Electricity question

Quote: kenarman

As I mentioned in an early post it is usually total overkill. If you do not have electric heat you would seldom need to install a 200 Amp service. A residence seldom draws over 10 amps @ 240 volts unless the oven, dryer or hot water tank are on. Take your electric bill and divide the KWH for the month by the number of hours in the month and you can calculate what the average amperage draw is.

Quote: Pacomartin

So the transformer has a turns ratio of 7200:240 = 30:1.

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But these online tutorials are very confusing. One say "A 200 amp service for a home can consume 48,000 VA (E*I) or 48 KVA". While I realize that most homes never get close to 200 Amps, it still seems like a 15 kVA transformer is rather small (15,000 Volts/240 Volta/Amp = 62.5 amps) . It seems like the 200 Amp home wiring is ridiculous overkill.

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But the daily readings show some days with well over 110 kWh/day, and the hourly meter once showed an hour with 11,000 Watts in a single hour.

Quote: petroglyph

The big expense on adding/removing a pole and moving the xmfr. is labor. What I think you suggest is [WAG] about 12 hours labor plus a kicker for overhead. If those parts of a system have to be moved, often depending on the age, they will get changed for new. The old stuff thrown in the garbage heap, with the lifespan/depreciation never realized. That is also probably a 40 foot pole, plus labor and materials, and equip. I think how they look at it is, yours is already working, why change it?

Quote: petroglyph

Interesting that you would pick up on the turns ratio. Transformers between the primary and secondary coil are only magnetically coupled. My electric toothbrush must work that way as well, I just set it near the charger and the charge indicator light comes on. Also this is how Japan's bullet train works. There is no physical connection. Note that although the voltage/turns ration is 30-1 creating 240 from 7200/12470, the amperage is inverse using OHM's law V=A*R

That is how I have thought electric vehicles could be powered on the road with the Primary being under the pavement and cars just having a secondary coil underneath them. It's possible but probably not probable?

Something I haven't yet figured out, is wrong with my picture host "tinypic" so I am unable for now to post a picture. However, look here:https://duckduckgo.com/?q=picture+of+200+amp+service+panel&ia=images That right there, if it was all on one leg, 11000 watts divided by 110 volts is your 100 amps, realized.

The 2 thick black leads are the feed for the panel. Right there is the only place on the panel that is rated at 200 amps, and that rating is phase to phase, not each. They are usually 1-4/0 CU. Each of those legs, connected to the panel get labeled as 100 amps each. So far, yes overkill. Those conductors will carry quite a bit more than the demand. The overall truth of it is, if there is going to be an electric failure because somebody didn't use large enough wire, it is not going to be the utility's fault. This has all been settled in courts of law. If there is an amperage failure it will be on the customers side, period.

Each leg of the of your service is rated for 200 Amps at 120 V for a total of both legs of 200 Amps at 240 V. You do not add each side to get to the 200 Amp rating. This is a common mistake lay people make.

Also that rating is in the lab with perfect connections. Not outside after thousands of cycles of heating and cooling.

Other than an electric stove, water heater, or electric heat, most all residential wires are # 12. The SWL [safe working load] on #12 is 18 amps with an absolute burn down rate of around 27 amps IIRC. So the potential for overheating and possibly fire usually lies there.

Realize how many outlets in an average house, which are usually rated 20amps each, and also that several rooms may all be on the same 15/20 amp breaker at the panel. Add up all the plug ins in your house and multiply by 20 amps and see what you come up with, plus lights, heat, and stove, and possibly hot water heater at 4kw.

Not sure what you are trying to say in the paragraph above. As you say many of the receptacles can be on the same circuit by code (In Canada up to 12 lights or plugs can be on the same circuit). All these loads are protected by one breaker adding up all the plugs in your house and multiplying by 20 is pointless and provides no use full information. As my early post mentioned I had a site with 132 poles of breakers which ran fine on a 100 Amp service. By your math above we would have 20 Amps X 132 = 2640 Amps. As I said a meaningless figure. What keeps the load down in a residence is that relatively few people live there so few of the loads get used at the same time. If you are cooking Xmas dinner and have the electric range maxed you are probably not doing the wash at the same time. If you are using your table saw you aren't welding at the same time, or in the sauna or hot tub or shower.

In most electrical systems failures, it isn't the conductors that fail, it is the contacts.

Utility's on the original build don't know if you are going to bump up to a 3-4 hundred amp panel and each neighbor will add a garage/shop with electric heat and welders. The design engineering can't be, for every single meter in the system. There are standards which allow for some future increase in demand on each circuit. They build it to set it and forget it. When that is over reached, they will add capacity. The big expense on adding/removing a pole and moving the xmfr. is labor. What I think you suggest is [WAG] about 12 hours labor plus a kicker for overhead. If those parts of a system have to be moved, often depending on the age, they will get changed for new. The old stuff thrown in the garbage heap, with the lifespan/depreciation never realized. That is also probably a 40 foot pole, plus labor and materials, and equip. I think how they look at it is, yours is already working, why change it?

Quote: Pacomartin

Quote: petroglyph

The big expense on adding/removing a pole and moving the xmfr. is labor. What I think you suggest is [WAG] about 12 hours labor plus a kicker for overhead. If those parts of a system have to be moved, often depending on the age, they will get changed for new. The old stuff thrown in the garbage heap, with the lifespan/depreciation never realized. That is also probably a 40 foot pole, plus labor and materials, and equip. I think how they look at it is, yours is already working, why change it?

The foreman told me the pole that would be the new destination of the xmfr is too old, and has been reinforced already. He also said the utility no longer reinforces old poles, the new policy is to replace them.



You can pay someone to pull down a 80' to 1000' dead tree for less than $1000 if it is in the open. They use arrows to tie ropes to top branches to try and control the fall. But if it doesn't fall perfectly, there is nothing permanently damaged. But if you are near high voltage wires, roofs, or other valuable things, you have to hire a truck with a cherry picker so he can take down offending branches or even take a tree down section by section. The price immediately triples because of the truck renta. The utility pole is actually five feet on my neighbor's property, but who knows which limb will hit it or if it will just break the wire or start a fire.

So bottom line if a tree breaks the HV wire they come and fix it (like they did in the early season snowstorm of Oct-NOv 2011). If there is a big fire and it takes out a home roof they are OK because it is the property owner's responsibility to trim trees. So I've been told by other people (not just you) that the foreman will feign interest and possibly replace the old utility pole, but he will send me a nice e-mail that says they don't want to touch something that has not failed.

Quote: kenarman

Quote: petroglyph

Each leg of the of your service is rated for 200 Amps at 120 V for a total of both legs of 200 Amps at 240 V. You do not add each side to get to the 200 Amp rating.

Good catch. So, are you saying that a 200 amp breaker can be used each side [according to code]?

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Not sure what you are trying to say in the paragraph above. As you say many of the receptacles can be on the same circuit by code (In Canada up to 12 lights or plugs can be on the same circuit). All these loads are protected by one breaker adding up all the plugs in your house and multiplying by 20 is pointless and provides no use full information.

I was trying to explain to Paco about overkill, in my primitive way. If it was an entirely useless exercise on my part, than I surely wasted my time, and apparently yours, and possibly Paco's? My bad.

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As my early post mentioned I had a site with 132 poles of breakers which ran fine on a 100 Amp service.

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As I mentioned in an early post it is usually total overkill. If you do not have electric heat you would seldom need to install a 200 Amp service. A residence seldom draws over 10 amps @ 240 volts unless the oven, dryer or hot water tank are on.

I don't really want to get into nit picking the nuances of electric power, but. I have gas water heater, heat, and stove... but a pretty good electric bill during air conditioning season, add to that the pool circulation pump. Otherwise, no need at all for 240.

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Take your electric bill and divide the KWH for the month by the number of hours in the month and you can calculate what the average amperage draw is.

Like I said, I don't want to nitpick, but how useful would that be?

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By your math above we would have 20 Amps X 132 = 2640 Amps. As I said a meaningless figure.

Is that how you interpreted what I said, if so I will hopefully quit trying to help. You may think of my electrical skills as god like, but I assure you my typing skills are not.

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What keeps the load down in a residence is that relatively few people live there

Really? Is that what you want to go with? I can point out several homes with several family's living in them, the washer and dryer never stop

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If you are cooking Xmas dinner and have the electric range maxed you are probably not doing the wash at the same time.

Why not?

The last official act of any government is to loot the treasury. GW

Quote: kenarman

Not good for trees that are too close to the power line

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but most urban coniferous trees here are taken down by a logger and it is not all that expensive.

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He climbs to the top of the of the tree and cuts branches but lets them swing into the tree trunk before cutting completely through so they fall more or less straight down.

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Usually doesn't take more than an hour for a tree.

Quote: petroglyph

So you say you can average a tree per hour near energized primary? Sure, sharpen your hooks and your saw and come on down.

Quote: kenarman

The first line in my post on taking down a tree from the top is "Not good for trees that are too close to the power line".