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Community and Q&A

Phantom Load – Ductless Minisplit

Jimmy Nguyen | Posted in Energy Efficiency and Durability on

Hello,

I have an LG ductless minisplit system. The condenser is an LG LMU480HV. There are 8 indoor units (6 wall units, 2 ceiling mounts) connected to the condenser. The system was installed and powered up in January 2017.

I am monitoring the power usage of the minisplit system and even when all of the indoor units are turned off, which is going to happend during the shoulder seasons – the system is still consuming 0.489 kw. Doesn’t seem like much, but that’s about $36/month without it being used. Is there something that can be done about this? Do centrally ducted heat pump systems do the same?

Thanks for any help.

Sincerely,
Jimmy

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Replies

  1. User avatar
    John Semmelhack | | #1

    No...that doesn't sound normal. And, no, central ducted heat pumps don't do the same while in "standby" waiting for a heat/cool "call" from the thermostat. The few that I've measured we're in the 10-20W range.

    What are you using to measure/monitor the power input?

  2. Jimmy Nguyen | | #2

    Hi John,

    I'm using the Efergy Elite 4.0. There are two monitoring cables that I hooked up to each of the hot wires in the 240 v system. I've read some reviews that it's bad at monitoring low usage. For example, someone said that the monitor says 25 watts when it should be 5 watts. So even if my monitor was off by 500%, I would still be drawing about 100 watts.

    Very weird stuff.

  3. User avatar
    Dana Dorsett | | #3

    With 8 heads that's 61 watts per head, which is pretty high when no blowers or compressors are turning, and extremely high if it's actually in a power-down state.

    By "off" do you mean it's not blowing, but still "on" in the sense that it's still monitoring air temp, or "off" meaning that you have turned it off with the remote?

  4. Jimmy Nguyen | | #4

    Hi Dana,

    When all of the heads are off (powered down with the remote), it reads .489 kw. When most of the heads are on, but they are idling (condenser is not on), it reads on average .55 kw.

    Am I correct in hooking up both monitoring clamps to both hot wires in the breaker box?

    I think the efergy monitor might actually be correct because in the middle of the night, when most things are powered off, I still register on average 0.5 kw use every hour.

  5. Jimmy Nguyen | | #5

    Okay, I think I had the settings wrong in my Efergy monitor. Since I was monitoring an individual 240v circuit, I thought I had to set the voltage setting in the monitor to 240v. However, I believe it's supposed to be set it at 120v, since each hot leg of the 240v circuit is actually only 120v. Each clamp (there are two) on the efergy monitor is set to monitor each 120v hot line powering the minisplit system.

    In any case, doing this only halved my phantom draw to 0.243 kw. Still pretty high, although, my monitor might be off. The only way to test this further is to turn off the power at the breaker overnight and see how that affects my energy usage.

  6. Jimmy Nguyen | | #6

    So I turned off the power for the multisplit system at the breaker and tried to see any difference in kwh using my utility's online monitoring platform, which updates daily. It breaks kwh usage down by hour. I suppose the best time to monitor for any change is in the middle of the night when most items are not being used.

    Well, it looks like in the middle of the night I am still getting roughly 0.51 kwh with the multisplit system on and with it totally shut down. I was thinking the efergy monitor was off, but I hooked it up to monitor my Renewaire EV200 and it was nearly spot on for the ERV usage. The Renewaire guide says that average power usage during cooling is 155 watts. My efergy monitor reads 159 watts.

    Maybe the efergy monitor doesn't do well with 240v appliances?

    In any case, I got to track down these phantom loads that are drawing 500 watts all night.

  7. User avatar
    John Semmelhack | | #7

    Jimmy,

    The Efergy Elite does not measure true power. The power factor of the mini-split system when "off" is extremely low, so it's throwing off your readings. The Elite assumes a power factor of 1.0. This kind of device is normally "accurate enough" for measuring whole-house energy/power, but it's not so good when trying to measure an individual device with a variable speed motor.

    You would need to use the Efergy True Power Meter (http://efergy.com/us/energy-monitors/online-access/manage-energy-online/elite-true-power-meter-engage-hub) or similar monitor that measures true power.

  8. User avatar
    Jon R | | #8

    Turning off the breaker and watching the effect on the utility's meter will work too (it measures power properly).

  9. Jimmy Nguyen | | #9

    Thanks John. I am learning all about power factor now. Can the Efergy True Power Meter monitor individual circuits? I might be confusing it with another product, but I read somewhere that it can only monitor the whole house.

    I am breathing a slight sigh of relief knowing that my minisplit is not drawing so much wattage during idle mode. I still believe it is using too much energy when on and cooling. With the minisplits off at the breaker these past few days, our baseline kwh usage is 25kwh/day. With the minisplits on, we used on average 55.89 kwh/day from July 1 - August 1, 2017 with an average temperature of 77 degrees. That means the minisplit accounts for more than 50% of our energy usage. I thought that number would be lower in a well-insulated and air-sealed house.

    Again, the problem is probably 1. an oversized condenser, 2. uninsulated basement (might not be a big factor during summer), 3. improper installation of multisplit system

  10. User avatar
    John Semmelhack | | #10

    Yes...you can use the Efergy True Power Meter to monitor an individual circuit. I've been doing so for the past 12 months with my ducted mini-split.

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