Phase Academy · Power Panel Insulation Resistance Test Record

Job / Site Information

Identifies the record. Ambient temperature and humidity are part of the test conditions — insulation resistance is strongly affected by both.

Customer

Site

Location

Equipment

Job Number

Report Date

Test Type

Ambient Temp (°C)

Relative Humidity (%)

Test Instrument & Technician

NETA requires test instruments to have current calibration traceable to NIST. An expired calibration invalidates the record — the app flags it automatically.

Instrument Manufacturer

Instrument Model

Instrument Serial #

Calibration Date

Calibration Due

Technician Name

Technician Qualification / Cert

Test Date / Time

Pre-Test Safety Checklist

An insulation resistance test applies hundreds or thousands of DC volts to the bus. Every item below must be confirmed by a qualified person before test voltage is applied.

Equipment de-energized, isolated, locked out and tagged out per the employer's LOTO program required

Absence of voltage verified on every conductor with an adequately rated tester, tester proven before and after (NFPA 70E 120.6) required

Manufacturer instructions reviewed for test method, test voltage and duration limits (NEC 110.3(B))

Loads, solid-state electronics, surge protective devices, potential transformers and control circuits disconnected or otherwise protected from the test voltage

After each test, capacitive charge bled off and conductors grounded until fully discharged before handling required

Insulation under test stores a dangerous capacitive charge at the end of a DC test. Leave the instrument's discharge function connected, then apply safety grounds, before anyone touches the conductors.

Panel Nameplate

Nameplate data establishes the equipment voltage class that drives the acceptance criterion, and documents the ratings that must not be exceeded.

Panel Designation

Panel Location

Manufacturer

Catalog Number

Serial Number

Equipment Type

Nominal Voltage (V)

Ampacity / Bus Rating (A)

Short-Circuit Withstand (kA)

SCCR (kA)

Panel Configuration & Condition

As-found and as-left condition, breaker position during the test, and surface condition are what make a field record defensible months later.

Number of Sections

Main / MLO

# Feeder Breakers

# Feeder Disconnects

Feeder Count Reconciliation

Type of Loads

Fed From

Connected Equipment

Breaker / Switch Position During Test

As-Found Condition

As-Left Condition

Surface Condition

Weather (optional)

Dew Point °C (optional)

Comments & Deficiencies

Anything recorded as a deficiency is carried straight into the exception list and the printed report.

Comments / Environmental Notes

Deficiencies

Acceptance Criteria

The minimum acceptable insulation resistance follows the equipment's voltage class. Values below come from the widely published ANSI/NETA Table 100.1 — confirm against the edition adopted for your project.

Criteria Basis

Standard Edition

Criteria Source

Equipment Voltage Class

Equipment Category

Test-Point Configuration

Test Voltage (V DC)

Test Duration (s)

Investigate Factor (× min)

Manufacturer Min (MΩ)

Custom Min (MΩ)

Temperature Correction

Insulation resistance roughly halves for every 10 °C rise, so readings taken at different temperatures are not comparable until they are corrected to a common reference.

Method. The correction factor is CF = 2^((measured − reference) / 10) and corrected = raw × CF. A reading taken warm reads low and is scaled up. The reference defaults to 20 °C, matching the ANSI/NETA conversion table for non-rotating apparatus. Correction behaviour varies by insulation system, so the method used is stored with every reading. Do not use this 20 °C method for rotating machinery — IEEE 43 corrects motor and generator windings to 40 °C.

Measured Equipment Temp (°C)

Reference Temp (°C)

Correction Method

Manual CF

Applied Correction Factor

Insulation Resistance Readings (MΩ)

Enter a numeric value in MΩ, or a qualifier such as >1000, <5, OL for overrange, or a G suffix for gigohms. Points that were not tested must be marked N/A with a reason — a blank required point reads as INCOMPLETE, never PASS.

Test Point	Applicable	Raw / Qualifier	CF	Corrected	Min (MΩ)	Result	Notes / N/A reason	Actions

All Panel Results

Corrected values across every panel in this record. Click any row to open that panel for editing.

Exception List

Auto-generated from the readings, the criteria, the safety checklist and the instrument calibration. This is the punch list that goes back to the customer.

What this record is for

Insulation resistance testing is one of the most common measurements in NETA acceptance and maintenance testing. On a panelboard, switchboard, MCC or switchgear line-up it answers a narrow but important question: is the insulation between each energized conductor and ground, and between conductors, still doing its job?

The measurement itself takes a minute. Making it defensible takes the rest of this form — the instrument and its calibration, the criteria you judged against and where they came from, the temperature the equipment was at, what was disconnected, and the as-found and as-left condition of the gear.

A megohm value with no temperature, no test voltage, no criterion and no instrument serial number is a number, not a record.

Before test voltage is applied

An insulation resistance tester applies 250–15,000 V DC. Establishing an electrically safe work condition first is not optional.

Determine all sources feeding the equipment, including back-feeds, control power and UPS or generator sources.
Open the disconnecting means for each source and visually verify open where the design allows.
Apply lockout/tagout per the employer's program (OSHA 1910.147 and 1910.333, NFPA 70E Article 120).
Verify absence of voltage on every phase conductor and the neutral with an adequately rated tester, proving the tester on a known source before and after the check (NFPA 70E 120.6).
Apply grounds where induced or stored voltage is possible.
Disconnect what the test would destroy — surge protective devices, electronic trip units and metering, potential transformers, control circuits, VFDs and anything with solid-state components. This is also where NEC 110.3(B) bites: the manufacturer's instructions govern the test method and any voltage limit.

After every test, the insulation holds a capacitive charge that can be lethal. Leave the instrument connected in discharge mode until the voltage decays, then apply safety grounds before touching conductors. Larger gear and long cable runs take considerably longer to bleed off than most people expect.

Test voltage and minimum values

Test voltage is selected from the equipment's rated voltage class, not from the actual operating voltage of the moment. The values below are the widely published ANSI/NETA Table 100.1 recommendations, which this tool uses as its representative criteria. Verify them against the edition of the standard adopted for your project, and remember that the manufacturer's published minimum always takes precedence when it is higher.

Equipment voltage rating	Minimum DC test voltage	Recommended minimum insulation resistance
250 V	500 V	25 MΩ
600 V	1,000 V	100 MΩ
1,000 V	1,000 V	100 MΩ
2,500 V	1,000 V	500 MΩ
5,000 V	2,500 V	1,000 MΩ
8,000 V	2,500 V	2,000 MΩ
15,000 V	2,500 V	5,000 MΩ
25,000 V	5,000 V	20,000 MΩ
34,500 V and above	15,000 V	100,000 MΩ

The standard test duration is one minute. This tool defaults to 60 s and records the duration with every reading, because a 30-second reading and a 10-minute reading on the same insulation are different measurements.

Why temperature correction matters

Insulation resistance falls as temperature rises — roughly halving for each 10 °C increase. A panel tested at 35 °C in August and the same panel tested at 15 °C in February will produce readings that differ by a factor of about four with no change whatsoever in the insulation.

That is why every reading in this record is corrected to a common reference temperature before it is compared against the acceptance criterion or against a previous test:

CF = 2^((measured − reference) / 10) · corrected = raw × CF
At a 20 °C reference: 10 °C → 0.50 | 20 °C → 1.00 | 30 °C → 2.00 | 40 °C → 4.00

Use the right reference. 20 °C is the reference for the NETA conversion table covering non-rotating apparatus — panels, switchgear, buses, cables. Rotating machinery is a different discipline: IEEE 43 corrects motor and generator windings to 40 °C, and mixing the two conventions will make good insulation look bad or bad insulation look acceptable.

Humidity and dew point. Surface leakage across dirty or damp insulation can dominate the reading. If the equipment temperature is at or near the dew point, moisture is condensing on the insulating surfaces and the measurement reflects that film rather than the insulation itself. This tool flags readings taken within 2 °C of the recorded dew point.

Reading the results

PASS — every required point is recorded and its corrected value is at or above the investigate threshold (the minimum multiplied by the investigate factor, 2× by default).
INVESTIGATE — the corrected value clears the minimum but sits below the investigate threshold. It is not a failure, but it is a trend worth watching and worth a note in the report.
FAIL — the corrected value is below the minimum. Investigate before energizing: the usual culprits are moisture, contamination, a load or SPD left connected, or genuinely degraded insulation.
INCOMPLETE — a required point is blank, or a point was marked N/A without a reason, or measurements exist but no criterion was resolved to judge them against. A panel in this state can never report PASS.

Trending beats absolute values. A single reading proves very little beyond a gross failure. The value of a record like this one is comparison — panel against identical panel, and this year against last year, both corrected to the same reference temperature.

A very high reading is not automatically good news. Confirm the leads were actually on the conductor and the panel was not still isolated by an open link — an open circuit also reads as overrange.

Codes and standards referenced

Reference	What it covers
ANSI/NETA ATS	Acceptance Testing Specifications — inspection and test procedures for newly installed equipment, including insulation resistance test values in Table 100.1.
ANSI/NETA MTS	Maintenance Testing Specifications — the equivalent procedures and criteria for existing equipment being maintained.
ANSI/NETA ETT	Standard for certification of electrical testing technicians — the basis for the technician qualification recorded on this form.
IEEE 43	Recommended practice for testing insulation resistance of rotating machinery — 40 °C reference, polarization index. Not applicable to the panels covered here.
NFPA 70E 120	Establishing an electrically safe work condition, lockout/tagout, and verification of absence of voltage.
NFPA 70E 130	Work involving electrical hazards — risk assessment, approach boundaries, PPE.
NEC 110.3(B)	Listed and labeled equipment must be installed and used in accordance with the instructions included in the listing or labeling — including test limits.
NEC 110.26	Working space about electrical equipment — the space you need to safely perform this test.
NEC 230.95(C)	Ground-fault protection equipment must be performance tested when first installed on site — a companion field test frequently performed on the same visit.
OSHA 1910.147 / .333	Control of hazardous energy, and selection and use of work practices for electrical safety.

Educational and recordkeeping aid. This tool does not certify NETA, NFPA or manufacturer compliance. Acceptance and maintenance judgments must be made by a qualified person using the current adopted standard edition, the project specification and the manufacturer's instructions. Built-in criteria are representative published values and must be verified against your adopted standard.