I am looking to replace several recessed dimming incandescent light fixtures. However, these were installed over 20 years ago and there is no equipment grounding conductor in the lighting branch circuits. Only a hot and neutral conductor.
The new fixtures will be recessed dimming CFL and the...
I was wondering if one electrical feeder can be used to serve two rooftop condensing units (identical electrical ratings) provided the feeder and overcurrent protection devices for each are sized per Article 440.
Is this permitted by NEC as it is for multiple motors on a single feeder?
Thanks!
I have estimated a connected load of about 4,000 KVA for a chiller plant (serving several other buildings) design. I simply used the voltage (460V) and amperage of all the equipment (chillers, cooling towers, and pumps) and calculated the total KVA load. Also included 10 KVA for lights and...
I am working on a lighting design involving a relay panel. The fixtures are located 150'-300' away from the relay panel and the source panel. The relay panel is fed from three (3) 20A,1P breakers from a 120/208V,3ph,4w panelboard. There are 6 relays coming out of the relay panel. I am having...
I am working on a design for a new pump room addition to an existing building. The pump room shall have a fire pump (7.5HP,208V,3ph), jockey pump (1.5HP,208V,3ph), and other equipment (unit heater, lighting, fan, and a motorized damper which have a combined load of approx. 15A). I am having...
I am preparing for an electrical inspection/survey of an existing commercial office building? The existing electrical system is to be inspected for code compliance, deficiencies, safety hazards, etc.
Is there a good book or reference out there that anyone recommends which covers how to...
I am trying to figure out the Amps rating of a 240V panel and the wire size feeding it. It is being fed from a 100A, 120/208V, 3%%C panel through two 2kva, single phase transformers in 1" conduit. The supply breaker is 90A/3P. I assume the 240V panel is single phase and three wire. It...
I am having trouble understanding a situation I saw in field with a 240V Panelboard. A 100A,120/208v. 3phase panel has a 90A/3P circuit breaker labeled "240V panel transformer". A 1" conduit from the bottom of this panel feeds a Square D load center panel through two-2kva, single phase ACME...
I was wondering if code allows more than one wire to connect to a single pole circuit breaker? I was told that there is a circuit breaker available that is rated for 2 wires.
A 100A 120/208v panelboard is being replaced and many of the circuits are being backfed into the new panel. The...
I know that there are calculations to determine the minimum conduit size required for conductors, but is there also a maximum size that can be used? I am replacing a handful of 208V,3 phase rooftop units. The new units have significantly less load than the existing. Therefore lower rated...
It is my understanding that overcurrent protection of a panelboard can be done inside of the panelboard itself(with a main circuit breaker) or a panel with main lugs only will have a disconnecting means outside of the panel (circuit breaker in the panel serving it) or a disconnect switch.
I...
I have an existing air handling unit with a 30 HP/460V/3 phase motor with a wall mounted motor starter. A variable frequency drive is to be installed on this air handler. I am not sure what needs to be changed do to this installation. Will the wire sizes and overcurrent protection need to be...
I have a 225A, 120/208V,3ph,4w panel that serves two boilers, two pumps, exhaust fan, receptacles, and other equipment in a boiler room. I want to add a 200A/3P breaker to it to serve a new rooftop unit. Total load is estimated at about 180A for the panel including the RTU. I was told by the...
I am working on an electrical service upgrade at an administration building. The power utility company is scheduled to provide 800A, 120/208V, 3phase service. An 800A MDP is being installed and will feed the other panels in the building. After design development, a server room was added and...
I am currently designing an elevator and machine room for a three story building. The machine room will have a new panel that powers the new elevator and all the necessary lighting and power for the machine room, elevator cab, and elevator pit. I have a 100A/3p disconnect switch for the...
I received an RFI from an electrical contractor regarding problems with an electrical panel. They are having problems terminating the feeder cables for a panel (120/208v,3phase,4wire, with a 225 Main Circuit Breaker). The cables are too large and the panel or the main circuit breaker cannot be...
Hi guys. I have a general questions regarding the sizing of circuit breakers and disconnect switches when given the FLA of a motor. I have read and heard a few different ways to determine what sized breaker and what size disconnect switch to use for equipment based on the motor FLA, so I...
I had a quick question about branch circuit wiring. I have a 277V, single phase motor to power from a 277/480V electrical panel. I just want to make sure that I should use 2 #12 AWG + 1#12 AWG Gnd. in 3/4" in Conduit. I mainly want to know whether it should be 2 or 3 #12 Awg non-ground...
Does anyone know if plugmold (wiremold) is available with gfci receptacles? as well as plugmold suitable for wet locations? I tried contacting a couple of manufacturers of plugmold but did not have much luck.
I am installing a new 50kw emergency generator for an existing office building. I am having trouble sizing the necessary wires for design. Inside the building there is an 80A emergency panel that will be wired to a 200A, 3phase, automatic transfer switch. The building uses 120/208V. The...
