Gridtie overnight vampire usage

gtojohngtojohn Registered Users Posts: 20 ✭✭
I have a small 1.4kw array with 6 panels and 6 enphase microinverters. I just installed a Mieo inductive power monitor at my pv breaker to monitor my output remotely without using the envoy. I noticed after sundown it reads 90-100watts all night long . With the breaker off I get a zero reading. What I've read is standby power should be closer to 1 watt not 15 watts each. I read here on another post this might be sensing reactive power. Is there a way to differentiate? I have another power monitor on my service entrance after the power company meter and it shows about the same load when i turn the pv breaker on/off.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 28,144 admin
    The "easy" way to see if the load is AC Watts or reactive power... Turn off all circuit breakers in the house at night, except for the one connected to the GT inverters. And see if the meter registers the load or not.

    An electronic utility meter will usually show a 0.10 kWatt reading (and an arrow showing discharge), or it will show 0.00 or very close. If the meter is showing 0.10 kWatts, you are being charged for that electricity usage (not a good thing).

    If you have a meter with a moving disk--You can measure how fast the disk turns and convert that into Watts--The disk may creep very slowly (own meter's load--many tens of minutes to make a revolution), or it will turn faster if there is a load (you can plug in a 100 Watt lamp to see what that draws as a comparison).

    I would doubt that the Enphase units are drawing that amount of power... Many meters are not very accurate when measuring near zero watts.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Looking at the Amazon page for the Mieo, it is hard to say for sure whether it is capacitively sensing the voltage waveform at the same time it is measuring the current with the clamp-on. But it is likely that it is indeed just giving you VA and not true watts. Do you have to input the system voltage during configuration to get a power reading?
    A KillAWatt meter gives pretty good measurement of true power, but you would have to build an adapter cord to put it inline with a micro.
    SMA SB 3000, old BP panels.
  • BB.BB. Super Moderators, Administrators Posts: 28,144 admin
    The US kaw meter is 120vac. The enphase are 240vac as I recall.

    It could be done with a kaw,but you need to know exactly what you are doing and 2x the kaw power reading.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gtojohngtojohn Registered Users Posts: 20 ✭✭
    On the Mieo you do have to input the system voltage. I assume its just an inductive amp clamp the device multiplies voltage input to display the wattage for you. It displays down to 10 watt measurements. Originally I installed the clamp over one wire and input the voltage as 240. That showed me 90 watts at night. To help make it more sensitive I looped the wire through the clamp twice to double the reading and changed the voltage to 120. It fluctuates between a little 80 and 100 watts. It seems 90 watts is a far ways from zero, If I were getting 10 or 20 watts I might choose to ignore it. I might have to build the killawatt adapter. It might be quieter to do the adapter than shutoff power to a house full of family at night. Either way, if its reading 90 VA aren't I likely consuming around the same power in watts? Should I just plan on installing a timer to disconnect the circuit at night?
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    gtojohn wrote: »
    On the Mieo you do have to input the system voltage. I assume its just an inductive amp clamp the device multiplies voltage input to display the wattage for you. It displays down to 10 watt measurements. Originally I installed the clamp over one wire and input the voltage as 240. That showed me 90 watts at night. To help make it more sensitive I looped the wire through the clamp twice to double the reading and changed the voltage to 120. It fluctuates between a little 80 and 100 watts. It seems 90 watts is a far ways from zero, If I were getting 10 or 20 watts I might choose to ignore it. I might have to build the killawatt adapter. It might be quieter to do the adapter than shutoff power to a house full of family at night. Either way, if its reading 90 VA aren't I likely consuming around the same power in watts? Should I just plan on installing a timer to disconnect the circuit at night?

    I would guess that much of that 90W is actually inductive VA in lightly loaded transformers like your doorbell transformer and input transformers in power supplies and wall warts.
    To see how much effort you need to put into tracking down those loads you really need to know the wattage and not just the VA.
    PS: If you have a standard 120/240 service and are using only a single amp clamp, you need to loop both line wires through the clamp, but in opposite directions and then enter the voltage as 120.
    SMA SB 3000, old BP panels.
  • gtojohngtojohn Registered Users Posts: 20 ✭✭
    Thanks for the advice everyone. The Mieo is just covering my pv feed just before the breaker. since its 240v I'm just reading one leg with one clamp. My whole house monitor (Efergy Classic) has 2 clamps, one on each hot. Its 2 ought coming in, I'm pretty sure I can't fit more than one wire through the clamps.
  • new2PVnew2PV Solar Expert Posts: 305 ✭✭
    Where can i find out more info on the Mieo system?
    XW6848 inverter with 2 X mppt 60 150 CC , with Canadian solar 260Watt panels 2 x 3.5 kw array
  • gtojohngtojohn Registered Users Posts: 20 ✭✭
    www.mieo.com does exist but not all the pages are working. I found this in addition to the amazon and ebay listings. http://www.monitorsystem.com/pid14896250/wireless+energy+monitor%28HA102%29.htm
    Overall I like it, perhaps more than the Efergy Classic because it shows a bar graph for the last 6 hours, nice when I'm curious about my output. This is really a whole house energy usage monitor but also works fine as a solar ac monitor.
  • gtojohngtojohn Registered Users Posts: 20 ✭✭
    I Just shut off all the breakers except PV feed. My power monitor showed 80 watts so 13.33 VA per inverter or .055 amps each per hour all night. I think I'll be installing a 240v timer switch for overnight. I wonder how much power they use
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    gtojohn wrote: »
    I Just shut off all the breakers except PV feed. My power monitor showed 80 watts so 13.33 VA per inverter or .055 amps each per hour all night. I think I'll be installing a 240v timer switch for overnight. I wonder how much power they use

    Before you go to that trouble, I would definitely get a "second opinion" from a meter that measures power and not just volt-amps!
    If the power consumption is coming from a control circuit fed by a transformer, the idling current of the transformer will give you a volt-amp figure many times the actual power consumption.
    13.33 VA per inverter does not necessarily cost you anything as the reactive component does not spin the POCO meter.
    i would be surprised if the actual power consumption was more than a watt or two per inverter.
    Although if they keep the wireless data interface powered up continuously through the night that could draw more power.
    SMA SB 3000, old BP panels.
  • gtojohngtojohn Registered Users Posts: 20 ✭✭
    I'll hack an extension cord and try the killawatt first
  • BB.BB. Super Moderators, Administrators Posts: 28,144 admin
    If you can access an Enphase at night--Put your hand on one and see if it is warm. Putting ~10 watts into a small device like that should feel pretty warm. If it is dead cold, I would suspect the reported power usage.

    With your existing power monitor--At night, if you turn off the breaker just to the GT Inverters, does the power reading change?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • hurstsahurstsa Registered Users Posts: 2
    Can someone please post the resolution. I have an almost the exact setup. 1.7KW system consisting of six Enphase IQ6+ micro inverter and six sw290 Solar World panels. I'm reading .07A per micro inverter at night for a total of 100.7watts for all six. As for the 0.07A or 17watts per inverter I can unplug any inverter and it will drop by 0.07A. I have also used my DMM and wired it in series and received the same values as my Fluke clamp meter readings. I'm assuming since I'm not using the Envoy that the units never go into Night Tare Mode but can't confirm. Logically it would make since that the Envoy uses NTP protocol to set its time and then using some db knows when the sun is set and in turn putting the units in night mode. Please please if this is the case I'll buy the Envoy. Thanks in advance and two thumbs up to whom can answer.
  • BB.BB. Super Moderators, Administrators Posts: 28,144 admin
    The manual says maximum 50 mW (0.050 Watts) of Night Tare Loss (page 36 of manual):

    https://enphase.com/sites/default/files/downloads/support/IQ6-IQ6Plus-Micro-Manual-EN-US.pdf

    When dark, can you turn off all of your breakers in the main panel, see what you utility meter reads for power consumption (should be zero, nothing connected), then turn on just the Enphase branch circuit and see what the power reading is?

    There is a difference between Watts (Power=Volts*Current*Power Factor; PF = Cosine of the angle between voltage and current in this case) vs VA (VA=Volts*Amps).

    With standard DMM (and current clamp meters), they only measure Voltage and Amperage... They do not measure the phase angle between the voltage and current (PF/Cosine of angle).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • hurstsahurstsa Registered Users Posts: 2
    edited November 20 #16
    Just wanted to thank and tip my hat for the clarification. I was referencing VA and not Watts.

    I powered down all breakers besides the Enphase breaker and watched both (GE)consumption and (GE)production smart meters for 10 minutes which never advanced one bar. In turn ruling out the 100watts notion.

    So the 100watts if I'm understanding correctly is reactive and the Nite Tare Loss is less than 50mW.

    I'm going to add some other key phrase words as my search never concluded to a resolution till now. Just would like to help someone else if they come across the same issue. Enphase IQ6 plus inverter power drain short high night time consumption short internal capacitor leak.

    Thanks again BB for the advise of using the Smart meters. I had been watching them for weeks calculating dryer loads, refrigerator, EV and other big watt monsters. I should of looked to that to verify what I was seeing on the meters. Would of saved a lot of time and stress.

    Sincerely S.H.    
  • BB.BB. Super Moderators, Administrators Posts: 28,144 admin
    edited November 20 #17
    SH,

    You are very welcome--And thank you for your kinds words.

    Just one other sanity check... If you can get a 100 Watt filament type light bulb (or 2x 60 Watt, etc. bulbs) on put them on one circuit--And show that the utility meter will register the ~100 Watt load as you would expect.

    A filament load (or any resistive load) is pretty much a PF=1.0 (Cosine of Zero degrees = 1.0).

    AC power is actually a very complex, math heavy, concept... Here is a quick explanation:

    https://en.wikipedia.org/wiki/AC_power

    And an interesting piece of history: War of the Current (Edison vs Tesla):

    http://www.pbs.org/tesla/ll/ll_warcur.html

    Longer term, I would worry about that "reactive current" (VAR) draw of the micro inverters... That is not a small amount of current.

    For residential systems, most (all?) utilities only charge for true (active) power (Watts). Generally only large installations with lots of (for example) electric induction motors (such as oil refineries) are charged for Power Factor... Literally, the (our local) utility measures the worst case Power Factor (15 minutes out of the month) and multiplies the electric bill by 1/PF. For example, a 1/0.67 PF is x1.49 larger bill (as I recall, I looked this up years ago).

    With "linear" loads like induction motors, it is possible to correct the power factor to ~0.95 by adding "motor run" capacitors in parallel with the motors (capacitors are sized to application, and the capacitors are switched with the motors).

    Other non-linear type loads ("simple" computer power supplies, "cheap" LED and CFL lamps and such, have poor Power Factor because they draw current in non-sinewave pulses (for example: rectifier/diodes rectify AC voltage to an intermediate high voltage capacitor bank). And this poor PF cannot be "fixed" with capacitors.

    Someday, I worry that our utilities will start charging for kVAH (kilo Volt*Amp*Hours, no PF, no kWatt*Hours). It makes sense, and if poor PF devices are used for heavy conservation--Utilities will have to account for this issue... VA affects wire sizing, transformer sizing, and even utility generator sizing. Poor PF takes "capacity" of the circuit, but utilities generally only charge for actual power (kWH) used, not used capacity.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.