A/C SEER rating hogwash!!!

[Sam the Caveman]

Been looking into these "SEER" ratings and it looks like the way they rate the units with 2 stage compressors is by measuring the electricity used on the lowest compressor speed and then they will use the btu rating for the unit, which is measured with the compressor on the highest speed.

To me, this is nothing but trickery. A 13 seer 5 ton a/c unit and an 18 seer 5 ton a/c unit both running on full blast use the same amount of electricity!!!

It's a bunch of nonsense hogwash.

I can only assume it is the same way with those mini splits with "inverter" technology. The inverter allows the use of a DC compressor motor which can be speed adjusted and reduce electricity usage, whereas an ac compressor can only be set for predetermined speeds the motor is designed for. The way those mini split inverter a/c's can have those 26 SEER ratings is because they put a dc motor in there that can be adjusted down to, say, 1rpm (exaggeration, but you get the idea).

Another thing, the way they measure SEER ratings is they measure the electricity usage of the specific a/c with the outdoor air temp at 82f and the indoor temp at 80f. ignore>(ooooo, wow, big F'in deal, 2 whole degrees, who comes up with this shit?)

The EER ratings is what measures the efficiency of the units running the compressors at full speed. This is the number you use to judge how efficient your unit is. Also, when they run these tests, they measure electricity usage of the unit when the outdoor air temp is 95f and the indoor air temp is 80f.

If there are any a/c folks out there who may be able to correct my judgement here, please do so, I would love to be wrong.

(last year I spent a lot more money on an a/c unit for my house that was an 18 seer, thousands more than the 13 seer, I would love to be wrong on this, but my electricity bill says otherwise)

 

[habeeb]

man, I can't even tell you..

I just got the highest SEER I could, SEER 23

here's some more info on SEER, for people who can understand it.. I can't...


electric bill might not really accurate though to gauge? as many things can change that.. drying machines, light bulb use, summer rates, tier rating, house air cons, stoves.... and on and on and on.

 

[Sam the Caveman]

Alright, for your house, having an a/c with a high SEER value will save you money when the temp difference from inside your home and outside your home are small, say, like 5 degrees. During those times the electricity bill isn't that high anyways, so your not really saving that much for the extra thousands you spend on a high SEER unit. When its 100f+ outside and the unit runs nonstop, those are the days that run the electricity bill up and on those days it makes no difference if you have a 10 seer unit or an 18 or a 26.

My initial post was in regard to cooling grow rooms, where an ideal room that has a properly sized a/c may only cycle off a handful of times a day.(<5) The rest of the time it is running full blast, so it makes no difference it you have a 10 seer or a 26 seer, they will both use the same amount electricity.

 

[Midnight]

http://www.acdirect.com/popups/truth_about_seer_ratings.php

The Truth about Seer Ratings

As with anything having to do with energy conservation SEER is probably the least understood concept, both by homeowners and contractors. Simply put, SEER stands for Seasonal Energy Efficiency Ratio. The resulting number that is applied to an air conditioner is called it's SEER rating. The higher the SEER rating the more energy efficient a given air conditioner is. (we're assuming for comparison purposes that all other variables are the same between the systems compared).

Here's where the confusion begins: How high is high enough? Given a choice of 5 different SEER rating which one should you select? The answers provided to homeowners here are almost always incomplete, if not just plain wrong.

Let's start by remembering that the most efficient air conditioner known to man is one that is in the "off" position. Period. The least efficient air conditioner is one that runs continually, never shuts off and never cools the home. Between these two extremes are many shades of gray that we will attempt to clarify here. Think of SEER ratings the same way you do MPG ratings for automobiles, but instead think of Btu's per watt.

Assuming that you are offered 4 choices of SEER ratings that span the gulf between the federal minimum (13 SEER) and the current extreme high (23 SEER) and are left to fend for yourself in the selection process, let's examine how you can make the one right choice every time. (And there will always be just one right choice for you).

Your odds are much greater than 1 in 4

Chances are, you would be offered 2, or 3, or 4 SEER rating choices along with some limited and/or biased information about the best choice and finally settle after discovering that you haven't been equipped with the right information to choose the one (and only one) right SEER rating for your needs. Now for a little light math.

SEER is simply a formula that is described by the outcome of the following:

Divide the system's rated Btu's by it's stated SEER rating to determine how many watts it consumes per hour, (Kwh stands for kilo-watt hour).
Here's the formula (we'll use a 3 ton, 15 SEER system for this comparison):

36,000 Btu's (3 tons) divided by 15 SEER = 2400 (**remember this number**)
Not too bad so far (your past the hardest part) but what does the outcome (2400) mean? This is simply the number of watts consumed each operating hour by the system.

The last step is too determine your annual operating cost to use as a basis of comparison to determine which of the multiple SEER rating choices you've been offered is best.

To do that we need to know how many hours, on average, your system will operate. While many factors are involved here let's assume that you operate your system the same way most people in your geographical area do. This assumes that you:

Set your thermostat at or near 78 most of the time

Turn up/ off your system when you're gone for 4 hours or more

Change your filter about 40% less than you should

Have the system tuned up periodically

Live in a home of average insulation and have average quality windows.

Let's agree to agree

If we can all agree that these relatively simple assumptions will form the basis for our comparison, let's move to annual operating costs as an outcome of SEER rating.

Fortunately, a lot of study has been done to tell us how many hours our air conditioner will operate based on our geographical area and using the assumptions listed above. To keep it simple, we'll use an average in Florida, or 2500 hours of operation hours annually.

Remember the number 2400 from above? That was the amount of watts our example 15 seer air conditioner consumed each hour it operated. Now that we know our number of operating hours annually (2500) we simply multiply these two numbers to get the total numbers of watts consumed on an annual basis.

Here's how it works:

2400 hours of operation X 2500 watts consumed per hour = 6,000,0000????
Now hold on just a minute

I know what you're thinking - "you promised 'light' math and 6,000,000 is hardly light!" You are correct so let's simplify. If you have a copy of your power bill handy (I'll wait) you'll notice you are billed in increments they refer to as Kwh. This is simply a unit of 1000 watts, which is how they calculate your bill. We just need to convert our formula to theirs, which we will do by dividing the total watts consumed per hour (2500) by 1000, which equals 2.5

2500 divided by 1000 = 2.5

This new number (2.5) represents the number of watts your system consumes hourly, expressed in one thousand watt units, or in this case 2.5 of these thousand watt units (Kwh)

Now let's go back to our previous calculation:

2400 hours of operation X 2.5 Kwh consumed per hour = (ta da) 6000 Kwh consumed by our example air conditioner annually.
(Don't worry - at the end I'll give you a simple review calculation that will have you getting annual operating costs faster than a cat's ear on a fly farm).

Quick review

Here's how we determine energy consumed (watts)

Divide Btu's produced by the stated SEER rating

Ex. 36,000 (3 tons) divided by 15 SEER = 2400 (watts)
Convert this to a figure used by your power company to calculate your bill

Ex.2400 watts divided by 1000 = 2.4 Kwh (2.4 one thousand watt units)
Determine the number of annual hours used by the operation of your air conditioner based on your geographical region.

Ex. Florida air conditioners operate an average of 2500 hours annually.
Multiply the number of Kwh your air conditioner consumes (2.4) each hour times the number of hours it operates annually (2500) to determine annual Kwh usage

2.4 Kwh X 2500 hours annually = 6000 Kwh annual consumption

Home at Last

Now all that is left is to convert these numbers to an annual cost in terms of something we all know a thing or two about - dollars. To do that lets look again at your power bill and determine the total cost per Kwh. (Hint - It will be between 10 - 12 cents around most areas of Florida). This is your cost for each Kwh your air conditioner (or any electronic appliance for that matter) consumes. Our studies show that FPL customers pay 11.5 cents per Kwh, including taxes, franchise fees, peak usage, feudalistic surcharges, (just kidding, Mr. Power meter reader) etc.

6000 Kwh consumed annually X 11.5 cents per Kwh = 690 or $690.00. (enter it in your calculator exactly as 6000 x .115 to avoid confusing decimals and zeros).

Light Speed review

36,000 Btu's divided by 15 Seer = 2400
2400 divided by 1000 = 2.4 Kwh consumed each hour

2500 hours of operation annually

2500 x 2.4 = 6000 Kwh consumed annually

6000 x 11.5 cents cost per Kwh = 690 or $690.00 annual cost of operation for a 3 ton, 15 SEER air conditioner.

Use this quick formula for each Seer option you are offered.

Let's fast forward to the annual operating cost for each of the following using the same 3 ton system:

13 SEER = $805.00

14 SEER $747.50

16 SEER = $632.50

23 SEER = $448.50

3000 SEER (Just kidding - but can you do it??) Get it right and we'll knock an additional $75.00 off your price of any complete system.

You'll notice when you divide 36,000 by 13 SEER you get 2769.2307. Don't be confused, just drop everything to the right of the decimal and round 2769 to 2800. You'll be very, very close.

Now What?

You now want to determine the one and only one SEER rating that is right for you. The answer is simple and here is what everyone leaves out: (signed non-disclosure required at this point - aw, what the heck)

Before we get to that let's establish what we are really trying to accomplish; which is the one (and only one) right SEER choice for you, or, which one will cost you the least to own in terms of purchase price and operating costs. (We assume that you are receiving a 10 years parts and labor warranty like offered by AC 4 Life on all systems at no additional charge so repairs will not be a factor)

Here is the most important variable you need to answer (not your salesman)

How long do you plan on owning and operating the system, or, how long will you live in the home the system is purchased for? This is the absolute key to your decision because the shorter your ownership period the greater your total cost will be due to a shorter amitorization time of the purchase price. (the fewer years you can spread the purchase price over before you no longer receive any operational benefits - genius, huh?). Unfortunately, from my years in the field this is almost never brought into the equation.

The time value of money is defined (by me) as the opportunity value of other investments missed because of your increased investment in a SEER rating higher than 13. Huh? Let's assume your system is broken and you need a new one. We know that 13 SEER is the "floor" pricing because, assuming you shopped around, 13 SEER will be the lowest price you are offered as it the federal minumum in terms of efficiency, hence it is the base, or floor pricing.

Incremental What?

Let's assume your "floor" pricing is the pricing of a 13 SEER system sold by AC 4 Life. (funny how their name keeps coming up isn't it?), that price being $4148. Let's assume AC 4 Life (or any contractor) offers 3 other SEER options with installed pricing as follows:

14 SEER - $4870

16 SEER - $5925

23SEER - $8177

We don't need to calculate the return on the 13 SEER because you have no incremental increase in investment because it is your "floor" pricing - everything else is compared to the 13 SEER to determine if the increased price will pay itself back to you. Remember, your system is broken and you need it replaced so 13 SEER is the choice everything else is compared to, hence the "incremental" increases are the price differences associated with any given (higher SEER) system as compared to the 13 SEER system... Just the difference, not the total price.

*Hint - Don't let your contractor "assume" your existing system is a 6 or 7 or 3 SEER and compare the new one to it. This is a trick of the trade that you want to avoid at all costs if you have to replace your air conditioner anyway.) Make all comparisons to a 13 SEER and don't let them play what I like to call the "Make up a SEER rating and play the Investment Shenanigans" game. No fun for you at all.

Let's see what we have using the pricing above.

Begin by comparing the 14 SEER to the base pricing of the 13 SEER

13 SEER - $4148

14 SEER - $4870

Difference between the two is $722.00. I asked you earlier about your expected ownership period and that is the next variable in our search for true value. Let's use 5 years because that is the number most quoted when homeowners are asked how many more years they plan to live in their current residence. (the fact that they usually stay longer is irrelevant to us).

That means that the additional (incremental) increase to purchase the 14 seer over the 13 seer is going to cost you $722.00. This is the base number you are trying to determine whether or not will be returned to you from the annual operating cost reduction achieved by the 1 point increase in SEER rating.

Let's look at the annual cost again to determine the savings achieved by the one point advantage the 14 SEER has over the 13 SEER

13 SEER = $805.00

14 SEER $747.50

16 SEER = $632.50

23 SEER = $448.50

The 14 SEER saves $805.00 - $747.50 = $57.50 over the 13 SEER each year. Multiply this annual savings times your expected years of occupancy and you have a grand total over our 5 year assumption that equals $287.50 (5 X $57.50=$287.50). This falls way short of the total incremental increase in floor pricing of $722.00, therefore based on SEER rating alone this would not be a good investment for only 5 years of ownership.

Be sure to factor in utility rebates and federal tax credits when calculating your return as these reduce your purchase price accordingly. There are federal and local utility enticements in place to make the higher SEER rating options more attractive to homeowners. Using AC 4 Life pricing, these credits will generally smooth out the pricing difference to some degree, but that assumption can't be made with all pricing you'll receive elsewhere. (There is another argument that can and will be made for the 14 seer, but for our purpose here, we are strictly confining SEER rating as your selection criteria. I have also ignored the opportunity cost of incremental price increases purposely*)

*Hint - Don't fall for another common trick whereby the 13 SEER option is prohibitively priced to make the higher SEER ratings seem like an outstanding value. The idea here is to make higher SEER ratings appear to provide lower incremental price increases, thereby unfairly enticing you to consider them. Avoid this shell game entirely by using the average of your 13 SEER estimates to establish your floor pricing, throwing out any pricing from shell game antics.

When you purchase a new air conditioning system for your home, you may be offered a bewildering maze of options, including higher SEER ratings. It is your contractor's job to provide you with clear, concise information that will allow you make a confident, informed choice about these options without resorting to the "trust me" principle. Call us toll-free at 1-866-862-8922 if you are having trouble getting the answers you need and we will be happy to spend a few minutes with you, even if you are purchasing elsewhere.

* For you financial types out there, actuarial data and time value is ignored here primarily because most of us don't actually invest our savings, but instead spend it in a discretionary basis on items of depreciating value. As a secondary issue, other ROI comparisons for various consumer products don't calculate these values either, serving to skew any comparison of products (of dissimilar nature) using unlike values of comparison.

 

[Sam the Caveman]

All that data is F'ed up because they fail to use one HUGE piece of info.

When they make a statement such as "a 36,000 btu 15 seer unit uses 2400watts" they fail to say if that electricity consumption is with the compressor in high or low. The SEER rating agency runs them on low to determine the electricity usage, but then it's not a 36,000 btu unit if the compressor is on low, but then they still use the 36,000 btu rating to calculate the SEER rating.

Did ya'll even read my first post?

 

[supersmallgiant]

Been looking into these "SEER" ratings and it looks like the way they rate the units with 2 stage compressors is by measuring the electricity used on the lowest compressor speed and then they will use the btu rating for the unit, which is measured with the compressor on the highest speed.

To me, this is nothing but trickery. A 13 seer 5 ton a/c unit and an 18 seer 5 ton a/c unit both running on full blast use the same amount of electricity!!!

It's a bunch of nonsense hogwash.

I can only assume it is the same way with those mini splits with "inverter" technology. The inverter allows the use of a DC compressor motor which can be speed adjusted and reduce electricity usage, whereas an ac compressor can only be set for predetermined speeds the motor is designed for. The way those mini split inverter a/c's can have those 26 SEER ratings is because they put a dc motor in there that can be adjusted down to, say, 1rpm (exaggeration, but you get the idea).

If your ac is sized correctly it doesn't run full blast 100% of the time so... Does your car get better gas millage if you stomp on the gas every time you want to move or if you use just enough throttle to go the speed you need.

 

[Sam the Caveman]

If your ac is sized correctly it doesn't run full blast 100% of the time so... Does your car get better gas millage if you stomp on the gas every time you want to move or if you use just enough throttle to go the speed you need.

not a very good analogy, but I see what you are getting at. Thats not the point I'm making. I'm saying the specific way they calculate the SEER rating is very misleading based on the numbers they choose to use, which don't make any sense.

In grow rooms, you need to remove heat produced by the lights, that produce a constant amount of heat over the time span that they are on. If you have an appropriate sized a/c, during the hottest part of the year it should be able to cool your room to the desired temp while running nearly non-stop. This also helps remove humidity in the room the longer the a/c runs. If the a/c is over powered it will constantly cycle on and off without removing much humidity. Then your de-humidifier will have to work overtime to get the humidity down and in turn it produces more heat.

Say you have 7, 1kw lights you want to cool. Should you get a 13 seer 3 ton unit or a 18 seer 3 ton unit?

It doesn't matter, because both units can only remove 36k btu's/hr. So having a 2 speed compressor with a high and low is pointless, since the low will never be utilized on the 18 seer unit since there will always be 36k btu's that need to be removed. Now if you wanted to buy a 5 ton 18 seer unit, it probably could cool the place on the low speed, but it would still use the same amount of electricity it takes to remove 36k btu's, and maybe even more since the EER ratings on the larger units are sometimes less than the smaller ones.

The only valid ratings to compare the efficiency of an a/c unit is the EER ratings, for grow rooms. For a house, the SEER ratings are only accurate in the spring and fall when you only need to cool the house a few degrees and for summertime cooling the eer rating is more accurate. Having a 2 speed unit that will run on low and cool the house at a lower rate will also remove more humidity in the air, so this is good for someone who lives in a more humid environment. If your climate is dry, its pointless.

 

[MIway]

i actually never new any of the rating methods, so this is kind of enlightening. what i've gotten on it... and sam i totally agree w u'r above post regarding wanting the a/c to be on as often as possible to remove as much moisture as possible... is that you just have to look at max watts used, within same btu ratings.

but now that you bring up testing procedures... curious to know how they get btu's as well. wouldn't be surprised if it's a dbl whammy... that the btu's aren't apples to apples either.

 

[stillsmokin843]

good thread sam. ive wondered about this same topic a few times. it makes since so is the over priced units with high eer and seer ratings gona make that much of a differance in our application? i was also wondering about the mini split new inverter stuff is really that much better and will it make that much of a differance in a room with that many watts?

 

[Sam the Caveman]

The EER rating is what tells you how efficient it is when running full blast. So a 4 ton unit with an EER of 12 will use less electricity running full blast than a 4 ton unit with an EER of 11 running full blast.


I'm not saying SEER rating are totally useless, it does give you some insight on how efficient the unit is for you house in the spring and fall, but its a useless bit of info for a grow room.

 

[stillsmokin843]

so do you think that the new inverter minisplits is good fpr a grow room or not gona make much of a differance in a grow room?

 

[Sam the Caveman]

compare these two units and tell me if its worth the extra money, look at the amp draw of each one, they are no different

http://www.ductlessdepot.net/product_details-btu-6-0-211.html

and

http://www.walmart.com/ip/Frigidair...nted-Heavy-Duty-Room-Air-Conditioner/14977844

Notice the EER of the one from walmart is only 9.4 and it uses the same amps as the 16 SEER mini split!

 

[Sam the Caveman]

but now that you bring up testing procedures... curious to know how they get btu's as well. wouldn't be surprised if it's a dbl whammy... that the btu's aren't apples to apples either.

The total btu's of a unit is divided up into "sensibe" and "latent". I don't know the difference well enough to describe it, but have a go at trying to understand it if you want. Some specific models of air conditioners will have more or less latent capacity, the more appropriate one will depend on your climate. It has something to do with humidity.

 

[Midnight]

The total btu's of a unit is divided up into "sensibe" and "latent". I don't know the difference well enough to describe it, but have a go at trying to understand it if you want. Some specific models of air conditioners will have more or less latent capacity, the more appropriate one will depend on your climate. It has something to do with humidity.

Sensible heat is the heat, or lack of heat, that you can actually feel. Latent heat is a state at which a change in a compound (in this case the refrigerant) takes place and changes either from a liquid to a gas or a gas to a liquid.

And the stuff I posted, the stuff you neg reped me for, that has all your answers in it. I could explain it to you so it makes since, but, you neg repped me so good luck with that. I am, after all, one of the crooked hvac contractors who has no fucking clue what he is talking about.

 

[Sam the Caveman]

Sensible heat is the heat, or lack of heat, that you can actually feel. Latent heat is a state at which a change in a compound (in this case the refrigerant) takes place and changes either from a liquid to a gas or a gas to a liquid.

btu's, as it relates to latent heat specifically, have nothing to do with changing the state of the refridgerant. Its about changing water vapor into condensation/removing humidity.

And the stuff I posted, the stuff you neg reped me for, that has all your answers in it. I could explain it to you so it makes since, but, you neg repped me so good luck with that. I am, after all, one of the crooked hvac contractors who has no fucking clue what he is talking about.

It has none of my answers in it, it only perpetuates the folly of which I'm discussing. Which is what the SEER rating is specifically made up of, the values used to calculate it and where they come from and the conditions under which they are calculated. Your cut and paste article addressed none of this.

 

[Sam the Caveman]

The difference between a unit with higher latent btu's is the cfm's of the blower on the indoor coils. The lower the cfms, the more humidity is removed. It can only vary so much though, if its too slow the inner coils will freeze up and possible cause a leak in the refridgerant. (= F'ed)

 

[Midnight]

Sam, you really should quit while you are ahead because you don't have a clue what you are talking about. You are interposing one set of data to fit another, you are extrapolating where there is no extrapolation to be made... I'm done, you just keep spreading your nonsense. And fyi, part of what you are saying is true, but not the part you think.

 

[Sam the Caveman]

well, if your talking about the sensible and latent discussion, I was just bringing up that aspect to MIway in relation to his post. I'm not making any correlation to the whole non-credibility issues with the SEER ratings.

Found what I would consider a fairly reputable source for info about SEER and EER ratings, except for the last statement. Its about 3 pages long, if your interested.

http://www.lacool.ws/SEER Tutorial.htm

 

[MIway]

thank you guys for the info... just trying to understand why certain a/c's really seem to do better than others, of like kinds too.

bringing it down to practical info (i'm lookin into some units myself)... what are the 'best' ones you guys have found... not nec the ratings that seem to be contention, but the models/units that really kick ass while working?

i wouldn't mind having a list of all the reputable, proven models... say splits, bangers & portables...? thanks guys!

 

[Sam the Caveman]

I tried to get hard data from some of the more popular brand air conditioners like Trane and Lennox, but they offer no specific data other than the SEER ratings. Rheem and Goodman both give you very detailed specifications about each and every model. To me, the regular models of goodman and rheem have the highest EER ratings, if I remember right goodman's are slightly higher.

Other things that will help with a/c efficiencies is having the unit charged with refridgerant to the proper specifications. For single speed compressor units, find one with a scroll compressor, they are more efficient than rotary compressors for single speed units. A scroll compressor is designed for maximum efficiency at one rpm.

It also depends on what size your getting, the bigger you get the less variance in efficiencies between brands.

Its all kind of nit picky as far as getting the most efficient unit since difference between a 4 ton with an EER of 11.5 and one at 12.5 won't really amount to much savings in the end, but if it doesn't cost any more, why not go with the higher one.