Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Electrical Power Monitoring and Metering
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| IEEE 1459 | Standard Definitions for the Measurement of Electric Power Quantities |
| IEEE C57.13 | Standard Requirements for Instrument Transformers |
−| IEC 61869 series | Instrument Transformers (metering classes 0.2S and 0.5S) |
| UL 61010-1 | Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use |
| ASHRAE 90.1 | Energy Standard for Buildings Except Low-Rise Residential Buildings |
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## Branch-circuit monitoring shall be provided where individual circuit-level data is required for the building area served.
+## The metering tier at this point shall be as indicated in the datasheet.
+
```datasheet
label: Metering tier at this point
type: select
+drawing_ref: "metering point schedule"
options:
- Service entrance (revenue / whole-building)
- Feeder / switchboard (tenant sub-metering)
- Panelboard (load category)
- Branch circuit (BCPM)
−default: Feeder / switchboard (tenant sub-metering)
−drawing_ref: true
+default: deferred
```
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### Square-footage thresholds vary between ASHRAE 90.1 and the IECC; the more stringent of the adopted code and the Owner's program governs. The thresholds above reflect common adopted editions and shall be confirmed against the locally adopted code. {note}
+### The code basis governing the metering thresholds shall be as indicated in the datasheet.
+
```datasheet
label: Code basis for metering thresholds
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### Class M5 to M6 is acceptable for branch-circuit energy management because branch loads are individually small and the aggregated reporting tolerates wider per-channel error than a billing meter. {note}
+## The meter accuracy class shall be as indicated in the datasheet.
+
```datasheet
label: Meter accuracy class
type: select
+drawing_ref: "metering point schedule"
options:
- ANSI C12.1 Class 0.2 (revenue)
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- IEC 61557-12 PMD Class M5
- IEC 61557-12 PMD Class M6
−default: IEC 61557-12 PMD Class M3
+default: deferred
```
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### A Rogowski coil outputs roughly 150 mV or 333 mV and cannot drive a standard 5 A or 1 A CT input; specifying a Rogowski coil with a 5 A-input meter results in no signal, so the meter input type shall be confirmed explicitly. {note}
+## The current-sensing method at this metering point shall be as indicated in the datasheet.
+
```datasheet
label: Current-sensing method
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- Split-core CT (locking)
- Rogowski coil
−default: Solid-core CT
−drawing_ref: true
```
+## All three sensing methods are correct in their own conditions — solid-core on new work with a disconnectable conductor, split-core on energized retrofit, Rogowski on oversized or congested and harmonic-rich installations — so the field carries no default and the Engineer selects per point. {note}
+
## Current Transformer Ratio and Secondary {toc}
### The current transformer ratio at each metering point shall be selected so that the expected load current is at least 10 percent of the CT rated primary current.
−### A CT operating below about 10 percent of its rated primary current loses accuracy; a 600:5 CT on a circuit averaging 80 A runs near the lower accuracy limit, so a 200:5 CT is more appropriate for that load. The ratio shall match the actual load, not only the conductor ampacity. {note}
+### A CT operating below about 10 percent of its rated primary current loses accuracy; a 600:5 CT on a circuit averaging 80 A runs near the lower accuracy limit, so a 200:5 CT is more appropriate for that load. The ratio shall match the actual load, not only the conductor ampacity.
### The current transformer ratio shall be selected so that the CT does not saturate at the available fault current of the served equipment.
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### A CT delivers its rated accuracy only within its rated burden (for example B-0.5 to B-2.0); an undocumented long 5 A lead run routinely exceeds the rated burden and introduces systematic error, so the burden calculation is a required submittal. {note}
+### The current transformer secondary rating shall be as indicated in the datasheet.
+
```datasheet
label: CT secondary rating
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```
+### The current transformer primary current rating shall be as indicated in the datasheet.
+
```datasheet
label: CT primary current rating
type: range
unit: A
−min: 100
−max: 4000
+drawing_ref: "metering point schedule"
+min: 50
+max: 6000
step: 50
−default: 400
−drawing_ref: true
+default: deferred
```
+### The current transformer accuracy class shall be as indicated in the datasheet.
+
```datasheet
label: CT accuracy class (IEEE C57.13 metering)
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- Class 0.3
- Class 0.6
−default: Class 0.3
```
+### The CT accuracy class follows the accuracy class of the meter it serves, which is assigned per metering point, so no class is correct across the schedule and the field carries no default. {note}
+
## Voltage Transformers {toc}
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### Voltage transformer secondaries shall be grounded in accordance with NFPA 70 Article 250.
+### The voltage connection method shall be as indicated in the datasheet.
+
```datasheet
label: Voltage connection method
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- Through voltage transformers (> 600 V)
default: Direct connect (≤ 600 V)
−drawing_ref: true
```
+### The voltage transformer accuracy class shall be as indicated in the datasheet.
+
```datasheet
label: Voltage transformer accuracy class
type: select
options:
+ - Not applicable — direct-connect metering
- IEEE C57.13 Class 0.3
- IEEE C57.13 Class 0.6
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## Each meter shall measure and report the parameters assigned to its metering point on the metering point schedule.
+```datasheet
+label: Measured parameters required at this point
+type: checkbox
+options:
+ - Real energy (kWh)
+ - Real demand (kW, 15-min)
+ - Reactive energy / demand (kVARh)
+ - Apparent power (kVA)
+ - Power factor (displacement and true)
+ - Voltage (L-L and L-N)
+ - Current per phase
+ - Frequency
+ - THD voltage and current
+ - Voltage unbalance
+default:
+ - Real energy (kWh)
+ - Real demand (kW, 15-min)
+ - Voltage (L-L and L-N)
+ - Current per phase
+```
+
## Real energy in kilowatt-hours shall be measured at every metering point.
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### Not every parameter is available on every tier; branch-circuit and basic sub-metering devices may report energy and demand only, while feeder and service meters report the full power-quality set. The schedule assigns parameters per point so that meter selection matches the data actually needed. {note}
−```datasheet
−label: Measured parameters required at this point
−type: checkbox
−options:
− - Real energy (kWh)
− - Real demand (kW, 15-min)
− - Reactive energy / demand (kVARh)
− - Apparent power (kVA)
− - Power factor (displacement and true)
− - Voltage (L-L and L-N)
− - Current per phase
− - Frequency
− - THD voltage and current
− - Voltage unbalance
−default:
− - Real energy (kWh)
− - Real demand (kW, 15-min)
− - Voltage (L-L and L-N)
− - Current per phase
−```
−
# Data Logging and Time Synchronization {toc}
−## Meters required to log data shall record measured parameters at a 15-minute interval.
+## Meters required to log data shall record measured parameters at the interval indicated in the datasheet.
### ASHRAE 90.1 and the IECC both require 15-minute interval data for compliant energy metering; a coarser interval cannot satisfy the code, and a finer interval consumes log memory without code benefit. {note}
−## On-board data log depth shall be sufficient to retain at least 35 days of 15-minute interval data where the meter buffers data locally.
+## On-board data log depth, where the meter buffers data locally, shall be as indicated in the datasheet.
### Local buffering bridges network or EPMS outages so that no interval data is lost; 35 days of depth covers a monthly polling cycle plus margin. Deeper logs are specified where the EPMS polls less frequently. {note}
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## The Contractor shall configure the time source and submit evidence of synchronization.
−## Metered data shall be retained for at least 36 months where required by the adopted energy standard.
+## Metered data shall be retained for the period indicated in the datasheet.
+## The logging interval shall be as indicated in the datasheet.
+
```datasheet
label: Logging interval
−type: select
+type: range
+unit: min
options:
− - 15 minutes
− - 5 minutes
− - 1 minute
−default: 15 minutes
+ min: 1
+ max: 15
+ setpoints: [1, 5, 15]
+default: 15
```
+## An interval coarser than 15 minutes will not satisfy the adopted energy standard where code-required metering applies. {note}
+
+## The on-board log depth shall be as indicated in the datasheet.
+
```datasheet
label: On-board log depth at 15-min interval
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```
+## The time-synchronization source shall be as indicated in the datasheet.
+
```datasheet
label: Time-synchronization source
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```
+## The data retention period shall be as indicated in the datasheet.
+
```datasheet
label: Data retention period
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```
+## Where the adopted energy standard mandates a retention period longer than the value indicated, the code period governs. {note}
+
# Communication and Integration {toc}
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## The communication protocol shall be selected from Modbus RTU, Modbus TCP/IP, BACnet MS/TP, or BACnet/IP based on compatibility with the EPMS or BAS.
−### Modbus RTU on RS-485 supports up to 32 devices per segment and is economical for clustered panel meters; Modbus TCP and BACnet/IP scale across the building network. The protocol shall match what the receiving platform can ingest natively, because protocol gateways add cost and a failure point. {note}
+### Modbus RTU on RS-485 supports up to 32 devices per segment and is economical for clustered panel meters; Modbus TCP and BACnet/IP scale across the building network. The protocol shall match what the receiving platform can ingest natively, because protocol gateways add cost and a failure point.
## Modbus RTU segments shall not exceed 32 devices per segment and shall use a single baud rate per segment.
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### Register-map configuration and point mapping are routinely excluded from both the electrical and controls scopes, producing unconnected meters at closeout; this standard requires the scope to be assigned in writing so the gap cannot occur. {note}
−## Meters using Modbus TCP or BACnet/IP shall reside on an isolated operational-technology network segment separated from the building information-technology network.
+## Except where the datasheet indicates a shared building network, meters using Modbus TCP or BACnet/IP shall reside on an isolated operational-technology network segment separated from the building information-technology network.
### Panel meters placed on the general IT LAN expose operational equipment to network threats and can themselves be an attack surface; an isolated OT VLAN with read-only acquisition from the BAS side limits exposure. {note}
## Data acquisition from the building automation system to the meters shall be read-only where the OT segment is isolated for cybersecurity.
+## The communication protocol shall be as indicated in the datasheet.
+
```datasheet
label: Communication protocol
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- BACnet MS/TP
- BACnet/IP
−default: Modbus TCP/IP
```
+## The protocol is set by what the receiving EPMS or building automation system ingests natively, so no protocol is correct across projects and the field carries no default. {note}
+
+## The integration programming scope shall be assigned as indicated in the datasheet.
+
```datasheet
label: Integration programming scope assigned to
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```
+## The network segmentation shall be as indicated in the datasheet.
+
```datasheet
label: Network segmentation
type: radio
options:
− - Isolated OT VLAN (read-only from BAS)
+ - Isolated OT VLAN with read-only acquisition from the BAS
- Shared building network
−default: Isolated OT VLAN (read-only from BAS)
+default: Isolated OT VLAN with read-only acquisition from the BAS
```
+## The isolated segment is the default because a panel meter on the general IT LAN is both exposed and an attack surface; the shared-network value exists for small buildings with no separate OT network, and selecting it is an Owner risk acceptance. {note}
+
# Local Display {toc}
−## Each meter shall provide the local display assigned to its metering point.
+## Each meter shall provide the local display indicated in the datasheet.
−## Where a local display is required, it shall show at minimum real energy, real power, voltage, current, and power factor.
−
−### A local display lets a technician verify a meter is live and reading correctly without a laptop or network access, which speeds commissioning and troubleshooting; meters intended for data-only service may omit the display to reduce cost. {note}
−
```datasheet
label: Local display
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- Integral LED display
- Remote display panel
− - None (data via network only)
+ - None — data via network
default: Integral LCD display
```
+## Where a local display is required, it shall show at minimum real energy, real power, voltage, current, and power factor.
+
+### A local display lets a technician verify a meter is live and reading correctly without a laptop or network access, which speeds commissioning and troubleshooting; meters intended for data-only service may omit the display to reduce cost. {note}
+
# Form Factor and Installation Location {toc}
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## Switchboard-mounted and panelboard-mounted meters shall be coordinated with the switchboard or panelboard manufacturer for factory-installed or field-installed mounting.
−### A meter mounted in the door or compartment of a switchboard affects the equipment listing and arrangement, so its mounting is coordinated with the gear manufacturer rather than improvised in the field. See [[sync/low-voltage-switchboards]] and [[sync/low-voltage-panelboards]]. {note}
+### A meter mounted in the door or compartment of a switchboard affects the equipment listing and arrangement, so its mounting is coordinated with the gear manufacturer rather than improvised in the field. See [[sync/low-voltage-switchboards]] and [[sync/panelboards]]. {note}
## Branch-circuit power monitoring modules that clip onto the panelboard bus shall be factory-installed by the panelboard manufacturer where the design requires bus-bar mounting.
−### Field-installing a bus-bar-mounted branch-circuit monitoring module that is rated for factory installation only voids the panelboard listing; the installation method shall be stated in the Contract Documents and on the drawings so the panelboard is ordered correctly. {note}
+### Field-installing a bus-bar-mounted branch-circuit monitoring module that is rated for factory installation only voids the panelboard listing; the installation method shall be stated in the Contract Documents and on the drawings so the panelboard is ordered correctly.
+## The meter form factor shall be as indicated in the datasheet.
+
```datasheet
label: Meter form factor
type: select
+drawing_ref: "metering point schedule"
options:
- Socket-type (ANSI meter socket)
- Switchboard-mounted panel meter
- DIN-rail panel-mount meter
- Bus-bar branch-circuit module
−default: DIN-rail panel-mount meter
−drawing_ref: true
+default: deferred
```
+## The branch-circuit module installation method shall be as indicated in the datasheet.
+
```datasheet
label: Branch-circuit module installation method
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## The Owner shall confirm with the serving utility whether the utility requires its own meter or will accept a sub-metering meter model at each revenue point.
+## The designation of this metering point shall be as indicated in the datasheet.
+
```datasheet
label: Metering point designation
type: radio
+drawing_ref: "metering point schedule"
options:
- Revenue-grade (billing, sealed)
- Energy-management grade (PMD)
−default: Energy-management grade (PMD)
+default: deferred
```
+## Whether legal-for-trade certification is required shall be as indicated in the datasheet.
+
```datasheet
label: Legal-for-trade certification (tenant re-billing)
type: radio
options:
- Required (NIST HB 44 certified)
− - Not required (energy management only)
−default: Not required (energy management only)
+ - Not required — energy management use
+default: Not required — energy management use
```
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## The energy monitoring software shall produce the compliance reports required by the adopted energy standard.
+## The energy monitoring software platform source shall be as indicated in the datasheet.
+
```datasheet
label: EPMS platform source
…3 unchanged lines
- Third-party EPMS platform
- Integrated into building automation system
−default: Integrated into building automation system
```
+## The platform is an Owner program decision that drives protocol and register-map compatibility, so it carries no default and shall be identified before meters are ordered. {note}
+
+## The reporting granularity produced by the energy monitoring software shall be as indicated in the datasheet.
+
```datasheet
label: EPMS reporting granularity
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- Annual
default:
+ - Hourly
- Daily
- Monthly
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## Current transformers shall be installed with the correct polarity orientation relative to the metered conductor and the source.
−### A CT installed backwards reverses the measured power direction, reporting export when the load imports; polarity marks on the CT and the meter terminals shall be matched so the sign of real power is correct. {note}
+### A CT installed backwards reverses the measured power direction, reporting export when the load imports; polarity marks on the CT and the meter terminals shall be matched so the sign of real power is correct.
## Current transformer secondary circuits shall be grounded at one point only in accordance with NFPA 70 Article 250.
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## The Contractor shall submit a commissioning report documenting the verifications for each metering point.
+## The commissioning verifications performed at each metering point shall be as indicated in the datasheet.
+
```datasheet
label: Commissioning verifications required
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# Warranty {toc}
−## The meter manufacturer shall warrant each meter against defects in materials and workmanship for a minimum of 3 years from substantial completion.
+## The meter manufacturer shall warrant each meter against defects in materials and workmanship, measured from substantial completion, for the period indicated in the datasheet.
−## The meter manufacturer shall warrant the metering accuracy for the warranty period where accuracy warranty is offered.
−
−## Energy monitoring software licenses shall be warranted and supported for the warranty period.
−
```datasheet
label: Meter warranty period
…6 unchanged lines
```
−# Spare Parts {toc}
+## The meter manufacturer shall warrant the metering accuracy for the warranty period where accuracy warranty is offered.
−## The Contractor shall furnish spare current transformers of each ratio used, in a quantity sufficient to replace failed units without procurement delay.
+## Energy monitoring software licenses shall be warranted and supported for the warranty period.
−## The Contractor shall furnish spare fuses for each voltage transformer type used.
+# Spare Parts {toc}
+## The Contractor shall furnish spare current transformers of each ratio used, in the quantity indicated in the datasheet.
+
```datasheet
label: Spare current transformers per ratio
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```
+## The Contractor shall furnish spare fuses for each voltage transformer type used, in the quantity indicated in the datasheet.
+
```datasheet
label: Spare VT fuse sets
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default: 2
```