So NFPA says that the mere presence of a flammable does not necessitate a hazardous area classification. So no one would question the lab chemist pouring acetone from a one liter beaker into a test tube on a lab bench, insisting that necessitates a hazardous area classification. At least I...
Got a G&W SF6 4-way switchgear 25KV. Think a CT inside the tank went bad. Unit is 20 years old but in excellent condition. Do you know of any shop that is doing quality repair of SF6 gear. I'm on the East Coast but could ship it anywhere in US. Any leads appreciated.
TEFC motors in a Class 1 Division 2 locations is permitted per NEC providing no arcing contacts NEC 501.125B4.
But TEFC motors don't normally come with T codes on the label. If a Div2 area is say T3, can you use a generic TEFC motor without thermostats (without surface heaters or arcing...
Showing my age, but, years ago motor manufacturers would make Class 1 EX motors, and Class 1 and 2 EX motors. Motors that were exclusively Class 1 often didn't have internal thermostats and would have a T code of T2B (or T2C). Today, most manufacturers are limiting inventory and only selling...
Few questions regards Hazardous area classification.
I understand the need for T code limits in Class II area as dust have a much lower auto ignition temperature than gases.
But how are T codes assigned to Class I in Groups A,B,C,D. I know you would look up the auto ignition temperatures of...
On a solidly grounded wye medium voltage distribution, say switchgear to switchgear, using 100 percent foil shielded 105C EPR cable, is is required to run an Equipment Grounded Conductor. If it is, can the EGC be bare or 600V insulated. There is a CT per phase conductor and zero sequence CT.
250.194 ... a substation with exposed electrical conductors and equipment.
I'm really confused with regards to whether or not it is necessary to ground the metalic fence around deadfront switchgear. In an industrial setting (not utility) where you have an outdoor substation, say with medium...
I have a series string of 92 each Alcad MC14P NiCad batteries. Need to set up the charger and have some questions.
Alcad recommends 1.40V/c for these batteries but doesn't provide an Equalization voltage or duration, any recommendations?
Also, what would you set for Low Voltage warning, and...
Need some help with Siemens RLE Low voltage switchgear trip programmer.
Feed to the gear is via a 12.4KV - 480/277 2000KVA Xfrm. Three phase conductors and 50% neutral are carried to the switchgear. The switchgear has a neutral bus to land the neutral conductors. This bus also has a 2000:5...
Need to add 200KVAR of capacitors to my 2000KVA 12.4KV-480/277 Padmount transformer. Trying to add small KVAR units to each individual motor just isn't practical as MCC space is almost non-existent, and motors are all small, like 30hp. Thinking the easiest, cheapest approach is to add two...
Studying the MVA method for its simplicity. Understand its limitations, but for quick calc to determine min AIC of equipment seems like a good approach.
I can follow and comprehend the method for 3 phase faults. But I am having some difficulty with phase to phase, and phase to ground.
Phase...
Replacing existing MV trip relays with new Multilin 350's.
I have a lot of identical padmount xfrms being fed and would like some recommendations on trip curves.
Xfrms: 1500 KVA padmounts, 4160 delta to 480/277 Y, 3ph, 5.0% Imp.
Feeders: 1x 500 MCM CU 15KV, lengths between 300 and 700 feet...
Because of the age and make of my transformers I can no longer get information from the manufacturer. I'm installing some new protective relays on the feeders to my building transformers. I'd like to set Inst at 2x no load inrush current. But I can't find what the in rush is. Is there a way...
One of the relay on our main circuit breaker is a GE#12ICR53A1A, Ansi#47, Phase Sequence and UnderVoltage Relay.
I've read the manual but still not sure of how it works. This is from the manual:
The Type ICR relays are used to protect AC machines from undervoltage and when
starting from open...
Can anyone lay out a method to calculate the equivalent %z of two single phase transformers wired as autotransformers in open delta when the %Z impedance as an isolation transformer is given on the nameplate. I need to calculate fault current on the load side of the transformers.
I have an application where I need to boost 480V 3ph to 600V 3ph. Total KVA required at 600V is 400KVA, or 385A @600V.
I've seen charts on manufacturer's websites to select the correct size KVA of each of the two single phase 480-120V transformers I will need to make an open delta connection...
I have two of the old Wheelock DV-200. Great product and wish it was still available. It hasn't been made in 8 years so there is no factory support. So I'm posting here to see if anyone else solved this issue.
Channel 4 will program and the display will read ‘Message Playing’ but there is...
We are doing a Group replacement of all the sprinkler heads in our boiler room and machine room. The original design from the 1960's has 286F heads in both spaces. Check the 2010 NFPA code in Chapter 13, Table 6.2.5.1 says that ceiling temps up to 150F should be 'Intermediate' with max...
I am not sure what this section is saying about interlacing messages. If the Risk Analysis determines that the safest course of action is some prescribed method of interlacing messages, ie, three plays a priority 1 message followed by one play of a priority 2 and one play of a priority 3...
I am managing the relamp program for some 400 hazardous EX fixtures using 250 watt metal halide bulbs. These are the original type, not the pulse start of the newer technology.
I've tried GE, Sylvania, Phillips, Ushio, Venture - they all dissappointed. Bulbs are on all year, and we relamp...
