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Potential energy waster in your house: air conditioner crankcase heater

holeydonut

Supporting Member
Jun 27, 2020
1,294
782
East Bay NorCal
I dunno if anyone here cares about this, but I figure someone might since it’s energy related hah.

I just learned that some newer air conditioner outdoor condensing units (in my case with a scroll compressor) come with a crankcase heater. This contraption will heat the lubricant in the compressor so the refrigerant “boils” and doesn’t soak into the lubricant oil.

The worst case is if a compressor that has been idle for months ... and then the first time it turns on, the lubricant froths causing damage to the compressor.

So why would you care about this inane topic? If you’re like me you weren’t expecting to run the air conditioner between October and March. But these crankcase heaters take 40 watts of power.

The better condensing units will have a relay or thermo-couple set point driven switch to only run the crankcase heater when it’s very cold. But I bought two top of the line Lennox Signature series in 2020, and they only have a “dumb” crankcase heater that runs 24/7 no matter what.

Since, I have two condensers, I’ve basically been running what amounts to an 80 watt bulb non stop for the last few months for absolutely no reason. That’s about 57 kWh of power in December that literally did nothing for me.

The easy fix for me is to just kill the breakers heading to my condensers. But, I need to remember to run the crankcase heater about 24 hours before the first time my air conditioning runs in the summer. This way the heater has enough time to boil out the refrigerant from the lubricant. It also helps I’m in East Bay Northern California and it never gets that cold. I don’t even prep my sprinkler and spigots for the winter since it doesn’t freeze.

Some more info is here.
Crankcase Heaters and Compressors | HVAC Refrigeration

TLDR, if you have a crankcase heater on your air conditioning condenser, you could be wasting money.
 

holeydonut

Supporting Member
Jun 27, 2020
1,294
782
East Bay NorCal
Sorry I heard back from my Lennox installer and he was able to confirm that Lennox Signature series condensers (including the XP heat pump) have a factory installed crankcase heater that also has a thermometer to activate the heater only when it's cold. The Signature Series does not use the "dumb" type of crankcase heater that is always-on.

I don't want to be accused of libel, but I cannot edit my original post.


I am under the new understanding that the crankcase thermostat triggers the heater to turn on at 50F, but doesn't turn it off until the thermometer hits 70F. This is is why I perceived it as "always on" since our ambient temperature in December is cold enough to trigger the heater even though I have no intention to start the condenser.

upload_2021-1-27_18-32-49.png



If you do turn off the breaker to save electricity, Lennox advises:
upload_2021-1-27_18-30-32.png
 
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Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
Sorry I heard back from my Lennox installer and he was able to confirm that Lennox Signature series condensers (including the XP heat pump) have a factory installed crankcase heater that also has a thermometer to activate the heater only when it's cold. The Signature Series does not use the "dumb" type of crankcase heater that is always-on.

I don't want to be accused of libel, but I cannot edit my original post.


I am under the new understanding that the crankcase thermostat triggers the heater to turn on at 50F, but doesn't turn it off until the thermometer hits 70F. This is is why I perceived it as "always on" since our ambient temperature in December is cold enough to trigger the heater even though I have no intention to start the condenser.

View attachment 631429


If you do turn off the breaker to save electricity, Lennox advises:
View attachment 631427

Interesting, so the heater basically turns itself on all winter. That's not a super bad design and protects you just in case your kids wanted to start that AC some chilly January morning at 65 degrees to play north pole.
 

holeydonut

Supporting Member
Jun 27, 2020
1,294
782
East Bay NorCal
Thx OP. hmm, my carrier unit is about 15 yrs old. Too old to have this problem?

I found this issue because I got an Emporia Vue to start hunting evil energy gremlins. I forget who here calls it "suds" but I chuckle at that euphemism. I think the Vue has basically paid for itself at this point since I've discovered many sneaky-bastard energy leeches with it.

If you don't want to blow that much money, you can get a handheld clamp meter with a CT and just stick it on the hot wires entering your condenser unit. Amazon has this example (I can't vouch if this brand is any good, but the link should give you an idea of what I'm talking about).
 
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holeydonut

Supporting Member
Jun 27, 2020
1,294
782
East Bay NorCal
Interesting, so the heater basically turns itself on all winter. That's not a super bad design and protects you just in case your kids wanted to start that AC some chilly January morning at 65 degrees to play north pole.


Lol turning off the breakers for the condensers also prevents the harm haha. Now I know why my dad would get so pissed if I touched the thermostat.

I guess there are some climates where daytime gets super hot, but the night time is below 50F. If your condensers aren't in the direct sunlight, there's a chance your AC kicks on before the compressor has heated up enough to boil away the refrigerant. It's a weird use case, but I guess it helps with compressor longevity.

I just wish the freaking manuals would talk about this in more detail (like in layman terms) so you'd know to kill the breaker when it's winter-time. After having a 20 year HVAC guy at my house who was stumped, it appears this crankcase heater isn't common knowledge.
 

CrazyRabbit

Member
Apr 21, 2020
386
117
Fort Worth TX
what other sneaky bastard energy leeches have u found?

looks like thermostat is on liquid line so i doubt it will ever turn off till it is warm out.

i don't like hvac service people, you always feel raped after they service your system. i now do my own work, i even installed a new condenser unit. i converted over from r-22 to the new stuff, installed expansion valve and flushed the system. works great and draw 2/3 the power. hvac people don't like it if you do your own work, they think you are stealing food from the mouth of their children. isn't that what they are doing to us!
 
Last edited:
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holeydonut

Supporting Member
Jun 27, 2020
1,294
782
East Bay NorCal
what other sneaky bastard energy leeches have u found?


I was able to monitor the usage pattern of my wine fridge and found the compressor never turned off. It turns out we set it to 40F, but it simply couldn't cool down that low so it kept running all the time. We set it to 45F, and it started to cycle normally. Went from taking 3 kWh per day to 1. That alone basically made the Vue worthwhile haha.

I found some bulbs that I neglected to change to LEDs. Like the kitchen vent hood was using 200 watts for lighting during cooking. And my mother in law liked to keep her walk in closet light on since it gave a nice glow during night-time.

There were some technology stuff in the family room that sucked about 100 watts overnight (DVR, Xbox, laptop charger, subwoofer, etc). I put one of those smart timers on the plug so the things would be completely shut off overnight and turn on by itself later. I guess if I ever do a late-night Xbox session I'll be pissed when it auto-shuts-off lol.

I put my garage lights on a timer switch and the laundry room on a motion switch so I never had to worry about "did those turn off?" Sometimes they were accidentally left on before.

I also replaced some hallway outlets and bathroom GFCI those ones that have integrated night lights so people would stop turning on lights at night and not turning them off.

But for sure the biggest winter-time savings is going to be the two crankcase heaters. 5% of my December power kWh usage was literally these things and I received zero benefit since I don't run AC in December.

Here's a study from the NRDC that identifies some other common energy wasters.
https://www.nrdc.org/sites/default/files/home-idle-load-IP.pdf
 

vickh

Active Member
Dec 16, 2018
3,097
480
az
I was able to monitor the usage pattern of my wine fridge and found the compressor never turned off. It turns out we set it to 40F, but it simply couldn't cool down that low so it kept running all the time. We set it to 45F, and it started to cycle normally. Went from taking 3 kWh per day to 1. That alone basically made the Vue worthwhile haha.

I found some bulbs that I neglected to change to LEDs. Like the kitchen vent hood was using 200 watts for lighting during cooking. And my mother in law liked to keep her walk in closet light on since it gave a nice glow during night-time.

There were some technology stuff in the family room that sucked about 100 watts overnight (DVR, Xbox, laptop charger, subwoofer, etc). I put one of those smart timers on the plug so the things would be completely shut off overnight and turn on by itself later. I guess if I ever do a late-night Xbox session I'll be pissed when it auto-shuts-off lol.

I put my garage lights on a timer switch and the laundry room on a motion switch so I never had to worry about "did those turn off?" Sometimes they were accidentally left on before.

I also replaced some hallway outlets and bathroom GFCI those ones that have integrated night lights so people would stop turning on lights at night and not turning them off.

But for sure the biggest winter-time savings is going to be the two crankcase heaters. 5% of my December power kWh usage was literally these things and I received zero benefit since I don't run AC in December.

Here's a study from the NRDC that identifies some other common energy wasters.
https://www.nrdc.org/sites/default/files/home-idle-load-IP.pdf

pf 17 is interesting. Here in AZ. HVAC is the #1 consumer of power by far no big offenders.
 

getakey

Active Member
Jan 28, 2020
1,134
373
95762
I was able to monitor the usage pattern of my wine fridge and found the compressor never turned off. It turns out we set it to 40F, but it simply couldn't cool down that low so it kept running all the time. We set it to 45F, and it started to cycle normally. Went from taking 3 kWh per day to 1. That alone basically made the Vue worthwhile haha.

Even 45 is cold for wine. I have dual settings on mine and I keep it at 50/57
 

Barrygold

Member
Jun 20, 2019
421
466
Midwest
On the subject of saving some kWh. I switched to a full size heat pump clothes dryer. Here is the power draw. On eco-mode she peaks at 1.7kWh. Dry cycle is approx 1.5 hrs.
4BF52AB9-23DD-45E1-A5A7-022949124B93.jpeg
 

CrazyRabbit

Member
Apr 21, 2020
386
117
Fort Worth TX
i use smartthings to control every light in my house; thermostats, lights, locks and alarm integration. so if i open a window, my ac/heat will shut off (unless it is freezing, i don't want pipes freezing), doors will lock if left unlocked, motions will turn on lights inside and outside based on sunset/sunrise, etc.

I noticed my subwoofers in my entertainment system draw about 40 watts in standby so i plugged them into a smart plug and added them to my harmony routine to turn on. my xbox won't turn off on me, lol.

but each smartthings device has a small current draw.. but still save me energy.
 

holeydonut

Supporting Member
Jun 27, 2020
1,294
782
East Bay NorCal
only drawback is clothing will wear a little more due to longer dry cycle.


Since you got Smarthings, you should check out the smart Samsung smart washer/dryers.
https://www.lowes.com/pd/Samsung-Fl...d-Electric-Dryer-White-Energy-Star-Certified/
https://www.lowes.com/pd/Samsung-Fl...ront-Load-Washer-White-ENERGY-STAR/1000210037

I got the pair with crazy discounts form Lowes and Samsung rebates in 2019. I couldn't find any of those ventless dryers in the 7+ cubic ft size.

For the Samsung dryer, in "Eco" mode it takes 1:15 to run a dry cycle. And my Emporia Vue measured it to be about 2 kWh.

Plus for the washer, you can start the washer remotely where you prep a load before you leave for work, but start it before you get home. So it's ready for transfer over to the dryer. The top loads are also super handy if you've got workout clothes or delicates.
 

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