Hoping someone can help with this problem.
I got called to a customer site today. One building with two tenant spaces. Space 1 is supplied by a pole mounted transformer, 208V Y, 200A. The primary connected loads are bandsaws, lathes, drill presses, milling machines, etc. Nearly all are 3Ph loads, and everything in the building runs perfectly.
Space 2 is fed with a 480V delta, 800A service, pole mounted utility transformer fed from the same primary as the 208V. I can see the primary conductors jumping from transformer to transformer. When the tenant left yesterday everything was running properly, when he returned this morning his 3Ph motors (air compressor, HVAC, and dust collector) were reversed rotation. I have checked voltage and rotation from the main lugs on the switch gear through every bucket and transformer I could find, and everything is phased properly.
They do have a 208V, 200A panel supplied by a 75kva transformer. When the secondary conductors hit the main breaker, B and C phases are reversed. This, to me, indicates that the original system was reverse rotation, and when the sub panel was installed they reversed rotation to correct it. The air compressor and HVAC system are fed from the 208V system, and the dust collector is fed from the 480V system.
Any idea what can cause this?
*Additional note, there is another building on the property and another one down the street who are also customers of mine, and who are fed by the same utility branch circuit. I checked the line side power on those buildings and they are both correct.
I got called to a customer site today. One building with two tenant spaces. Space 1 is supplied by a pole mounted transformer, 208V Y, 200A. The primary connected loads are bandsaws, lathes, drill presses, milling machines, etc. Nearly all are 3Ph loads, and everything in the building runs perfectly.
Space 2 is fed with a 480V delta, 800A service, pole mounted utility transformer fed from the same primary as the 208V. I can see the primary conductors jumping from transformer to transformer. When the tenant left yesterday everything was running properly, when he returned this morning his 3Ph motors (air compressor, HVAC, and dust collector) were reversed rotation. I have checked voltage and rotation from the main lugs on the switch gear through every bucket and transformer I could find, and everything is phased properly.
They do have a 208V, 200A panel supplied by a 75kva transformer. When the secondary conductors hit the main breaker, B and C phases are reversed. This, to me, indicates that the original system was reverse rotation, and when the sub panel was installed they reversed rotation to correct it. The air compressor and HVAC system are fed from the 208V system, and the dust collector is fed from the 480V system.
Any idea what can cause this?
*Additional note, there is another building on the property and another one down the street who are also customers of mine, and who are fed by the same utility branch circuit. I checked the line side power on those buildings and they are both correct.