roy@alanine.phri.nyu.edu (Roy Smith) (03/06/91)
The building I live in (a 54 unit residential cooperative) is
getting whomped by peak usage charges on our electric bill (last month was
$650 in kWh charges and $350 in peak usage). Our peak last month was 18.0
kW (our average was about half that). I have been given the task of trying
to figure out how to cut our electric bill. A few years ago, we got timers
for all the lobby and hallway lights (which are more than half of our power
usage) but while that cut our total usage, it didn't lower our peak any.
What I'd like to do now is put a recording meter on our main power
feeder and watch our power usage during the course of the day for a few
weeks. What's the cheapest way to do that? I could go to the board and say
"Look, if you front me $2000 for equipment, I'll find a way to save you
$300/month in electric and you'll make back your investment in 7 months" but
I suspect they won't go for it, so it's got to be something I can do out of
pocket. I can probably scrounge up an old chart recorder, but I'm stuck for
sensors. Any ideas? It has to be non-invasive (I can't interrupt the wire
to insert a series-shunt ammeter) so I'm stuck with clamp-on meters. Are
there clamp-on power meters that one can get cheap in these sorts of power
ranges? I can get some clamp-on ammeters, and volt meters for each phase,
but that I'll only get me kVARS, which isn't very useful for my purposes.
Something built around a junk PC with a cheap A/D board might be
feasable, if the sensor problem could be solved, but I suspect that if I
could solve the sensor problem, a plain old chart recorder would be fine.
--
Roy Smith, Public Health Research Institute
455 First Avenue, New York, NY 10016
roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy
"Arcane? Did you say arcane? It wouldn't be Unix if it wasn't arcane!"wb8foz@mthvax.cs.miami.edu (David Lesher) (03/06/91)
In <1991Mar5.161244.503@phri.nyu.edu> roy@alanine.phri.nyu.edu (Roy Smith) writes: > The building I live in (a 54 unit residential cooperative) is >getting whomped by peak usage charges on our electric bill (last month was >$650 in kWh charges and $350 in peak usage). Our peak last month was 18.0 >kW (our average was about half that). I have been given the task of trying >to figure out how to cut our electric bill. A few years ago, we got timers >for all the lobby and hallway lights (which are more than half of our power >usage) but while that cut our total usage, it didn't lower our peak any. > What I'd like to do now is put a recording meter on our main power >feeder and watch our power usage during the course of the day for a few >weeks. What's the cheapest way to do that? Wattmeters cost real money. I suggest you just assume you have a reasonably constant power factor, and just stick to measuring volt-amps, vice watts. To do so, you will need appropriate current transformers. Some are available clamp-on, but I don't know if that would include sizes suited to your application. As I recall, 1000 to 1 is at least one ratio available. You may wish to buy none-clamp-on models, and get an electrician's help to cut building power, disconnect each feed cable, ship it thru the donut, and reconnect it. (the solid model are MUCH more likely to be available surplus, i.e much cheaper.) You MIGHT be able to get them from the utility - push the "energy saving/cut peak loading" angle. As for the metering, you could get a chart recorder. I would avoid this. Most chart recorders have pens. These are devices designed to put ink on your hands and clothes, but NEVER on the chart. They succeed. Some chart recorders do use non-ink (thermal paper, electro-discharge marking, etc.) schemes. If you could get a PeaSea with an A/D board, it could not only log data, but plot charts, and also generate real-time alerts, etc - all a SMOP {simple matter of programming ;-} One question I have is: what ARE your loads? The most well-known peaks are elevators. But at least in my experience, the utility bills them on a separate account, with ultra-premium rates. The #2 peak is HVAC. Do the suites have individual window units? In general, what do you plan to do with this data you get? The commercial systems offer load-shedding on peaks. Will the residents go along with this? (Have you considered using PIR sensors/timers on the hall lighting, so it is off until someone enters the area?) -- A host is a host from coast to coast.....wb8foz@mthvax.cs.miami.edu & no one will talk to a host that's close............(305) 255-RTFM Unless the host (that isn't close)......................pob 570-335 is busy, hung or dead....................................33257-0335
dbell@cup.portal.com (David J Bell) (03/06/91)
> The building I live in (a 54 unit residential cooperative) is >getting whomped by peak usage charges on our electric bill (last month was >$650 in kWh charges and $350 in peak usage). Our peak last month was 18.0 >kW (our average was about half that). I have been given the task of trying >to figure out how to cut our electric bill. Roy, I can't add too much to what Dave Lesher already posted, but you could pursue your idea of a high-speed A/D in a PC. Keep in mind that you have to sample fast enough to make essentially simultaneous readings of voltage and current on all three phases. The best way to achieve this is to have six sample-and-hold amplifiers feeding into the A/D in sequence, with the S&H's triggered at the same time... On another subject, did I understand you correctly, that you are "getting whomped" for about $1000 a month for *54 UNITS*??? TOTAL??? In New York??? In WINTER?????? I just paid $379 for last month for four people (one a baby) in a single house!! In California!!! I wish I had your problem (proportionally, of course)! :{) Dave
larry@kitty.UUCP (Larry Lippman) (03/07/91)
In article <1991Mar5.161244.503@phri.nyu.edu> roy@alanine.phri.nyu.edu (Roy Smith) writes: > The building I live in (a 54 unit residential cooperative) is >getting whomped by peak usage charges on our electric bill (last month was >$650 in kWh charges and $350 in peak usage). Our peak last month was 18.0 >kW (our average was about half that). I am assuming that this is a separate service for common building functions, since such a low amount of usage and peak demand would be highly improbable for all 54 tenants. >I have been given the task of trying >to figure out how to cut our electric bill. A few years ago, we got timers >for all the lobby and hallway lights (which are more than half of our power >usage) but while that cut our total usage, it didn't lower our peak any. > What I'd like to do now is put a recording meter on our main power >feeder and watch our power usage during the course of the day for a few >weeks. What's the cheapest way to do that? I could go to the board and say >"Look, if you front me $2000 for equipment, I'll find a way to save you >$300/month in electric and you'll make back your investment in 7 months" but >I suspect they won't go for it, so it's got to be something I can do out of >pocket. There must be some motor or electric heating loads that account for the peak demand. I would guess elevator loads, for one. Many older elevator systems can create a significant demand. All you need is to have that demand present just ONCE for ANY 30 contiguous minutes in one month and you are saddled with that figure! I can envision morning go-to-work elevator operation as readily accounting for your peak demand. Also, older elevator systems are not that efficient - some use a motor-generator to provide DC power for the elevator motors. I have a feeling that you are NOT going to save $ 300.00 per month, no matter what you do. Being generous, 18.0 kw demand is no more than 20 effective horsepower by itself - not much of an elevator load! >I can probably scrounge up an old chart recorder, but I'm stuck for >sensors. Any ideas? It has to be non-invasive (I can't interrupt the wire >to insert a series-shunt ammeter) so I'm stuck with clamp-on meters. Are >there clamp-on power meters that one can get cheap in these sorts of power >ranges? I can get some clamp-on ammeters, and volt meters for each phase, >but that I'll only get me kVARS, which isn't very useful for my purposes. You can probably rent a recording system from General Electric Rentals, EIL Instruments, etc. for probably $ 200.00 per month. You certainly should be able to see where you stand in one month. Even before doing that, I would suggest taking a serious look at your elevator system - which could well be your most significant cause of peak demand. Since you may not have any options here, why even go to the trouble of setting up a recording system? If you are bound and determined to assemble your own recording system, then let me know, and I can give you more specific advice. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry
wb8foz@mthvax.cs.miami.edu (David Lesher) (03/21/91)
{Roy Smith asked about recording wattmeters. I suggested just
reading volt-amps instead.}
I suggested that Roy should look at getting surplus current
transformers for his application. This weekend, I happened to find a
possible supply.
Skycraft Surplus in Winterpark (aka Orlando area) Florida 407 628-5634
has a whole shelf full of current transformers at reasonable prices.
For example, a 1500-5 amp unit was $12.00, and a 300-5 amp was $15.00.
Both were rated at 600 volts, but I have not decided what that REALLY
means. If you had (say) 1200 volt feed, already adequately insulated, I
can't see why you could not use them. But I suspect that Roy's loads
must be at 480v or less.
Now, I have no idea what's available in data acquisition cards for
PC's, but widely extrapolating.....
If there is one with AC voltage functions, you could use it to measure
the drop across the shunt R you put on these transformers. Forget the
instantaneous stuff. You are looking for PEAK charge info. ISTM that
power companies think peaks are things longer than 10 or 15 MINUTES.
You don't even need to measure the the supply voltage, as it should be
reasonably stable. Just log amps, and crunch numbers later.
On the other hand, for the esoteric type, get a card fast enough to
sample several times a cycle. Do measure both E and I, and you can
figure true watts. But, get a big hard disk to store then 15 zillion
datapoints per hour. Given how much exotic gear such as recording
wattmeters cost, I would not be in the least bit surprised if the clone
based beast was cheaper to produce, plus a whole lot more flexible. But
it sure would need a bigger carrying case ;-}
In any case, happy wattwatching...
--
A host is a host from coast to coast.....wb8foz@mthvax.cs.miami.edu
& no one will talk to a host that's close............(305) 255-RTFM
Unless the host (that isn't close)......................pob 570-335
is busy, hung or dead....................................33257-0335