Retrotec FanTestic Integrity (ISO) - Manual (Page 22)

rev-2014-10-27
Page 22 of 50
©Retrotec Inc. 2012

“Building description”
Enter a brief description of the building you are testing.

“Enclosure Description”
Enter a brief description of the enclosure in the building you are testing.

“Building Address”
Enter the address of the building you are testing.

“Customer details”
Enter the name and contact information of the person/company that you are doing the test
for.

“Elevation above sea level”
Enter the building’s elevation above sea level. This value is used to perform a small
correction to the agent concentration.

“Maximum flooded volume”
Calculate and enter the enclosure volume as it is defined in ISO 14520 (net protected
volume).

“Maximum flooded height”
Enter the maximum flooded height as it is defined in ISO 14520

“Over-ride default value of 90% of flooded height”
Checking the box permits entry of any “Required protected height” which would typically be
“the elevation of the protected hazard”. By doing so would mean you were not fully compliant
with the letter of the Standard but there are reasons why this might make sense; read on.
The 2006 version of this Standard requires agent concentration to be held at 10%, 50% and 90%
of the total flooded height for Descending Interface Hold Time calculations. Check with your
local jurisdiction to determine what is required because many do not require this conservative
approach. Both the 2000 version of ISO and the version about to be released in 2015 require:
“At the end of the hold time, the extinguishant concentration at the elevation of the protected
hazard shall be not less than 85% of the design concentration”.
In practice, using 90% of the total flooded height for Descending Interface Hold Time
calculations will reduce hold times by 50 to 75%. This forces enclosures to be 2 to 4 times
tighter to pass which is often difficult, expensive and/or impossible. For this reason, many
jurisdictions do not adhere to this requirement but some do.
Continual Mixing is often a way to comply with the Standard because mixing maintains the
same concentration at all heights making the 90% requirement irrelevant. This is often the only
way the enclosure will pass the required hold time because mixing will always yield longer hold
times. If the Initial Concentration is greater than the Design the hold time will increase even
more. For example, if the Initial is 40%, the Design is 40% and the Minimum is 34% and the hold
time is 7.1 minutes, then, if the Initial is increased to 44%, the Design is still 40%, the Minimum
is still 34% but the hold time increases to 11 minutes. When increasing the Initial, the Design
stays the same but the hold time increases. Do NOT make the common mistake of making the
Minimum 85% of the Initial which would nullify the effect of adding extra agent. Instead, always
make the Minimum 85% of Design.
In order to comply using continual mixing, there must be mechanical or thermodynamic effects
during the hold time that would ensure Continual Mixing does occur. Fortunately, these
conditions are often present when dedicated HVAC is left running during the hold time or where
hot equipment will cause mixing due to convection or where an extended agent discharge is
used.