pedorrero79
Member
Hello all,
I need a little bit of help clarifying my thought process on this. When sizing the fuses for a fused disconnect, should the fuse(s) be the same size as the breaker protecting the branch circuit?
For instance, my ME is installing humidifiers that have an FLA of 61.3A and the OCP, per the manufacturer, is 80A. My understanding is that these are considered a continuous load. However, we have to provide a fused disconnect at the unit. Normally, when we provide disconnects, the disconnect is sized for 115% of the FLA, correct? If so, that leads me to believe that we'd have a 100A disconnect, but what size fuses should be installed? I'm thinking 80A, to match the OCP on the branch circuit - any smaller, and we'd run the risk of nuisance trips, any larger, and it won't effectively protect the circuit. Am I right in thinking this?
I'll be honest, I have nothing concrete to back up my thought process on this, so if anyone here can point me to a code reference that will lead me in the right direction, I'd appreciate that. BTW, I'm in CT where we're still on the 2005 NEC.
Thanks in advance,
Andy
I need a little bit of help clarifying my thought process on this. When sizing the fuses for a fused disconnect, should the fuse(s) be the same size as the breaker protecting the branch circuit?
For instance, my ME is installing humidifiers that have an FLA of 61.3A and the OCP, per the manufacturer, is 80A. My understanding is that these are considered a continuous load. However, we have to provide a fused disconnect at the unit. Normally, when we provide disconnects, the disconnect is sized for 115% of the FLA, correct? If so, that leads me to believe that we'd have a 100A disconnect, but what size fuses should be installed? I'm thinking 80A, to match the OCP on the branch circuit - any smaller, and we'd run the risk of nuisance trips, any larger, and it won't effectively protect the circuit. Am I right in thinking this?
I'll be honest, I have nothing concrete to back up my thought process on this, so if anyone here can point me to a code reference that will lead me in the right direction, I'd appreciate that. BTW, I'm in CT where we're still on the 2005 NEC.
Thanks in advance,
Andy