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Have you ever wondered why some power ratings are expressed in WATTS, some in AMPS, some in VOLTS, and some in KVA? For many in the hosting business this can be a very confusing topic. Face it, professionals in the content business are probably not electrical engineers, and most electrical engineers know nothing about the creation and delivery of content.

This article will explain in simple terms the difference between the major power ratings, and describe when each should be used in your network architecture planning.

According to APC, the main difference between watts and volt amps is the watt rating determines the actual draw of power from a power source and the heat generated from equipment. The VA rating is used for sizing equipment such as circuit breakers, wiring, and UPS. The VA rating is normally equal to or higher than the watt rating, as it includes the “power factor” in its calculation.

Power Factors

The Power Factor is a calculation used to account for the difference in power supplies used to convert AC power into DC for use in electrical appliances and computer equipment. There are two types of power supplies – the capacitor input supply and the power factor corrected supply.

Power factor corrected supplies are used in most high end computing and switching equipment, and have a ratio of 1VA:1W – allowing a very simple calculation for scaling electrical equipment and UPS. Thus, in theory, if your power factor is 1:1, and your UPS is an 80KVA UPS, then you would be able to load the UPS to 100% of its rating.

Older electrical equipment, as well as most lower end computers and video equipment use capacitor input power supplies and have a power factor anywhere from.55 to.75 times the VA rating.

Typically when scaling a UPS for use in a data center you will use a 60% load factor on the UPS. If you overload a UPS it is almost certain to fail during a power outage, as the draw on the batteries will exceed the capacity of the UPS. Most new UPSs will automatically go into battery bypass when an overload condition occurs. The 60% load factor accounts for the high probability that most of the equipment drawing power through the UPS will be of a category that has a power factor of between.55 and.75.

Example 1

You have a 10KVA UPS. Your data center has racks of low end self-assembled computers with a total estimated rating of 9000 watts. Your UPS will most like fail, as the power factor is probably around.70. You would need at least 12.85KVA to adequately backup the data center.

Example 2

You have a 10KVA UPS. Your data center has racks of low end self-assembled computers with a total estimated rating of 6000 watts. Your UPS will be able to handle the load, as the power factor corrected rating will require approximately 8.5KVA of UPS.

Some modern UPSs will actually tell you the average power factor and real time load capacity of the UPS.

Some Useful Conversion Factors

o Refrigeration

- 1 watt =.86 kcal/h

- 1 watt = 3.412 Btu/h

- 1 watt = 2.843 x 10-4 tons

- 1 ton = 200 Btu/min

- 1 ton = 12,000 Btu/h

- 1 ton = 3,517.2 W

o kVA Conversions

Three phase

kVA = V

There are a lot of lovers of flora and fauna who go in for the creation of ponds. Those ponds that are created out of concrete also need to be given a final coat of Concrete Pond Sealer. This protects the concrete pond from the perils of snowing as well as thawing. Make sure that when you are getting your pond sealed with Concrete Pond Sealer you get at least two or three coats, whatever is recommended for the Concrete Pond Sealer that you happen to be using.

It is possible to get these Concrete Pond Sealers in clear as well as colored finishes. The Concrete Pond Sealer helps in giving an added protection against lime to the pond. The use of the sealer is going to be determined by the porousness of the concrete. It is not advisable to use something like oil-based sealer for the pond, in case you intend to have life in the pond. It is actually a good idea to use a solvent-free Concrete Pond Sealer, as this would be an absolutely safe environment so the plants and animals in your pond will not be harmed in anyway.

A case in point would be something like the Koi-Kote Concrete Pond Sealer. This sealer wouldn?t harm any of the fishes. It does not emit any smells or fumes, and it has a seamless lining which ensures that bacteria are unable to grow in such cases.

While applying this Concrete Pond Sealer, make sure that the sand particles are removed, as the smoother the surface the better the quality of the finish that arises from it. There are also certain pond sealers that use the moisture present in the air to harden, and also give you the option of putting it onto slightly damp substrates. However, you should ensure that the substrate is sufficiently dry to be porous. Thus, use these Concrete Pond Sealers to good affect, and resolve your pond-lining problems.

When looking to build a guitar yourself, or to hire a luthier to build one for you, you’ll discover that there are many more options that you may originally have thought which go into the creation of a custom acoustic guitar. Wood selection, shape, size, binding, purfling, and many other items are part of the decision and design process, and many of these have a profound impact on the sound and tone of the instrument, not to mention the look and feel.

Let’s define and examine three of the major choices you’ll have when building a custom acoustic guitar.

Acoustic Guitar Tonewood

The term “tonewood” refers to any wood that is used in the making of a musical instrument. Different woods react differently to the guitar construction process, but just as importantly, they react differently to sound, so the selection of tonewood will affect the sound of the instrument.

For the guitar body, common tonewoods are Alder, Basswood, Swamp Ash, Walnut, Mahogany, Koa, Maple, and Spruce. They will each have different tones based on the hardness of the wood, the consistency of the grain, and how porous the wood is, all of which affect the resonance and sustainability of a sound as it reverberates in and around the guitar. For example, a soft wood with tight grains such as Basswood will produce a sound where the highest frequencies are dampened, whereas a hard Maple will produce sharp high notes that are bright and clean.

Guitar Shape

Acoustic guitars come in many shapes, with the “dreadnought” shape being common. This shape of guitar, popularized by the C.F. Martin company in the 1930′s, was named after a battleship which supposedly had a similar shape. The dreadnought shape makes for a large-bodied guitar, where sound will be bolder and have more “boom” than you’d find in a smaller guitar.

Other guitar shapes are parlor guitars, which are smaller and curvier, and “orchestra model” guitars, which are more used by fingerstyle players of either classical or bluegrass music.

Fretboard

There is also a tonewood choice involved in the fretboard, because the fretboard doesn’t have to be made of the same wood as the body or neck of the guitar. Many players like a rosewood fretboard, which has a little bit of “give” to it, and is naturally oily. Rosewood produces a sound that is cleaner and more pure than Maple, for example, because stray overtones may get absorbed by the oily surface of the wood. Ebony is another fretboard choice, and since it is more brittle, it provides a sound that is more crisp and percussive.

These are just some of the many options you’ll find when you start designing a custom guitar. The best advice is to learn about how each wood choice will combine with others, and combine with the size and shape of the guitar, to create the effect you are looking for. Some folks want a small guitar that still produces good low tones, so they will want to take careful consideration when selecting wood and materials. Talk to an expert luthier to learn about these options, and don’t work with any guitar builders who do not have experience across multiple types of guitar tonewood. Guitar making requires a variety of experience, and it’s not worth hiring someone who only uses the same materials on each instrument.