UL 3141 is an outline for a new listing that covers PCS, taking it out of UL 1741. Maybe with this it will be more compelling for inverter manufacturers to integrate PCS into residential inverters. But in the end, it will add cost to the inverter and if it's not increasing sales it's not going to be added.
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2023 NEC 705.12(B)(6) (Engineering Supervision)
- Thread starter wwhitney
- Start date
Elect117
Senior Member
- Location
- California
- Occupation
- Engineer E.E. P.E.
I would like to add that at a recent conference, PCS and the new section in 220 was mentioned and they do not test for for power factor or reactive power at the panel. It is only real power (W). They can ask UL to test their reactive power but that test is not mandatory to call themselves PCS by UL3141. The local UL rep was with me and the CMP panel member for the 700s when we found this out. They put that section in without consideration for it.
The guys pushing these code sections are the manufacturers of that equipment.
Just be careful when using PCS as a reason to install more load or increase generation. It is more of an issue on 3PH and larger systems obviously.
The guys pushing these code sections are the manufacturers of that equipment.
Just be careful when using PCS as a reason to install more load or increase generation. It is more of an issue on 3PH and larger systems obviously.
The primary function of PCS is to limit current and as an option UL 3141 provides testing for power limitation of import and export. But having the power limitation functionality is not a requirement to be a PCS. That is probably why you heard that the testing is optional. There is also a note in UL 3141 for the power import/export test that the testing does not currently comply with IEEE 1547-2018 and it will be revised to include active and reactive power control in the future. This is in section 8.6.1.1 of UL 3141. Keep in mind that UL 3141 is an Outline of Investigation and not a standard. It should be considered a work in progress and may have significant changes before it is issued as a standard.I would like to add that at a recent conference, PCS and the new section in 220 was mentioned and they do not test for for power factor or reactive power at the panel. It is only real power (W). They can ask UL to test their reactive power but that test is not mandatory to call themselves PCS by UL3141.
Elect117
Senior Member
- Location
- California
- Occupation
- Engineer E.E. P.E.
The primary function of PCS is to limit current and as an option UL 3141 provides testing for power limitation of import and export. But having the power limitation functionality is not a requirement to be a PCS. That is probably why you heard that the testing is optional. There is also a note in UL 3141 for the power import/export test that the testing does not currently comply with IEEE 1547-2018 and it will be revised to include active and reactive power control in the future. This is in section 8.6.1.1 of UL 3141. Keep in mind that UL 3141 is an Outline of Investigation and not a standard. It should be considered a work in progress and may have significant changes before it is issued as a standard.
Energy Management System and PCS are the same thing if I am remembering correctly and they are changing EMS to "Power Control System" in the 2026. Or vise versa. I can't remember. SPAN is one of the companies that makes a board with the system installed.
They told me EMS is UL3141 but maybe I misremembered that also. They covered both as the same topic. It is in the 2023 as a method for installing more load than the rating of the panel as long as it can be monitored at the panelboards rating. (220.70)
UL is about 3 years behind on the standard for the system that is currently being used as a method to overload equipment.
Since we are both in CA, we are not on the 2023 yet. But you can see how not having a standard on measuring the current for a system designed to limit the possibility of overloading conductors is funky. The method requires measuring apparent power and they only currently measure active power which is normally any where between 70% to 100% of the actual current being seen by the conductors.
It is just something to keep in mind when doing design work. It won't impact residential. It is a issue on commercial and manufacturing where power factors vary drastically and harmonics are more commonly found.