brockbone
Member
- Location
- Glendale, CA
________________________________________
I come to this forum when after researching thru my Uglys, NEC and fellow electricians I can't come up with an answer. Telling me to 'look it up in the book' kind of defeats the whole purpose of this forum. Please help.
I need to replace 3 fuses in a disconnect adjacent to the switchgear behind a grocery store.
The circuit is 3 phase 208V and the disconnect feeds a large Evaporative Cooler /Condenser on the roof.
The ?spec? plate of the control cabinet on the roof is obliterated.
The disconnect feeders that connect to the roof cabinet are 1/0.
The cabinet feeds a:
20 HP Baldor Super E,
200V useable at 208V,
55.2 AMPS,
3PH,
NEMA NOM. EFF 93%,
40 degrees centigrade
....And a 3HP, 3PH, 208V, 8AMP pump motor
From the "prints" in the MCC room I have:
MCA. 395
MOPD 502
FLA 368.1
What size/type fuses should I install in the disconnect?
________________________________________
The situation was that I was called at the request of the refrigeration tech to deal with a blown fuse on B phase.
By the time I got there he had replaced a 125 Fast-Acting fuse with a 150 timed delay.
He claims when he opened the disconnect A PH had a 150 Timed delay and C & D had the 125s.
He then proceeded to replace the last 150 with a 125.
The company that manufactured the equipment is no longer in business, and it is a variable speed motor, the 20HP one, and is feed on what looks like #4?s the pump on 12?s.
With a clamp on meter I get 18 to 50AMPS at the disconnect and on just the feed legs from the cabinet to the motor I get 10 to 40AMPS while under load
Cow
Senior Member Join Date: Dec 2006
Location: Eastern Oregon
Posts: 1,327 _______________________________________
So you have a 200 amp fused disconnect feeding 23 HP of total motor load?
It sounds like you need fuse reducers and a megger to me. Art. 430 explains how to size motor feeder overcurrent protection. Art. 440 for HVAC equipment.
This equipment, in this configuration, has been operating for many years and since I am not an electrical engineer I don?t want to redesign it.
And since the feeder wires from the disconnect to the roof are over 80' I wont be re-pulling them.
And since that wire is 1/0 I think 200's are out of the question, right?
I come to this forum when after researching thru my Uglys, NEC and fellow electricians I can't come up with an answer. Telling me to 'look it up in the book' kind of defeats the whole purpose of this forum. Please help.
I need to replace 3 fuses in a disconnect adjacent to the switchgear behind a grocery store.
The circuit is 3 phase 208V and the disconnect feeds a large Evaporative Cooler /Condenser on the roof.
The ?spec? plate of the control cabinet on the roof is obliterated.
The disconnect feeders that connect to the roof cabinet are 1/0.
The cabinet feeds a:
20 HP Baldor Super E,
200V useable at 208V,
55.2 AMPS,
3PH,
NEMA NOM. EFF 93%,
40 degrees centigrade
....And a 3HP, 3PH, 208V, 8AMP pump motor
From the "prints" in the MCC room I have:
MCA. 395
MOPD 502
FLA 368.1
What size/type fuses should I install in the disconnect?
________________________________________
The situation was that I was called at the request of the refrigeration tech to deal with a blown fuse on B phase.
By the time I got there he had replaced a 125 Fast-Acting fuse with a 150 timed delay.
He claims when he opened the disconnect A PH had a 150 Timed delay and C & D had the 125s.
He then proceeded to replace the last 150 with a 125.
The company that manufactured the equipment is no longer in business, and it is a variable speed motor, the 20HP one, and is feed on what looks like #4?s the pump on 12?s.
With a clamp on meter I get 18 to 50AMPS at the disconnect and on just the feed legs from the cabinet to the motor I get 10 to 40AMPS while under load
Cow
Senior Member Join Date: Dec 2006
Location: Eastern Oregon
Posts: 1,327 _______________________________________
So you have a 200 amp fused disconnect feeding 23 HP of total motor load?
It sounds like you need fuse reducers and a megger to me. Art. 430 explains how to size motor feeder overcurrent protection. Art. 440 for HVAC equipment.
This equipment, in this configuration, has been operating for many years and since I am not an electrical engineer I don?t want to redesign it.
And since the feeder wires from the disconnect to the roof are over 80' I wont be re-pulling them.
And since that wire is 1/0 I think 200's are out of the question, right?
