Visible Signaling Appliances Codes & Standards
Ralph Coco Potter Electric Signal
It can be agreed that visible signaling appliances were designed to be seen rather than heard, therefore where would the advantageous areas of installation be? The building codes will direct us in this area.
Here is an overview of the National Building Codes from 2015 and 2020. Since different provinces are referring to different versions of the NBCC, we have included both here and highlighted the changes to each.
We will now review the changes in the standard in reference to strobe intensity and how we may need much higher candela ratings for the strobes in residential suites. These are largely now in alignment with the requirements in the US.
S524-2019
42.3 Where ceiling heights allow, wall-mounted strobe lights shall be installed such that the entire lens is not less than 2000 mm and not more than 2400 mm above the finished floor.
42.19 Where visible signal devices are installed in sleeping rooms, each visible signal device shall have a minimum candela rating of 177 cd where the device is installed less than 610 mm from the ceiling and a minimum candela rating of 110 cd for all other locations.
NOTE: The visible signal device should be located within 4.87 m of the pillow.
Total height of room will need to be more than 2.61m (8’6”) to be at 110cd. (Based on 2000mm min. mounting height). This means that any sleeping area with a ceiling height of less than approximately 2.6m will most likely need strobes with a candela rating of 177cd. This will increase the need for more current per suite in jurisdictions where strobes are required in all floor areas (for example - Manitoba). Here is the reference to the Manitoba Building Code:
2(8) Sentence 3.2.4.19.(1) is replaced with the following: 1) Visible signal devices shall be installed in addition to alarm signals in all buildings. – MBC 2023
BC Building code still says (in 3.2.4.19.4) “Not less than 75 cd for sleeping areas”. But it does have the same mention as the NBCC model code (in A.3.2.4.19.1):
“In addition, CAN/ULC-S524, “Standard for Installation of Fire Alarm Systems,” requires that high-intensity strobes be used in sleeping rooms.”
So this may prove a little confusing in application, as it could be interpreted as only needing above 75cd, though it does refer to ULC 524 in the appendix and the need for high candela.
As we can see by these examples, there is a need to clearly understand the code changes in each jurisdiction. This overview is not an exhaustive review of all of the changes in all particular jurisdictions, but should be used as an example of why we need to review our local code changes and see how each province is deciding to take on the increased need for more strobes and, in some cases more strobe intensity.
Here is a reminder of the occupancy types for Buildings in Canada:
BUILDING OCCUPANCY TYPES
A1 Assembly occupancies intended for the production and viewing of the performing arts
A2 Assembly occupancies not elsewhere classified in Group A
A3 Assembly occupancies of the arena type
A4 Assembly occupancies in which the occupants are gathered in the open air
B1 Detention occupancies
B2 Treatment occupancies
B3 Care occupancies
C Residential occupancies
D Business and personal services occupancies
E Mercantile occupancies
F1 High‐hazard industrial occupancies
F2 Medium‐hazard industrial occupancies
F3 Low‐hazard industrial occupancies
Now that we have reviewed the relevant codes and standards for when to use strobes and how bright they should be, let’s take a look at the installation requirements of visible signaling appliances. Most of this information can be found in the ULC-S524 installation standard.
Wall mount installations: require the entire lens not less than 2000 mm and not more than 2400 mm above the finished floor area. The number of strobes and their respective candela rating depends on the room size and corridor length as well mounting configurations such as wall and ceiling mounted installations.
Corridor Installations
Table 42.3 for Corridor Spacing
The key installation instructions for corridors are as follows.
- Corridors only require 15 candela strobes
- Strobes must be located no more than 4.5 metres from each end of the corridor
- Additional strobes placed not more than 30 metres apart
Please refer to the diagram examples below where we show installations for short, long and interrupted corridors.
Wall Mount Installations
Chart For Wall Mounting in Various Room Sizes Including Candela Rating
We will now review the installations for wall mounting strobes in various size rooms. Table 42.1 chart in ULC-S524-2019 is self-explanatory as it covers candela rating and number of strobes to install. We will also look at incorrect and correct strobe allocation principles.
In our first example, we will look at an installation for a room size of (6m X 5m). Since the exact room dimensions are not shown in this table, we will need to interpolate Table 42.1. In this table, the closest room size is (6.10m X 6.10m). Since our room size of (6m X 5m) falls below (6.10m X 6.10m) a 15 Candela Strobe will meet this application. We just simply follow the chart that provides candela rating and number of strobes to install.
The next example covers installations for oddly shaped rooms. The solution is to divide the room into smaller areas and use the Table Chart for the appropriate Candela rated strobe.
To facilitate this exercise, we will review a step-by-step process using a room size of (24.4m X 22.6m). Using our imagination and a little math we sub-divided the room to create two 12.2m X 12.2m rooms along with two 6.1m X 6.1m rooms. One room at the far right fell just short of 6.1m, so we created an imaginary wall to extend the room to 6.1m. The imaginary wall size should be squared to meet the minimum candela rated strobe. In our case we had a 6.1m X 4.36m room, hence, squaring it gives us a 6.1m X 6.1m room. Now we can refer to our wall mount Table 42.1 and install the appropriate Candela rated strobe for each respective room size. (One 60 candela strobe for each 12.2m X 12.2m room and one 15 candela strobe for each 6.1m X 6.1m room. This brings our total to four strobes. Two 60 and two 15 candela strobes)
In rooms with visible signal devices not centered on a wall, the effective intensity (candela) from one wall-mounted visible signal device shall be determined by maximum room size dimensions obtained either by measuring the distance to the furthest wall or by doubling the distance to the furthest adjacent wall, whichever is greater.
In this scenario, the greater distance is obtained by doubling the distance to the farthest adjacent wall which is (6m). (6m x 2 = 12m) In table 7, a (12m X 12m) room requires a 60 candela strobe or two 30 candela or four 15 candela.
The intent is to centre the appliance by creating an imaginary room size. Recall that we had a (7m X 5m) room and the distance from our visible appliance to the furthest adjacent wall was (6m) Hence, by doubling the distance of (6m) we get (12m) or a (12m x 12m) room. Then we select the appropriate strobe intensity to cover those dimensions to ensure full room area coverage. Table 42.1 selects a 60 candela strobe. (Two 30 candela or four 15 candela can also be substituted)
Good Mounting Practices
Another question that may come up is, whether to install the strobe light on the short or long side of the wall? According to NFPA 72, spacing allocation for wall mounted strobes are to be located at the mid-point of the longest side of the area served. (The midpoint of the longest side is preferred.)
Strobe Allocation
Allocating strobes on a wall can be challenging because we need to ensure maximum area coverage and avoid sound wave conflicts. In this example, we are meeting minimum Candela rating by installing four 15 candela strobes (illumination) but the strobe allocation is incorrect. Notice that the strobes are facing each other. Area Coverage of each appliance is not maximized. Moreover, if these were (Horn/Strobes or Speaker Strobes) the result may be conflicting sound waves cancelling sound.
The correct method is by following CAN/ULC-S524-19 diagram figures D2 & D3 incorrect & correct method of allocating strobes. Subdivide the room into multiple squares (6.1m x 4m) and place a strobe at the centre point of each room. This will provide better area coverage and avoid conflicting sound waves that will negatively impact sound.
RECTANGULAR ROOMS
In our example we have a rectangular room size that is 14m X 28m. The solution is to divide the room into two 14m X 14 m rooms. Using ULC–S524 Table 42.1 (wall mounting) requires a 94 candela strobe in a 15.2m X 15.2m room (One in each subdivided room) Notice that the strobes are staggered at the opposite side of the walls, so no conflicting sound waves are created.
Two 60 candela or four 30 candela strobes in each subdivided area can be substituted. It will be more economical to install one 94 candela strobe than multiple smaller intensity units.
Please note that more than two visible signal devices within the same field of view require synchronization.
In this article, we reviewed the newest codes and standards that have been adopted (up to Summer 2024) and how these newer codes and referenced standards have changed some parts of our placement and design of strobes. We also reviewed the current (and mostly unchanged) principles of designing for effective use of strobes (and horn/strobes) to meet placement criteria as laid out in CAN/ULC S524-2019.
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