Delta vs Wye SUPPLY to 3-phase motor

[Electrified1]

Hi folks, i'm really sorry for such a trivial question but this manufacturer has got me second guessing myself.

We have a small electrical shelter/room that we are planning an exterior wall mounted HVAC unit for.

Our power supply is 3-phase 480VAC WYE (i.e. 3L + Neutral), the HVAC unit we were looking at stated 460V 3-wire in it's catalog (no schematic/wiring diagram available as that would be too easy).
When I contacted the manufacture for clarifications they told me that the HVAC unit will only work on a 480V DELTA supply.
I told them that we had a 480V WYE supply but they reiterated that we needed a 480V DELTA supply.
This is where I started second-guessing myself...
The question is can't I just connect this HVAC unit to my WYE supply (i.e. connect the 3 Lines from my supply to the hvac and leave the neutral of my supply not connected)?

 

[electrofelon]

Hi folks, i'm really sorry for such a trivial question but this manufacturer has got me second guessing myself.

We have a small electrical shelter/room that we are planning an exterior wall mounted HVAC unit for.

Our power supply is 3-phase 480VAC WYE (i.e. 3L + Neutral), the HVAC unit we were looking at stated 460V 3-wire in it's catalog (no schematic/wiring diagram available as that would be too easy).
When I contacted the manufacture for clarifications they told me that the HVAC unit will only work on a 480V DELTA supply.
I told them that we had a 480V WYE supply but they reiterated that we needed a 480V DELTA supply.
This is where I started second-guessing myself...
The question is can't I just connect this HVAC unit to my WYE supply (i.e. connect the 3 Lines from my supply to the hvac and leave the neutral of my supply not connected)?

I suspect they are using delta and wye in the "jargon" sense as referring to the number of wires. I Cant think of a situation where the load cares about the actual transformer winding connections, except of course in the case of a neutral being needed.

 

[Besoeker]

Hi folks, i'm really sorry for such a trivial question but this manufacturer has got me second guessing myself.

We have a small electrical shelter/room that we are planning an exterior wall mounted HVAC unit for.

Our power supply is 3-phase 480VAC WYE (i.e. 3L + Neutral), the HVAC unit we were looking at stated 460V 3-wire in it's catalog (no schematic/wiring diagram available as that would be too easy).
When I contacted the manufacture for clarifications they told me that the HVAC unit will only work on a 480V DELTA supply.
I told them that we had a 480V WYE supply but they reiterated that we needed a 480V DELTA supply.
This is where I started second-guessing myself...
The question is can't I just connect this HVAC unit to my WYE supply (i.e. connect the 3 Lines from my supply to the hvac and leave the neutral of my supply not connected)?

I'm with electrofelon on this. I don't see any reason why you can't - 460V 3ph is 460V 3ph .

In fact, where I'm from, the LV supply is almost always three phase and neutral- 400/230V in our case. Three phase motors work quite happily without the neutral being connected.

 

[Jraef]

I suspect they are using delta and wye in the "jargon" sense as referring to the number of wires. I Cant think of a situation where the load cares about the actual transformer winding connections, except of course in the case of a neutral being needed.

I agree. If anything, it MIGHT be the other way around if the HVAC equipment has VFDs inside. Using a Delta system can be really problematic for the line surge protection devices (MOVs) in the VFD front-end because they are referenced to ground and therefor rated for the line to ground voltage found in a Wye supply. But in a Delta supply, the line to ground voltage potential can be the line to line potential, so the first time there is a problem, the MOVs vaporize and take out the nearby components in the drive.

It's highly more likely that your HVAC supplier person has no clue what they are talking about and got it wrong.

 

[electrofelon]

Yeah if anything it would be the system grounding configuration that would matter. It is certainly theoretically possible to have a piece of equipment that needs, say, a corner grounded supply due to voltage ratings, ground references, etc. I doubt there is any modern equipment designed like that (other than the 277/480 case mentioned). A fun academic question to ask this manufacturer would be if there is any specific grounding configuration requirement for this required delta supply: ungrounded, corner grounded, CT grounded - just to see what they say.

 

[Jraef]

Yeah if anything it would be the system grounding configuration that would matter. It is certainly theoretically possible to have a piece of equipment that needs, say, a corner grounded supply due to voltage ratings, ground references, etc. I doubt there is any modern equipment designed like that (other than the 277/480 case mentioned). A fun academic question to ask this manufacturer would be if there is any specific grounding configuration requirement for this required delta supply: ungrounded, corner grounded, CT grounded - just to see what they say.

Lol, yeah and if he says it needs to be ungrounded, you will know he is a nincompoop.

 

[__dan]

Most likely the load is delta and floating (straight motor load). If so and you bring it three phase three wires, the (floating) load will have no way of knowing if the supply is Y or delta. Any modern equipment built for standardized installs imo will assume the supply is a grounded system.

If the load is fussy about the supply, if it has the internal VFD's, it will be somewhere in the manufacturer's instructions that the supply has to be grounded Y, probably three phase three wire Y (no neutral is brought to the load). The drive's front end is typically internally Y connected and grounded.

Checking with the manufacturer is the smart way to do it, comparing the cost of the call to the cost of smoking something. In this case sounds like you did not get to speak to the right person.

Just in case the manufacturer was correct on the first call, I would recheck with them that the unit in fact "needs" a delta only supply. Load may be delta but the supply may/could be either.

 

[mike_kilroy]

I think it is time to go further. There is no Drive that requires Delta only input. There are many drives that require wye only input. Give us manufacturer name and model number of the supposed Delta only input Drive. Let's put some numbers on this. Hitachi for instance will often burn up input phase to ground movs on Corner grounded Delta inputs. They use 600 volt Mov's. 480 volt Corner grounded is 650 Plus volts to ground. Y 480 is about 400 volts to ground.

Sent from my SM-G900V using Tapatalk

 

[Jraef]

I think it is time to go further. There is no Drive that requires Delta only input. There are many drives that require wye only input. Give us manufacturer name and model number of the supposed Delta only input Drive. Let's put some numbers on this. Hitachi for instance will often burn up input phase to ground movs on Corner grounded Delta inputs. They use 600 volt Mov's. 480 volt Corner grounded is 650 Plus volts to ground. Y 480 is about 400 volts to ground.

Sent from my SM-G900V using Tapatalk

It was just speculation that there was a drive, I brought it up as a possible reason why the truth could be the exact opposite of what the HVAC mfr told him.

 

[Electrified1]

Thanks for the responses folks!
The HVAC unit we are looking at is a Marvair Compac II AVP (haven't determined the cooling/heating capacities yet). As far as I know there is no vfd on the unit.

I agree with all of you that this unit shouldn't be concerned with a wye or delta supply (other than the grounding configuration) just started second guessing myself when the manufacturer stated that it needs a delta supply to work. I started wondering if maybe I'm missing something or if I just never came across this type of setup.

 

[Jraef]

Thanks for the responses folks!
The HVAC unit we are looking at is a Marvair Compac II AVP (haven't determined the cooling/heating capacities yet). As far as I know there is no vfd on the unit.

I agree with all of you that this unit shouldn't be concerned with a wye or delta supply (other than the grounding configuration) just started second guessing myself when the manufacturer stated that it needs a delta supply to work. I started wondering if maybe I'm missing something or if I just never came across this type of setup.

Ok, a quick look at the installation manual for that shows absolutely no mention of delta or wye, it's just standard 3 phase. There are single phase fans inside that are 208-230V, so on the 480V models it tells you there is an internal transformer for them, meaning all you do is bring in 3 lines of 480V and a ground, it does not need the neutral brought in, ergo it would work on a delta or wye system. So I'm convinced this goes back to what electrofelon said right in the beginning, it's just a nincompoop salesman who is conflating 3 wire and 4 wire as always meaning delta vs wye. It does not, as we electrical professionals understand.

 

[kwired]

It's highly more likely that your HVAC supplier person has no clue what they are talking about and got it wrong.

What, that happens?

Recently had a warranty issue on a failed cove heater - factory rep on the phone didn't believe me when I said it was a 208 volt heater - the supply system at an apartment complex could never be 208 volts, I must have over driven my heater with 240 volts.:roll: