Load Management Device Installation and Verification

Purpose

A load management device is not an accessory. The moment one is installed to make a calculation work, that calculation depends on a piece of equipment continuing to function, and the shop has traded a permanent margin for a permanent control. That trade is legitimate and it is what the code contemplates, but it only holds if two things are true: the device actually sheds under real conditions, and everyone who touches the building later knows the calculation depends on it.

The characteristic failure is not a device that never sheds. It is a device that sheds and immediately restores, over and over, because the restore threshold was set where a person would guess rather than where the arithmetic puts it. The customer hears the compressor cycling every ninety seconds and calls it a broken generator.

Scope

Covers installing, configuring and verifying a load management or energy management device that limits total demand on a backup source or on a service, at a dwelling or small commercial building, 120/240 V single phase.

Does not cover retrofitting management onto an already-installed EV charger, owned by the EV charger load management retrofit SOP, which calls this procedure for the device verification itself; the critical circuit selection, owned by the critical load panel SOP; or the transfer switch's own settings, owned by the automatic transfer switch commissioning SOP.

Roles and responsibilities

Procedure

1. Name the calculation this device exists to satisfy, and state its pass condition as a number. Whether the device is limiting demand on a backup source under NEC 702.4 or limiting a load under NEC Article 750, the pass condition is a specific current or kilowatt figure that must never be exceeded. Acceptance: the calculation identified by name and date, the limiting number written at the top of the configuration sheet, and the adopted NEC edition recorded. Wrong looks like a device installed because the equipment came with one; stop rule, no governing calculation means no device, because a control with nothing to control cannot be verified. Hazard: none, a desk step, and it is what makes step 6 a test rather than a demonstration.

2. Confirm the device's listing and how it actually sheds. Read whether the device opens a contactor in the load's circuit, signals the equipment to stop through a control input, or reduces a load's setpoint, because the three fail differently and are wired differently. Acceptance: listing confirmed on the label, control method recorded, and the manufacturer's stated behavior on loss of the device's own power written down. Wrong looks like assuming a device that signals a compressor will also stop a resistive load; stop rule, a device whose failure mode leaves a managed load energized without limit is not acceptable where the calculation depends on it, and that goes back to the office. Hazard: none while reading a label, though anything mounted in an existing enclosure brings step 4's rules forward.

3. Choose the managed loads and their priority order with the customer, and check each one tolerates interruption. A water heater tolerates it, an air conditioning compressor tolerates it only with its anti-short-cycle timer intact, and an oven mid-bake is a conversation to have before it happens rather than after. Acceptance: a signed priority list, first to shed at the top, with a note beside each load naming what it does when interrupted; anything serving a medical, life-safety or freeze-protection function excluded in writing. Wrong looks like a priority list built from what was easy to reach with a control conductor; stop rule, a load the customer will not accept losing comes off the managed list and the calculation is re-run without it. Hazard: none in the conversation, but a compressor shed and restored inside its anti-short-cycle window starts against head pressure, so the timer's presence is confirmed rather than assumed.

4. Install the current transformers on the right conductors, in the right direction, and land the control wiring. Place the sensing transformers where they see the total the calculation limits, not a branch of it, and orient each one as the manufacturer's arrow requires. Acceptance: each transformer on the conductor named in the manufacturer's drawing, arrow oriented per the instruction, control conductors landed terminal for terminal, and the device's own supply circuit protected as its listing requires. Wrong looks like a transformer reversed, which reads a plausible current with the wrong sign and can shed exactly backwards; stop rule, a reading that does not rise when a known load is switched on stops the commissioning until the sensing is corrected. Hazard: fitting a split-core transformer around a service conductor is energized work at a point that cannot be de-energized from inside the building, so it is done by a qualified person with arc-rated personal protective equipment, or the utility pulls the meter first; where the transformer can go on a load-side conductor that the main de-energizes, open the main, lock and tag it, and prove the conductor dead on a known live source immediately before and after per NFPA 70E-2021, 120.5, with work practices at 29 CFR 1910.333(b)(2), which governs because 1910.147 excludes electrical utilization work at (a)(1)(ii)(C).

5. Configure four parameters and derive the restore threshold rather than guessing it. Set the shed threshold below the limiting number from step 1, set a shed delay so a momentary surge does not shed the house, set a restore delay that respects the longest anti-short-cycle timer among the managed loads, and set the restore threshold at least the managed load's own running current below the shed threshold. Acceptance: all four written on the configuration sheet, with the restore threshold shown as a subtraction from the shed threshold rather than as a bare number. Wrong looks like a restore threshold set equal to the shed threshold, which guarantees that restoring the load immediately re-trips it; stop rule, a device that will not accept a restore threshold low enough to satisfy that subtraction is the wrong device for this load, and the office is told before step 6 runs. Hazard: none at the keypad, but these numbers are what will open a contactor on a running motor, so they are read back after entry.

6. Verify by producing the real condition and measuring at the point the device measures. Bring the building to a load above the shed threshold using the actual equipment, not a simulated input, and watch what happens with a clamp meter on the same conductors the device senses. Acceptance: shed occurs within the set delay, measured current after the shed recorded, no second shed or restore for a stated observation period of at least 15 minutes, and restore confirmed once load falls below the restore threshold and the restore delay expires. Wrong looks like a shed followed by a restore followed by another shed, which is the chatter this procedure exists to prevent; stop rule, any chatter sends the settings back to step 5 and the observation period restarts from zero. Hazard: this step deliberately drives the building to its limit with people in it, so no test is run by forcing a value into the device or by jumpering its sensing, no managed load that serves a freeze-protection or life-safety function is included, and the source is watched for alarms throughout since the whole point is to approach its capability.

7. Label the dependency and close the record. Put a label at the panel and at the device naming the device, the loads it manages, the shed threshold, and one sentence saying the load calculation for this building depends on it remaining in service. Acceptance: labels installed and photographed, the customer's signed acknowledgment on the record, and the as-left settings filed. Wrong looks like a device with no label, which a future occupant or contractor removes as a mystery box; stop rule, no label, no close-out. Hazard: none, and the label is the only part of this job that will still be working in fifteen years.

The record this produces

One configuration and verification sheet per device.

Header: the governing calculation by name and date, its limiting number, adopted NEC edition, device make, model and control method, the manufacturer's stated behavior on loss of device power. Body: the priority list with the interruption note beside each load; the four step 5 parameters with the restore threshold shown as its subtraction; the step 6 measurements, meaning pre-shed current, post-shed current, elapsed shed time, the observation period length and the restore event. Footer: label photographs, customer acknowledgment, deficiencies with owners.

The next technician reads the limiting number and the shed threshold before adding anything to this building, because a device set for yesterday's load list does not know about a new circuit.

Worked pass: 14 kW standby set, two compressors managed

Step 1: the governing calculation is the backup design for a 14 kW set, whose continuous rating is 14,000 divided by 240, or 58.3 A. That 58.3 A is the limiting number.

Step 3: the priority list is compressor B first to shed, then the water heater, then compressor A. The compressors both carry anti-short-cycle timers with a stated 5 minute delay.

Step 5, first attempt: shed threshold at 80 percent of the limit, which is 58.3 times 0.8, or 46.6 A. Shed delay 30 seconds. Restore delay 5 minutes to match the timers. Restore threshold entered at 46.6 A, the same as the shed threshold.

Step 6 fails. Base house load on the set measures 22 A. Compressor A brings it to 40 A. Compressor B brings it to 55 A, which is above 46.6, and the device sheds compressor B after 29 seconds, correctly. Load falls back to 40 A, which is below the 46.6 A restore threshold, so five minutes later the device restores compressor B and the load returns to 55 A and sheds again. Four shed-and-restore cycles are logged inside 24 minutes. The stop rule fires and the observation period is abandoned.

The fix is arithmetic, not judgment. Compressor B draws 15 A running, so restoring it can only be safe when the load without it sits at least 15 A below the shed threshold: 46.6 minus 15 is 31.6 A. The restore threshold is set to 30 A, which leaves 1.6 A of margin, and written on the sheet as that subtraction rather than as a bare 30.

Re-test: base 22 A, compressor A to 40 A, compressor B calls and the load reaches 55 A, shed at 28 seconds. Post-shed current measures 40 A, which is above the 30 A restore threshold, so compressor B stays shed. Observed 22 minutes with no further events. Compressor A then satisfies and drops out, load falls to 22 A, below 30 A, and compressor B restores 5 minutes later to a total of 37 A, which sits 9.6 A below the shed threshold and holds.

Step 7: labels at the panel and the device naming compressor B, the water heater and compressor A in shed order, the 46.6 A shed threshold, and the sentence about the calculation. Customer signed.

References

• NEC (NFPA 70) Article 750 for energy management systems and 702.4 for standby source capacity where load management is used; confirm the adopted edition, because both have been revised across recent cycles
• 29 CFR 1910.333(b)(2) for de-energizing and verifying at step 4, with NFPA 70E-2021, 120.5 for live-dead-live, and the energized-work provisions of your employer's electrical safety program where a service conductor cannot be de-energized
• Manufacturer's instructions for the device: current transformer placement and orientation, parameter ranges, and behavior on loss of device power
• See related: the critical load panel design SOP, the EV charger load management retrofit SOP, and the automatic transfer switch commissioning SOP