sprinklernotes
Mixing Sprinklers with Different Temperatures and Operating Elements
You have asked the following question: “Can you have a 165-degree fusible link
sprinkler and a 155-degree glass bulb sprinkler in the same compartment?” In
response to your question, we have reviewed NFPA 13, 2016 edition as the
applicable standard. Our informal interpretation is a 165-degree sprinkler can
be installed in the same compartment as a 155-degree sprinkler.
165-degree sprinklers and 155-degree sprinklers are both rated as
ordinary-temperature per Table 6.2.5.1. Section 8.3.2.1 states:
“ordinary-temperature and intermediate-temperature sprinklers shall be used
throughout buildings.” The same temperature rated sprinklers are required in
the same compartment to reduce sprinkler skipping. Sprinkler skipping is when a
sprinkler that is not in the immediate vicinity of the fire activates. This
will decrease the flow and pressure of the sprinklers closer to the fire
causing those sprinklers to be less effective. 165-degree sprinklers and
155-degree sprinklers (and even larger differences such as a 135 and 165) will
have an insignificant difference in activation times. The bottom line is that
both are ordinary-temperature sprinklers thus allowing them to be installed in
the same compartment.
An interesting unasked question is can you combine both ordinary- and
intermediate temperature ratings. A literal application of the text implies you
can since it says “and” in Section 8.3.2.1. Not long ago we had to use only
ordinary-temperature sprinklers unless there was a localized higher temperature
risk. The committee finally realized that mixing in intermediate sprinklers for
localized temperature exposures made a lot less sense than allowing
intermediate-temperature sprinklers to be used throughout. As stated in the
Sprinkler Handbook, “the response time of quick response intermediate
sprinklers is not that different from standard response ordinary sprinklers.”
This should be read that you can use one or the other (when not addressing
localized exposures). Although there is no significant difference in activation
of a 165-degree (ordinary-temperature) sprinkler and a 175-degree
(intermediate-temperature) sprinkler, there is a line in the sand needed to
avoid mixing 135-degree and 225-degree sprinklers.
