# Is 18 Seer overkill?

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• 06-25-2008, 10:56 AM
gary_g
Outdoor temps for SEER ratings
Its important to understand the outdoor temperatures at which SEER is calculated (BeenThere: you've read this before so please don't beat me up too much :) )

For a variable speed motor in the air handler, SEER is calculated from EERs at representative (seasonal) temperature "bins" starting at 67F thru 102F in 5 degree increments.

The following are the outdoor bin temperatures and their weight% in the SEER calculation:

67F------21.4%
72F------23.1%
77F------21.6%
82F------16.1%
87F------10.4%
92F-------5.2%
97F-------1.8%
102F------.4%

Total-----100%

Now I don't know about the rest of you fine folks, but in Baltimore, I don't run my central a/c when its 67F or 72F outdoors, so 44% of the value of the SEER calc is meaningless to me.

The reason why systems attain 16+ SEER ratings is because they are dual-speed or dual-stage, and they are capable of running on low stage where they have very high EERs at the lower outdoor temperatures where the SEER calc has its highest weighting. Once these systems run on 2nd stage at real-world summer temps, the EER becomes more relevant to operating costs.

I agree that dual-stage systems can enable a higher temperature setpoint since they remove humidity better than a single stage by running on 1st stage longer.

I always like to say "Whichever SEER system someone chooses, get a 12 EER minimum".
• 06-25-2008, 11:05 AM
beenthere
Quote:

Originally Posted by gary_g
(BeenThere: you've read this before so please don't beat me up too much :) )

LOL...

Speaking of beating up..
What were your cycle times during our heat wave?
• 06-25-2008, 11:27 AM
gary_g
Quote:

Originally Posted by beenthere
LOL...

Speaking of beating up..
What were your cycle times during our heat wave?

I don't have any data to support it, but I believe that my system may be 1/2 ton oversized. Since it is a heat pump in an all-electric house, I am OK with that because I need all the heating btu's that I can get for the winter. I don't have issues with humidity removal in the summer time. As mentioned in an earlier post, I have good ductwork and no problems with air flow.

I tend to run the air handler fan when the wife is home on a hot summer day. The reason I do this is to keep air circulating (pull cooler return air from the below-grade family room) and also trick the wife into not knowing when the compressor turns off. This keeps her away from the thermostat.

At 74F indoor setpoint, the system did cycle off during that week of 95+ weather, but I'd only be guessing at cycle times. My old thermostat used to keep track of compressor run time, but my new Honeywell does not track run time. I even dropped the setpoint to 73F and I believe the compressor ran much longer but was able to maintain setpoint.

Take care.
• 06-25-2008, 11:24 PM
rustwood
As a consumer who was on the other end of this decision not long ago, I think this has been an interesting discussion. FWIW, I will share my experience and reasoning.

I was definitely influenced by the energy credits last year. That incentive made it a little easier to spend more up front than I might have otherwise. When I bought, my exact system combo wasn't in the database, but it was at tax time and the AC fell just short of qualifying - bummer.

I don't recall what the difference in cost was after adjusting for the rebates and tax credits, but I think I ended up paying at least 30% more to get the Infinity system with a 2 stage 24ANA7 (vs a performance system with a single stage 14 SEER, IIRC). Before I decided I ran a spreadsheet that calculated the difference in energy savings between the 2 new systems for my location and rates (I think from energystar.gov). It also took into account inflation and the loss of interest income on the additional up-front cost. It was clear that it will take the life of the system (if I am lucky) to recover the cost of the upgrade. However, I then calculated the ROI for each of the new systems against my old inefficient system and the difference wasn't all that long. I know that isn't the correct comparison, but thinking of it as giving up some months of future energy savings makes it easier to swallow.

How did it work out for me? The system is great. I never touch thermostat - it is just always comfortable in the house. Until this system, I never realized that the temperature swing on my previous system (and the one in my previous house) caused me to keep the house warmer in the winter and cooler in the summer (to try to avoid being uncomfortable). Plus, as energy prices rise, I am glad I am saving as much as I (reasonably) can. With the humidity control and the 2 stage, I've been able to keep the thermostat at 76 this summer and even on the hottest days I think I am more comfortable than I was with it 2-4 degrees lower on the old system. My wife is thrilled because she always thought it was too cold in the house with the AC on.

Obviously I am now convinced the comfort of the higher SEER, 2 stage system was well worth the extra cost. If someone else wrote this I would think, "Of course you do, you are already invested in it", but believe me I much more prone to having "buyers remorse" than patting myself on the back. Of course I also have to admit that while I certainly don't think I am rich, I could easily afford the extra cost of the upgrade.

Hopefully my experience will be useful to someone - perhaps on both sides of the aisle (so to speak).
• 06-25-2008, 11:32 PM
beenthere
Good to hear.
• 06-25-2008, 11:45 PM
Mr Bill
Quote:

Originally Posted by rustwood
As a consumer who was on the other end of this decision not long ago, I think this has been an interesting discussion. FWIW, I will share my experience and reasoning.

Well good you have been Blessed but for every story like yours your will find a negative one also trust me,
glad to hear yours worked out good for you.
• 06-26-2008, 03:56 PM
Jack2007
Rustwood.
Thanks, I'm contemplating the infinity system, but heat pump version. Good info.

I presently have a "10" seer mismatched air conditioner system. Looking forward to better humidity control.
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• 06-26-2008, 04:02 PM
Jack2007
Quote:

Originally Posted by beenthere
Currently, higher SEER equipment is like plasma TVs were.
High priced because of a some what low demand.

As energy prices continue to rise, their demand will go up and teh price will come down some.
Yes, the super high SEER will still have a much highr price tag.

Eletric rates are not coming down. PA gets a 30 to 40% electric rate increase in 2010. I expect the request for higher SEER equipment to increase a lot then.

Those people that are currently opting to only get 13 SEER equipment will be wishing they had gone to 14 or 15 SEER equipment.

Installing equipment based on only the current cost of electric is not always wise.

Isn't that interesting. I believe the "transition" charge will expire in that very year.

The "transition" charge allowed the utility to lower their "generation" charge (so they could compete with other utilities "generation charges") without losing any money.

Politicians, you gotta love em.
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• 06-26-2008, 04:31 PM
gary_g
Jack2007:

Your avatar is outstanding. Was the intruder armed just before the photo was taken? That's a mean-looking kitten :)

Take care.
• 06-26-2008, 04:40 PM
Jack2007
Quote:

Originally Posted by gary_g
Jack2007:

Your avatar is outstanding. Was the intruder armed just before the photo was taken? That's a mean-looking kitten :)

Take care.

Thanks.
I must confess, found it (cat burglar) while looking for something else.
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