A common mistake is not running a load on the structure.A lot of companies will replace the system with the same size because it cooled fine.That is a big mistake.The new higher seer units have lower capacities at higher temps.If you look at the ratings for a 10 seer unit at 95 degrees it will be higher than a 13 seer unit at the same temp.Just one possibility of a problem you may have.

Last year, I posted info on the SEER rating testing. It appeared flawed. The people who should know, asked me what kind of drugs I was on. Others opposed my incontrable proof that the newer variable speed systems will never produce full rated capacitys.

I was called dumb, stupid, on drugs, and various names that suggested that I did not have a clue. The comments were made by programmers, and other experts. No one that installs HVAC for a living tried to comment about the testing methods and what they mean.

Today someone asks why?

I have answered your question at least 15 times over the last year. The SEER rating system is a method to rate power usage for off the grid or power companies only. The higher the SEER the poorer the actual cooling. The SEER rating tests are multiple attempts to meet a minimum criteria and only last for 6 minutes of 10 minutes. When a new system is installed, it must operate for more than 30 minutes to meet a minimum output level. This costs more money. Even the thicker coils are smoke and mirrors.

How could I possibly know this? I am a degreed engineer that lives in the real world, and does not spend money unless needed. I use the same facts to determine the real story. I guess I am just dumb or something.

The only company that I recommend to do this is the worst rated company in HVAC. Who buy-the-way produces more residential equipment than the better rated companies. I am not offering this product this year to my direct customers. I am offering a less controversial product. I gave up trying to convince the public of the truth.

I heard radio advertizing for the "worst" company, that wants you to believe they make equipment for the downtrodden, and loosers. By insinuation, this is most of the population. Thier commercial was not appealing to me in the least. I do not want to associate myself with thier comments. In thier book, I am a looser, that decides to buy the product because I do not do research, I do not get my hair styled, I don't drink bottled water. I cannot afford to spend $8.00 for a lunch, (I can't afford to buy a burger, frys and milkshake at McDees) I can't afford to buy a starbucks coffee, I am a looser. I believe in thier product, but I refuse to lower my standards to fit thier advertizing.

I sure wish I knew what bob was trying to say.

Anyway- In laymans terms, in order for a system to be cheaper to operate, a little loss in capacity is a result. It is important as mentioned, for a heat gain load to be done and the new system applied using a sensible capacity mostly in more humid areas, than using a rated btu capacity.
Compressors are able to pump as much refrigerant as the old ones using less power and motors run on less amperes now as well, however the rating on the compressors capacity is a little less than before. When high efficiency first started out, some 3 ton systems had a compressor of 2.75 tons, and now some 3 ton systems actually have a compressor rated between 2- 2,5 tons. They try and make up the difference by using more efficient indoor coils with easier heat transfer as well as refrigerant pressures per sey.
You may have a problem with your system as well. I would have another company check it out.

I think I know what Bob is saying. Is it true what he's saying, all you other Techs? What Bob is saying, "I'm" assuming is the following and just an example--- You purchase a 2 story home in Houston, tx. where the temps and humidity get mighty hot. The house is 3000 sq. feet and has a single 20 year old 5 ton Trane (split system) cooling the house and it takes everything it'll do to keep the house a comfortable level for about a month during the summer time. But it does keep up!!!! Just barely. So you spend some money---upgrade the attic with R48 insulation, change out some windows with Low e, install automatic roof vents and more soffit vents to help out the old unit during the peak of the summer and it does help the old Trane. Payback will probably be 6-7 years on the upgrades to help out the old unit but now the old Trane dies and you want to install a new unit and they slap a new high eff 5 ton in the place of the old Trane and your house doesn't get cool because the compressor is really a 4ton instead of a 5ton and we already know the original 5ton was squeaking by. So what do we do. Do they make a residential high eff single phase 6 ton that would give you an actual 5 ton? And for you Techs that say "zone it" or "install dual ACs and zone it"--why would I want to spend that kind of money when the old Trane did the job and only strained 2 or 3 weeks out of the year? Am I assuming correct or is Bob full of it?

What y'all are saying makes so much sense - new units with SEER ratings focus on energy costs/savings, rather than actual cooling efficiencies.

Bama-dude, you said higher SEER ratings work worse at higher temperatures, but that is when we need the cooling abilities most - when heat index with humidity is high - what a crock of @#$!

Insulation upgrades should be gravy and help with overall $ savings, not substitute for units not working as well. Bama dude you said lower SEER ratings cool better (Ie higher ratings) than higher SEER units. Is it also true that R-410 cools worse than "old" type?

So, I am with piein sky - what do we do? This forum has lots of cautions about oversizing units to be just as bad as undersizing units.

by the way, daddo, I need to check paperwork to see what new AC compressor is compared to ton unit size, and will let you know.

Thanks. I so appreciate intellegent answers, instead of the usual "AC is supposed to only cool to 20 degrees less than outside" answers we consumers usually get!

pieinsky,to answer your problem you would need 2 systems instead of trying to cool a 2 story house with just one.rfbcville,the new 410a systems are more efficient than the r22 systems.Its not about what tonage system you have its about capacity of the matched equipment.If you had a 3 ton 10 seer that cost a arm and leg to operate why would you care if the new one was a ton bigger and cost half as much to operate.The higher the seer the more money you will save to do the same job,although it may be a bigger unit.Who cares ,if its cheaper to operate and you are comfortable.

bama_dude- I need your "bob brown de-coder book".

As no one argued Bob's ideas about SEER and the criteria by which the HVAC (and government) industry has set up when giving a particular AC system a high eff rating, I'm going to jump on the band wagon and assume most all of the ratings are BS. Is there anyone in the hotter-- humid regions--Tx, La. Florida, Miss., Alabama that can say they changed out an old low eff system for a new high eff systems and they noticed a big difference in electric usage? And I mean a big enough difference to make you want to run out and buy a new system even though the old system is running fine. Not a 15 year pay out for the new system over the old!!! I can understand your old system crashing and you find it necessary to put in a new unit but perhaps it's better to keep that old unit running as long as possible or buy the lowest Seer required by or know nothing Govt. The way I read this forum, a 21 Seer 5 ton system could no more deliver a true 21 seer and true 5 ton rating (in the hot regions with lots of hot days) than I could jump over the moon. Perhaps 4 tons and maybe 10 or 12 seer on those hot days which there is a whole lot of in my area and what you purchased the thing for in the first place. Correct me if I'm wrong. And I'm not trying to be ugly or start something. Just wanting honest opinions as
I'm moving from my home in Houston and re-retiring to a small town 100 miles further South of Houston and I will be having a new system installed in that house in the next 2--3 months.

pieinsky,I have replaced many,many systems with new high seer units.I can tell you they save big dollors if sized correctly.I have seen energy bills actually cut in half by just changing the a/c system .There is no way to argue with Bob Brown his views are too far out of the box.He dissputes anything that is not a Goodman non variable speed r22 system.He is stuck in the past.There are many ways to set up a new system for optimal perfomance and enrgy savings.I preffer the 2 stage variable speed setups in my climate because of our load swing.They will save you money and keep you more comfortable.I know they work and work well.The proof is in the pudding.When a manufacturer has one system that achieves a higher seer rating like 21 they can claim they have the highest rated unit on the market.It might be a straight cool 2 ton and nothing else but thats been going on for years.The new equipment is weeding out the jacklegs of the industry because you cant just throw a system in by sq ft and tonage or guessing at it any more.It works out better for the customer when the contractor has to put skills and thought into what your needs are.

Thanks bama_dude for the info. Another words, don't be afraid of the new stuff if you have a capable HVAC contractor in your corner who will stand behind their work.

Goodman's performance ratings on their product spec sheet lists a 3 ton 14 SEER heat pump at 33,480 BTUs (total) with a fixed speed motor in the air handler and 32,178 BTUs (total) with a variable speed fan. The fixed speed fan is 7% less than the 36,000 BTU nominal size while the variable speed fan is almost 11% less than nominal.

The average report I get from customers here is between 30 and 45% drop in their elect bill after installing a typical seer 13 system or a seer 14 system. Some old units in really bad shape bring as much as 60%. They do notice it runs a little longer, but the humidity in the home is lower they say and set the thermostat a little higher too as it's drier and feels more comfortable. The benifits could also be that the ducts are sealed up in the proccess of installing the new system. I've always sized the sensible capacity about 10% higher than the heat load calculation shows.

Unfortunately, I did not discover this forum until after purchasing new system, and, although we discussed several systems with several contractors, no one talked about running a load on the house. Here is what we have for a main floor of 1250 sq ft and same amount of unfinished block wall basement: Bryant Split System AC with Puron refrigerant 13 SEER
Model CK5PXW030017ABA - Cooling Coil and Outdoor unit 550ANX030 In basement, Bryant model 352 MAV Series C 2 stage direct vent condensing gas furnace 352MAV036080
Thermostat Honeywell Focus Pro 5000 TH522OD

daddo - do you know what size compressor this AC unit has? I am guessing it or the system must be undersized from your comments and bama_dude's comments. At around 3-5pm, it can't cool to 77 degrees. Central VA does have humidity, though not as bad as Dallas.

Any suggestions? Our "spring" tune-up will be coming up this month by same company that did install. Thanks

rfbcville,you have a 2.5 ton a/c with a 3 ton drive furnace looks like 80,000 btu,s of input heat.I would venture to say that is border line too small a/c at your sq ft.You would need to run a load on your house and then check the actual capacity of your system.It may also not be performing up to its potential if the system charge is incorrect.I often find 410a system charged incorrectly causing a big capacity drop.

bama_dude - is there any info on the initial installation sheet or Spring Tune up Sheet (from last yr) that would tell you about the charging? ie return temp/Delta temp ffor cooling coil or info from outdoor unit like suction pressure or line temp? Original 7/05 install notes showed "5 oz 410A per mftr spec"

I would really appreciate any help you can give me. Thanks

The average report I get from customers here is between 30 and 45% drop in their elect bill after installing a typical seer 13 system or a seer 14 system. Some old units in really bad shape bring as much as 60%. They do notice it runs a little longer, but the humidity in the home is lower they say and set the thermostat a little higher too as it's drier and feels more comfortable. The benifits could also be that the ducts are sealed up in the proccess of installing the new system. I've always sized the sensible capacity about 10% higher than the heat load calculation shows. Daddo
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We must consider that many of those old systems have dirty blower wheels & evaporator coils.
Condensers may also be dirty or have other problems, including imbalanced charging.
In addition, without a meter on the AC unit & all the precise weather data there is no way to make those comparisons.

In my opinion, they should not have eliminated the 10-SEER units as they performed well in tougher latent & sensible load application conditions.

I comprehend what Bob Brown is saying & hear many complaints on he higher SEER units.
In my opinion, it does NOT pay to raise the volumetric capacity of a smaller capacity compressor by raising the suction pressure, which means a warmer E-Coil. In the higher outdoor temperatures, the pressure & temperature ratios get worse & capacity wanes more rapidly, (than say a 10-SEER), when it is most needed.

Payback is a nefarious equation when the new initial equipment costs & added retro labor are considered.
If you live in a high humidity climate zone & have a 10 or 12-SEER R-22 system I would seriously consider keeping it running at its top efficiency. Consider other ways to reduce the heat-gain heat-loss of your home or business.
You can do a lot to reduce the radiant heat load! udarrell _ 2007

Here is a link that might be useful: udarrell.com

Udarrell,

This is a follow up on just what you stated and hopefully you can give a bit of advice. My AC was not working real well and had someone come out for a tune up/check of it. His diagnosis was an inside coil leak (iced up pretty good - twice - I deiced it before he came out). Put in 2 pounds of Freon and it's been cooling better in the 2 weeks since than it has in 3-4 years. In that two week time, I have been getting free estimates for replacement of the HVAC in my house. It is original build equipment from '90 (one guy guessed SEER 6 or so for my current unit). Well, one of the contractors mentioned the possibility of getting a 10 SEER unit that the manufacturers are trying to dump - "might be big savings". Well, my house was built in '90 and is only 1200 sq. ft. ranch w/cathedral ceiling and fans in all rooms. It's been cheap to run everything so far, but I know replacing the ac and furnace at the same time will be better in the long run. Would you jump at getting a 10 SEER at a discount rate? I know anything will be better than what my current system is. I am currently still waiting on pricing for an old unit (if available). Thanks for any feedback!!

Jeff

Jeff:

The new outside unit (condensor) must be matched with a new indoor coil (evap) to achieve the 10 SEER. Are they offering you an indoor coil as well? Putting a 10 SEER condensor with a 6 SEER evap coil will give you a SEER rating between 6 and 10 SEER and may shorten the life of the outside unit.

About 1 1/2 months ago I replaced my 15 year old 4-Ton system with a 4 Ton Rheem 15 SEER. It absolutely does not cool as well as the old system did, although the house is comfortable.I have only had the new unit for 1/2 of the last billing cycle (July bill) and my electricity usage did not drop at all. I am going to wait for a full billing cycle and hope I see a drop in usage. If I don't, could it be installed incorrectly? Shouldn't I seem some drop in usage with the new system?

Sorry, I get so much to reply to I don't usually get back to these posts. You need to e-mail me because I may never see your replies & questions.

If my memory is correct, around 35 years ago occassionally the compressors had higher BTUH ratings than the condensing units.

Laxer49 I just checked your page & my birthday is on Dec 8th, too, I will be 73.

Those 10-SEER condensers' used to do real well.
If the E-Coil has a leak it should be replaced anyway.
Laxer49, If it were me, I would put a New half ton larger BTUH rated Coil in there with a TXV refrigerant control.

If you can get a real good deal on a new 10-SEER with that combination & the correct tightly sealed ducts & airflow it should cool okay in the hottest weather.

If you want the most cost-effective payback I would do all I could to reduce the radiant & other heat gain as the insulation will also reduce the heating bills.

The Installation is the most important thing, it has to be done right! Read & learn allyou can.

Funkeruski, I suppose they replaced the evaporator with a matching TXV controlled coil?

Everything has to be performed just right & even then if it is real hot & the indoor load is also heavy it may not equal the old unit which would have a larger BTUH capacity compressor on that 4-ton condenser.

Those high SEER tests are performed under rather light load conditions.
The SEER of a system is determined by multiplying the steady state energy efficiency ratio (EER) measured at conditions of 82°F Outdoor Temperature, 80°F Dry Bulb and 67°F Wet Bulb (near 50%RH) indoor entering air temperature by the Part Load Factor (PLF) of the system. (The PLF is supplied by the government.)

IMO, they ought to be tested at 95 or 100-F outdoor temperature. Which SEER do you think will perform better at 100-F plus ambient temperatures, the one with the larger capacity compressor or the smaller one?

You could slow the blower CFM down to keep the suction pressure & E-Coil temp somewhat lower, but that also drops sensible capacity some.
At 82-F outdoors, the 15 should do real well against the 10. Just my viewpoint. udarrell _ 2007

Here is a link that might be useful: udarrell.com