Just installed new BAC Cooling Towers on job. The motor is rated at 230v - not 208-230v just 230v. Its a Leeson two speed motor. The incoming power to my starter is 204/202/206v (below the allowable 10%)and drops to 198v when motor is operating at high speed. I am having a problem with the new starter pitting the contacts badly and quickly. The operating amperage is within range - rated 33/13 actual 26/8. It seems the problem is at startup or when the contactor pulls in.Sometimes its ok but the contacts are wearing out quickly.This being a cooling tower the starting torque is high. The decreased voltage I believe is creating very high starting current ( measured it in the 150- 160 range)causing the contacts to pit and soon after fail.
Question - will changing the motors to 208-230v motors help. The incoming power is what it is. Everything else on the job Chillers, AHUs, ACs, CUs,Exhaust Fans are 208 -230v and have had no problems. I realize that the decreased voltage increases the amperage but should be ok as long as it within Nameplate rating, but wondering if this help my starter problem. Also the control tranformer for the cooling tower starter is only producing 107v because of the low incoming power - coils are 115-120. This maybe adding to the problem and not giving the starer the full control voltage needed to pull in properly. Do the coils have the same voltage tolerance as the motors?
Thanks in advance.