How much higher is refrigerator draw during the summer?

benthere · June 2010

Hi folks.

We recently bought an 25-cubic-foot bottom-freezer energy-star refrigerator (LG LFC25776SW) that is using 30% more than it's energy-star rating even with the ice-maker turned off. Energystar.gov says 416kwh/year, which should be about 1.14kwh/day. We're seeing more like 1.5kwh/day over the first 3 days. Surprisingly the first day was not different from subsequent days. The temperature controls are at the factory default of 0 and 37.

Our home is concrete block on a concrete slab in the high desert. We use a fan in the evenings to ventilate it down to about 70 deg. at 7am, then close the windows and ride the thermal mass all day. We open the windows again when the inside/outside temperatures are equal or nearly so - usually at about 80 deg. at 5:30pm. I guestimate, based on this, that the ambient indoor temperature averages 75 though we may heat faster than we cool thus raising the average. There are only two of us, but we rarely eat the same thing so door-openings may be more than the average couple.

So I recognize that the ambient temperature in the house is high, and that there is convection when the house is cooler (come to think of it, the refrigerator is near the exhaust window and maybe that exiting air isn't so cool) and so the refrigerator will require more energy. But 30%? I'm skeptical that this refrigerator is going to beat it's energy-star rating by 30% this winter.

I guess I'm just wondering if I should harass the manufacturer before I see how it performs in the winter. I bought from a vendor who will allow me to exchange the unit for a short time, but don't know if I could really do any better. It's not that we don't have the power to run it, more that I want it to operate as advertised.

I did a bunch of research here, at energystar.gov, and at consumerreports.org before buying this fridge. In the end the energystar.gov ratings were somewhat in conflict with the consumerreports.org ratings, and I chose a model that shined at energystar.gov but had not been tested by Consumer Reports. I'm starting to feel like that may have been a mistake.

Do you think a 5 deg. increase in inside temp would have nearly the same effect as running at the 5 deg. lower ambient test conditions of 70 deg. Maybe a short test could determine if the unit is operating as advertised?

Thoughts?

mike95490 · June 2010

Re: How much higher is refrigerator draw during the summer?

It's a lot like car mileage stickers. A good starting place, but nobody ever drives a car the way they get tested. Any idea how it compared to the old fridge you had ?

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

Mike,

The old fridge was propane, so I have no idea.

PS. My Honda Civic HX is rated at 39mpg and I get 45. If only I could coax that kind of performance out of my refrigerator!

mike95490 · June 2010

Re: How much higher is refrigerator draw during the summer?

benthere wrote: »

....PS. My Honda Civic HX is rated at 39mpg and I get 45. ...

Well, it obviously defective, and possibly dangerous to oil company profits. You should have it towed back to the stealer right away and tell them something is very wrong

BB. · June 2010

Re: How much higher is refrigerator draw during the summer?

For small appliances--the old Kill-a-Watt is difficult to beat for conservation work.

-Bills

solar_dave · June 2010

Re: How much higher is refrigerator draw during the summer?

Make sure you have good airflow around the fridge. check the internal temps and if colder than required adjust as needed.

I really suspect it is an optimistic test situation, like in the middle of an open room @ 20C (68F) with plenty of air flow it will use 1.14 kWh a day.

BB. · June 2010

Re: How much higher is refrigerator draw during the summer?

When I looked up one of the Off-Grid systems (don't remember brand)--their 90F testing results (WH per day) had the same results as the Energy Star Rating--So I would suspect that a steady state fridge at 90F, not making any ice, and possibly a few door openings per day--would be the test.

Interestingly, I have never found the actual Energy Star Tests themselves (fridge, freezer, washing machine, etc.) when I looked for them a couple of times.

-Bill

icarus · June 2010

Re: How much higher is refrigerator draw during the summer?

Make sure any auto defrost mode is shut off. Also, a fridge, full but not too full, will run more efficiently than one partially full. A freezer very full is better. A good solution is to keep large water jugs in the fridge if it is not full, and freeze water jugs to fill the freezer. Takes a bit to get it all cold, but the thermal mass will stay cold better than the air in the box will.

Tony

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

All,

Thanks for burning some brain-cycles on this. The refrigerator is well-ventilated on all sides and not in direct sunlight.

Bill,

1. My measurements were taken with a Kill-A-Watt meter.

2. I found the outline of requirements for refrigerators here: http://www.energystar.gov/index.cfm?c=product_specs.pt_product_specs. Google also returns some results for "10 CFR 430, Subpart B, Appendix A1" though I have not pursued them. It appears that the test simulates normal operation at 70, by running with the door closed at 90.

http://www.energystar.gov/index.cfm?c=product_specs.pt_product_specs wrote:

Test Criteria: Residential refrigerator manufacturers must self-test their equipment according to DOE’s test
procedure defined in 10 CFR 430, Subpart B, Appendix A1. Residential freezer manufacturers must self-test
their equipment according to DOE’s test procedure defined in 10 CFR 430, Subpart B, Appendix B1. When
determining energy performance for purposes of ENERGY STAR certification, the following principles of
interpretation should be applied to the existing DOE test procedures. The energy test procedure simulates
typical room conditions (approximately 70ºF) with door openings, by testing at 90ºF without door openings.
Except for operating characteristics that are affected by ambient temperature (for example, compressor
percent run time), the unit, when tested under the DOE test procedure, shall operate equivalent to the unit in
typical room conditions. Energy consuming components that operate in typical room conditions (including as a
result of door openings, or in response to humidity levels), and that are not exempted by this standard, shall
operate in an equivalent manner during energy testing under the DOE test procedure, or be accounted for by
all calculations as provided for in the standard. Examples: (i) energy saving features that are designed to
operate when there are no door openings for long periods of time shall not be functional during the energy
test; (ii) the defrost heater should not either function or turn off differently during the energy test than it would
when in typical room conditions; (ii) electric heaters that would normally operate at typical room conditions with
door openings should also operate during the energy test; and (iv) energy used during adaptive defrost shall
continue to be tested and adjusted per the calculation provided for in this standard.

solar_dave and Tony,

I recognize that there are measures that can be taken to improve our performance and I am interested in those measures, but what I'm trying to understand right now is if I'm starting at the best place.

Tony,

The fridge is not full but maybe 50% so by volume. Obviously, not all the space is usable. The freezer is practically full.

Mike,

Fat chance!

--
Ben

BB. · June 2010

Re: How much higher is refrigerator draw during the summer?

Tony mentioned turning auto-defrost off---I am not sure you can on a modern refrigerator (or frost-free freezer too??)--and you probably should not as the evaporator coils will ice-up in the matter of a day or so and the air flow will be blocked--and efficiency will go down the tubes.

Some of them have "anti-sweat" heaters on door edges (humid climates, keeps water from condensing around door openings). And those may have a switch (winter/summer setting?).

In my mild weather area--I seem to get a bit under the Energy Star numbers for fridge and freezers.

-Bill

solar_dave · June 2010

Re: How much higher is refrigerator draw during the summer?

benthere wrote: »

All,

Thanks for burning some brain-cycles on this. The refrigerator is well-ventilated on all sides and not in direct sunlight.

<Snip>

solar_dave and Tony,

I recognize that there are measures that can be taken to improve our performance and I am interested in those measures, but what I'm trying to understand right now is if I'm starting at the best place.
--
Ben

If you think about it 80F room temp is a increase in load of about 30% over 70F considering the internal temp to be 40F.

icarus · June 2010

Re: How much higher is refrigerator draw during the summer?

One of the best ways you can get higher efficiency from any fridge is to add insulation to the cabinet. Issues can arise with adding foam board over the steel case of a conventional fridge. You can (and do) get condensation between the foam board and the cabinet depending on the indoor humidity. The result can be rust on the cabinet. Also many small chest freezers actually have the condenser coils built into the side of the case, so adding insulation over the case will result in a disastrous lack of breathing of the condenser.

On my L/P fridges, they are designed to be built into RV enclosures, and as such they have no steel on the outside of the case. This makes adding insulation very easy. I just mount 2" foil faced thermax on the top, and sides of the cabinet adding ~r-10. Then I build these into the cabinetry of the house so that the added insulation isn't even seen. I have also added foam board to the outside of the doors on some installations, but then you have to make a false cover making it bit more of a challenge.

Tony

Jburgess · June 2010

Re: How much higher is refrigerator draw during the summer?

Is it an LG?

http://www.homeenergy.org/blog.php?id=44

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

Jburgess wrote: »

Is it an LG?

http://www.homeenergy.org/blog.php?id=44

Some may think me a fool, but I was aware of this settlement and bought a model that it does not apply to. I figured if anyone would be on the up-and-up it would be LG right after getting spanked by the DOE. I wonder if I bet wrong?

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

This is interesting. Assuming it's correct and that my average temperature is 5 deg over 70, I should be using about 113% of advertised or 1.29kwh/day.

I checked the kill-a-watt meter yesterday and it's running dead-on 1.5kwh/day (5.92kwh for 95 hours). I increased both refrigerator and freezer temp by 5 deg last night (5/42) to see if I can simulate operating in 70 deg. and what the results might be.

http://energystar.custhelp.com/cgi-bin/energystar.cfg/php/enduser/popup_adp.php?p_faqid=3099&p_created=1180467065 wrote:

Each 1 degree F variation in ambient temperature from the normal ambient temperature of the kitchen leads to a 2.25% to 2.5% variation in energy consumption

niel · June 2010

Re: How much higher is refrigerator draw during the summer?

increased the temp? or do you mean lowered the temp?

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

I increased the temp inside the fridge/freezer (it's much colder than our propane unit was) to try to simulate lowering the ambient temperature (which I am pretty much unable to do).

My point is to find out if the refrigerator is performing anywhere near spec.

niel · June 2010

Re: How much higher is refrigerator draw during the summer?

i think you might want the inside temp lowered to simulate the wider temp diference hotter days will yield.

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

niel wrote: »

i think you might want the inside temp lowered to simulate the wider temp diference hotter days will yield.

The average high temperature is going to peak in a couple weeks here. Soon the monsoons will cool us off!

Maybe I'm missing your point? It seems the general assumption is that I'm trying to find out if I have the power to run it or to optimize conditions to be able to run it, or just to save power (that may come yet). This is not the case.

For now, I'm trying to find out if it is performing to spec. I bought a fridge that claims 416kwh/year, and I expect it to meet that spec. THEN I will think about ways I might reduce it's actual consumption.

At 414kwh/year, this unit should be drawing 1.14kwh/day in standard conditions. Applying the maximum referenced adjustment for our actual conditions, it should be drawing an additional 12.5% or total 1.28kwh/day. This leaves 0.22kwh/day or 19% of expected draw unaccounted for.

Applying the same calculations to Jim's post here: http://forum.solar-electric.com/showpost.php?p=6254&postcount=36 it seems that he is 10% above the same calculation. Maybe the referenced 2.5% adjustment per degree is more suitable for smaller refrigerators and is not appropriate for larger ones?

Maybe my calculation is incorrect, maybe the referenced temperature offset is not enough, maybe it would only use .8kwh/day if we were 5 deg. under 70 (I'd be thrilled), maybe the Energy Star test does not simulate normal operation, or maybe I'm crazy, but the Energy Star program uses 20% as the benchmark. I don't think I should have to write-off 19% as a mystery.

I suppose another possibility is that the power off my VFX3648 is "untrue-sine" enough to account for some or all of the discrepancy. What do you think about that?

I have tested other appliances and found them right in line with my expectations. This, I think, is the first one that's been substantially different.

BB. · June 2010

Re: How much higher is refrigerator draw during the summer?

Usage also matters--Ice maker, placing warm items in fridge/freezer to cool down, etc.

-Bill

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

BB. wrote: »

Usage also matters--Ice maker, placing warm items in fridge/freezer to cool down, etc.

-Bill

True. Not guilty on either count though.

I wonder about the effects of altitude. (We live at 6,000 feet.) I would speculate there to be less conductive loss from the cabinet due to the lower air density, but the circulating and cooling fans would be adversely effected. Heat dissipation from the condenser seems like it would also be adversely effected. Anyone think that's a valid hypothesis?

solar_dave · June 2010

Re: How much higher is refrigerator draw during the summer?

this PDF talks ab out this brands condenser efficiency at altitude
http://69.41.183.10/documents/Condenser_WCE.pdf

sea level = 1.0
6000ft = 1.151

Could be an effect.

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

solar_dave wrote: »

this PDF talks ab out this brands condenser efficiency at altitude
http://69.41.183.10/documents/Condenser_WCE.pdf

sea level = 1.0
6000ft = 1.151

Could be an effect.

Very interesting. Unless I'm misunderstanding, 6000ft of elevation has a 15% reduction in condenser efficiency since the factor is applied to the THR!

Unless there are related gains elsewhere to counteract that on the cooling side, it explains enough of my extra watts to call my mystery solved.

Thank you, solar_dave!

solar_dave · June 2010

Re: How much higher is refrigerator draw during the summer?

benthere wrote: »

Very interesting. Unless I'm misunderstanding, 6000ft of elevation has a 15% reduction in condenser efficiency since the factor is applied to the THR!

Unless there are related gains elsewhere to counteract that on the cooling side, it explains enough of my extra watts to call my mystery solved.

Thank you, solar_dave!

I suspect, At 6000ft the air density is lower hence the air has less ability to transfer the heat. I also wonder about the humidity effect on heat transfer, one would think dry air is also less efficient.

icarus · June 2010

Re: How much higher is refrigerator draw during the summer?

Humidity has a significant effect on fridge efficiency, particularly with an ammonia absorption fridge. (L/P)

T

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

I have to say that I think if the condenser 15% less efficient at loosing heat, it seems like the cabinet should also loose heat 15% less "efficiently."

Here are some junk numbers to ponder. After setting the fridge/freezer to 42/5 last night, we used .91KWH in the next 24 hours. Of course we were coasting because the cabinet and food were already to the lower temperature. It will be interesting to see where the numbers stabilize in the next few days.

Dave Angelini · June 2010

Re: How much higher is refrigerator draw during the summer?

Ah the White mountains! Nice place! Just a quick question, what is the indoor temperature of the house?

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

Dave Sparks wrote: »

Ah the White mountains! Nice place! Just a quick question, what is the indoor temperature of the house?

Thanks, I agree. My long-winded answer:

benthere wrote:

Our home is concrete block on a concrete slab in the high desert. We use a fan in the evenings to ventilate it down to about 70 deg. at 7am, then close the windows and ride the thermal mass all day. We open the windows again when the inside/outside temperatures are equal or nearly so - usually at about 80 deg. at 5:30pm. I guestimate, based on this, that the ambient indoor temperature averages 75 though we may heat faster than we cool thus raising the average. There are only two of us, but we rarely eat the same thing so door-openings may be more than the average couple.

It was 65 in the house this morning. 8)

Dave Angelini · June 2010

Re: How much higher is refrigerator draw during the summer?

OK so 80F max does not put you up in higher than normal ambient. Do we get some pix? I am seeing it from memory and I looked alot in Arizona. Still burning up near Flagstaff?

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

I guess it's time I added to the "Reasons We Live Off-Grid" thread. http://forum.solar-electric.com/showpost.php?p=59662&postcount=72

PS. The fridge used just over .9KWH yesterday. I guess we're still coasting from the earlier colder settings, or that it's because we had the house down to 65 yesterday morning.

benthere · June 2010

Re: How much higher is refrigerator draw during the summer?

I'm just checking in to report that with our fridge/freezer temps set 5 deg. higher to account for higher ambient, we've used 4.44 KWH in the last four days.

I guess that probably indicates that the quoted 2.5% efficiency per degree ambient is not high enough for a large refrigerator.

How much higher is refrigerator draw during the summer?

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