| William H. Magill on 21 Aug 2004 00:27:04 -0000 |
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William H. Magill wrote:
However, the issue has to do with the way your bathroom is wired... Wiring codes have evolved over the years, however, they still allow single circuits to handle both lighting and convenience outlets. [Today, it is recommended that all branch circuits be 20 Amps, but 15 amps for "lighting" circuits are still common.] In older properties, anything built prior to WWII, and in many cases up through the early 1960s, you only have 40 or 60 amp service to the entire house. (100 amp service didn't become "all the rage" until sometime in the 1960s.) Consequently you may discover that you in fact have only one circuit for an entire floor! Undoubtedly, your bathroom is a classic single circuit style -- lighting and convenience outlets on one 15 Amp branch circuit. Consequently, when you power on the hair dryer the other lights on the circuit dim. The dryer is a big "sucker" 1875 watts! ... that's a lot of 75 watt light bulbs. How much for a whole-house surge arrestor?
BTW, I've heard that really all that PECO provides is what your house is supposed to have by code anyway -- "Service Entrance grounding." The stories have implied that something like 90% of homes have inferior at best and usually nonexistent grounding. The kinds of "surges" which PECO's system protects against are "major" ones, like lightning strikes and the like. (Automobiles crashing into power poles...) They are not particularly "fast acting" and I doubt that they use the new "non-burning" protector technology. (Another separate topic.) Imaging the size of a whole-house UPS! I would guess that a whole-house UPS would be highly impractical without an automatic fail-over to a generator. The state of the art today is such that it is simply "very expensive," down from "ridiculously expensive," a few years ago. There are quite a few Solar Powered "co-generating" houses in the Delaware Valley. These houses have full photo-voltaic arrays which provide all, or some, of the household power when the sun is out, feed the excess back into the grid when generating more than the house needs, and draw from the grid at night or whenever the array is not generating sufficient power to meet demand. The economics have improved recently, and there are a number of programs (The DOE's Million Solar Roofs initiative being one) in the Delaware Valley to promote this approach. But even with the grants, you are looking at something like a $25K investment for "whole house power." At current generating costs (something like 8 cents per KWH) the payback time based only on credits from PECO, is something like 40 years. The payback time based on the reduction in your bill to PECO is a more reasonable 15 years. [Note that these numbers are about 2-3 years old now and have changed, but I don't have more current ones.] [ AND if the price of oil stays at $35 a barrel or over, compared to the "historic $27 per barrel, the economics will change even more, and probably very quickly. Already in the past six months as oil prices started to climb, we have seen an increase in oil exploration activity as well as retrofitting of plants to burn coal again. The best Photo Voltaic research is still only capable of getting about 18% efficiency from the "most expensive" arrays. Those that are "commercially viable" are only about 15% efficient. But, again, much of the costs associated with production are amortized against very small production runs. If demand increases and production runs increase, prices will come down quickly -- just look at LCDs as a prime example of how fast the prices dropped and how rapidly the research expanded after Apple started buying 17 inch LCDs in large quantities! Their new 30 inch LCD costs the same thing that the 17 inch LCD cost nominally 5 years ago. But I digress...] A UPS is the same thing. Despite a lot of marketing to the contrary, a REAL UPS includes a duplicate source of power - typically an independent motor-generator system. Look at your PECO bill and it will tell you what your average daily KWH consumption for the billing period was. However, keep in mind that "billing period" includes DAY and NIGHT, or put another way very high usage periods and very low usage periods. Providing power requires that you be aware of the concept of "peak load demand." That is to say -- how much power do you consume when all the lights in the house are on, all the devices in the home entertainment system, the electric range, radios, microwave, washer, dryer, clock radios, etc. That number is how big your batteries and generator need to be. Like the US Strategic Petroleum Reserve which contains a finite amount of oil -- a 15 day supply as I recall, -- a battery only UPS is designed to deal with a "brief" interruption in supply. Nominally on the order of 15-30 minutes. However, if the supply is completely "interrupted" for an extended period of time, you will drain that reserve completely and then have nothing. So what do you do for the "whole house?" Do like a hospital. They have "red" outlets in various areas which are connected to the UPS system. Equipment plugged into them is controlled and the circuits protected (often) by "lower limit" breakers. This way the load on the UPS can be controlled. And, instead of needing one for the "peak load demand" they only need a UPS big enough for the "controlled load." The UPS you get from APC is following this same principle -- you can only put so much load on it before it cuts out... so you only put the CPU and disks on it. This gives you time to shut stuff down if the outage extends in time to where your batteries will be exhausted. It doesn't give you a mechanism to keep operating without the grid for an extended time. As I said, power is a fun topic.
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