leitmotif
Member
At work have Gardner Denver screw type compressor. Nameplate motor data
Volt 480 current 61 amp.
Motor is Toshibe (?? am at home cannot double check nameplate).
Right on the door is legend wye delta start.
Have six leads 123 456 tied to two relays.
OK so I have wye delta start. No big deal no problem works great.
Many of the questions below will be answered I thing when I put a clamp on ammeter in there and do simultaneous voltage checks. Will do volt to ground instead of phase to phase so I have direct comparison to line current. Then will convert volt reading by 1.73 factor. So in wye I should be drawing approx 57% full line current ie 36 amp. Delta should be about 60 or less depending on load and if unit is unloading. Has panel display of pressure. May be able to get load unload status by getting into programming.
QUESTIONS
1. It appears to me that time in wye is too long - about 10 seconds.
2. Conductor feeding disconnect approx 10' (wire length) away is #8. Wire from disconnect to controller is also 8. Assume wire is THHN or MTW. Wire to motor is 6. Just from the visual comparison of building wire to factory wire this branch circuit is undersized. It is just fine for wye assuming 36 amp estimate from full load amp is correct and not considering higher starting current. In delta and IF motor is pulling full current (clamp on will tell me that) then it is clearly undersized. HOWEVER can the wire be downsized due to unloading?? I assume that the only load would then be just spinning the motor and compressor and estimate it to be 20 amp (again clamp on will confirm).
I am REAL LEERY of this but am also considering "dont fix if aint broke".
3. We leave unit running with no one in bldg over the weekend ie supplying leaks. I am arguing to shut it down - don't like unattended equipment running, waste of power, useless wear and tear. If someone has better estimate than mine of 20 amp to spin motor and compressor unloaded and an estimate of load unload time, I would appreciate it. Clamp on should be the final answer of course.
4. What mistaken assumptions have I made, and what am I forgetting or not thinking of??
Dan Bentler
Volt 480 current 61 amp.
Motor is Toshibe (?? am at home cannot double check nameplate).
Right on the door is legend wye delta start.
Have six leads 123 456 tied to two relays.
OK so I have wye delta start. No big deal no problem works great.
Many of the questions below will be answered I thing when I put a clamp on ammeter in there and do simultaneous voltage checks. Will do volt to ground instead of phase to phase so I have direct comparison to line current. Then will convert volt reading by 1.73 factor. So in wye I should be drawing approx 57% full line current ie 36 amp. Delta should be about 60 or less depending on load and if unit is unloading. Has panel display of pressure. May be able to get load unload status by getting into programming.
QUESTIONS
1. It appears to me that time in wye is too long - about 10 seconds.
2. Conductor feeding disconnect approx 10' (wire length) away is #8. Wire from disconnect to controller is also 8. Assume wire is THHN or MTW. Wire to motor is 6. Just from the visual comparison of building wire to factory wire this branch circuit is undersized. It is just fine for wye assuming 36 amp estimate from full load amp is correct and not considering higher starting current. In delta and IF motor is pulling full current (clamp on will tell me that) then it is clearly undersized. HOWEVER can the wire be downsized due to unloading?? I assume that the only load would then be just spinning the motor and compressor and estimate it to be 20 amp (again clamp on will confirm).
I am REAL LEERY of this but am also considering "dont fix if aint broke".
3. We leave unit running with no one in bldg over the weekend ie supplying leaks. I am arguing to shut it down - don't like unattended equipment running, waste of power, useless wear and tear. If someone has better estimate than mine of 20 amp to spin motor and compressor unloaded and an estimate of load unload time, I would appreciate it. Clamp on should be the final answer of course.
4. What mistaken assumptions have I made, and what am I forgetting or not thinking of??
Dan Bentler