seer rating doesn't match power draw

Page 1 of 2  
I am looking afor a new central AC. I live in Florida so efficiency is important. I looked at Tranes, and found that the 4 1/2 ton unit I looked at was rated at a 14 SEER, yet the specs stated it drew 27.5 amps for the compressor, an amp or so for the compressor fan, and 7 amps for the air handler blower (full speed). Now 4 1/2 tons is 54000 BTU's per hour, and the power draw is (27.5+1+7)amps X 220V, or 7800 watts. This would seem to me to give a SEER of 6.9. This is less than half of the stated SEER of 14. Can anyone explain this? I looked at the ARI website and this seems to be the case for every manufacturer. If I buy a buy a 14 SEER 54000 BTU/hour AC, I would expect it to draw 54000/14 watts, or 3850 watts. Can anyone explain this? Neither the Trane dealer or distributor could answer this. Thank you in advance.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Depending on the unit the inside fan is probably 120v. Especially if it is a VFD. 7 amps is pretty high for a 240v motor. My American Standard with a VFD never drew full load amps. My American Standard 5 ton 12 seer said it stated 28 amps, ( older model ) I never measured more than 23 amps usually it was 19 or 20. Also you should be using 240v not 220. Calculations are done (usually) on nominal voltage. Have you measured the draw?
www.advancedenergy.org/buildings/knowledge_library/heating_and_cooling/seer_ facts_bulletin.pdf
The installer is the one who makes the job. Not that your installer did a bad job.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
SEER ratings are done at specific Dry bulb & Wet bulb temps for both the exterior and interior. Interior Temps: 80 F Dy bulb, 67 F Wet Bulb Exterior TEmps: 82 F dry bulb, 65 F Wet bulb
High SEER system see can see a faster degradation in efficiency than lower SEER systems as it gets hot outside. ASHRAE recommended a better system for testing efficiency, where a perforance range is calculated over a range of indoor and outdoor conidtions. So far, the Feds have ignored this advice. As a result, using the SEER rating to estimate what your operating costs will be, will not give you an answer close to what you really get!
snipped-for-privacy@hotmail.com wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I should also mention that the quality of power coming into your home will affect the efficiency. During the summer, the voltage going into your home could drop as much as 5%, raising the amp draw. Also, if there are a lot of inductive (motors) or capacitive (flourescent lights) on the grid you draw power from, the power factor could be off. Since simple amp meters don't read power factor, you may not be measuring what the true power draw of your A/C system is.
snipped-for-privacy@hotmail.com wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This is moot, since household kWh meters only charge for real power.
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
i would have thought that the seer does not consider the air handler blower. but leaving that out still dont get you there. look here if its 28.5 amps at 120v it just about figures (again we leave out the blower fan)
On Fri, 29 Jul 2005 19:31:43 GMT, snipped-for-privacy@hotmail.com wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@hotmail.com wrote:

The S in SEER stands for "Seasonal". Most of the run time during the cooling season occurs at lower ambients, i.e. when the compressor draw will typically run half or less than half of the RLA. You also need to figure in power factor, which will improve your numbers. HTH.
hvacrmedic
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@hotmail.com wrote:

As I recall SEER ratings are given based no actual test under specific conditions. The amps listed are generally the highest amps expected, and an AC will not draw the same amps under all conditions.
--
Joseph Meehan

Dia duit
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The 27.5 amps were stated by the Trane distributor to be running amps, not the peak amps on the housing. Perhaps he misspoke. The 7 amps on the blower was peak, though. The blower moter is hp 240V, and runs at close to peak most of the cycle, even though it's variable speed. I ignored power factor to keep things simple, and used 220V rather than 240V to compensate, since the power factor according to Trane is typical 0.9. Nevertheless, any adjustments to the 7800 watts consumption is still very far from the 3800 watts implied by the SEER. I appeciate everyone's ideas, The message I'm getting is that SEER is determined by an average of EER's at different times of the season, and was initially defined at 82 degrees outside ambient, and that efficiency is defined under an unrealistic condition, is not constant, and is much lower under normal summer conditions. I guess SEER is useful to compare units, but I'd like to know before I buy what power draw to expect, so I can compare other options. It seems a bit dishonest to sell AC units in Florida, define SEER as BTU's per hour over watts, and state an SEER of 14, if the unit is only going to run at an efficiency of half that when it is used most. Anyway, thanks to everone for their ideas.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You also know that your contractor must make over 150 measurements to make sure you have the SEER you bought, right? SEER for all intents, is marketing in this example. You DO normally get a higher quality unit with the higher SEERs, but with most, once you leave the 14SEER realm, and go into the 14+ you have over engineered equipment, that while it IS of higher than 10 SEER quality, it also is more expensive to replace, or work on. If you want the best of both worlds, might I suggest GeoThermal, altho, expect to pay out the nose for your initial installation, and you DO have to make repairs to it every so often, but with the right installer, and the right equipment, you can achieve SEER values that are sky high compared to a conventional air to air unit.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
What is more common around here is water to air, the ground water is constant 72 degrees. I have another house that has it installed. It uses an artesian well. I thought the air to air designs had started to catch up in SEER ratings from looking at the advertised numbers. Anyway, in 1989 a 4 ton water to air unit was $1100 with a built-in ECU hot water recovery unit. Installation was almost trivial since the artesian well was already in, just connect the water lines, pump, and electrical. I'll check and see if that route is still available.
On Sat, 30 Jul 2005 12:34:31 -0400, "Carolina Breeze HVAC"

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri, 29 Jul 2005 19:31:43 GMT, snipped-for-privacy@hotmail.com wrote:

You are wrong to assume that amps are indirectly proportional to SEER.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

What I mean.....
I notice that increasing the size of the evaporator will increase the SEER. The figures from several evaluations show that a 3 ton compressor connected to 5 ton evaporator is a couple of points higher in SEER that when matched.
Using controls that let the inside fan continue blowing after the compressor shuts down also increases the SEER.
In other words, it's not all about the amps.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sherman wrote:

Right, it's about true power, of which amps are required to compute. IOW, it is indeed about amps, but in ways that you apparently don't understand.
hvacrmedic
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

How does a bigger coil reduce the amps?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Reduces load for starters.
Amps mean nothing of great importance here..you can have a 16SEER unit pulling 50 amps and its still 16SEER.
Bottom line, for every watt used, how many BTUs are being removed?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You might enjoy learning the difference between power and energy :-)
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

And you might enjoy learning what ASHRAE says about SEER.. :-)
No flame, just back at ya.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Carolina Breeze HVAC wrote:

Oh no Nick, not the BTU vs. BTUH thing again :) Of course as Steve wrote it, it was incorrect. OTOH the convention of saying BTU when BTUH is meant has set in and will be difficult to purge from the language.
hvacrmedic
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
wrote:

I must have wasted a good horsepower hour downloading and reading these threads.
-----BEGIN PGP SIGNATURE----- Version: PGP 7.1
iQA/AwUBQuyMswIk7T39FC4ZEQIc+ACg9C657tCE0u/+FS3bG6e4vjqDIFQAoL4U 32R+tyKX7zijQ/TTlczSLW3X =MjII -----END PGP SIGNATURE-----
--
-john
wide-open at throttle dot info
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.