sparky 134
Senior Member
- Location
- Joliet, IL
I'm pulling my hair out over this one. Customer is a golf course with an irrigation control cabinet set in the middle of the course. POCO transformer is located next to the cabinet and provides a 480volt 100amp 3phase Bphase grounded service. Power enters the meter on the back of the cabinet, then to a 3R disconnect, then nipples into the control cabinet which was manufactured years ago by a vendor. Power enters a disconnect switch, load side of switch feeds a distribution block which is tapped to feed three 100amp 600volt fuses and tapped to feed two 15amp 600volt fuses. The 100amp fuses feed a motor starter which in turn powers an irrigation pump. My problem is with the 15amp fuses.
The two 15amp fuses feed a 480volt to 120/240volt dry type transformer which is located outside the irrigation control cabinet but within the overall cabinet. Let me explain, there is a large 5'x5' 3R cabinet and inside this cabinet is the irrigation control panel, transformer and other miscellaneous equipment . There is a sealtite whip from the irrigation control panel to the transformer and it contains both the primary and secondary conductors. The secondary conductors terminate to two 30amp 250volt fuses and these feed a small Square D QO load center.
The 15amp 600volt primary fuses keep blowing intermittently. The load on them is only 2.5amps. The load on the secondary fuses is only 5amps. This problem first surfaced two years ago and I replaced the transformer and surge protection device and the problem went away. Now it's back. I thought maybe one of the branch circuits which feed various equipment was shorting so I went ahead and installed small 5amp fuses on each of the branch circuits hoping one of them would blow and give me a clue. No such luck, none of them blew but the 15amp fuses did.
The transformer is tapped into the A and C phases of the incoming power. I'm at a loss as to my next step. I've contacted the POCO and requested they install a PQ meter on the service to see if maybe there's an intermittent spike coming in and blowing the fuses. The fuses are a current limiting time delay style.
Any ideas ?
The two 15amp fuses feed a 480volt to 120/240volt dry type transformer which is located outside the irrigation control cabinet but within the overall cabinet. Let me explain, there is a large 5'x5' 3R cabinet and inside this cabinet is the irrigation control panel, transformer and other miscellaneous equipment . There is a sealtite whip from the irrigation control panel to the transformer and it contains both the primary and secondary conductors. The secondary conductors terminate to two 30amp 250volt fuses and these feed a small Square D QO load center.
The 15amp 600volt primary fuses keep blowing intermittently. The load on them is only 2.5amps. The load on the secondary fuses is only 5amps. This problem first surfaced two years ago and I replaced the transformer and surge protection device and the problem went away. Now it's back. I thought maybe one of the branch circuits which feed various equipment was shorting so I went ahead and installed small 5amp fuses on each of the branch circuits hoping one of them would blow and give me a clue. No such luck, none of them blew but the 15amp fuses did.
The transformer is tapped into the A and C phases of the incoming power. I'm at a loss as to my next step. I've contacted the POCO and requested they install a PQ meter on the service to see if maybe there's an intermittent spike coming in and blowing the fuses. The fuses are a current limiting time delay style.
Any ideas ?