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Enphase IQ8 night-time power consumption

lapsmith

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Apr 10, 2022
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I just bought some used IQ8M's. With 8 panels and inverters connected in one string, the night time current draw is .56 amps on one leg. This was measured with a Fluke clamp-on ammeter. They function normally during the day. Is this typical? It seems like a lot of wasted power. I have not connected them to an IQ Gateway yet, but one is on order; however from what I read that is only needed to change grid parameters and for monitoring.
 
I just bought some used IQ8M's. With 8 panels and inverters connected in one string, the night time current draw is .56 amps on one leg. This was measured with a Fluke clamp-on ammeter. They function normally during the day. Is this typical? It seems like a lot of wasted power. I have not connected them to an IQ Gateway yet, but one is on order; however from what I read that is only needed to change grid parameters and for monitoring.

Probably not an accurate measurement. It depends on the error of the fluke, which depends on the measurement scale range and the meter error, especially in the significant digit rating.

What Fluke?

I created an issue with my neighbor where it appeared his new A/C unit had a steady 80W draw based on a ~.35A @ 240V measurement with a Klein CL800. 80W was MAJOR for his system and would have represented about 25% of his total consumption w/o running the A/C.

When I moved to the DC side, the draw was 7W to power the electronics.

When I ran the error numbers, I discovered the meter was essentially useless for measuring low current AC draw.

Example:


States a 1.8%±5 accuracy.

This means a 1.8% error in on the total scale, PLUS a ±5 variation in the least significant digit.

That units lists a 400.0A range.

This means that the total range can vary by 1.8% as well as an additional ±0.5A, so if you're trying to measure a current small current, you're going to get a ±0.5A or 1A total error. This error is larger than the value measured. It's basically worthless.

To get a truly accurate measurement of <1A, you'd need something like this:


On the 3A scale, it would be accurate to ±1% and ±.005A
 
What Fluke?
337. Specs say accuracy is 2% - 5 count (whatever that means) @60Hz. Range is 999A. So accuracy is only 2 amps? Now I can see why you say not an accurate measurement.

20250320_083257_resized.jpg


Today I tried the meter below. I have no idea what the accuracy is, but it appears to take into account power factor. Last night, it was showing that all 8 panels were only drawing 5 watts, while the current was still .6 amps. (The picture was taken in the morning with the sun very low, thus the higher power).

So it looks like everything is working as it should. Thanks!

20250320_083530_resized.jpg
 
The "5" means ± "5" in the last digit displayed, so in addition to the 1.8%, it will have another ±0.5A.

My neighbor and I chased this down for half an hour. Learned that compressors have a ~40W heater that keep the oil from getting too cold, so I thought it might be that, but it was like 70°F out, so it didn't make sense.
 
The "5" means ± "5" in the last digit displayed, so in addition to the 1.8%, it will have another ±0.5A.

My neighbor and I chased this down for half an hour. Learned that compressors have a ~40W heater that keep the oil from getting too cold, so I thought it might be that, but it was like 70°F out, so it didn't make sense.
Got it, thanks. I never knew AC compressors have a heater. Makes sense if it is a heat pump which operates in cold weather. Wonder why one would care if the oil gets cold, if it never runs. Unless it was a commercial unit.
 
Got it, thanks. I never knew AC compressors have a heater. Makes sense if it is a heat pump which operates in cold weather. Wonder why one would care if the oil gets cold, if it never runs. Unless it was a commercial unit.

I've forgotten some details since this was a couple years ago. After a little brush up...

It has less to do with the oil (though maintaining viscosity is part of it) than it has to do with keeping the temperature above the refrigerant's boiling point to prevent the refrigerant from condensing in the compressor. The compressor is designed to pump vapor, not liquid.

Here's a blurb from a random Lennox manual:

Crankcase Heater (HR1) and Crankcase ThermostatSwitch (S40)

The reference models are equipped with a 70 watt, belly band type crankcase heater. HR1 prevents liquid from accumulating in the compressor. HR1 is controlled by a thermostat located on the liquid line. When liquid line temperature drops below 50° F the thermostat closes energizing HR1. The thermostat will open, de−energizing HR1 once liquid line temperature reaches 70° F .


@Supervstech can probably elaborate.
 
I've forgotten some details since this was a couple years ago. After a little brush up...

It has less to do with the oil (though maintaining viscosity is part of it) than it has to do with keeping the temperature above the refrigerant's boiling point to prevent the refrigerant from condensing in the compressor. The compressor is designed to pump vapor, not liquid.

Here's a blurb from a random Lennox manual:

Crankcase Heater (HR1) and Crankcase ThermostatSwitch (S40)

The reference models are equipped with a 70 watt, belly band type crankcase heater. HR1 prevents liquid from accumulating in the compressor. HR1 is controlled by a thermostat located on the liquid line. When liquid line temperature drops below 50° F the thermostat closes energizing HR1. The thermostat will open, de−energizing HR1 once liquid line temperature reaches 70° F .


@Supervstech can probably elaborate.
A little off topic, but I learned something new. Although after a bit of googling, I'm not sure why more residential HVAC systems don't have crank case heaters. I personally never use the AC until the outside temps are in the upper 80's. I've also never had a unit with CCH in any of my homes.

There was some good discussion here.
 

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