larmee
Member
- Location
- Jackson, TN 38301
Thanks in advance for any help. I have a problem child at a major department store here in my hometown. In the beginning there were 4 ac units that were being feed from a 480 switchgear. Someone in the near past replaced these 4 units with 208 volt units feed with number 10 wire on 3 phase 30 amp breakers. The panel that now feeds these units is has a 225 amp rated bus fed from a 45 kva transformer. Initially the secondary voltage was operating at a very low voltage. The secondary of the transformer was producing around 199 volts and I changed the tap and increased the voltage by about 10 volts and that helped 3 of these units. One of the units continues to trip and the entire panelboard as well and all breakers are very hot to the touch. I did an amprobe reading and am getting around 105 amperes per phase but that is not the entire load. There is a bailer on a 40 ampere 3 phase breaker that runs momentarily as well as a few other minor loads. It is my recommendation to the customer that the 45 kva xfmr be increased to a 75 kva. The ac units are pulling around 26 -28 amperes per phase. I know that is borderline but with the 45 kva xfmr there I don't have much wiggle room to increase the ampere rating for the units. I suspect that someone changed the units and added them to this panel without do much homework. I have as well changed all the ac unit breakers and that has helped up until now but this heat problem needs to go away.
:slaphead:
Many thanks,
:slaphead:
Many thanks,
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