Electrical rooms, along with the space of mechanical, electrical, and plumbing (MEP) areas are all too often forgotten about when designing a building. They are an afterthought and as a result are left with the areas that are undesirable for the main purpose of the building or just what is left over after everything is planned out. This can cause down the line for systems in these areas in terms of operation, flexibility, and cost.

The National Electrical Code (NEC) states the minimum room needed around all of the equipment for operation, safety reason, access, and conduit installation. These requirements along with the equipment itself, it what determines the minimum size of the room.

There are three main interior electrical spaces that affect new building design, these are distribution pathways, branch/local equipment rooms, and the main equipment rooms. The minimum amount of dedicated and working space for these rooms must be satisfies as per the code. This article will go through electrical room sizing for new buildings with regards to the building type, size, intended occupancy and the expectations for the future of the building and its systems.

What Are Working & Dedicated Spaces?

Working spaces help to maintain a clear working area around every piece of equipment and makes sure that all of the works and occupants of the room will be safe. This involves stating a minimum depth, height, and width requirement for the space, which will vary due to specific equipment that is in the room and the voltage being used. The higher the voltage that is being used by the equipment, the more depth is need in the working space. The width of the room should be the same as the width of the equipment, while not being less than 30 inches, and allowing any panels and doors to open to 90 degrees. The minimum height of the room is six feet six inches, or the height of the equipment itself if the equipment is taller than that.

*Sufficient space must be provided around electrical equipment as it can be dangerous. Source: Unsplash*

The construction and style type of the equipment will determine whether it needs just front access, or both front and side/rear access is needed. For every access point to the equipment, the minimum working clearance must be adhered to.

Dedicated spaces refer to a zone that resides above the electrical equipment. This space is put aside for future access to the equipment below, it also gives the systems protection from other systems in the building, and gives space for installing raceways and conduit that supports outgoing and incoming circuits. The minimum requirements for this room depends on the switchboards, motor control centers, panelboards, and switchgear. It should also be the same width and depth as the equipment below and be at least six feet from the floor to the ceiling, this can be shorted is a structural ceiling is lower. Other systems are not allowed in this area as per the NEC code.

Foreign system may be allowed in the dedicated space if the necessary protection is provided to prevent any leaks, breaks, or drips from the systems. However, most engineers will advise to avoid these rooms altogether with foreign systems as it is good practice.

Now, lets go through the various rooms that will be features in new buildings, main equipment rooms, branch/local equipment rooms, and distribution pathways:

Main Equipment Rooms

The service entrance space, or main equipment room, should be coordinated directly with the local electrical utility. Main equipment rooms have minimum requirements that will determine the access to the room from the outside for maintenance, service feeder installation, and servicing. The equipment type within the room will also affect the room requirements. The service entrance room is generally found on an exterior wall for a couple of reasons, both practical and code. It makes the length of service entrance conductors as short as possible and makes general installation easier. Service conductors are usually the biggest in the facility, so making them as short as possible will help to reduce costs.

When arc resistant switchgear is used this will also affect the room. This particular switchgear will make the equipment taller and maybe take up more space on the ground. This will need to be accounted for when the engineers assess the arc flash energy and exhaust gases that will be generated. A pathway will have to be created to bring these away from the equipment and reduce the buildup of pressure on the building inside the switchgear.

Branch/Local Equipment Rooms

The branch/local equipment rooms are sometimes referred to as the equipment closets. Branch circuit panels, low voltage transformers, and distribution panels are generally found in the electrical closets and serve the end user loads directly. Lighting control panels and other electrical devices are also sometimes found in these rooms. Due to the amount of changes and upgrades that buildings are always gong through, a blank wall should always be include in every electrical closet to account for extra equipment being installed down the line.

Distribution Pathways

These are needed for connecting all of the various groups of electrical equipment and user devices located in the building. The pathways will affect where the electrical rooms are, and they can be ran below ground, above the equipment, or in the ceiling of the floor below. Bear in mind that conduit needs space to leave the equipment and change route in the desired direction and feed the rest of the building. Below ground conduit must be coordinated with the foundation and other utilities that are below ground. Similarly, conduit cannot be ran through any structural beams or slabs.

If you need you electrical room sized, or any consulting on your next or current project, please don’t hesitate to contact Engineering Solutions and we would be happy to help!