AriSEIA Submits Comments to APS on Interconnection Manual

May 9, 2025
 
Arizona Public Service
400 N 5th Street
Phoenix, AZ 85004
 
RE: AriSEIA Comments on the APS Interconnection Manual Draft Rev. 10
 
Dear APS Interconnection Team,
 
As agreed, we are submitting this summary of the five specific handbook topics of present concern to AriSEIA in advance of APS filing the revised manual with the Commission. We would like to reach resolution prior to filing, if possible.

Section 8.2, Utility Disconnect

Supply side connections of non-residential systems and the use of the National Electrical Code (NEC)-required external Fused Service Disconnect as the approved Utility Disconnect – Rev. 9.0 to the manual allows the Fused Service Disconnects for customer GF supply side connections in section 8.2(A) to be used as the Utility Disconnect. This language was explicitly negotiated and agreed to by APS during the 2021-2022 manual revisions and was approved by the Commission in November 2022. The use of a Fused Service Disconnect also as a Utility Disconnect is ubiquitous across the country, with those requiring redundant disconnects being the exception rather than the rule. Notably, Tucson Electric Power (TEP) allows the Fused Service Disconnect to serve as the DG Disconnect (see TEP’s Interconnection Manual for Distributed Generation, Section 9.2.1.b) as does Salt River Project (see SRP’s DER Technical Requirements, Section 2.8.1.b). All California utilities also allow for Fused Service Disconnects to serve as the Utility Disconnect – see PG&E’s Supply Side Interconnection Requirements for reference.
 
An additional Utility Disconnect for line-side/supply-side taps beyond a Fused Service Disconnect per NEC is redundant, arbitrary, and a costly requirement, and ARISEIA objects to the Rev. 10 proposed language that limits the dual-purpose potential of Fused Service Disconnects to residential single-phase systems. Moreover, the unilateral and retroactive enforcement of changes to the approved APS Interconnection Manual language, which were negotiated in good faith and approved by the Commission, is a significant oversight by APS management and has led to countless thousands of dollars of additional cost burdens on its customers since approval in 2022. APS staff should immediately adhere to the original intent of the language as previously approved, and attached to these comments are an exhibit demonstrating the written and clear intent to modify the language to remove unnecessary equipment from customer-owned GF installations (See Comment 3 and Response).
 
Furthermore, the verbal comments offered by APS that non-residential GF installations have greater public access than residential systems is specious, as requiring separate fused disconnects and utility disconnects results in double the number of devices the public can access and operate. Locking provisions are readily accessible for both residential and nonresidential versions of Fused Service Disconnects and are a simple solution to the otherwise costly approach administered by APS requiring an additional Utility Disconnect.
 
The NEC is the governing standard for the safe installation of electrical wiring and equipment in the United States. It is fundamentally a safety standard. Its primary purpose is to protect people and property from electrical hazards by preventing electrical fires, reducing risk of shock, setting clear installation standards, ensuring safe use of new technologies, promoting uniformity, and setting guidelines for inspections and permits. The NEC does not require a second utility disconnect for commercial-scale solar projects that are interconnected on the utility side of a customer’s meter; the only equipment required for safety purposes is a single fused service disconnect in accordance with NEC 2017 230.82(6), 705.12(A), and 705.31. Therefore, an additional Utility Disconnect is not necessary for the safe operation of a solar photovoltaic system, and APS should align with its state and national utility counterparts by removing this requirement.
 
Section 9.2, Production Metering Requirements

APS requires production metering for Static Inverter based Energy Storage Systems unless they are co-located with a PV system and properly configured, or unless the customer agrees to provide equivalent data hourly.  AriSEIA has consistently objected to metering battery discharge, including Rev. 9 of the manual which limited the requirement to standalone battery systems. Note that an Energy Storage System does not produce power at all, so the need for a “production meter” is nonsensical. This requirement will prove even more excessive as APS continues to progress toward adopting electric vehicles as an additional means of balancing the load on the electric grid. Meter disconnects further exacerbate the cost of this requirement. Short of an optional utility program to monitor or dispatch customer battery discharge and compensate customers, the customer’s site meter is sufficient to support the financial transaction for exported energy from battery systems. Utilities do not need real time measurement of battery usage any more than for sub-metered loads turned on or off. AriSEIA recommends that section (C) be removed in its entirety.

Section 10.4, Inadvertent Export or Active Power-Limiting Protection Requirements

The second sentence says “For GF’s with kVA rating greater than POI kVA rating protection requirements…” This sentence is missing a limiting kVA rating value separate from the POI rating. The value should be above the Commission limits that apply to Inadvertent Export Systems considered Fast Track.

Section 4.1, Separate System

The revision to include all Non-exporting systems as separate systems needs adjustments. Unlike backup systems, they do serve customer loads in parallel to the utility system on a continuous basis. The language confuses the issue of needing a Transfer Switch, which only applies to those Non-exporting systems incorporating a Backup System operating mode. The non-exporting feature can be provided by control systems and/or relays instead of a transfer scheme. Other sections deal with Non-exporting systems and appropriate exemptions from requirements for exporting systems. AriSEIA suggests limiting the Separate System definition to Non-exporting systems that can function as a Backup system. The new provisions of section 4.1(D) are appropriate for Non-Exporting systems regardless of the Backup capability, which should be clarified as part of the discussion.

Section 2, Definitions

The new definition for Point of Service describes the identical location as the current definition for Point of Interconnection, except without a GF operating in parallel. Is it needed in the Interconnection Manual? Also, the current definition claims the POI is also known as the Point of Common Coupling. In the industry, the POCC refers to the connection that could be at a different location than customer service equipment, such as a utility transformer. Even in the absence of a deregulated generation market, a change to this language could be useful for developers of APS distributed solar systems and future Community Solar systems.

Thank you for considering these comments. We would appreciate a response before filing the manual revision.
​
Sincerely,
/s/ Autumn T. Johnson
Executive Director
AriSEIA 
(520) 240-4757
[email protected]
 

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