1000 Volt Inverter Not UL Certified

[Frederick2]

We have a large photovoltaic system that connects directly to the local utility grid through a 1000V inverter that is not UL certified.


My boss says that this is fine, that no UL certification is needed because it connects to the utility grid. However, someone else in our company (with more clout than my boss) says we must use a UL certified inverter.


I tend to agree with my boss on this issue as it appears that only recently have UL certified 1000V inverters become available.


Can anyone point me to reputable/defensible literature (e.g., a webpage) that explains how UL certification is not needed when connecting to the utility grid?

 

[iwire]

It is the NEC that requires a listed inverter but the NEC does not apply to utility equipment.

90.2 Scope.

(B) Not Covered. This Code does not cover the following:

(5) Installations under the exclusive control of an electric
utility where such installations

a. Consist of service drops or service laterals, and associated
metering, or

b. Are located in legally established easements or
rights-of-way designated by or recognized by public
service commissions, utility commissions, or other
regulatory agencies having jurisdiction for such installations,
or

c. Are on property owned or leased by the electric
utility for the purpose of communications, metering,
generation, control, transformation, transmission, or
distribution of electric energy.

 

[don_resqcapt19]

I would doubt that 90.2 applies to this installation. I would expect that this is a privately owned system that is connected to the utility for the purpose of selling "green" power to the utility.

 

[iwire]

I would doubt that 90.2 applies to this installation. I would expect that this is a privately owned system that is connected to the utility for the purpose of selling "green" power to the utility.

I agree if it is privately owned, for some reason I was assuming it was for the utility.

 

[ggunn]

We have a large photovoltaic system that connects directly to the local utility grid through a 1000V inverter that is not UL certified.


My boss says that this is fine, that no UL certification is needed because it connects to the utility grid. However, someone else in our company (with more clout than my boss) says we must use a UL certified inverter.


I tend to agree with my boss on this issue as it appears that only recently have UL certified 1000V inverters become available.


Can anyone point me to reputable/defensible literature (e.g., a webpage) that explains how UL certification is not needed when connecting to the utility grid?

I don't think it's a code question but rather one for your AHJ concerning their interconnect agreement.

 

[hillbilly1]

Also it does not have to be "UL" specific, it can be CTL or any number of listing labs. I hurt the CTL inspectors feelings when I told him the electrical inspector would not pass my level II DC car charger installation until it had a "UL" sticker on the charger. I had a catch 22 for a while, because he would not inspect it until the power was on, and the inspector would not let the power be turned on till it had the label. The city finally gave us a temporary power on so the testing could be done.

 

[ron]

I have run into this, and the AHJ wanted it inspected by a NRTL. The NRTL wouldn't approve because it wasn't grounded type.

 

[iwire]

I have run into this, and the AHJ wanted it inspected by a NRTL. The NRTL wouldn't approve because it wasn't grounded type.

We have installed some grid interconnected 400 KW fuel cells and they are not listed.

The only way we got around that was by installing a 'Beckwith' device that could watch the current direction and dump the fuel cell if the utility supply failed.


http://www.beckwithelectric.com/products/protection-dg.html

 

[Frederick2]

Thank you Don and Iwire (and everyone),

Yes, we are a private company (well, a publicly traded company), not a utility. And, yes, it is a privately owned system connected to the utility for the purpose of selling "green" power to the utility.

Can you explain why you doubt that 90.2 applies to this installation?

I believe you are right, but how do I defend that opinion to others?

What we may end up doing is just have the inverter(s) field certified by UL. Do you know if that is a difficult process?

 

[jaggedben]

Thank you Don and Iwire (and everyone),
Can you explain why you doubt that 90.2 applies to this installation?

If it is not directly owned or exclusively controlled by the utility, and you have indicated it is not, then 90.2 does not apply. The language is pretty straightforward.

What we may end up doing is just have the inverter(s) field certified by UL. Do you know if that is a difficult process?

It costs money and is time consuming. In the one instance I was able to witness (I had no role in organizing it), the UL rep was very thorough and particular but ultimately helpful in getting us the field listing.

Why is this an issue? You have made it sound like the installation is finished, rather than that you are deciding whether to install this inverter. Is your AHJ not singing off on the inspection because of this? Is it an insurance issue? If the system has passed safety inspections and is working, then I don't understand why "someone in your company" is making an issue out of the lack of a UL listing.

 

[Frederick2]

It costs money and is time consuming.

Do you know how much money or time? The only reference I have is some hearsay of a transformer that was UL field certified for a cost of around $500. Inverters are more complex than transformers, so they would cost more. Any ideas on how much more?

Also, the project is not yet installed, nor is it contracted. But we have two well-developed bids from vendors who have worked hard to optimize their systems to meet some very particular conditions/constraints set by the utility's requirements and our own.


Both bids use 1000v inverts, and we (i.e., boss) likes that because they are more efficient the 600v inverters.


Due to the hard work of the vendors and some good state and federal incentives, we've lowered the cost of PV electricity to that of grid electricity--and everybody is happy with that.


But now some guy (with clout) in our risk assessment department is complaining and he wants us to use UL certified inverters. But we do not want to force the vendors to redesing their systems (and their bids) to accomadate this. We don't want to make the vendors use an inverter with which they are not familiar. (It's not a problem with the AHJ; it's an "in-house" issue.)


So I have been asked to come up with a defensable argument to support not forcing the vendors to change their inverters (and thereby not change their systems/bids).

 

[BillK-AZ]

Cost of UL field certification

Cost of UL field certification

Two years ago when I was bidding a project that required line side connections in service entrances that did not provide an approved connection for this, I got bids from UL and ETL for field certification. The bid price for the certification was $6K to $10K for one, reducing to $3K to $6K for six systems, each with a different cut-over date on weekends. This covered initial evaluation of the service entrance to make sure it was still in compliance with its initial listing (one was 30 years old), approval of a proposed modification, and field supervision of the modification (requiring complete shut down of a school, modification, inspection, new certification label, AHJ inspection, and finally restoration of utility power).

 

[jaggedben]

The instance I was party to was also a line-side connection issue. I believe the $ numbers were similar. I'll just add that the whole process took months (although that may have been partly due to other issues with the project that were not entirely part of the UL process).

 

[Jraef]

Thank you Don and Iwire (and everyone),

Yes, we are a private company (well, a publicly traded company), not a utility. And, yes, it is a privately owned system connected to the utility for the purpose of selling "green" power to the utility.

Can you explain why you doubt that 90.2 applies to this installation?

I believe you are right, but how do I defend that opinion to others?

What we may end up doing is just have the inverter(s) field certified by UL. Do you know if that is a difficult process?

One MAJOR problem I think you will find is that UL does not evaluate any power devices over 600V. The only standards they have for equipment over 600V is for Medium Voltage Switchgear (as in 5kV class), and you do NOT want to have to meet those standards!

That is why you will find that "commercial" grade PV inverters are all 600V and below, only "utility" grade inverters are 1000V, because as mentioned, utility equipment is not covered by the NEC.

 

[quogueelectric]

1000 v inverter

1000 v inverter

I Thought there was a 600v limit on privately owned pv systems that 1000 v inverters are for utility . The pv arrays for the BP project are tied to SMA inverters Sunny Central The Arrays put out between 700----800 volts depending upon weather at the BP LI solar farm.