NLAB, NAB, CCB and TLM panelboards: differences and uses

TLM, NLAB, NAB and CCB panelboards differ in the type of breaker they house, the current they handle and the electrical system they are designed for. The TLM is a single-phase residential load center; the NLAB is a lighting and receptacle panelboard for commercial use; the NAB covers commercial and light industrial distribution with higher currents and three-phase configurations; the CCB is a power distribution panelboard that houses molded-case circuit breakers. Choosing the right one depends on the point in the installation where it will operate.

What is a low-voltage switchboard?

A low-voltage switchboard is a metal enclosure with copper or aluminum busbars that receives a feeder and distributes it to several circuits, each protected by a breaker. Its practical classification depends on three things: the type of breaker (plug-in or bolt-on), the current of the main bus and the system (single-phase 120/240 V or three-phase).

TLM: residential load center

The TLM is the typical residential panelboard. It is single-phase 120/240 V, with a bus for 1- and 2-pole THQL plug-in breakers. It is manufactured with or without a main breaker, in surface and flush-mounted versions, and with a number of spaces ranging from small panels with a few circuits to units with 40 or more spaces. The most common main bus ratings for this type of panelboard are in the range of 100 to 200 A.

• Use: apartments, houses, small premises fed at 120/240 V.
• Breakers: THQL 1 and 2 poles (20 – 60 A).

NLAB: lighting and receptacle panelboard

The NLAB is a lighting panelboard of more robust construction than the load center, intended for commercial buildings, offices, schools and clinics. It accepts THQL and THQC plug-in breakers, in single-phase and three-phase configurations, and can be supplied with a main breaker or main lugs. Its typical bus capacity is higher than that of the TLM, and its enclosure accommodates a larger number of circuits and conductors.

• Use: lighting and receptacle circuits in commercial buildings.
• Breakers: THQL and THQC with 1, 2 and 3 poles up to 100 A.

NAB: commercial and light industrial distribution

The NAB follows the same logic as the NLAB, but is specified when higher bus currents, three phases with neutral and the capacity to feed subpanels as well as branch circuits are required. In practice it is the intermediate panelboard between the lighting panel on a floor and the building's distribution switchboard. It accepts 2- and 3-pole THQC breakers and, depending on the configuration, higher-current breakers for the feeders.

• Use: floor or area panelboards in large commercial premises, healthcare facilities, light industry.
• Breakers: THQC up to 100 A; feeders with higher-range breakers according to design.

CCB: power distribution panelboard

The CCB (circuit breaker panelboard) is the power panelboard. Instead of plug-in breakers, it houses bolt-on molded-case circuit breakers: A2A up to 250 A, and XT5N, XT6N and XT7S for 400, 630, 800 and up to 1600 A. Its function is to receive the service entrance or the transformer output and distribute it to the area panelboards, the motor control centers and the large loads.

• Use: main switchboard in buildings, industrial plants, compact substations.
• Breakers: A2A, A2C, A3N, XT5N, XT6N, XT7S molded-case circuit breakers.

Summary comparison

Type	System	Breaker	Position in the installation
TLM	Single-phase 120/240 V	THQL plug-in	Home, small premises
NLAB	Single- or three-phase	THQL / THQC plug-in	Commercial lighting and receptacles
NAB	Three-phase with neutral	THQC and feeders	Floor or area panelboard
CCB	Three-phase	Bolt-on molded case	Main power switchboard

How is the right panelboard selected?

1. Determine the total current of the feeder reaching the panelboard; that sets the main bus rating.
2. Count the outgoing circuits and reserve at least 20 % of the spaces for future expansion.
3. Define whether the system is single-phase or three-phase and whether a neutral is required.
4. Verify the short-circuit level: the bus and the breakers must withstand it.
5. Choose the enclosure protection rating according to the environment (dry indoor, outdoor, corrosive area).

At MARPE we build custom low- and medium-voltage switchboards with ABB and GE product, as well as power houses and compact substations. See our distribution and auxiliary services line for the full scope.

If you have the single-line diagram or the load schedule, send it on WhatsApp and we will indicate which type of panelboard applies and which breakers to equip it with.

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