Shinteetah
Member
Thank you for the FAQ and subsequent commentary! It helped me with my own planning. I think I'll go with the HPWC and keep the UMC for travel, as I'll likely be charging away often.
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FlasherZ said:For 120V, to keep the voltage drop within range, you can use a 14 AWG cord if your TOTAL one-way circuit length from the car to the breaker panel is < 50 ft., 12 AWG if your total is < 100 ft., and you'd need to go to 10 AWG if you're at 150 ft. or greater.
So I called.There are signs that your current service is being strained: if lights dim significantly when your air conditioning or heating unit starts or your electric range or oven is turned on, you may need to have the power company assess your service – in the US, they should do this for free.
I want to give a special shout-out to FlasherZ for this FAQ. It might have saved serious property damage or even a life.
I live on a rural property, total electric, and our house is the only one on this power stub, or whatever you want to call it. We built about ten years ago, and there's always bit a bit of a power dip when my HVAC kicked on or some other big draw. Because it had always been so, I just assumed it was normal.
Well, Flasher's post included this:
So I called.
Technician came out, listened to me, didn't think there was a real problem, but I talked him into looking at stuff. We checked my panel, my meter and line in, and finally walked out to the transformer which feeds my property. He started that sick, horrified-amused laughter as we got close. I said, "That doesn't sound like that's what you expected it to look like?" and he started a lot of invective on whichever moron had done that work.
I don't know the field well enough to follow all of his outraged jargon, but the short version was, it was badly done. Bad enough that he had a team of a half-dozen guys there with a new transformer and all-new lines that same day, working overtime in the dark to finish at 10:30 pm. Apparently it was a serious safety issue, and I'd never known it should be different, and I would never have asked about it if not for FlasherZ's FAQ.
AND I now have a charger installed as well, so the FAQ served its intended purpose as well! Thanks!
And I guess that's at 120 V? But I always learned that home power stuff was at 110 V, is the difference important?
So then it sounds like to do this we would need to know how far the the cable travels in the walls of the house between where we the house's breaker box and the receptacle on the wall, and then add the length of the extension cable? If we need to get, say, a 10 AWG extension cable because of the distance, should we be concerned that the cables inside the walls of the house might not be thick enough? Also, what happens if we use a cable that's too thin? You say that this is necessary "to keep the voltage drop within range," which doesn't sound terribly important—shouldn't the UMC be able to handle that at a lower charging rate, or at worst, just not send power? Basically, if we screw up and use a cable that's way too thin, are we risking a fire (or other significant danger)?
I want to give a special shout-out to FlasherZ for this FAQ. It might have saved serious property damage or even a life.
In older neighborhoods, it's common to find 2-3 homes connected to a 10 kVA transformer. The investor-owned utilities will generally wait until it blows up to replace it with something bigger, or they'll try to charge the consumer.
Does that "100" painted on mean 100 kVA? could they have actually planned for 25 kVA power per house?
And while we're at it, what does kVA mean? I see UPS units rated at 1500VA but can only protect 865 watts of load. What am I missing?
kVA is just kilo VA. VA is what the industry uses because if they used Watts (which is what V * A is) they might be held to it. VA is more flexible so the marketing department likes is (similar to HP, but that's already on another thread). Someplace there should be a rating plate, although it might be inside the cover.
This is my transformer:Just for giggles I took some pictures of the transformer feeding the houses around me. It's one transformer for four houses...
Just for giggles I took some pictures of the transformer feeding the houses around me. It's one transformer for four houses. The only numbers I could find on it are below.
...
Does that "100" painted on mean 100 kVA? could they have actually planned for 25 kVA power per house?
And while we're at it, what does kVA mean? I see UPS units rated at 1500VA but can only protect 865 watts of load. What am I missing?
Yes... It's not the easiest subject to explain in layman's terms. It was once taught to me this way: imagine a handle connected to a shaft on one of those souvenir penny-smashing machines... The energy you put into that crank is real power because it all goes to the load (smashing the penny).
Now attach a heavy weight to the crank such that you need to work harder in the upstroke, but on the downstroke, the weight makes it easier and so you have to use less energy. That's reactive power, you've stored it in the weight. It hasn't been applied until the crank makes its full revolution.
Still not perfect but is a start to understanding it.
I always found this DOE paper with a horse pulling a railway car from the side of the tracks was a good analogy...
In the reactive power scenario, you're "lending" power to the reactive load, but eventually the magnetic field (inductor) or power field (capacitor) is going to give most of the power back to the circuit -- that's why I use the weight-attached-to-crank analogy myself.
For sure, but I just liked how it showed the angles comparable to the X (real) and Y (reactive/inductive) power diagram. We have a guy here that uses beer and foam in a glass as his analogy, but that never seemed clear to me. Probably because I had to keep re-setting the experiment by draining the beer :tongue:
On come on, how hard is the integral of the product of two sinusoids with varying phase angle offsets, going from power consumed to no power transfer to power produced...just kidding. :biggrin:
On come on, how hard is the integral of the product of two sinusoids with varying phase angle offsets, going from power consumed to no power transfer to power produced...just kidding. :biggrin: