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Which SEER Rating?

lisapal
13 years ago

I never imagined HVAC could be so complicated.

I have an 100+ year-old folk Victorian house in New Orleans that will be getting a whole new HVAC system. I have replaced the asbestos roof with a galvalume-finish metal roof, all but three of the windows have been replaced with new, energy-efficient ones (historically correct, of course), and I will soon have the entire structure sealed with soy-based spray foam insulation, top to bottom. After many attempts, I finally found an HVAC contractor who will actually calculate a manual J for me. The contractor asked me what SEER rating I wanted and I'm not sure how to answer this. I know that higher SEER is more meaningful in warmer climates and that 14 SEER is the minimum for Energy Star. But how high is too high? I know there is a point of diminishing returns. I just don't know where that is. Anyone got any ideas?

Also, I hear a lot of great stuff about Trane, but this guy is big on Amana. Any opinions in this would be appreciated as well.

Thanks,

Lisa

Comments (21)

  • ryanhughes
    13 years ago
    last modified: 6 years ago

    I'm not big into high-SEER systems and 2-stage systems, but you may benefit from Amana's 2-stage 16 SEER unit for enhanced dehumidification. However, I believe that a properly-sized single-stage system (according to Manual J and Manual S) does a fine job, especially when put with a variable-speed blower. 2-stage isn't for energy savings as much as it is for comfort, though. A solid 14/15 SEER system with a variable-speed blower should do a great job when done right. This is the 'sweet spot' as far as SEER goes in my opinion. Also you'll want to look for an EER rating with a minimum of 12. I suggest you look into Trane's XR13 and XL15i units. Nothing wrong with Amana in my opinion, though, provided it is one of their premium units (models beginning with 'A').

  • tigerdunes
    13 years ago
    last modified: 6 years ago

    lisa

    tell us about your home-size, single story or two story?

    overall insulation qualities?

    what type and size HVAC are you replacing? one system or two?

    for New Orleans, you want a system that has superior dehumidification properties.

    I would think a high eff heat pump is the way to go.

    here are my personal specs...

    15 SEER, 12+ EER, 9 HSPF
    matching variable speed air handler
    R-410a refrigerant(Puron)
    full BTUs in both cooling and heating for your rated size
    scroll compressor preferred
    electronic demand defrost preferred
    staged backup heat strips
    thermostat that has "dehumidify on demand" feature

    I am not a fan of the high end two stage condensers unless a special application such as zoning and/or attractive pricing.

    my personal single stg favorites are Carrier Performance 15(Bryant Preferred 15) and Trane's XL15i(Am Std Heritage 15).

    If two stg, then Carrier Infinity 16 HP or sister company's Bryant Evolution 16.

    IMO

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  • energy_rater_la
    13 years ago
    last modified: 6 years ago

    I'd go as high as 16 SEER (heat pump of course)
    but not higher. and yes, it can get complicated!
    I think I know who you are using..just about the only
    hvac guy in N.O. who does load calcs.
    Make sure that insulation values (actual R-values not
    Quantive Values ) are used in load calc. Also if
    you purchased windows with Low e or Argon this info
    should be included in load calc also.

    higer SEER/efficiency is important for everyone.
    with a higher efficiency unit you will save money
    for the life of the unit. heat pumps will save
    you in the winter. trying to heat that house with
    12' ceilings will be a nightmare with electric strip heat.
    with a heat pump electric strip is emergency or back up
    heat and will only be used if temps get to 30 degrees
    and stay there. Not often that happens for us. (thank God!)

    with entergy costs you'll need to save as much $$
    as possible..after all their customers have to pay for
    those outrageous fuel adjustment costs!

    if you have a chance would you email me the foam co
    that is doing soy based foam? you can email me from
    this site.

    Now go have some beignets and cafe au lait.

    best of luck!

  • lisapal
    Original Author
    13 years ago
    last modified: 6 years ago

    Wow! Thanks so much for your thoughtful responses. Let me see if I can cover all the questions.

    The house is ~2145 sq ft, (1245 sq ft downstairs, 900 down two stories with 10.5' ceilings downstairs and 11.5' upstairs. The original interior construction was 3-coat horsehair plaster over wood lath. (No insulation.) The house was VERY drafty and I had more problems staying warm in winter than cool in summer. I have a picture of the house's compass point orientation and a floor plan with all the insulation values and EE info for the new windows posted here. http://audiblevision.com/pages/CohnHVAC.html
    (I put this together to make it easier for the HVAC contractor to perform the Manual J-load calcs.)

    Everything has been gutted now and the soy-based spray-foam insulation that will go in will produce the following R-values (according to the contractor):
    R-20 for the sub-flooring
    R-25 for the walls
    R-40 for the roof rafters of the 345 sq ft addition
    R-45 for the metal roof of the main house

    The flooded units to be replaced were 3 ton for the first floor and and 2 1/2 ton fur upstairs. (5 1/2 total) The duct configuration for the first floor only covered 3 rooms, but it but it was reasonably comfortable in summer, and pretty cold in winter. The second floor seemed a little strained in summer, but I think we had significant duct leakage.

    Latest contractor says the Manual J-load puts us at a 2 1/2 ton down and a 2 ton upstairs and that the furnaces can be 45-50K btu each.

    We never discussed a heat pump and everyone I talk to seems to want to dismiss it in favor of natural gas, which is what I've always had. I would appreciate more of a dialog about this.

    Thnaks again for your reponses. You guys are awesone!

    Here is a link that might be useful: Info for my Manual J-load.

  • tigerdunes
    13 years ago
    last modified: 6 years ago

    "We never discussed a heat pump and everyone I talk to seems to want to dismiss it in favor of natural gas, which is what I've always had."

    lisa

    I really am surprised at the above statement. I would think excellent cooling and humidity control is more important for your area/climate. you get this plus great heating with today's high eff HPs.

    I am attaching a link to a fuel comparison calculator. I would expect electric HP to offer operating savings over nat gas. check with electric utility and see if they offer any special incentive/rate for HP heating. of course, you do live in an area that has a great deal of nat gas production.

    IMO
    Good Luck!

    Here is a link that might be useful: Fuel Comparison Calculator

  • veesubotee
    13 years ago
    last modified: 6 years ago

    I'm a little suspicious of the heat calc, specifically the heating requirements.

    I'm in a 2500 SF 2 story house with R30 roof; R13 walls in NJ (winter design temp: 14 degrees. House also has Andersen double pane, low-e, Argon filled windows throughout. Fairly decent construction.

    Heating requirement: just under 60,000 BTU. Did you see (study) a printed copy of the calc? I also think the a/c needs might be a little high.

    V

  • lisapal
    Original Author
    13 years ago
    last modified: 6 years ago

    I didn't see a print-out of the calculation. (Yet.) I considered getting the residential version of the software to run it myself, but I'm on a Mac and it's for Windows. I'm also a little worried that I'd screw it up.

    After reading about results others have had with their manual j-loads, I was a little surprised with the sizing change as well, particularly given that the improvements I'm making are leaps and bounds better than what I had. I do have pretty high ceilings, which may put a bit more of a burden on the heating needs. But I really have no frame of reference for any of this.

    The HVAC contractor mentioned a variable speed furnace but I thought the variable speed thing was related to cooling and removing humidity. Obviously, there's still a lot I don't know.

    All of this is a pretty overwhelming, but I appreciate everyone's input. I will post the bids I get, in the event that anyone has an opinion to share.

    Lisa

  • lisapal
    Original Author
    13 years ago
    last modified: 6 years ago

    Energy_Rater_LA,

    Did you get my e-mail? GardenWeb is supposed to send me e-mails for all follow-up comments to this post but I haven't gotten any. I'm now wondering if this problem extends beyond just the response notification. If you did not get my note, please contact me directly: lisa at audiblevision d0t com and I'll resend it.

  • lisapal
    Original Author
    13 years ago
    last modified: 6 years ago

    Tigerdunes, V,

    My HVAC contractor's contention is that the heat pump is very efficient for heating but not so much for cooling, and we spend a greater proportion of the year trying to stay cool. I don't recall reading anything about how efficiently a heat pump cools, but from what I know about the concept, it seems like it should be pretty efficient.

    I guess I have more reading to do.

  • tigerdunes
    13 years ago
    last modified: 6 years ago

    "My HVAC contractor's contention is that the heat pump is very efficient for heating but not so much for cooling, and we spend a greater proportion of the year trying to stay cool. I don't recall reading anything about how efficiently a heat pump cools, but from what I know about the concept, it seems like it should be pretty efficient."

    lisa

    I can't let a statement like that go unchallenged. absolute nonsense. and this certainly raises questions about the quality/competence of your contractor.

    IMO

  • garymunson-2008
    13 years ago
    last modified: 6 years ago

    lisapal..I'll include my energy rant for you to peruse. I found, on my old house, that the bright metal roof was the defining moment in energy savings, cutting my electric bill significantly. I'm always concerned with foam on underside of roof decking since leaks may then go undetected for long periods of time allowing trusses and decks to rot without one knowing...

    Currently the U.S. is sending an exorbitant portion of it's energy money overseas. Anyone who does not take some initiative to cut their power bill (and therefore energy usage) needs to realize that they are providing 'aide and comfort' to those who would love to see us dead and are taking great delight in our current difficulty. Drilling for more domestic oil is not the panacea for this mess as prices are not being controlled by the mechanism of supply and demand, rather by a combination of speculators and OPEC who control such a large portion of the world's oil supply that they can easily negate any of our drilling efforts by simply closing the tap at their end just a little. Any oil we produce won't save us any money. We currently produce a large amount of oil in Alaska but do you see us getting a break on it because it's domestic? No, we pay the going world rate, set by the aforementioned OPEC and speculators...and provide another windfall for the oil companies. They sit before Congress smiling saying their huge profits are necessary to allow them to explore....excuse me....we are talking about NET PROFITS here...what's left AFTER exploration expenses. We the people have no control over this sort of manipulation of our government, whether we have Republicans or Democrats in charge. . .there's too much money involved. Our only hope is to cut energy usage, not drill and give them more avenues for profit. We all need to realize the best thing we can all do to help the energy situation and economy is to take individual action. Rather than waiting around for the government to do something we can each cut our electric usage dramatically....up to one half of your bill if you are willing to spend a little time and money. Every time you see your power bill shrinking, that's money for you rather than some oil producer. Money you can spend here to help the economy or save as you prefer. Here are several sites worth visiting that aren't selling anything but tell it like it is. Plenty of simple and painless techniques to cut your power bill.

    http://michaelbluejay.com/electricity/

    Mr. 'Bluejay' does a great job explaing away a lot of scams...see his section on surge suppressors for example.

    http://www.builditsolar.com/index.htm

    Be sure to look at the 'Half' program.

    The current situation has people grasping at all sorts of non-cost effective solutions that sound great on paper but don't hold up to scrutiny in the real world. Solar electricity is one of those as would be wind power in cent. Florida. Solar PV (photo voltaic) just costs too much at the present. Hopefully ongoing research will change that in the future but it's not ready for prime time yet. The rental program below will probably be practical if it gets underway.

    Check out this site for info on a possible contender for solar PV at home.

    http://renu.citizenre.com/index.php?c=1218495642

    The 'Build it Solar' site also has some good info about costs.

    http://www.builditsolar.com/Projects/PV/pv.htm

    Plenty of outright scams getting too much press also. The 'run your car on water' crowd is one I can think of (apparently many people didn't pay attention in high school physics). A good site explaining the physics that negates that scheme is here along with other interesting info about some of those behind the current revival.

    http://www.alternative-energy-resources.net/browns-gas-the-reality....

    Another scam that's been revived is the 'phase controller' that supposedly saves electricity by making motors run more efficiently. Home show demonstrations with an electric motor show it's electricity usage dropping dramatically when the motor is plugged into the device rather than straight into the incoming power. These devices actually do work in the applications they are designed for...this has the unfortunate effect of helping the scammers (or to give them the benefit of the doubt, uneducated-in-electricity folk) sell these things. An industrial application that produces savings would be a big table saw in a woodworking shop that runs constantly. When it's not cutting wood, the motor is under no load and at that moment, a phase controller will save energy. The goal of electrical engineers is to make sure anything with a motor runs that motor at rated capacity at all times...that's the point a motor is most efficient. Their striving for this is what has made ACs and refrigerators much more efficient lately. The point here is motors in your home all run at rated load all the time. There is no 'off load' time like with the big table saw. A 'phase controller' saves nothing in this situation.

    In hot climates a proven strategy that works well is a heat recovery unit attached to your AC unit. It provides free hot water and also increases the efficiency of the AC a couple of SEER points by reducing head pressure (and electricity draw) on the compressor. You're paying for your A/C to move a great deal of heat out of your house, you might as well use that heat to provide you with hot water. Adding one of these to an older AC unit that still runs well is a good way to cut $30-$50 off your monthly power bill during AC season (which here in cent Fl can be about 9 months). The neatest thing about this solution is that it's cost-negative. In addition to being free hot water as opposed to other 'high efficiency' heaters that still consume energy, it actually lowers your cost of air conditioning. Here is a manufacturer's site for two of these and a power company document about it as well. The second mfg site has a neat calculator for your savings...but my experience shows it to be somewhat under-optimistic. I don't think it's taking into account how a hru will improve your AC's efficiency. There are claims that they don't work with higher efficiency unit, but I have two HRU connected to 13 SEER heat pumps that provide plenty of hot water.

    http://www.trevormartin.com/about.asp

    http://www.turbotecproducts.com/EPhome.html

    http://www.p2pays.org/ref/11/10104.pdf

    Another real saver in hot areas is a radiant barrier in the attic or metal roof. Both create similar savings. If you are re-roofing, consider changing to a metal roof. When installed over a normal wood-decked roof, noise is not a problem. Most people thinking of a noisy metal roof have heard one that's been installed over wood 'stringers' as was the case many years ago...very noisy in a rainstorm. If you have a hip roof house or a lot of dormers metal may be too costly due to the waste from all the cutting to fit...metal is most cost effective on a two-slope 'shed type' roof. Radiant barriers can either be installed during construction..an easy way is using foil-backed plywood roof decking ...or added later. See this site for info and material.

    http://www.atticfoil.com/

    Tankless water heating is also a problem area for accurate claims of savings. A gas tankless heater can be much more efficient since it eliminates the flue that passes through the center of a conventional tank heater and becomes a chimney to carry away your water's heat once the flame shuts off. Electrics are another story... Big savings are claimed that are not supported by data. No studies are shown that give specifics telling you what make/model/year tank unit is being compared with the advertised tankless. Maybe they use an ancient cast iron tank heater insulated with sawdust? Verifiable details please. Somehow electric tankless heaters dodge the requirement for the yellow government 'EnerGuide' label that every other appliance must have. If they had to carry it, their claims would show to be false. Claims of better durability because of 'no tank' are a red herring also...the 'tank' still exists, only it's now smaller. Buildup from hard water deposits may be more of an issue with tankless, possible surcharges from the power company later due to high instantaneous current draw, heavy wiring needed, new construction with planned tankless can make retrofit of tank type later very difficult due to lack of dedicated hot water piping, incompatibility with future solar or other alternative power sources due to aforementioned high current draw. These are all serious disadvantages of the tankless electric. All electric hot water heaters are 100% efficient at heating water. That's a function of an electric element immersed in water. The only added efficiency of a tankless is the reduction of standby losses which are very minimal in new technology insulated tank heaters. Put your hand on one and you'll see they pretty much run at room temperature...very little standby loss.

    Another myth is that shading a A/C condenser saves '10-20% or more. The reality is not much. Similar situation to a garden hose left out in the sun...you turn on the water and what comes out is scalding hot....but in a few moments the water is cool...sun impinging on something will make it very hot but that is a function of 'accumulated heat'. What heat is striking something and being carried away by a fan is very small. See the following link about this subject...

    http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-302-96/index.htm

    A free, online calculator that can help you plan upgrades is here:

    http://hes.lbl.gov/

    Two technologies have the potential to really turn things around..see these two links for something both companies say will arrive sometime next year...Still better to get moving with your own plan that to wait with your fingers crossed..

    http://www.eestorbatteries.com/

    http://www.nanosolar.com/

    Please use due diligence when deciding on ways to save energy. There are LOTS of scams out there. The internet is a great source of info and you can easily see both points of view on any energy saving strategy. Just simple conservation by time-tested means is still the best way to approach our dilemma. If we all cut our power bill in half, we'd all have much more money in our pocket and our nation would be much more secure. This action, along with Mr. Picken's ideas on wind power, WILL free us from imported oil and rather quickly.

  • lisapal
    Original Author
    13 years ago
    last modified: 6 years ago

    Tigerdunes,

    Let me cut and paste what HVAC contractor wrote in his message:

    "Heat pumps are more efficient only in the heating mode. Yes, over an entire year they are more efficient. They are anywhere from $600-900 more per unit than a straight split system (gas or electric). Yes, our winters are mild here. You're talking about $1200-1800 (two systems) extra that you can recover only during the winters and only when not using makeup heat. Difficult to talk about payback times due to differences in usage but it’d be a long time. Yes, you can do a gas furnace heatpump system instead of electric but it’s about 500 more."

    I've been looking around for some solid info on heat pump efficiency during the cooling season in our climate but don't feel I have enough information to challenge this.

  • garyg
    13 years ago
    last modified: 6 years ago

    "Heat pumps are more efficient only in the heating mode".

    - Absolutely wrong. Someone doesn't understand the basics, or doesn't want to tell you them.

    A heat pump is simply a central a/c condenser (outside unit) that has a reversing valve which allows the refrigerant to reverse flow and provide hot refrigerant to the indoor coil for heating. It's the same except for the reversing valve and defrost board.

    The summer efficiency ratings for either a straight a/c condenser or heat pump condenser are SEER and EER. A 3-ton, 15 SEER, 12 EER heat pump condenser has the exact same efficiency and cooling capacity as a 3-ton, 15 SEER, 12 EER straight a/c condenser. Same.

    This joker doesn't want to sell you a heat pump, for whatever reason. $900 additional for each heat pump condenser is way too high. He's making more money on the 2 gas furnaces so he's raising the cost of the heat pump condensers.

    What are your utlity costs? Electric is how many cents per kw-hr delivered? What is your cost of gas in $ per ccf or $ per therm?

    Post your rates and someone will do the math - I'll check back on Monday and run the numbers if no one doesn't.

    Good luck.

  • tigerdunes
    13 years ago
    last modified: 6 years ago

    gary,

    thanks for your post. I really believe OP is receiving not only poor advice but also incorrect information. you and I know a high eff HP system is perfect for the New Orleans area/climate. I provided the fuel comparison calculator in a previous post for Lisa. So if the numbers work between electric and gas rates, the decision seems to be a no brainer. It is amazing how people come on this forum asking for information, advice, suggestions. As the old adage says, "you can lead them to water, but can't make them drink it".

    Oh well.

    Thanks again for the backup.

    TD

  • lisapal
    Original Author
    13 years ago
    last modified: 6 years ago

    Gary, thanks for explaining this is such a clear and simple way. I only have the latest electricity rates (~.055/kWh + .07066/kWh fuel adjustment charge = .12566/kWh) because my gas has been turned off at the house and I'm currently living in another parish (the La. version of county) with a different power company and different rates. But I'm working on getting that info.

    Tigerdunes, I'll drink the water. I never argued against any of the advice I've gotten here, just passing along what I'm being told. I trust you guys. You're the experts. It's just that it's me, a layperson with a limited understanding of all this, dealing with HVAC contractors who have their own agendas. I wish I had all the info you guys have in your brains when these interactions take place. It would be easy and I would be a much more formidable opponent in the battle of wills. But as it us, a lot of this stuff is like Greek to me; I'm slowly learning the language and the nuances of the semantics.

    And truly, I am awestruck by the generosity of those of you who take the time to share your expertise with people like me. I can't overstate my gratitude. You're like having GPS in the big, dark forest, helping me figure out where I am and where I need to go.

    BTW, I spoke to some friends who are in a similar situation and they bought the manual J software and ran it to compare to what their HVAC contractor showed them. I think there was a difference of about a ton because of details the contractor made assumptions about. I looked over the software demo and realize my contractor's manual J probably made similar assumptions. My friends' house is about 2400 sq ft and 3 stories (slightly lower ceilings) with batt insulation and they were at 4 tons compared to my 4.5 tons indicated in the contractor's J-load. So, I'm going to get the software and run the calcs myself. I know I risk the ire of the HVAC contractor, (and maybe that's not a bad thing), but I just want this done right. Is that so wrong?

    Sigh.

  • tigerdunes
    13 years ago
    last modified: 6 years ago

    lisa

    I see nothing wrong with running your own load calcs particularly if you have any doubt about the accuracy of sizes from your GC/HVAC dealer. Please get load calc in writing for each zone and carefully review for each zone. make the comparison between your dealer's and your calculation.

    I will say this.I looked at the sizes of your condensers and felt they were more reasonable than the furnace size. Depending on brand and eff, it can be difficult to find small furnaces-which is another plus for HPs. For New Orleans area/climate though, I do not want to be borderline or undersized for cooling BTUs. Make certain your design temps for both inside comfort level and outside temp is correct for both summer cooling and winter heating.

    IMO

  • fsq4cw
    13 years ago
    last modified: 6 years ago

    Re: lisapal

    Heres something else to think about. Instead of the conventional equipment youÂre currently considering, a geothermal system can achieve a SEER equivalent of about 30 without even trying. Remember, over the life of the system, your greatest expense is not the system itself but the energy to run it!

    I often visit clients facing the replacement of air-sourced equipment 2 or 3 times over what would have been the life of 1 geothermal unit. Some clients are replacing 2 air-sourced heat pumps at a time for larger homes where 1 geothermal unit would have sufficed.

    IMO

    SR

  • lisapal
    Original Author
    13 years ago
    last modified: 6 years ago

    SR,
    Geothermal was my first choice. First contractor wanted to charge me $11,000 just to drill the well. (And I'm on a corner with easy access.) Second one came out, took measurements, etc. and never returned a proposal. No one else I spoke to did them. I gave up.

    Lisa

  • garyg
    13 years ago
    last modified: 6 years ago

    Lisa:

    I know that you finally found a contractor to do the Manual J, and many may not be too happy with this suggestion, but you can always get competitive quotes from other HVAC contractors based on your Manual J numbers.

    Keep asking the tough questions.

    Don't be satisfied with answers that you feel are bullsh%t.

    You're doing a great job.

  • garyg
    13 years ago
    last modified: 6 years ago

    Lisa:

    Compare the cost of 1 million btu's of heat for a gas furnace vs a heat pump. Plug in your own costs and efficiencies for more accurate $$.

    Natural gas at $1.30 per ccf, 80% efficient furnace:
    (1,000,000 / 103,000 btu per ccf) x 1.3 / .8
    = $15.77

    Heat pump w/electricity at 13 cents per kw-hr delivered, C.O.P. (Coefficient of Performance) = 3.25 at 35F ambient:
    (1,000,000 / 3414 btu per kw-hr) x .13 / 3.25
    = $11.71

    In this case, the heat pump costs 35% less to operate than the 80% efficient furnace.

    C.O.P. increases with increasing ambient temps.

    At 45F ambient, COP = 3.6, so the cost of 1 million btu's is $10.58. At 55F ambient, COP = 4, so 1 million btu's is $9.52.

    Note that below the balance point of the home (25F - 35F ambient depending on home construction, etc.), the heat pump requires supplimental heat. This would be a gas furnace or electric strips in the air handler. Strip heat is very expensive to use but very cheap to install. $38 for 1 million btu's at $.13 per kw-hr.

    Take care.

  • speedracer2013
    13 years ago
    last modified: 6 years ago

    It appears everyone is caught up on the SEER rating rather than comfort. The highest seer rating won't do any good if the equipment doesn't have the capacity to do the job. I too am not a proponent of HIGH SEER units. You have done the right thing by first getting a load calculation. Without this you are just guessing like so many other do and then complain about their systems performance. Now that you have the numbers your structure requires look at the various mfgrs systems and weed out those that are under or grossly oversized by your specs. Then compare the various SEER for those remaining units. Now you can compare the cost to run and in the end find the system that fits YOUR needs. Unless you have some very strange or poorly designed duct system I personally do not like variable speed blowers. As several others have stated IF you find the equipment that meets your Manual J specs, and IF you design the ducts to properly handle and distribute the air then it WILL work right. Also consider the cost to repair the variable is MUCH greater than a standard evap fan motor. Every little bit helps or hurts... Good luck in your choice.