Hello,
Which fuse to select, RK1 or RK5?
I want to select 15 amp fuse, but whats the difference between Rk1 and Rk2?
15amps is the min circuit amps for a/c unit. RLA is 49.50amps. 480V three phase.
My wired is sized for 15amps
The application recommended for these fuses [RK1] is exactly the same as for the Edison ECNR/ECSR fuses [RK5] except for the advantages of greater current limitation.
The Edison LENRK/LESRK fuses have up to 40% more current limitation and up to 350% more Amps-Squared-Second (I2t) limitation under fault conditions than Edison ECNR/ECSR fuses to reduce potential for damage.
In addition, LENRK/LESRK fuses allow better selectivity for electrical power system designers and better short circuit protection for breakers having inadequate interrupting ratings.
ECNR/ECSR and LENRK/LESRK fuse lines are physically interchangeable (and electrically interchangeable per U.L. equipment listing conditions)....
It appears (see http://www.omega.com/Auto/pdf/ecnr_ecsr_lenrk_lesrk.pdf, quoted below) that the only difference between the two types is that the RK1 limits the fault current to a lower value, which could reduce calculated Arc Flash incident energy and help avoid over stressing other breakers which are in series. Unless you have some really exceptional conditions, I doubt it will matter for you.
Hello,
Which fuse to select, RK1 or RK5?
I want to select 15 amp fuse, but whats the difference between Rk1 and Rk2?
15amps is the min circuit amps for a/c unit. RLA is 49.50amps. 480V three phase.
My wired is sized for 15amps
3 PH HVACR machines if at all possible should never be fused but protected with HACR type breakers.
If you arrive at a fault that takes out one fuse but the compressor is not compromised, it will then in most cases be very quickly killed by the resulting single phase condition, where as a circuit breaker will " often " allow the attending Tech to correct the lower level fault before the most expensive part of the machine is destroyed. I have seen this countless times and the commercial trend in the state I came from was definitely away from using fused disconnects on that type of gear.
In the real world, single phasing is pretty rare, so I just do not worry all that much about it unless someone wants to pay extra.
In the real world, single phasing is pretty rare,
I agree with your post other than what I quoted.
We respond to a large number of single phasing events each year. Most common is the utility dropping a phase during a storm. Often this will last for many hours.
At this point most of our customers have phase loss protection on larger 3 phase equipment but we almost always end up replacing at least a few contactor coils that burn out due to under voltage resulting from these lost phase events.
how does single phasing result in under voltage that burns out contactor coils???
Back feeds through other equipment.
Back feeds through other equipment.
How does it burn out the COIL?
How does it burn out the COIL?
In a mechanically latching relay, the contact assembly may not move to the position where the coil circuit is interrupted.
Also the current in a continuously energized coil will vary with the armature position. (The inductance changes because the magnetic circuit changes.)
Hello,
15amps is the min circuit amps for a/c unit. RLA is 49.50amps. 480V three phase.
My wired is sized for 15amps
If the RLA is 49.50 why 15 amp fuses and wire?????