Power monitor for a single 20a circuit.

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Ozymandias

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Missouri
I was called to bid the installation for a circuit that feeds a lighted sign, no issue there, but the tenant is required by the landlord to install a power monitor on this circuit. The building does not have separate services for the tenants so the electrical use is included in the lease. The tenant wants a lit sign on a timer during the night. The landlord wants to monitor the use in order to charge the tenant accordingly. I did a search here and found http://www.theenergydetective.com which seems reasonable, I only know of egauge but seems costly, I still have to call the supply house for other options, maybe someone could give some input on the matter, thanks!
 
If I were that tenant, I would suggest to the landlord that the energy usage will be

([sign wattage] x [hours turned on]) / 1000 x [kilowatt-hour electric rate]

which will result in a fairly fixed cost for running the sign. No monitor is required. Of course, this does you no good as it eliminates the need for part of the work.
 
n1ist said:
Emon Dmon comes to mind
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Will check, thanks!
Coppersmith said:
If I were that tenant, I would suggest to the landlord that the energy usage will be

([sign wattage] x [hours turned on]) / 1000 x [kilowatt-hour electric rate]

which will result in a fairly fixed cost for running the sign. No monitor is required. Of course, this does you no good as it eliminates the need for part of the work.
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Excellent tip, I know the tenant in a roundabout way and being frank could lead to more work, thanks.
 
180430-224 EDT

I agree with Coppersmith but the equation is not clear, and I would calculate the cost per kWh as total kWh per year / the total bill for the year, or average actual cost per kWh averaged over a year.

Then I would write the equation as:

Cost per month = ( measured sign wattage / 1000 ) * hours of on time per month * average actual cost per kWh .

If there is a power factor cost, then that may need to be added in.

A TED system would work, might be less accurate, and a moderate cost.

.
 
It is probably not the case in Missouri (but be sure to verify!), but in California such an arrangement would be explicitly illegal.
Nobody but a publicly regulated utility is allowed to charge for metered usage of utility-provided power.
It would be legal to charge a fixed energy fee which is renegotiated each year based on the historic energy consumption, though. :)
 
gar said:
180430-224 EDT

I agree with Coppersmith but the equation is not clear, and I would calculate the cost per kWh as total kWh per year / the total bill for the year, or average actual cost per kWh averaged over a year.

Then I would write the equation as:

Cost per month = ( measured sign wattage / 1000 ) * hours of on time per month * average actual cost per kWh .

If there is a power factor cost, then that may need to be added in.

A TED system would work, might be less accurate, and a moderate cost.

.
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It took me a minute to pick up what your laying down, thanks!
 
GoldDigger said:
It is probably not the case in Missouri (but be sure to verify!), but in California such an arrangement would be explicitly illegal.
Nobody but a publicly regulated utility is allowed to charge for metered usage of utility-provided power.
It would be legal to charge a fixed energy fee which is renegotiated each year based on the historic energy consumption, though. :)
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Dang! It might be the case here, thanks for the input!
 
Illegal in Wisconsin too. Can’t be a utility without a license.


Sent from my iPhone using Tapatalk
 
GoldDigger said:
It is probably not the case in Missouri (but be sure to verify!), but in California such an arrangement would be explicitly illegal.
Nobody but a publicly regulated utility is allowed to charge for metered usage of utility-provided power.
It would be legal to charge a fixed energy fee which is renegotiated each year based on the historic energy consumption, though. :)
Click to expand...

True, but it’s not illegal to install a meter. What the customer/owner does with the information would be their business. I have installed an emon demon on a rental cottage that didn’t have separate meter. The owner was able to figure out that the tenant was using space heaters instead of the natural gas wall furnace, which was really driving up the electric bill.
 
I have used ekm metering meters. They have an "inline" one for single phase that clamps right on the conductors. Probably put it in a 12x12 box or something. An even cheaper option if feasible is to get a kill-a-watt meter. It would have to be plug connected and those lose their data if unplugged.
 
180601-0933 EDT

electrofelon:

The Kill-O-Watt EZ does not loose data on loss of power. If my memory is correct 15 A is max and it is only 120 V.

The EZ is much better than the standard model, works over a wider voltage range, and does not loose cumulative kWh. But has more button pushing. Both models use a resistive shunt for current measurement. This means output neutral must float relative to ground or input neutral. Works well at low power factor compared to TED. But at near 0 PF results are not consistent from one EZ unit to another EZ unit.

Manufacturing or component quality is not good on the Kill-A-Watt, but measurement capability is good, and the device is low in cost, about $30.

.
 
gar said:
180601-0933 EDT

electrofelon:

The Kill-O-Watt EZ does not loose data on loss of power. If my memory is correct 15 A is max and it is only 120V.
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That’s another viable option.

electrofelon said:
I have used ekm metering meters. They have an "inline" one for single phase that clamps right on the conductors. Probably put it in a 12x12 box or something. .
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Their website has a watertight clear cover outdoor box which may just right. Thank you all.
 
GoldDigger said:
It is probably not the case in Missouri (but be sure to verify!), but in California such an arrangement would be explicitly illegal.
Nobody but a publicly regulated utility is allowed to charge for metered usage of utility-provided power.
It would be legal to charge a fixed energy fee which is renegotiated each year based on the historic energy consumption, though. :)
Click to expand...

It's sort of that way in a lot of places. Most states have regulations on who is allowed to meter and sell electricity. There are various ways to get around the restrictions that are usually not to onerous, but what is being proposed does not seem to me like the complete fix.
 
Ozymandias said:
Possibly an LED sign at four hours a night, how much could it be? Landlord is pushing it.
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If you had the power rating of the sign, there quite a few members here who can calculate energy usage for the operating period.
It wouldn't altogether surprise me if the cost of an energy monitoring system install would not be justified by the revenue the landlord would get.
 
Besoeker said:
If you had the power rating of the sign, there quite a few members here who can calculate energy usage for the operating period.
It wouldn't altogether surprise me if the cost of an energy monitoring system install would not be justified by the revenue the landlord would get.
Click to expand...

one could literally wire in parallel a hr meter post switch (perhaps in the sign, many are small 2-2.5" round like automotive dash meters) that will increment time when sign/power is on. one could simply look at it to see how long the sign has been on.

it is never accurate to just go by nameplate. amp clamp the sign to see what the actual amp draw is, and hopefully the PF is close to 1.
then with time from time meter and the known amp load, you can calculate power usage, but you cannot calculate costs unless you know exactly when sign turns on/off and the rate schedule for those times, etc.

probably easier to just write into lease a $100/mo fee for sign, whether tenant has a sign or not or leaves it on 0hr or 24hr/day doesnt matter, one flat rate, done, no hassle. or basically, bury that $100 into the base lease price and skip the rest. done.
 
GoldDigger said:
It is probably not the case in Missouri (but be sure to verify!), but in California such an arrangement would be explicitly illegal.
Nobody but a publicly regulated utility is allowed to charge for metered usage of utility-provided power.
It would be legal to charge a fixed energy fee which is renegotiated each year based on the historic energy consumption, though. :)
Click to expand...
Which I think is about all they are after is wanting to know what kind of energy this load is going to use to base the lease/rent on. If so it has already been mentioned to find power rating of the sign and calculate how many hours it will run and owner has what they are looking for.
 
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