What is the common voltage used in warehouse?

Q. In the United States, we used 110 Voltage as common voltage, while in some warehouses, surprisingly, they used 220 V. If anyone here is electrician, can you tell me if a light fixture used to 300 Watts to 400 watts of light, suddenly a 150 watts of light installed in, would it cause it instability or burn - out easily?

A. Most warehouses would nost likely be feed by either a 120V/208V three phase or 277V/480V three phase service. The most common voltage for most 300W or 400W commercial lighting is either 120V or 277V, single phase (utilizing only a single 'leg' or phase of the service). Most of these luminaire have "multi-tap" type ballast that essentially make them "universal" voltage luminaire. However, each ballast will be rated for a specific type of HID (High Intensity Discharge) lamp type (such as high pressure sodium or metal halide, for examples) at a specific wattage. Even though they may share a common sized base (most of them are "medium based") the lamps are NOT interchangeable. To down-rate these luminaire to a smaller wattage lamp, would require new ballast, capacitors, and ignitor rebuild kits to be installed inside their housing. Let me know if you know what the specific lamp type and luminaire (fixture) type you have and I'll see if there are any further details that I can help you with.

-Mitch Tolbert

Training as an electrician?

Q. Hi I am starting college to study my C&G 2330 Level 2 Electrotechnical Technology which lasts for 1 year and afterwards I will be wanting to do my C&G 2330 Level 3 Electrotechnical Technology was just wondering after these 2 courses will I be a fully approved electrician?? thanks guys

The college says the career opprtunities is an approved electrician but there is normaly something else I have to complete.

A. Well, I think the college's description of an "approved electrician" may be a bit mis-leading. Most states require licensing of some sort. Check your state or local licensing requirements to see what specifics are required. You MAY be living in a city that allows your college to offer some sort of locally "approved" apprenticeship training, but I seriously doubt that that is the case here. I would also ask someone in your college, who it is exactly, what person or organization, that offers this so-called approval. Next, contact your state or local licensing department and verify directly with them - whether or not it truly is an approved course. Also, be sure to ask how many hours will be credited towards your electrical license from your college courses. A lot of states only allow up to 50% of classroom hour credits to be applied towards the fulfillment of licensing requirements.

-Mitch Tolbert

How does an electrician size up what supply cable to connect on a new machine installation?

A. Sizing feeders or branch circuit conductors is not a simple calculation. When a new piece of equipment is selected for installation, a number of factors must be considered. Here are the most important items to be addressed when calculating your conductors:

1) Is the equipment specifically classified as a continuous load? Some equipment is directly labeled as continuous duty by the National Electrical Code. This means that it will stay in operation, or can be anticipated to, for periods of 3 hours or longer. An example is a typical water heater. Article 422.13 classifies them as a continuous load. (NEC). Continuous loads must be calculated and rated at 125% of their stated ampacity minimums.

2) Is the installation classified as a dry, damp, or wet location? Maximum ampacity levels are impacted in different environmental locations. Wet locations typically cause a significant de-rating of your conductors. Examples of wet locations are, but are not limited to, any underground (buried) conduits, in concrete slabs, or where outdoors and exposed to direct weather.

3) Ambient temperature considerations. Ambient temperature is the temperature of the air that surrounds the equipment. These temperature differences cause direct de-ratings of the ampacity of conductors. Article 310.15 and Table 310.16 help us select amperages for given wire sizes, and contain multipliers for ambient temperatures that are above 86 degrees F. Non-air conditioned factory or manufacturing facilities, especially in the South, can, in extreme circumstances, restrict normal wire ampacities by as much as TWO THIRDS or more of their standard ratings.

4) The number of current carrying conductors (hots and sometime neutrals can count), all in the same conduit, also restrict wire ampacity. See Article 310.15(B)(2)(a).

5) Specific code sections for your particular piece of equipment may increase or decrease your allowable ampacities.

6) Voltage drop considerations/calculations can significantly increase a wire size.

7) Copper heat losses vs the economical costs of larger wire sizes can also be considered. Larger amperage loads shed heat due to wire resistance. The smaller the wire, the larger the loses are. Overtime, your utility costs can be significantly more expensive due to these losses than what a single larger wire size would initially cost.

As you can see, it's really not just a simple answer. If you are looking for some examples, see our web site, or email us for questions. If you have a specific question about a particular piece of equipment, email the specifics to us and I will calculate what I think your conductor size should be. For more information, see my blogs under "Considerations for Branch Circuit Wire Sizing."

-Mitch Tolbert