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30 deg c vs 40 deg c

30 deg c vs 40 deg c

30 deg c vs 40 deg c

(OP)
Question for cooling electrcial rooms - if condcutors are tested at 30 deg c ambient but equipment terminations are tested at 40 deg ambient - what do you tell the mechanical engineer to keep the room temperature at?

Thanks.

RE: 30 deg c vs 40 deg c

>>>what do you tell the mechanical engineer to keep the room temperature at?

The proper temperature to ensure that any ambient derating factors do not cause any ratings to be exceeded. A 10 deg increase in ambient can possibly lead to derating cable ampacity to 80% or so.

RE: 30 deg c vs 40 deg c

(OP)
Would you use the averge or peak annual temperature to determine the maximum ambient temperature.
 

RE: 30 deg c vs 40 deg c

For conductors and terminations, I'd use the peak because the thermal time constant is low.  There could be justification for using a maximum 24 hour average for oil filled transformers because the time constant is higher.  ANSI oil-filled transformers are rated on a 24 hour average ambient temperature basis (30°C max) and a peak ambient temperature basis (40°C).
 

RE: 30 deg c vs 40 deg c

I think the HVAC people could manage it with the following data:                                                 DESIRED                                          ALLOWED FOR 12 H
DESTINATION           MAX.TEMP.     MIN.TEMP.     RH%                 MAX.TEMP.     MIN.TEMP.      RH%
CONTROL ROOM                  25                      20               60                   35                  10                 40
RELAY  ROOM                       25                      20               60                   35                  10                 40
Low Voltage Switchgear         35                     10                60                  40                  10                  40
Medium V.Switchgr.               35                     10                60                  40                  10                  40
CABLE ROOM                        35                     10                60                  40                  10                  40
But you have to get the  electrical losses for each room including lighting and crew[appr.150 w/man].

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