Turn off A/C unit over winter?

techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
As I was shoveling the snow around my heat pump yesterday, I glanced at the A/C unit sitting next to it and saw the warning about the crankcase heater that was stuck to the side. That got me thinking. About 65% of the year that A/C unit sits there doing nothing. The heat pump probably isn't used 10% of the year. During those times the crankcase heaters are heating away - 50 watts? 100 watts? 24/7. At 50 watts each that would be about 367 kw per year of useless heating! Why not kill the breakers to those units during the down times?

I realize when I need them again I would have to be careful about energizing them and keeping the thermostat off for whatever length of time is stamped on that warning. I didn't pay close attention to the timeframe since I had been shoveling snow for 3 hours straight and I was dead tired.

I will be converting over to mini-splits starting next year (doing one room at a time as money allows), and this question would apply to them, too. The kicker is when I'm done I'll have around 6 units instead of 2, and even though I could only turn them off for 10% of the year with 6 of them I'm still up at around 262 kw saved per year.

Ouch.
4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is

Comments

  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Turn off A/C unit over winter?

    Yes - if you know you won't be using your heat pump or AC for a while, it's not a bad idea to turn them off.

    50-100w is about right depending on the size of the unit.

    Most recommendations I have heard are to make sure it's on for about a day before using it after turning it back on for use.

    Sure would be nice if those crankcase heaters weren't needed - they can account for a substantial part of a home's usage!
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Turn off A/C unit over winter?

    Ok, dumb question.

    I know of the heaters on heatpumps, but on an AC only unit ???
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Turn off A/C unit over winter?
    n3qik wrote: »
    I know of the heaters on heatpumps, but on an AC only unit ???
    Yes - AC units are just like heat pumps - except they only run in one direction...
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Turn off A/C unit over winter?

    My two cents, which is probably worth even less. One suggestion is that A/C units be run once a month to keep the lube oil and the coolant circulating, and the seals in tact. Now, with that said, there are millions of window A/C units that sit for ten months a year, and then they are fired up. In the absence of other information, it (the OP's question) is not something I would worry about.

    T
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Turn off A/C unit over winter?

    On the other hand, those of us who live in cold climates are told by vehicle manufactures that about 80% of a vehicle's engine wear occurs during the first few seconds after start-up, before the lubricating oil has been fully circulated through the engine. If that were to hold true with compressors in AC etc, those extra and otherwise unnecessary starts could actually add to the units wear.
    Food for thought.
  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Turn off A/C unit over winter?

    Ok, so it sounds like its doable. I'm going to go turn off my A/C's breaker right now. My billing cycle starts in a few days so I'll know in a little over a month what affect its had. I assume it will be between 1.5 and 3 kw, a nice reduction and yet another vampire load found and fixed. Wish I had known about this years ago.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Turn off A/C unit over winter?

    I know commercial AC units have crankcase heaters (the larger they are, the more common they are) but I thought most small - especially residential - units didn't have them. (Thus the old warning not to run the AC below - usually - around 65 degrees outside.) Perhaps newer units do have them now as a standard item.

    I'll have to check mine - I remember when I was tracking daily power usage (reading the meter each morning) I had the feeling there was 3-4 kWh/day I couldn't account for. Maybe that's (part of) it!
  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Turn off A/C unit over winter?

    I double-checked the warning sticker this evening, it says to turn it back on for 30 minutes per pound of refrigerant charge. The charge is supposed to be stamped on the back on the name plate but since I haven't dug out around the A/C figuring that out will have to wait.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • solar_davesolar_dave Solar Expert Posts: 2,367 ✭✭✭✭
    Re: Turn off A/C unit over winter?
    techntrek wrote: »

    I will be converting over to mini-splits starting next year (doing one room at a time as money allows), and this question would apply to them, too. The kicker is when I'm done I'll have around 6 units instead of 2, and even though I could only turn them off for 10% of the year with 6 of them I'm still up at around 262 kw saved per year.

    Ouch.

    You may want to consider the multiple way mini splits. I just put in a 3 way mini split and a single base unit with 3 wall units would be much more cost effect. Each wall unit is separately programable and base unit only runs hard enough to meet the demand of each wall unit. You can also size each wall unit for a per room load, upto the capacity of the base unit.
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Turn off A/C unit over winter?

    I have a Sanyo mini-split (ASHP) and there was some periods of time last year,
    when we didn't need heat or cooling. So, I opened the breaker.

    I had a power monitor (actually two of them now) connected (to the Sanyo) and could see
    the wasted power displayed every day!
    The low end accuracy isn't too good, but I think the heater draws around 50-70 watts, 24/7.

    z002.jpg

    IIRC, I saw a bit lower power drain on warmer days..
    But, it's a continuous drain, no thermo shut offs..

    You can see the two white heater connectors at the base of the compressor.
    http://i46.photobucket.com/albums/f147/Xringer/NCL/r001smaller.jpg
    it's got a coil spring in the center, holding the heating wire tight around the casing.
    There is also some stand-by AC-DC power supply drain too.

    If you close the breaker on a cold day, you should give the heater a chance
    to warm up the compressor, before calling for heat.

    In the summer, I don't thinking waiting for warm-up is important.
    (Since the compressor will likely be really warm already)..

    Cheers,
    Rich
  • LucManLucMan Solar Expert Posts: 223 ✭✭✭
    Re: Turn off A/C unit over winter?
    techntrek wrote: »
    I double-checked the warning sticker this evening, it says to turn it back on for 30 minutes per pound of refrigerant charge. The charge is supposed to be stamped on the back on the name plate but since I haven't dug out around the A/C figuring that out will have to wait.

    Rule of thumb energize for 24 hrs before operation.

    Look into the Fujitsu Halcyon Hybrid Flex unit, they are capable of connecting from 2 to eight air handlers to one condenser. This system is replacing original multizone line.
    This is similar to the commercial Mitsubishi City Multi system. The latest technology in heatpumps.
  • BB.BB. Super Moderators, Administrators Posts: 31,054 admin
    Re: Turn off A/C unit over winter?
    XRinger wrote: »
    If you close the breaker on a cold day, you should give the heater a chance to warm up the compressor, before calling for heat.

    In the summer, I don't thinking waiting for warm-up is important. (Since the compressor will likely be really warm already)..
    I don't think I would want to risk that assumption.

    My guess is that the freon will settle to the coolest/lowest point in the system. The thermal mass of the pump plus crankcase oil (and in Rick's picture, the pump was insulated)--it is very possible that a system "at rest" for a period of time will still have freon/refrigerant condense in the pump.

    The case heaters setup a process were the motor is hotter than any other point in the system. And that (over time) drives any liquid freon from the crankcase to anywhere else in the system.

    With AC power/heaters off, the system is at equilibrium and there is no guarantee where the refrigerant will settle. Add the unknowns of inside unit/outside unit temperatures (day/night/sun/shade)--and I would not want to make a blanket statement that the heaters are not needed in the summer.

    Even with systems operating during summer (or winter) every few hours, I would not disconnect the heaters... It would be too unpredictable as to when freon would begin to collect in the pump (hours, days?, outside temperatures affect how? etc.).

    It would probably be nice if the vendors put an excess liquid detector in the crank case and controlled the heaters based on need instead of just 100% on all the time--But that may be for a new generation of pumps.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Turn off A/C unit over winter?
    BB. wrote: »
    I don't think I would want to risk that assumption.
    clip-clip
    and I would not want to make a blanket statement that the heaters are not needed in the summer.

    -Bill


    That's just me, I never turn on the cooling (after a long outdoor cooling period),
    unless it's really getting hot indoors. And that always means it's brutal outdoors..
    If we come home to a hot house (solar gain) and it's cool outdoors, we
    just open the doors and windows. It's only a little slower than using AC,
    but cool fresh air is a lot cheaper.


    One thing I noticed it my Sanyo manual, since it covers both my 24,000 BTU unit
    and the very similar 18,000 BTU unit.. Is, there is no heater on the 18,000 BTU unit.
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Turn off A/C unit over winter?
    BB. wrote: »
    It would probably be nice if the vendors put an excess liquid detector in the crank case and controlled the heaters based on need instead of just 100% on all the time--But that may be for a new generation of pumps.
    Yes - a temperature sensor in the sump along with an ambient temperature sensor should provide enough data to modulate heat to avoid a lot of the power draw.

    I believe that my Trane XL20i will keep the heaters off for at least a couple hours after it has been run, and if ambient temps are over 85*F or so it will also turn them off.
  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Turn off A/C unit over winter?
    solar_dave wrote: »
    You may want to consider the multiple way mini splits.

    Actually 6 condensers is with two multi-room systems and four single-room systems. My plan is to put the most-efficient single-room systems (26 SEER) in the rooms that are used the most, and the less-efficient systems (mid-teen SEERs) in the rest - leaving those rooms cold in the winter and warm in the summer.

    It would be nice if the heaters on A/C-only units were killed when ambient temps are below let's say 65 F.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • JESSICAJESSICA Solar Expert Posts: 289 ✭✭
    Re: Turn off A/C unit over winter?
    BB. wrote: »
    I don't think I would want to risk that assumption.

    My guess is that the freon will settle to the coolest/lowest point in the system. The thermal mass of the pump plus crankcase oil (and in Rick's picture, the pump was insulated)--it is very possible that a system "at rest" for a period of time will still have freon/refrigerant condense in the pump.

    The case heaters setup a process were the motor is hotter than any other point in the system. And that (over time) drives any liquid freon from the crankcase to anywhere else in the system.

    With AC power/heaters off, the system is at equilibrium and there is no guarantee where the refrigerant will settle. Add the unknowns of inside unit/outside unit temperatures (day/night/sun/shade)--and I would not want to make a blanket statement that the heaters are not needed in the summer.

    Even with systems operating during summer (or winter) every few hours, I would not disconnect the heaters... It would be too unpredictable as to when freon would begin to collect in the pump (hours, days?, outside temperatures affect how? etc.).

    It would probably be nice if the vendors put an excess liquid detector in the crank case and controlled the heaters based on need instead of just 100% on all the time--But that may be for a new generation of pumps.

    -Bill

    But:

    This is what one of the most knowledgeable members of this Forum (Dave Sparks)wrote in another thread in this same section. To be honest, I don't think there is any reason to doubt what he said:

    "My contact at Sanyo told me that these units are used all over the world in places where there is no way a technician is going to vacuum down a line set. He also told me that they are used in Iraq where they have 9 hours a day of electricity. Now if you beleive that people over there wait for 24 hours before using their air conditioning you should follow the manual. If you are grid-tied why in the ----
    would you even care?

    If the 9 watt idle power is something more than a dumb controller as was suggested I am willing to take that risk. I am getting close to the end of the 3 year warranty and my home was used on their website. They took care of me!

    The strategy that we are using off-grid of running from sunrise to sunset on a much smaller than reccomended compressor was one of the things that concerned Sanyo. They seemed to think that there could be more wear but that the increased wear might be offset by the fact that we very rarely run at full BTU with this strategy.

    Off-grid has always been the cutting edge for new ideas. That is how I feel and have felt since I first got chance to do this kind of thing at HP in the late 70's.
    Go for it!"


    __________________
    http://www.sierratel.com/offgridsolar/
    "we go where the power lines don't"
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Turn off A/C unit over winter?

    "there is no way a technician is going to vacuum down a line set."

    I think he might be talking about the 3rd-world-short-cut-install.

    Instead of vacuuming out the line-set, you crack open a flare nut on one line
    and open the refrigerant-release valve on the other line.
    That floods both sides of the line-set with R410a,
    When you see R410a gas escaping, you quickly tighten up the flare nut,
    turn off the valve, and do a soapy water bubble test on all the flare fittings.

    If you get no bubbles, you open both release valves and turn on the juice.

    I have to wonder if that flush really pushes much of the air out.?.
    It seems to me, that it would condense into water and then ice.
  • BB.BB. Super Moderators, Administrators Posts: 31,054 admin
    Re: Turn off A/C unit over winter?

    Regarding the heaters--For small systems (where balance of system does not contain that much freon), they do not need heaters (depends on the total charge vs pump size).

    Also, from what I have read, they heaters more more often used in cool climates and with heat pumps.

    Will a unit fail without a heater (lockup, burnout, pump damage etc.)--May or may not. There are lots of variables.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BilljustBillBilljustBill Solar Expert Posts: 218 ✭✭✭
    Re: Turn off A/C unit over winter?
    XRinger wrote: »
    "there is no way a technician is going to vacuum down a line set."

    I think he might be talking about the 3rd-world-short-cut-install.

    Instead of vacuuming out the line-set, you crack open a flare nut on one line
    and open the refrigerant-release valve on the other line.
    That floods both sides of the line-set with R410a,
    When you see R410a gas escaping, you quickly tighten up the flare nut,
    turn off the valve, and do a soapy water bubble test on all the flare fittings.

    If you get no bubbles, you open both release valves and turn on the juice.

    I have to wonder if that flush really pushes much of the air out.?.
    It seems to me, that it would condense into water and then ice.

    Here in North Central Texas, most of the AC installers never pull down their new lines..... Eleven years ago, when a "Trane" dealer installed a new furnace and AC system that used the old refrigerant, I questioned why they didn't...

    The owner of this large company said that they open the compressor's factory load and push it through the lines pretty much like you described, then they let the compressor's in-line dryer-filter catch any contaminates in both the 3/8" pressure line and the 1-1/8" return line....

    He said that pulling down the lines WAS needed when doing smaller window units, fridges, and freezers.....
    Bill
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Turn off A/C unit over winter?

    "let the compressor's in-line dryer-filter catch any contaminates".

    I wonder if any metal debris goes into the filter.?.
    Since some split units do both heating and cooling, the refrigerant goes
    both ways in the lineset.. Seems like the filter would be back-flushed.
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Turn off A/C unit over winter?
    Here in North Central Texas, most of the AC installers never pull down their new lines.....

    Wow... Perhaps you're talking about residential guys? I've been working around commercial HVAC techs for 16 years now, and every one of the guys I've worked with wouldn't dream of charging a new system without pulling a vacuum. Some of them also insist on flowing nitrogen through the lines while soldering so the inside of the line doesn't get oxidized. This is even for smaller (the most recent was 5 tons) split systems.

    Had one of them install a 9000 BTU mini-split in my house a few years ago, and he even pulled a vacuum on it, line set was a whopping six feet long.
  • mr.radonmr.radon Solar Expert Posts: 158 ✭✭✭✭✭
    Re: Turn off A/C unit over winter?

    My time on Sub's, we always pulled down a vacuum before filling our R114 units. This seems pretty odd ball to me.
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Turn off A/C unit over winter?

    FWIW - the 3-ton Trane heatpump I had installed for my house last year - they vacuumed the line very thoroughly before charging it.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,494 ✭✭✭✭✭
    Re: Turn off A/C unit over winter?

    If you want to have the excellent Sanyo warranty and if you want to the lowest energy consumption you will need a written reciept as a record that the line-set was evacuated. I do know of three installations that are fine without doing this!

    I heard they were going to Butane but after Panasonic bought them I lost my contact there and so, maybe not!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail offgridsolar[email protected]

  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Turn off A/C unit over winter?

    Proof of Vacuum... :p

    vacday1.jpg

    My pump started sounding funny at 198 microns. I figured anything under 200 was okay.
  • LucManLucMan Solar Expert Posts: 223 ✭✭✭
    Re: Turn off A/C unit over winter?

    Purging refrigerant lines with the included charge may have been OK when units were using R-22 and mineral oil (no good tech would ever take this shortcut). With the newer refrigerants such as R-410A that is a really bad idea. The included filter driers are inefficient at removing the moisture from the the POE oil (synthetic polyol ester). POE oil will absorb and not release moisture ( hydroscopic).
    Proper procedure pressurize with nitrogen to 600 PSI for 24hrs to check for leaks. Then evacuate to 500 microns and let it hold for an hour, if it doesn't hold, you have moisture in the system.
    The results of a sloppy install show up several years after, with a compressor burnout usually shortly after the warranty expires. At that point it usually is better to replace the condenser than to replace the compressor as the contaminants have destroyed the refrigeration system. That is a high price to pay for allowing the tech to save a couple of hours. A properly installed residential system should last for 20 years.
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Turn off A/C unit over winter?

    My problem with the long nitrogen pressure test, it got cold over night.
    That caused the pressure to drop. by the next afternoon, it didn't get as warm,
    as the previous day.

    So, the next time I do a nitrogen test, I'll let the tank chill all night
    in the garage, and pressurize the system early in the AM, before things warm up.
    In 24 hours, the pressure should be nearly back where it started.
    Unless there is a big temperature variation, during the night.

    I would hate to try vacuuming line sets in really cold weather.
    That must be a real pain in the posterior..
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,494 ✭✭✭✭✭
    Re: Turn off A/C unit over winter?

    We do less than 1 micron at -235F for space all the time. It just takes very expensive equipment. Leaks are a major PITA.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

Sign In or Register to comment.