208 AHU on a 480V panel????

[Chrissegura]

I did a site visit today for a commercial property and the AHU's are on the 480V panel but listed as 208 on the name plate.. Has anyone else ever came cross something like this??

 

[Dennis Alwon]

You sure about that? Is there a transformer along the way?

 

[Chrissegura]

You sure about that? Is there a transformer along the way?

Yes sir. It is a 225Amp 480V panel--25kva transformer--225amp 208v panel bussed @ 150amps

 

[StarCat]

AHUs

AHUs

Some 3 PH gear is dual voltage rated, but that is usually reflected on the cabinet nameplate as well.
IN that case the motors can be reconfigured for 460 as well as control transformers if they are present.
In such a case I usually open the units up and do a detailed inspection.
It makes things interesting when incorrect voltage machinery is already " roughed in."
One time I came to a plant which has bought an expensive control panel with output of 24VDC and the entire plant control system was 24 VAC.

All the best

 

[templdl]

I did a site visit today for a commercial property and the AHU's are on the 480V panel but listed as 208 on the name plate.. Has anyone else ever came cross something like this??

Are you implying that the AHU is being supplied from a 480v panel but the NP of the AHU is 208v? As Dennis said, are you sure about that? If you are right one would think that you would be letting the smoke out of the AHU.

 

[qcroanoke]

Yes sir. It is a 225Amp 480V panel--25kva transformer--225amp 208v panel bussed @ 150amps

Ok,
Is it 480 t0 xfmr to 208? Which would make sense.
Or,
208 to xfmr to 480 which makes no sense and is guaranteed to let smoke out if the AHU's are 208.

 

[JoeStillman]

What we have here is a failure to communicate.

That transformer is a bandaid on somebody's coordination booboo. I don't know why EE's don't take the initiative to communicate to the mech dept/contractor/consultant what voltage they need for the equipment they are supplying. Except in very rare circumstances, the units are available at whatever voltage you need them to be, and the EE knows best which voltage to use.

I have worked with designers who just take for granted that the mechanical people know what they are doing, voltage wise. They don't. You have to tell them what to use.

 

[augie47]

What we have here is a failure to communicate.
.......................................................
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[JDBrown]

What we have here is a failure to communicate.

That transformer is a bandaid on somebody's coordination booboo. I don't know why EE's don't take the initiative to communicate to the mech dept/contractor/consultant what voltage they need for the equipment they are supplying. Except in very rare circumstances, the units are available at whatever voltage you need them to be, and the EE knows best which voltage to use.

I have worked with designers who just take for granted that the mechanical people know what they are doing, voltage wise. They don't. You have to tell them what to use.

To be fair to the EE's, this is just as likely (if not more so) to be the HVAC guy's mistake. We always coordinate the electrical requirements with the ME, but it seems like about half the time (okay, that's an exaggeration) when the EC goes to connect power to the HVAC unit he discovers it's the wrong voltage. The EE, ME and EC are all on the same page, but whoever ordered the HVAC equipment ignored the drawings and bought units with the wrong voltage (or they bought single phase units instead of 3-phase).

Now, in my opinion, whoever made the mistake (vendor, HVAC installer, etc.) ought to be paying to have the equipment replaced with what was specified. What ends up happening is the owner can't wait the amount of time it would take to get the right units, and whoever was at fault is refusing to pay for them anyway. In order to avoid the delay and expense of a lawsuit, the owner has the EE and the EC work out a "band-aid" solution like what seems to have happened in the OP. The EE usually ends up doing this for free, in the hopes that it will show the customer how helpful he is and help him get more work with that customer in the future. If he's lucky, the EC might make some money off of a change-order for the band-aid, but far too often his change order ends up being rejected after he's already done the work.

As for the OP, I agree with Joe: your situation sounds like one of these band-aid type solutions.

 

[wallypiper]

Yes sir. It is a 225Amp 480V panel--25kva transformer--225amp 208v panel bussed @ 150amps

So, to be clear, you're saying there IS a transformer installed to provide the 208 the AHU's need. In that case, there is no problem assuming that everything is suitably rated for the load.

All the speculation over how this came to be doesn't really matter. Maybe the units were existing at another facility and the transformer cost much less than new ones. We do lots of projects involving old equipment being moved from one facility to another and although 208 equipment is becoming increasingly rare, it occurs.

 

[JoeStillman]

View attachment 9099

Nailed it.