> What are you looking to sense? When current is flowing through a > breaker? How much current? How much voltage? Both?
We moved into a different house last fall and our electrical consumption is about double our old house. Was trying to figure out where the power is going. The new place has mini-splits: electrically powered heat pumps which provide heat and AC. Wondering how much power they're chewing up. and if they're cheaper than oil... On Wed, October 22, 2014 3:30 pm, Tom Metro wrote: > Greg London wrote: > >> Was looking to instrument the circuits in my breaker box. >> > > What are you looking to sense? When current is flowing through a > breaker? How much current? How much voltage? Both? > > >> The only thing I could find commercially was this: >> >> >> http://www.theenergydetective.com/ >> > > There's also one of these: > http://www.bluelineinnovations.com/ > > > I bought one years ago for some trivial amount when NSTAR was > subsidizing the cost, and unfortunately never got around to installing it > (which I still should), so I can't speak to its effectiveness. > > > It has a consumer-friendly sensor that simply clamps onto your > electricity meter and optically monitors the spinning wheel or digital > display to track power usage. (Seems rather inefficient when you can > probably get that info directly from the meeter with a bit of RF hacking, > as the new meters can be talked to wirelessly.) > > >> But that only instruments the incoming circuit... >> > > I'm pretty sure one of the newer startups doing this claimed that with > some analysis of your usage patterns, they can figure out how much power is > going to each of your major appliances, despite only having a whole house > sensor. Seems a lofty claim. Or maybe they were just claiming that after a > learning period, they could tell you which combination of appliances were > running at any given time. > > >> (200 amp service, 40 circuits) >> ...and getting enough sensors to do all the breakers >> could cost close to a thousand dollars. > > A current probe for a multimeter will run you about $40: > http://www.amazon.com/Current-Clamp-Probe-for-Multimeter/dp/B00NRHB5PM/ > http://www.righttoolusa.com/p/Tpi-A250-Ac-Amp-Current-Probe-Adapter-400a-F > or-153-163-183-183a-And-31258602.html > > which would add up to $1600 for 40 circuits just for the probes. > > >> Seemed expensive. >> > > Like Drew said, probably pretty reasonable for a code compliant solution > that you can install yourself. > > Code-wise, there's probably more flexibility if you are installing the > probes outside of the main breaker box. Something you'll want to consider > if you go the more D-I-Y route suggested below. Obviously the probes are > low-voltage and electrically insulated from the power wiring, so they are > low risk. The challenge is that the probe needs to be placed over the hot > wire only, so you can't just clamp it onto the romex cable in any old > spot. Splitting open the jacket at a mid-point would undoubtedly be a code > violation, but you could do that inside a small work box. Consult an > electrician. > > >> Anyone know of a cheaper way? >> > > You can easily find multimeters with integrated current clamps for as > little as $12: > http://www.harborfreight.com/digital-clamp-on-multimeter-95652.html > http://www.amazon.com/Meter-Multimeter-Digital-Clamp-Probe/dp/B00E6NDZ22/ > > > (That a probe alone cost $40 and a probe + multimeter only cost $12 > probably tells you something about the relative quality.) > > But you'd have to do a lot of hacking just to get the mechanics to work. > And that's before you build whatever is necessary to process the signals > from all the probes. > > It looks like there are some lower cost current probes made for home > automation: > http://www.amazon.com/s/ref=nb_sb_ss_c_0_14?url=search-alias%3Delectronics > &field-keywords=current%20sensor&sprefix=current+sensor%2Caps%2C382 > > > Here's one that is good for up to 30 A that will only run you $7: > http://www.amazon.com/Current-SCT-013-030-Non-invasive-Split-Core-Transfor > mer/dp/B00L51AD3W/ > > One good for 120 A for $12: > http://www.amazon.com/0-01-120A-0-5M-Split-core-Current-Transformer/dp/B00 > 5FIFT4E/ > > > and it looks like there may be some interface boards designed to glue > these to an Arduino or something, but all you should need is an A-to-D. > (See user reviews on the last one for some tips on attaching it to an > Arduino.) > > > These are all "split-core" probes - meaning the coil opens to be placed > over a wire. For your branch circuits, you might be able to save by using > coils that don't open, like: > > http://www.amazon.com/Leviton-CDA02-L12-Sub-Metering-Current-Transformer/ > dp/B0055D6F92/ > > One of the Amazon Merchants is selling that particular one for $10, > which isn't really a bargain, but I bet similar coils could be found for > under $5. The savings trades off for higher installation effort, as you'll > have to remove the wire to each breaker to install it. > > > Another option to investigate is whether you can get a breaker with > integrated sensors. Such a thing might not exist for residential > applications. But if it did, you'd end up with a much cleaner > installation. (Some modern circuit breaker designs use current sensing > electronics instead of the old style thermo-magnetic design. So a lot of > the hardware you'd need is already in the breaker.) > > At one time SquareD (now Schneider Electric) had a line of breakers that > fit their QO family of panels (stay away from the lower-end Homeline > panels) that facilitated remote switching of the breaker. I don't recall > what sensor information it provided. I don't spot anything like that on > their breaker page now: > > http://www.schneider-electric.com/products/us/en/50300-circuit-breakers/ > > > And they do have a remotely operated breaker made for lighting panels: > http://www2.schneider-electric.com/resources/sites/SCHNEIDER_ELECTRIC/cont > ent/live/FAQS/228000/FA228072/en_US/1210CT0201.pdf > > but it's a pretty old-school design using a motor to mechanically move the > breaker, and no sensors. > > The breaker replacement approach, even if you can find then, is unlikely > to be cheaper. You'd probably have to start by replacing the whole panel > and the material costs would likely be twice what regular breakers would > run. ($1000 for a typical panel replacement parts and labor, so $2000+) > > > -Tom > > -- _______________________________________________ Hardwarehacking mailing list [email protected] http://lists.blu.org/mailman/listinfo/hardwarehacking
