Camera Install Issues - Plenum, UL and Conduit Connections

Published Oct 18, 2011 04:00 AM
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While image quality and reliability get the lion's share of discussion when talking about IP cameras, there's normally little discussion of installation issues, which can greatly affect system design and technician time in the field. Specifically, UL listing, plenum issues, and connection of conduit to camera housings are rarely discussed, but often a problem. In this update, we'll look at these three separate issues, and how they impact users.

Plenum housings

The first issue arises when users wish to recess cameras in plenum ceilings, so that only the dome is visible below the ceiling. For those unfamiliar, a plenum is a space used for airflow in a facility, typically between a drop ceiling and the deck of the floor above, or the space below a raised floor and the subfloor. For more detailed information, users may also refer to this article by AV manufacturer Extron, which we feel provides a good overview of plenum (as well as UL testing) issues.

Typically speaking, national and local codes require that cables and housings installed in these spaces be rated for use in the space, meeting certain requirements for the spread of fire and smoke. It does not mean that cables won't burn, or that they produce non-toxic smoke, which is commonly believed. It normally means that the cables will extinguish when the heat source is removed. Additionally, of interest for camera installation, connection points are typically not allowed in plenum spaces. This means neither high-voltage receptacles nor Ethernet jacks may be openly located in a plenum. They may be installed in a plenum-rated enclosure.

What all of this means for camera installation in a plenum is that in order to maintain plenum rating, the recessed camera enclosure must be fully enclosed so all connection points are covered, and made of a material which is suitable for the plenum, typically metal. Many recessed ceiling mounts do not meet these requirements, instead being comprised of an open frame in which the camera mounts. Most major manufacturers produce plenum housings, and some provide both styles of recessed camera housing. Users should double check that housings are plenum-rated where required.

Examples of plenum (on the left) and non-plenum mounts (on the right):

Conduit adapters for indoor cameras

Another complaint we hear from users is the lack of conduit knockouts on indoor dome cameras. When installing cameras in an area in which conduit is required, there is a question of how to transition from the conduit to the camera. Conduit decribes hard metallic tubing used as a raceway for data and power cabling. While formal 'conduit' means a rigid, pipe-like tube that is threaded on both ends, an cheaper alternative in "EMT" is often incorrectly referred to as "conduit".

For clarity, EMT is thin walled tubing that is not water-tight, but is a cheaper alternative to the heavier outdoor-rated conduit. While vulnerable to water infiltraction, EMT and conduit can be used interchangeably in a variety of situations, including indoor cable runs, concrete-embedded runs, and even outdoors where joints are protected against water, snow, and ice.

A brief survey of indoor dome cameras shows that this is generally not a thought. Only one manufacturer (Sony) provides a space in the dome where conduit may be connected. The most common way around this is to mount the dome camera to an electrical box. Normally, cameras are shipped with adapter plates which allow the dome to be mounted to 4" square or double-gang boxes. This method does technically solve the problem, but may be undesirable due to the aesthetics of the exposed electrical box. Unfortunately, there is little users can do without modifying the dome housing, which under most circumstances voids the warranty. As a result of all of the above, when an installation calls for cameras which will connect to conduit, outdoor, vandal resistant cameras are often used, which adds expense.


UL Listing

The final installation challenge, and perhaps the most difficult to manage, is that of UL listing. What makes this so difficult is that locales vary widely on their stance on listing. Some local authorities choose to ignore it altogether. Others will reject any product that does not have a UL sticker on each component. We have seen the full spectrum of local requirements. Users should consult with local inspectors prior to installation to see what will be required, and check components for UL listing. Most major manufacturers provide UL certificates for their products, but beware when using off brand or lesser-known cameras.

Making things more difficult, some authorities will only accept products if they are listed as an assembly. So for example, using an Axis camera with a third-party housing may not be allowed, since the products are not tested together, as an assembly. This may apply even if all components are individually UL-listed. Unfortunately, in these cases, there is little users can do other than comply with the local inspector's wishes. It is also possible to pay to have the assembly tested by UL or another testing laboratory, but this is very expensive and normally only pursued under extreme circumstances, or for very large installations.