Talk:Seasonal energy efficiency ratio

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[edit] Why this Article and the Term "SEER" is Confusing

Definition

First of all, the equation in bold at the beginning of the article (SEER = BTU ÷ Wh) is technically incorrect as being equivalent to the defining statement for the SEER (the acronym for Seasonal Energy Efficiency Ratio). Accordingly, the equation should be consistent with the word (stated) definition and therefore be expressed in the defining terms. Therefore, the equation should represent a SEER to be equal to the cooling capacity (Q(cooling)) divided by the input energy required (E(in)) and (specifically by definition) be in the units of BTU per watt-hr. Although this slight distinction may appear to be of minor importance, one also needs to consider that because of the definition of SEER, there is an applied unit of the SEER equal to the BTU/watt-hr. So, to avoid confusion between the term and the unit, let's call the unit a "seer" in lower case. So, by definition the unit of the seer equals one BTU/watt-hr. Accordingly, an improved definition of the SEER is as follows:

SEER = Q(cooling) / E(in) BTU/watt-hr

SEER = Q(cooling) / E(in) BTU/hr/watt (see explanation below)

SEER = Q(cooling) / E(in) seer

Technically, regarding the units BTU/watt-hr and BTU/hr/watt, although they are equivalent mathematically, BTU/watt-hr actually corresponds directly with the use of the terms Q and E (heat and energy). Also, because the term SEER used as a rating is representative of a "seasonal" or long term "energy" useage and not an instantaneous use as represented by heat transfer per unit time and electrical power, in that sense it may be considered more appropriate to use BTU/watt-hr. However, specificatiions for air conditioning systems do not provide Q and E, but rather Q per unit of time (Q/T) and E per unit of time (E/T), which is equal to power (P). So, in that respect it also makes sense to consider the units in the form of BTU/hr/watt as well. Therefore, to be technically correct:

SEER = [Q(cooling)/T] / [E(in)/T] BTU/hr/watt

SEER = [Q(cooling)/T] / [P(in)] BTU/hr/watt

Regarding the unit seer, whether or not the unit is officially sanctioned, the unit is implied by the definition of the SEER and is commonly used when stating ratings such as in the expression, "this unit is rated at 13 seers." Accordingly, the equation form of the definition of the seer unit is as follows:

seer = BTU/watt-hr

The SEER Rating

Also, although the SEER is commonly defined as a ratio, and would therefore change or vary with operational conditions of the system, the SEER is also (and perfaps upmost) a rating determined by the manufacturer of the system, and therefore has the contrasting property of being a fixed quantity. The SEER rating, which is required to be stated on an identification plate of all mass produced air conditioning systems, is determined by a DOE test standard that defines air flows, temperatures, and the algorithm for calculating the rating number. By comparison, one could consider the analogy of an automobile's EPA fuel mileage ratings, which are a combination of three related fixed values, in comparison to the actual fuel mileage, which varies substantually under operational conditions. Therefore, when one considers the SEER, it may be important to clarify whether one is considering the the SEER rating, the SEER at some specific operational point (as consistent from the general definition), or simply the unit of expression. Therefore, again to be technically correct:

SEER Rating = [Σ Q(cooling)] / [Σ E(in)] seer

where: Σ Q and Σ E represent the appropriate weighted sums (if so required) of all of Q's and corresponding E's specified in the DOE standards that define the SEER rating test conditions.

SEER, EER, and COP

Next, regarding the relationship between the SEER, the EER, and the COP (coefficient of performance), the SEER and the EER are both ratios (and ratings) for air conditioning systems. In contrast, the COP is a ratio for heat pumps and is not specifically defined by some industry standard as being a rating. In simple terms, the SEER and EER apply to air conditioning systems and the COP applies to heat pumps. The distinction here is that the SEER and EER represent a ratio related to the quantity of heat transferred into the system (for cooling) and that the COP represents the ratio related to the quantity of heat transferred out of the system (for heating). In a heat pump the energy required to operate the system (E(in)) is transferred into the building and is therfore included in the heat term of the calculation (Q(heating)). In an air conditioning system the energy required to operate the system is not included in the heat term of the calculation (Q(cooling)).

Also, for the purpose of discussion we could define another coefficient of performance as related to cooling. We could call it the Coefficient of Performance for Cooling or COPFC. Basically, it would be the same as the SEER or the EER but without expressed units, as with the COP. To convert the SEER or EER to the COPFC, it would be required to divide by 3.413, the number of BTUs per watt.

Also, an air-conditioning system and a heat-pump system having identical performance (and operating at identical temperatures) would have a different COP and COPFC because the calculations are different. In fact, the COP for the heat pump would equal one plus the COPFC of the air-conditioning system (COP = COPFC + 1). This is because COP equals Q(heating) divided by E(in), COPFC equals Q(cooling) divided by E(in), and Q(heating) equals E(in) plus Q(cooling).

Regarding the mathematical relationships between the SEER, the EER, and our defined COPFC, that depends on the distinction between whether one is referring to the term by its general definition or the rating number provided by the manufacturer. First of all, you can be pretty assured that the manufacturers of air conditioning systems are squeeking every bit of performance out of the systems being tested to acquire the highest possible SEER or EER rating. The SEER rating appears to be some kind of weighted average of different temperature and humidity conditions (all 95 degrees or below). The EER appears to be specified as having an operating point of 95 degrees F for the outdoor unit (the condensing unit). Therefore, it would be expected that the SEER rating would be higher than the EER rating for the same system. That is probably the origin of the stated equation which divided the EER rating by 0.9 to get the SEER rating.

Furthermore, the mathematical relationship between the SEER and the COPFC and the mathematical relationship between the EER and the COPFC are identical. Both the EER and the SEER are equal to 3.413 times the COPFC. However, in the case of the EER, the COPFC must be at the 95 degree F operational point and, and in the case of the SEER, the COPFC must be averaged at the required operational points as defined in the SEER testing standard. Therefore:

EER = 3.413 × COPFC(at 95 degrees F)

SEER = 3.413 × COPFC(at operating points definded for the SEER testing standard)

Regarding the state of Georgia having a SEER equal to the EER divided by 0.8, that cannot be. Every air conditioning system when evaluated by the test procedures for SEER and EER will provide some hopefully repeatable number. For that air conditioning system, these two ratings will have some ratio to each other. Accordingly, that ratio is fixed only by the SEER rating and the EER rating and is not affected by where the system is installed. However, where the system is installed and the conditions under which the system operates does impact the operational points. Furthermore, the operational points affect the operational efficiency, and in turn, the operational efficiency is reflected in the COPFC and in the operational SEER as defined by the loose definition (being the cooling capacity in BTU/hr divided by the energy required in watts).

First Example

Regarding the first example in the article, it states the capacity (5000 BTU/hr) and the derived required power (500 watts) as if the values were actuals and not ratings. Otherwise, the example would read: "For example, an air conditioning unit rated at 5000 BTU/hr with a SEER rating of 10 . . ." Accordingly, the bottom line cost is actually both an estimated and rated cost in the sense that it is dependent on the rated capacity, the rated efficiency, and the estimated usage.

References

Regarding Reference 1 (Definition of SEER), this definition of Seasonal Energy Efficiency Ratio does not state that it is a rating.

Regarding Reference 2 (SEER Conversion Formulas from Pacific Gas and Electric), this PDF document contains the same incorrect equations relating the SEER, the EER, and the COP as stated in the article.

Summary

In summary, probably the most confusing point to the discussion of the SEER is that most people have the perception that the efficiency of an air conditioning system is dependent on operational conditions. Then, when they are confronted with the term SEER, which is represented as a term representing efficiency, it is then expected or understood that this number should increase or decrease depending on those operational conditions. However, because the SEER is also defined as a rating derived from specific tests, it is also a fixed number similar to the previously mentioned EPA fuel rating for automobiles. Accordingly, one has to understand which of these two quantities is relevant in the same manner as in distinguishing EPA fuel mileage and actual fuel mileage in automobiles.

Also, I don't think that there is any question that because there is confusion over the exact definition of the term SEER, that there will be continued confusion in its useage. In the case of automobile fuel mileage, the concept was well understood and used long before the EPA developed a rating. However, for most people air conditioning efficiency and the SEER are newer and less familiar terms, and it appears that no one has stepped in and clarified the distinction. Before I spent the time to write the above discussion, I "Googled" the term SEER and explored probably ten definitions. Although many definitions state the term to be a rating, many did not. So, irrespective of the original intended meaning, the loose definition of a SEER being a ratio is probably the more widely used and understood. Perhaps the SEER should stand for Seasonal Energy Efficiency Rating and not Seasonal Energy Efficiency Ratio.

BillinSanDiego (talk) 06:49, 1 February 2008 (UTC)

[edit] This cannot be right

For example, if an air conditioner provides 5000 BTU of cooling, and has an SEER rating of 10, then on average over the cooling season it will consume 500 watts watt-hour of electric power (5000 divided by 10).

This cannot be right. A 5000 BTU AC uses about 600 watts, and thus will consume 500 watt-hours in *less than an hour*, not *over the whole cooling season*! -MichaelBluejay 22:52, 2 July 2006 (UTC)

Okay, according to the Department of Energy website, the correct formula is the BTU's OVER THE WHOLE SEASON, not the BTU's per hour. I'll edit the article accordingly. -MichaelBluejay 23:41, 2 July 2006 (UTC)

Yes, the SEER is defined 'over the whole season', or saying it another way, simply 'THE AVERAGE'!!

Why are people making this more complicated then it has to be? You see, I can walk into a store, and find an air conditioners with two numbers on the front of the box: the BTU/hr number, and the SEER number. I can quickly compare them by simply dividing the BTU/hr by the SEER, which gives the AVERAGE power consumption. This is a nice thing to know, and the formula is simple enough to memorize. I had put the simple formula it in the article, but it's been deleted twice now, apparently in favor of the calculation that is 4 times as long and yields the same result. In the future I hope people will keep it simple so that readers will have a better chance of getting the fundamentals right. Save the long winded explanations for wikibooks, this is wikipedia. Also, the '500 watt-hours' above was wrong, I added the strike-through, it should be 'watts'. Watts are units of power, and watt-hours are units of energy. Mikiemike 03:33, 16 November 2006 (UTC)

Mikiemike, you were correct to strike through the the watt-hours above and that correction is now reflected in the article. However, your simpler formula only works if the annual hours of usage is a power of ten (i.e., 10, 100, 1000, etc.). Otherwise, it does not yield the correct average amount of power. Try using your simple method for 900 hours and using the method in the article for 900 hours ... and you'll see the difference. I hope this clarifies it for you. Regards, mbeychok 04:39, 16 November 2006 (UTC)

mbeychok, I disagree. I think you should try the calculation you suggested. You see, even when you change the operating time to, let's say 900 hours, you still get an average power of 500 Watts. The reason for this is that the formulas in the article first multiply by the time, then divide by the time, so time actually has no net effect. That is precicely the point I wanted to make. Strictly speaking, the efficiency will vary depending on the operating conditions, but these are all approximations anyway. I still maintain that the operating time does not effect the efficieny or power usage; energy usage yes, power usage no. Mikiemike 18:02, 16 November 2006 (UTC)

Mikiemike, I stand corrected and I apologise. I must have suffered a brain fart. I have added your simpler equation back into the article's lead-in section ... using the same styles as the other equations. Thanks for correcting me, mbeychok 18:55, 16 November 2006 (UTC)

How can an air conditioner provide 5000 BTU/hr (roughly 1465 Watts)in cooling while only consuming 500W? Seems like you are getting something for nothing.

The simple answer to the above question is that the energy required to transfer heat can be significantly less than the amount of heat being transferred by the air conditioning system. In the case in question, the components of the system consume 500 watts to transfer 5000 BTU/hr from inside the building to outside the building. The amount of heat discharged to the outside is therefore the sum of the 5000 BTU/hr and the 500 watts required to perform the transfer. Because the 5000 BTU/hr is equivalent to 1465 watts, the heat discharged outside is 1965 watts (500 + 1465) or 6707 BTU/hr (5000 + 3.413 x 500). There is no something for nothing condition because heat energy into the system (the cooling effect) plus the electrical energy required to perform the transfer is equal to the heat energy discharged by the system. BillinSanDiego (talk) 02:32, 1 February 2008 (UTC)

[edit] Electric cost, climates, and performance

The article currently uses rather high electricity rates -- typical only of the U.S. West Coast and Northeast (in the US). For much of the country, where coal is used widely for generation, the rate is often only 7 to 8 cents per kWh.

The Chicago example was odd -- it is hot and humid in the suburbs (not lakeside, of course). I've adjusted the example to 'near Chicago' because houses aren't downtown. I also reduced the electric rate from 11 to 10 cents.

Isn't the official SEER evaluated using standard test conditions? If so, what are they, and what's the standard? For years Toa=85F, only, was used, but the standard was improved.

The distinction between a piece of equipment's 'official' SEER value and the actual site/climate performance still needs to be made clearer in the article. 129.237.114.171 15:34, 8 November 2006 (UTC)

[edit] The section on heat pumps should be merged into the Heat pump article.

The section on heat pumps more appropriately belongs in the existing Heat pump article. Would someone please remove it from this article and merge it into the Heat pump article? If no one does so within the next 7-10 days, I will probably just delete it from this article. - mbeychok 00:40, 5 January 2007 (UTC)

It has now been 14 days since I posted the above comment and no one has responded ... so I am going to delete the heat pump material from this article. - mbeychok 20:28, 20 January 2007 (UTC)

[edit] the SEER formula of California and Georgia

From the Formula: (1) SEER = EER / 0.9 For California and also From the Formula : 1) SEER = EER / 0.8 For Georgia. Where did 0.9 and 0.8 come from? Please specify the raw data and procedures that give the 0.9 (for California) and and 0.8 (for Georgia) from the above formulas. —The preceding unsigned comment was added by 202.44.210.31 (talk) 02:52, 15 January 2007 (UTC).

[edit] Fixed link on contract sizing reference

The old link was broken. I replaced it with a new link to the article: http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-289-95/index.htm —The preceding unsigned comment was added by 63.202.70.123 (talk) 02:50, 26 February 2007 (UTC).

The comparison of a "heat pump" to resistance heating is stated as "Up to 4" when there is little temperature differential, down to 1 at large differential I know there are a lot of factors involved in calculating a SEER , but quite simply, please compare raising the temperature of a house 10 degrees to "room temperature" with cooling the same house 10 degrees in terms of a Kwh ratio, given 10 degrees differential between outside and inside.

[edit] Formula and calculations are inconsistent

The formula says:

SEER = BTU ÷ W·h

In the calculations, a trivial (and obviously correct) rearrangement is used:

SEER = BTU ÷ W·h

=> (SEER)(W·h) = BTU

=> W·h = BTU/SEER

Then some values are substituted in and the number of watt-hours is solved for.

5,000,000 Btu ÷ 10 = 500,000 W·h

However, that can't be right, as the two sides are not equal. 5,000,000 BTU / 10 actually equals 146,535 watt-hours. (1 watt-hour = ~3.41 BTU)

The problem with the above "complaint" is that the BTU's are the ones being transferred (not the energy being consumed), and the watt-hours are the energy being consumed to perform the transfer (not the heat being transferred). Therefore you cannot just equate them by saying that 1 watt-hour equals 3.41 BTUs. The whole idea of SEER is to indicate how many BTUs can be transferred by a given number of watt-hours, so the ratio in these equations is variable, not a constant. Think BTUs = apples; watt-hours = oranges in this case.

Derobert 03:36, 9 September 2007 (UTC)

After doing some research, it seems that a SEER number carries units with it, even though those units could be simplified out (BTU/watt-hour = ~0.29)... Going to fix the calculation based on this Derobert 03:11, 13 September 2007 (UTC)