UL 555S Smoke Dampers and Fail-Safe Operation
UL 555S Smoke Dampers and Fail-Safe Operation
(OP)
Hi All, I am working on a retrofit job of a high rise condo building with an atrium where NC smoke dampers with electronic actuators are provided on exterior openings for atrium smoke exhaust system makeup air. The dampers are currently set to fail open during loss of normal power, which seems logical due to the fact that the dampers are part of the smoke control system. However, during the colder months when emergency power is being tested, these dampers are opening and allowing cold air to be pulled into building (stack effect) which in turn has frozen some pipes.
Looking through standards, I cannot find any requirement that says these dampers must be provided with a fail-safe operation, which makes sense considering they are required to have emergency power and fail-safe would require 3 simultaneous events. However, most of the dampers I am finding online with a UL 555S listing have fail-safe operation, which makes me think that this may be a requirement of UL 555S (which I do not have access to). I was wondering if anyone had any experience with a similar situation or any additional insight as to whether NFPA 90A/92 or the IBC or any other standards have any requirements for fail-safe operation of components of a smoke control system.
THANKS!
Looking through standards, I cannot find any requirement that says these dampers must be provided with a fail-safe operation, which makes sense considering they are required to have emergency power and fail-safe would require 3 simultaneous events. However, most of the dampers I am finding online with a UL 555S listing have fail-safe operation, which makes me think that this may be a requirement of UL 555S (which I do not have access to). I was wondering if anyone had any experience with a similar situation or any additional insight as to whether NFPA 90A/92 or the IBC or any other standards have any requirements for fail-safe operation of components of a smoke control system.
THANKS!





RE: UL 555S Smoke Dampers and Fail-Safe Operation
RE: UL 555S Smoke Dampers and Fail-Safe Operation
My question is more related to your testing protocols. How often and how long do you test that might result in a pipe freeze?
RE: UL 555S Smoke Dampers and Fail-Safe Operation
RE: UL 555S Smoke Dampers and Fail-Safe Operation
RE: UL 555S Smoke Dampers and Fail-Safe Operation
RE: UL 555S Smoke Dampers and Fail-Safe Operation
However it is good engineering practice to have the dampers go to their fail safe positions (e.g., exhaust smoke, exhaust labs with elevated bio-safety levels, or pressurize clean spaces) upon power loss.