Greetings and happy holidays to All,
I would like to determine exactly how much electric I am using and how much it is costing me to operate my geothermal heating system. What I want to do, I think, is be able to measure my electric consumption in kilowatts on those specific electrical circuit(s) over a known period of time. Can anyone explain how to accomplish this? What instrument do I want to use and can I safely hook it temporarily into my load center to measure the electrical load of the geothermal system? The Chief Financial Officer (wife) insists we keep the themostat at 66-68 degrees to save energy, which is a bit too cool for my liking, and yet, it was my understanding when we built our house 3 years ago that my Water Furnace geothermal is supposed to be efficient enough that I shouldn’t have to wear flannel shirts and long johns to watch television.
Thanks in advance for your expertise.
Regards,
BillB
Replies
You could determine the amp loading of the geothermal system with a simple clamp on ammeter, duration with a stopwatch.
This only will provide a "snap shot" and not over a long period of time. Amp reading could easily be converted to the kilowatt hours unit desired.
Amps x volts / 1000 x time in hours = KWH
This will only give a realistic answer to your question if loading is constant during operation and does not account for any cycling of the systems.
Some years ago there were auxilary electric meters installed by various POCOs to control when a household ran a hot water heater. These were regular electric meters and read in KWH - just what you want.
Chances are you will get a much better answer soon.
Jim
Edited 12/2/2008 11:21 pm ET by JTC1
http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU/ref=pd_bbs_sr_1?ie=UTF8&s=electronics&qid=1228283367&sr=8-1
Get one of these and it should do exactly what you are asking for.
It is essentially an ammeter and a clock that records cumulative current draw.
It might take some ingenuity to rig it up to a 220 volt load. Perhaps measure one of the hot legs and multiply consumption by two. It has a volt meter so maybe it could measure 220 volt loads as long as you rigged up an adapter to run your 220 volt load through the built in 110 volt receptacle.
Karl
For a pure 240V load like a heat pump, measuring one leg is sufficient to accurately measure total load. Only with a mixed 120/240V load like an electric range do you need to measure both legs.
[Though note that simply measuring current (and multiplying by voltage) vs wattage does not give a 100% accurate measure of total energy used with a reactive load like a heat pump, due to power factor.]
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Edited 12/3/2008 7:54 am by DanH
Does anyone know of a suitable meter for cumulative KWH on a 240v circuit?
Google "KWH meter". eg:http://www.powermeterstore.com/c853/electric_submeters.php
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
That looks exactly like what what I am looking for. I knew it existed, I just didn't know what to ask for.
Another question...I assume the CT (current transformer) senses a field around the wire and then converts that to a readable value. Is the performance of the transformer affected by the insulation on the conductor? Also, should the CT be located away from other conductors to insure an accurate reading only on the circuit you are trying to monitor? I'm just trying to understand the concept. I would have an electrician do the install.
Thanks for your help.
Bill B
Spend $ 273. to prove to CFO how much money you are saving with geothermal............................................
suggestions in xxxxx.8 or xxxxxx.10 would probably be more agreeable with the CFO.
Just a thought.
Jim Never underestimate the value of a sharp pencil or good light.
The current transformer isn't affected by insulation, or by nearby wires. It just measures the current through the wire or wires passing through the middle, and all other wire currents outside the transformer are cancelled.It's not clear precisely what this unit does, but to accurately measure POWER (vs current), there must also be voltage sensing connections to the wires being measured (or to the common bus to which the wires are connected).
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
There is a device named Kil-a Watt that measures power consumption on 120 v. You plug a tv or refrigerator and it will tell you what it is using. Some models even calculate the annual cost after you tell it your local rate. The local library even has em to loan. Harbor Freight also sells em. around $30.
http://cgi.ebay.com/Landis-and-Gyr-Watthour-Electric-Meter-200-AMP-5-Dial_W0QQitemZ250333478230QQihZ015QQcategoryZ66991QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Hialeah Meter will sell you a rebuilt utility meter for less than $20, calibrated and set at zero.
hav' bo't kwhr meters with base on ebay for $20 including ship'in
"The Chief Financial Officer (wife) insists we keep the themostat at 66-68 degrees to save energy, which is a bit too cool for my liking, ...I shouldn't have to wear flannel shirts and long johns to watch television."
Re-calibrate the thermostat to read 3° under actual setting. Problem solved, you can go back to wearing t-shirts and boxer shorts to watch television.
BruceT
Edited 12/3/2008 11:10 pm by brucet9
I call them dataloggers. Basically a device that uses clamp on amp (CT) readers connected to time logging device. You can usually specify the time interval you feel the need to collect data (every second? every minute? every 5 minutes? , etc.).
You could log it for a day or a year. Hobo makes them. They can be pricey. You might be able to borrow/rent some.
Log any circuit you want. This would tell you when your HP ran and how many amps it drew for how long. You're most interested in when it runs and how long. It's amp draw, my guess is fairly fixed in your case (an air source HP would vary w/ outside air temp). I may be wrong, but I'd think the load profile would be pretty steady ... assuming you're not bringing your house up to setpoint from e.g. 40 deg ... but even then, w/ a given system, it will only kick out so much and the ground source side will be pretty constant.