How is the setting established for a gfi on main switchgear. I know it cannot be over 1200 amps and 1 second. What criteria is used to determine the exact setting.
Thanks
I am having to change incandescent lamps out in our lobby about once week. I've considered replacing them with flourescent bulbs but don't want to remove my flags until I understand what is going on and why these bulbs are prematurly burning out.These are bulbs rated at 120 volts single phase...
Why is is on a phycrometric chart that the words "dry air" are used when the air could contain moisture or humidity?
Does this mean that anything not at saturation is dry regardless of moisture content.
Thanks
A rule of thumb in air conditioning work is that 400 cfm of air is equal to 1 ton. If 400 cfm of air and a delta T of 20 degrees is achieved, this is equal to only 400X20X1.08=8640 btu/h.. This is not 12000 btu's. What am I missing here besides a college education.
Could someone please explain how a hi effieciency dx split system is designed? Does a 4 ton 10 seer remove the same amount of latent and sensible as a 4 ton 13 seer? Is the volume of air the same for both units (2000 cfm).If I am considering replaceing my 4 ton unit with a higher efficiency unit...
Does anyone have a good way to control/stage 3-600 ton cooling towers?
Should a control sequence be created using wet bulb to stage these 3 towers. The fans do have vfd's.Thanks
Does anyone know why chiller copper tubes are able to be pressed into steel tube sheets. Doesn't this create electrolisys? I know plumbers and hvac mechanics are taught to always use a dielectric fitting type connection whenever this combination is formed. Why do chillers not have to conform to...
How can I calculate the heat load of a computer room. the power consumtion is 210,000 watts of variuos types of servers and mainframe. The room is 80' by 65' by 8'. the room temp is maintained @ 70 degrees. How would I calculate the tempature rise of this room if all the lieberts units were...
How can I calculate the heat load of a computer room. the power consumtion is 210,000 watts of variuos types of servers and mainframe. The room is 80' by 65' by 8'. the room temp is maintained @ 70 degrees. How would I calculate the tempature rise of this room if all the lieberts units were...
We have a size 5 starter operatinga 225 h.p. motor. The starter has c.t.'s (300:5)installed in the back of it to monitor the current going to the motor. The secondary makes up to heaters installed in the front of the starter. The motor normally runs anywhere from 40 amps to 135 amps throughout...
What does it mean for a transformer to have a rating of 1500kva @ 55 deg c and another rating @ 1680Kva at 65 deg c.
I would have thought the cooler temp. would have the higher rating.
Thanks
Could anyone tell me what the rated fault current would be with six 250Kva single phase networked transformers each with a 2.7% impedence. The secondary voltage is 120/208.
Thanks
What would be the ideal impedance for large commercial transformers (750 to 2000 kva). Is there any advantage to having lower impedance tranformers (2%)vs. (5%) transformers. I know the disadvanteges for the lower impedance tranformers are that the AIR rating of switchgear has to withstand the...
