Electrician Talk banner
1 - 7 of 7 Posts

·
Registered
Joined
·
327 Posts
Discussion Starter · #1 ·
A friend called me with strange voltage readings from his server PDU outputs.

Friend: This is strange, the building is wired for 208, yet I get 120V from 2/3 of the PDU output cords and 230V from the remaining 1/3. On the input side I get X to Y 240V, X to Z and Y to Z 120V, and Z to ground of 0V.

Me: You can't get 240V from 208V unless there is an additional transformer somewhere. Please look at the power pole and tell me what you see.

Friend: One transformer with three secondary windings and two smaller identical transformers with each two secondary windings. They are delta connected and 4 wires go into the building.

Me: Cool, when was the building constructed.

Friend: 1963 Why?

Me: 240 high leg delta was popular then.

I only bring this up so that we check the voltages and understand the building power system before plugging in a bunch of expensive servers and causing a lot of smoke.
 

·
Hackenschmidt
Joined
·
12,036 Posts
PDUs are almost always plugged into a UPS, and a lot of UPSs will take 208 in and make 240/120 out.
 

·
Registered
Power distribution and controls
Joined
·
1,004 Posts
I have seen PDU's that put out both 120v and 230v. Best to have your friend read what the input and output of the PDU says.
 

·
Registered
IBEW 6 volts to lightning bolts
Joined
·
1,140 Posts
Strange. Most PDU setups are fed via UPS with 3 wire 480 or 208. The XFMR within the PDU will give you 120/208 on the output stage.


Sent from my iPad using Tapatalk
 

·
Hackenschmidt
Joined
·
12,036 Posts
Strange. Most PDU setups are fed via UPS with 3 wire 480 or 208. The XFMR within the PDU will give you 120/208 on the output stage.
There are a lot of PDUs that are not that fancy, really just a fancy outlet strip.

Tool Office supplies Automotive exterior Font Auto part
 
1 - 7 of 7 Posts
Top