to this unit that 240volt delta 3/0 would be best.
Just want to double check.

 

[Jraef]

I would.

 

[ptonsparky]

You still need to provide an EG to that unit from the secondary of your step down. Corner ground or a High leg.

 

[synchro]

Seems since they’re no neutral to this unit that 240volt delta 3/0 would be best.

Although you don't need a neutral, a 480 - 240/139V transformer is another possubility. It gives you balanced L-G voltages in case there is circuitry in the unit that could be sensitive to this, for example MOV surge suppressors in a VFD. If that was true, though, I'd expect the installation instructions to mention it.

3-Phase 480 D - 240 Y 139 (Drive Isolation Transformer)

Drive-Isolation transformer converts 3-Phase 480D to 240Y/139. These units can handle demanding AC/DC variable speed drives and provide needed voltage change.

store.maddoxtransformer.com

 

[winnie]

HVAC systems are becoming more inverter based, and inverters prefer grounded wye supplies.

This is not as much a problem in the 200V class, but something to consider.

I'd probably go with 208/120V unless there was a performance hit or significant wiring cost change.

 

[augie47]

Even though the unit does not need a neutral, it may have a drive. I would go with a 120.240 secondary so you will have the neutral reference.
(or the two previous posts that popped up as I as typing )

 

[ptonsparky]

240 volt inclusive made me think it does not have VFDs, or the little jumpers need removed. RTFM is recommended of course.

 

[jim dungar]

Even though the unit does not need a neutral, it may have a drive. I would go with a 120.240 secondary so you will have the neutral reference.
(or the two previous posts that popped up as I as typing )

I am surprised by how many electricians become somewhat confused when they have to work on systems that do not have 'solid' Line-Neutral and Line-Ground connections tions, so I like to include neutrals.