A large facility builds one new building with 32 roof HVAC units. 10 ton compressors begin failing and each trade is pointing fingers at each other. To date, 13 scroll compressors have failed. The HVAC Co. believes somehow all units were run at length in reverse rotation.
Someone else says out loud that dirty power is the problem.
I have a Fluke 435 and an Amprobe DM-lll.
For several reasons the Amprobe is the go to meter. Easy to use and a good viewable display outdoors.
We agreed to do PQ test to remove "dirty power' from the list of options.
Service entrance to this new building is served by a POCO 1500kVA padmount, 480/277VAC. Six conductors per phase. This PQA does not have Flex current CTs, they are clamp types with jaws for cables up to 1.5". I clamped one conductor from each phase. All four voltage leads were connected. I would like to measure the bundle amps but not with this meter.
The PQA shows 90 amps with 1.4% ThdV, 10% ThdI. I say that since these conductors are in parallel and the run is less than 100' from POCO the service entrance, the difference in impedance for each cable will be very small. We have tested this concept in the past with conductor bundles that were too large for the Flex CTs that we owned at the time, and found the results acceptable.
I use 90 amps X 6 = approx. +or- 540 amps. The Thd is a percentage of the E or I and is fixed across the total
I report no problems based on this testing method and saw no reason to install recorders.
What are your thoughts.
Someone else says out loud that dirty power is the problem.
I have a Fluke 435 and an Amprobe DM-lll.
For several reasons the Amprobe is the go to meter. Easy to use and a good viewable display outdoors.
We agreed to do PQ test to remove "dirty power' from the list of options.
Service entrance to this new building is served by a POCO 1500kVA padmount, 480/277VAC. Six conductors per phase. This PQA does not have Flex current CTs, they are clamp types with jaws for cables up to 1.5". I clamped one conductor from each phase. All four voltage leads were connected. I would like to measure the bundle amps but not with this meter.
The PQA shows 90 amps with 1.4% ThdV, 10% ThdI. I say that since these conductors are in parallel and the run is less than 100' from POCO the service entrance, the difference in impedance for each cable will be very small. We have tested this concept in the past with conductor bundles that were too large for the Flex CTs that we owned at the time, and found the results acceptable.
I use 90 amps X 6 = approx. +or- 540 amps. The Thd is a percentage of the E or I and is fixed across the total
I report no problems based on this testing method and saw no reason to install recorders.
What are your thoughts.