Measuring power usage from a tool

bonesbr549 · Nov 15, 2015

Ok I'm looking for a way to measure the power consumed to make something so I have an idea of cost. I do woodworking, and the wife does stained glass. She "borrows" one of my 220 circuits for her glass kiln. She right now has a good little gig, melting wine bottles from a local winery to make cheese boards/spoon rests. She wants to know what to charge, and her only cost is some minor chemicals, and of course electricity. Since glass requires various times and firing temperatures, I can't just measure the usage at start and multiply time out.

I looked on line and there are all kinds of measuring tools but they are all for 110. Anybody have any ideas. If I could get one bottle run, I could tell if she's making money at it or just spending time

JoeinGa · Nov 15, 2015

Do a Google search for a clamp-on Ammeter. I think that's what you need.

bonesbr549 · Nov 15, 2015

Do a Google search for a clamp-on Ammeter. I think that s what you need.

- JoeinGa

Thanks, but I got one of those, but it only tells me at any given time what it is. I want to calculate kilowatts used. Something like P3 P4400 Kill A Watt Electricity Usage Monitor, but that will work with 220v.

MrUnix · Nov 15, 2015

I did a quick google and turned up a few - most under $100 and work with both 120 and 240v such as this one from EKM.

Cheers,
Brad

Karamba · Nov 15, 2015

Do a Google search for a clamp-on Ammeter. I think that s what you need.

- JoeinGa

Thanks, but I got one of those, but it only tells me at any given time what it is. I want to calculate kilowatts used. Something like P3 P4400 Kill A Watt Electricity Usage Monitor, but that will work with 220v.

- bonesbr549

Besides it is not a tool to measure consumed power. It tells you the magnitude of electric current, which you can multiply by 110V and by time and get kVA h, which is not what you pay for. You pay for kWt h, which is not the same. Get some refurbished electric meter, or simply figure out how to read your house electric meter tge days you use the tools and the days you dont.

ThomasChippendale · Nov 15, 2015

For having manufactured electricity meters for 20 years, I suggest you look at your meter and understand how to read it. Unless you know the wattage of the equipments you and your wife uses it is the most accurate, free solution. Measuring power is not simple and the meter on your house does it, as long as no other high load is on like heating or the water heater you will have a good idea. Have her melt the glass for an hour while you have the heat and water heater turned off and figure the KwH spent by subtracting the latest readings by the starting reading.

By the way, If she uses the oven in te winter, he heat will help heating the house so its free.

FancyShoes · Nov 15, 2015

Call your power provider to get the rate per KWH (kilo-watt-hour)

The wattage of your tool formula

75w tool multiplied by hours you plan to run it, lets say 4 hours equals 300w, since you are charge per kilo watt hour you would convert 300w to kilowatt which is .03kw then multiply that by the rate you are charged. Lets say $16/KWH then it would be .48 cents to run it for 4 hours.

I havnt usedvthe formula for a while, so I will confirm if I am correct, but you local power provider can help you with the formula as well.

This is how I show people the saving by converting to a high efficient AC.

clin · Nov 15, 2015

I'd just take the peak rating of the kiln times the hours it's on. That should give you a worst case value of energy used. That value would ensure she has not underestimated the cost of electricity.

bonesbr549 · Nov 16, 2015

Thanks for the replies. I'll go look at that pass through meter. The challenge is a kiln is not a constant. With a firing schedule, you have a ramp up rest ramp down and hold which can occur multiple times over that period which is 12-14hrs. I can read a meter, so I may do the down and dirty and cut all the stuff off like other tools, hottub etc, and watch it.

Late yesterday I did find a system for 130$ that provided a couple clamping coils and a monitor that would record it and an app I could see it on my phone. I could clamp the coil around the line and monitor it that way.

Thanks all.

hhhopks · Nov 16, 2015

Only tool require is pencil, paper and maybe a calculator.

Here's what I would do to estimate the cost:

1. Determine the cost of Kilo Watt Hour (KWh). Simplify it by taking the total of your billing and divide by the total KWh used from billing statements which would include taxes and all the special fees.

2. Determine what is the desired monitoring time duration (ex: 6, 8, or 12 hours which includes preheat & cool down time).

3. Establish a reference KWh reading used by your house without the kiln. You do this by using the utilities meter that is on your house (the meter that the electric company used to establish billing for your house).

Take a meter reading at the beginning of the duration.
Take a meter reading at the end of the duration.
The difference is your base KWh used by your house.

4. Repeated the above steps with the kiln being utilized. Make sure that there is no unusual load being used from the base reading (ex: air conditioning running on a hot day verses taking reading with the kiln on on a cool day). The difference in KWh is the energy used by your house and the kiln.

5. Subtract the above KWh from the based KWh reading used by your house without the kiln. The result is the approximate KWh energy usage by the kiln.

6. Multiply that by the estimated KWh cost that you pay and that should be energy usage of your wife's kiln.

Maybe should do the kiln reading first, that way you know exactly what is the desired time duration.

bonesbr549 · Nov 16, 2015

Only prob is I got a lot of electrical crap running. I have a small server farm that is chewing juice, a hot tub and some other things but I can do a minimalist calc like you said. I may try that. Dang shame how much elec I actually use. I have to have my espresso though! Cheers.

I'll retire in a couple years and a lot of that crap goes. I know I want very little to do with computers after I retire (if I make it)

kelvancra · Nov 16, 2015

I made a small box I plug a give device into and it has the insulated wires looping out with enough room to use a clamp on meter. This can be done for 120 VAC or 240 VAC. After that, it's just a matter of using HHHOPKS' pencil.

It should be noted face plate values can be worthless. Dust Collector, antique that it is, is pretty close to the stated face plate value of fifteen amps, so I can take that and run time, then use the wattage (amps x volts) to get kilowatt for figuring operating cost for my kilowatt costs. A couple of my saws state fifteen amps, but run at only seven (that is not confusion between 120 V and 240 V amp usage).

crank49 · Nov 16, 2015

Look up Kill-A Watt meters.
You can get one for about $18.
They only read 120 volts, but you could install it on half the circuit and just double the reading.

Otherwise, take the total watt rating of the kiln times the hours of the cycle. If the elements are 2500 Watts and the cycle is 12 hours long, you know the total will be no more than 12×2.5 kW = 30 kWh. I know it cycles on and off and ramps up etc. but the 30 kWh is the absolute maximum power that could be used. Most parts of the country pay around $0.12 to $0.16 per kWh so an average of $0.14×30 kWh = $4.20. Actual cost might be half that due to ramping and holding cycles.

splintergroup · Nov 16, 2015

I resemble this guy!

My wife does fused glass and I have a current monitor installed on her kiln. A kiln regulates temperature by switching on-off every few seconds so just measuring current draw won't work.
My system is rather sophisticated. using a computer to log power usage of various systems, but you can get the equivalent of the "Kill-A-Watt" that works for 240V (Not cheap though)

I have lots of data from my wife's kilns. The smaller kiln (Paragon-7, 120V) will use about 1700 watts of power when heating. A "normal" fusing cycle with all the stages will typically range from $0.70 to $1.00 (based on $0.15/Watt-hour).

Her bigger kiln burns 8000 Watts (240V). Costs more to run but has far greater capacity.

A typical run costs about $2.50 to $3.50

bonesbr549 · Nov 16, 2015

I resemble this guy!

My wife does fused glass and I have a current monitor installed on her kiln. A kiln regulates temperature by switching on-off every few seconds so just measuring current draw won t work.
My system is rather sophisticated. using a computer to log power usage of various systems, but you can get the equivalent of the "Kill-A-Watt" that works for 240V (Not cheap though)

I have lots of data from my wife s kilns. The smaller kiln (Paragon-7, 120V) will use about 1700 watts of power when heating. A "normal" fusing cycle with all the stages will typically range from $0.70 to $1.00 (based on $0.15/Watt-hour).

Her bigger kiln burns 8000 Watts (240V). Costs more to run but has far greater capacity.

A typical run costs about $2.50 to $3.50

- splintergroup

U da MAN!!!!!!!!!!!!!!!!!!!!!!! I got my wife the paragon 7, but mines 240v. I can us your numbers thanks. What is her bigger kiln? We are finding the one bottle at a time not very optimal. Where we will be retiring to, there are lots of winery's so we expect the volume to pick up.

Bill1974 · Nov 16, 2015

Since you are looking at the power consumed by an electric heater it's pretty simple. I am assuming there is only one heating element and it's on or off. If there is more than one heating element you will need to do a little more math and need one more piece of equipment. I am sure you could contact the mfg of the oven and get the wattage of each heating element. Now you just need to measure the amount of time it is on. There are plenty of cheap timers that you could wire up to the record the on time of the heating element coils. Then its just multiply the wattage by the time in how and divide by 1000 to get he kW-Hr. The looking at you bill you can see what the rate is for the power and the rate for the power delivery and find the true cost.

The are meters that you could use to measure the power but they are expensive. Looking at your electric meter is the other option if you can turn off all the power using devices.

Measuring the power consumed on devices with motors is more difficult than the voltage x amperage. The power factor of the motor comes into play and can significantly change your power consumption. Depending on the type of motor and load the power factor can swinge from .50 or lower to as high as .99.

The electric meter is the most accurate way to see how much power something is using but a challenge to use it to measure one device.

splintergroup · Nov 16, 2015

U da MAN!!!!!!!!!!!!!!!!!!!!!!! I got my wife the paragon 7, but mines 240v. I can us your numbers thanks. What is her bigger kiln? We are finding the one bottle at a time not very optimal. Where we will be retiring to, there are lots of winery s so we expect the volume to pick up.

- bonesbr549

It's the Big-Azz Scutt GM1414 (42"x25" opening, 13" deep).

Yep, for bottles you really need to get something coffin shaped to pack them in. We tried using her old ceramic kiln
which is deeper. You can stack layers of shelves, but the heat distribution just wasn't quite right.

bonesbr549 · Nov 16, 2015

U da MAN!!!!!!!!!!!!!!!!!!!!!!! I got my wife the paragon 7, but mines 240v. I can us your numbers thanks. What is her bigger kiln? We are finding the one bottle at a time not very optimal. Where we will be retiring to, there are lots of winery s so we expect the volume to pick up.

- bonesbr549

It s the Big-Azz Scutt GM1414 (42"x25" opening, 13" deep).

Yep, for bottles you really need to get something coffin shaped to pack them in. We tried using her old ceramic kiln
which is deeper. You can stack layers of shelves, but the heat distribution just wasn t quite right.

- splintergroup

Yea, we found that out. One on top would bubble and the one on bottom would not fully cook.

I am looking to get her a bigger one before I retire.

crank49 · Nov 20, 2015

Since no one read my suggestion of using the kill-a-watt on half the circuit (which I know works by the way) I'll try again.
You can build a kiln in any shape you want. I built a couple of burn-out-furnaces, same machine as a kiln, but used in jewelry casting, and it's really easy. You need K-23 insulating firebricks, a rasp and a bow saw to make grooves for the elements and to cut the bricks. The case can be made from thin sheet metal; I used 20 ga. Build the box, line it with ceramic fiber insulation and then bricks. You can buy replacement elements from kiln/furnace retailers because they are a consumable item that needs replacing occasionally. The ramp and soak, programable temperature controls are an easy off the shelf item at places like Omega.com . I found the cost of building v.s. buying to be about 1/4 the cost. But the ability to make any shape you want is the real value.

Measuring power usage from a tool

Top Contributors this Month

Recommended Communities