Del,
Your information often has the potential to mislead people. Your statement that fuses are better than PTC in the application appears incorrect.
Now you are saying you agree PTC's are required for Fire Alarm applications but not in Security or Access Control etc. Well then you need to refer to UL1610 (Commercial Burg), UL1023 (Residential Burg), UL294 (Access Control) etc that have the same basic requirements for Power Limitation as the fire alarm standards. You may also want to refer to Table 11 and 11 A and paragraph 725 of the NEC. For Fire Alarm applications also refer to paragraph 760 of the NEC as well as NFPA 72.
PTC's are specified in those standards because they provide the appropriate level of safety for these applications. Will you still see an occasional fuse in a FACP, Burg Panel or Access Control Panel? Sure but not protecting any circuit leaving the panel if its UL Listed. Exception would be if the circuit is run in conduit (treated as Class 1) or as a supplemental protection device (i.e. not relied upon for safety) in an inherently limited circuit. That is why you will only see a few power distribution devices with fuses.
Your saying the ELK Power Distribution devices are not UL Listed while correct does not mean that they did not design them to meet the UL Standards and the NEC by using PTC's. Elk is a responsible mfg making quality products.
By implying that a fuse would be better than a PTC in a Fire or Burg Power Distribution device could lead someone to use a fuse in place of a PTC and potentially not meet the NFPA or NEC requirements and possibly not properly protect the circuit.
As you are a very experienced professional installer I am sure you understand the liability of someone misinterpreting your statements etc. I suggest you always refer someone to the NFPA and the NEC and where applicable the UL Standards etc so that they can determine the correct protective device etc for the specific application.
As far as a PTC causing an overvoltage condition well they are overcurrent protective devices not over voltage protective devices that are required to act within 5 seconds compared to 60 seconds for fuses (refer to NEC tables 11 and 11A). Neither a fuse or a PTC will protect against over voltage (although enough voltage would cause anything to open). What you may be confusing them with are MOV's or Tranzorbs that protect against transients. Both PTC's (for current) and MOV's/Transzorbs/Sparkgaps etc (for transients) are used together in all of the applications noted above.
Will you find some cheap products from China etc that use fuses instead of PTC's for these applications? Yes I see them myself. That does not mean they meet our National Codes or UL Standards.
Can a PTC nuisance trip more easily than a fuse? Yes absolutely if the PTC is not properly rated for the application since they are designed to act faster than a fuse.
Again please be careful as what you state as facts and maybe consider referring people to the appropriate code or standard so they can verify their specific applications requirements.
Your information often has the potential to mislead people. Your statement that fuses are better than PTC in the application appears incorrect.
Now you are saying you agree PTC's are required for Fire Alarm applications but not in Security or Access Control etc. Well then you need to refer to UL1610 (Commercial Burg), UL1023 (Residential Burg), UL294 (Access Control) etc that have the same basic requirements for Power Limitation as the fire alarm standards. You may also want to refer to Table 11 and 11 A and paragraph 725 of the NEC. For Fire Alarm applications also refer to paragraph 760 of the NEC as well as NFPA 72.
PTC's are specified in those standards because they provide the appropriate level of safety for these applications. Will you still see an occasional fuse in a FACP, Burg Panel or Access Control Panel? Sure but not protecting any circuit leaving the panel if its UL Listed. Exception would be if the circuit is run in conduit (treated as Class 1) or as a supplemental protection device (i.e. not relied upon for safety) in an inherently limited circuit. That is why you will only see a few power distribution devices with fuses.
Your saying the ELK Power Distribution devices are not UL Listed while correct does not mean that they did not design them to meet the UL Standards and the NEC by using PTC's. Elk is a responsible mfg making quality products.
By implying that a fuse would be better than a PTC in a Fire or Burg Power Distribution device could lead someone to use a fuse in place of a PTC and potentially not meet the NFPA or NEC requirements and possibly not properly protect the circuit.
As you are a very experienced professional installer I am sure you understand the liability of someone misinterpreting your statements etc. I suggest you always refer someone to the NFPA and the NEC and where applicable the UL Standards etc so that they can determine the correct protective device etc for the specific application.
As far as a PTC causing an overvoltage condition well they are overcurrent protective devices not over voltage protective devices that are required to act within 5 seconds compared to 60 seconds for fuses (refer to NEC tables 11 and 11A). Neither a fuse or a PTC will protect against over voltage (although enough voltage would cause anything to open). What you may be confusing them with are MOV's or Tranzorbs that protect against transients. Both PTC's (for current) and MOV's/Transzorbs/Sparkgaps etc (for transients) are used together in all of the applications noted above.
Will you find some cheap products from China etc that use fuses instead of PTC's for these applications? Yes I see them myself. That does not mean they meet our National Codes or UL Standards.
Can a PTC nuisance trip more easily than a fuse? Yes absolutely if the PTC is not properly rated for the application since they are designed to act faster than a fuse.
Again please be careful as what you state as facts and maybe consider referring people to the appropriate code or standard so they can verify their specific applications requirements.
