Hello Wrenches, I have a site which is experiencing nuisance disturbance of the computer UPS systems at the site. The site owner "suspects" this is due to the PV system which is a 50 kW system using 6 SMA SunnyBoy inverters. The nuisance disturbance is a clicking noise in the UPS units. The disturbance is not enough to cause the UPS to engage, so it seems to be a small disturbance on the AC power. The site owner "suspects" the inverters are the source of this disturbance since 1) It seems to only occur when we have a good solar day. 2) If the inverters are shut down the problem goes away, and if you start up the inverters the problem exhibits again.
The site was commissioned in March of 2012 and has had no problems till this issue last month. In reviewing the event log on Sunny Portal there are no inverter anomalies. SMA tech support had not run into this issue and had no ideas, they too agree the inverters are not reporting any anomalies. The problem is not persistent but rather intermittent making this harder to troubleshoot. So my questions are 1) Has anyone else seen this sort of issue before, related to SMA SunnyBoy inverters. 2) Can you recommend an AC power monitoring tool which would support frequency and voltage monitoring on the AC line. Perhaps one data set on the circuit feeding the computers and another on the inverter output circuit. For clarity the six SunnyBoys feed into an AC Combiner panel which backfeeds into the building main distribution panel. The service is 240V single phase. With Regards Carl Adams, SunRock Solar NABCEP Certified PV Installer
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