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  1. #1
    Join Date
    Feb 2006
    Posts
    103
    I'm considering either the 4 ton RTG Ultron 16 seer or RHF Temp assure 14 seer. Both would be mated with the AMV9 96% Amana furnace. I live in the Atlanta area. My contractor says both are nice units, but recommends the 16 Seer based more on comfort than efficiency. In particular he believes the 401a in the 16 seer unit will serve me better in the cold months, and I won't complain about "cold blow". Although it will not even out the cost, I was also wondering if the Ultron will qualify for the $300 tax credit. Any thoughts or advice would be appreciated.

  2. #2
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,271

    Cool Energy Cost$ Evaluation

    Originally posted by georgiaguy
    I'm considering either the 4 ton RTG Ultron 16 seer or RHF Temp assure 14 seer. Both would be mated with the AMV9 96% Amana furnace. I live in the Atlanta area. My contractor says both are nice units, but recommends the 16 Seer based more on comfort than efficiency. In particular he believes the 401a in the 16 seer unit will serve me better in the cold months, and I won't complain about "cold blow".
    What are electric and gas rates in Atlanta?

    Do you really need a furnace?
    How many hours per year is it <25'F in Atlanta?
    _84 hours < 25'F
    218 hours < 30'F

    Life cycle cost evaluation may indicate adding a furnace
    (use heat pump + electric strip if <~$0.08/kW)
    is not the most economical.

    [Edited by dan sw fl on 02-14-2006 at 06:22 AM]
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  3. #3
    Join Date
    Mar 2004
    Posts
    1,042
    "Cold blow" is better fixed by using a variable speed furnace or air handler than by having a two speed heat pump. You'll have variable speed either way.

    Gas rates in Atlanta are largely deregulated and float at the price of the commodity. Right now very few consumers are paying less than $1.20 per therm.

    Georgia Power rates for a typical household work out to about (gross, all inclusive) 9-10c/kwh in summer months and about 7.3c/kwh the rest of the year. Summer rates increase with consumption (so a minimal amount of juice doesn't cost much, but what you use beyond the bare minimum gets charged at a higher rate). Winter rates actually decrease a tiny bit with consumption (they start low and get a few percent lower as your consumption goes up). There are no special rate plans for heat pumps, all electric households, etc. like there are in some other states.

    Ask tough questions about what thermostat and he's going to use to control such a system. Many popular thermostats, such as the Honeywell VisionPro, don't really know how to control two stages of backup heat (which you will have with a two stage furnace). There are very few thermostats that can control a two stage heat pump that uses a two stage furnace as its backup. There are some workarounds to make other thermostats do the job, but in my book it's best to let the thermostat have complete control over staging.

    I'd agree with Dan, though on using electric backup instead of a furnace. In this area it is cheaper to heat with an all-electric heat pump. If your electrical system is up to snuff and it won't be too hard to run a big circuit from the electrical panel to the old furnace location, consider dropping the gas backup completely.

  4. #4
    Join Date
    Feb 2006
    Posts
    103
    Not sure if the electric can handle the heat strips, but I'll check and give it some thought. How about the "cold blow" advantages of the 401a in a heat pump?

  5. #5
    Join Date
    Apr 2004
    Posts
    7,680
    410A has nothing to do with temperatures, both refrigerants operate at the same temperatures.

    If you are concerned with heating efficiency, dont assume the 16 SEER operates at a lower cost in winter. You need to look at the HSPF for heating efficiency. Since you are using the same air mover and coil, odds are the heating efficiency will not be much different, and there is always the possibility the 14 SEER is more efficient than the 16 come winter. Of course you need to look at the actual efficienty with the particular matches.



  6. #6
    Join Date
    Mar 2004
    Posts
    1,042
    Originally posted by georgiaguy
    Not sure if the electric can handle the heat strips, but I'll check and give it some thought. How about the "cold blow" advantages of the 401a in a heat pump?
    A few basics first:

    With gas heat or gas backup, you use a gas furnace for your indoor unit. It has the relays, transformer, blower, etc. If you have air conditioning or a heat pump in addition to the furnace, they put some coils on the output of the furnace that let the AC or heat pump do their heating or cooling of the airflow.

    With electric backup on a heat pump, you don't have a furnace, you have an air handler. It's pretty much the same thing as a furnace, except in place of the gas burners you've got a big electric heating element. Typically with air handlers the AC or heat pump's indoor coil is integrated into the same box.

    Cold blow happens with old-fashioned and/or low-end heat pumps because the control system doesn't recognize that it takes a few minutes of running before the heat pump warms up the coil that goes in the indoor airflow. So if the thermostat called for heat, the indoor blower would start immediately, along with the heat pump. The room-temperature air blowing at full speed would feel cold and drafty until the heat pump had a few minutes to build up pressure and heat up the indoor coil.

    Once you have a variable speed blower in your indoor unit- be it a furnace or an air handler- you generally have enough smarts that when you call for heat, the blower doesn't start up immediately anymore. The heat pump starts up, runs for a few seconds to get the indoor coil warmed up, and then the blower starts to ramp up to full speed slowly. There's no blast of cold air at the start of the cycle anymore.

    As for efficiency overall, don't assume that X SEER will be X SEER in your application, either. Typically only one size outdoor unit, paired with one specific set of indoor components, will hit the rated efficency. Other pairings and other sizes will have a variety of different efficiencies. Usually something rated 16 SEER will in fact be more efficient than something rated 14 SEER, but often the difference is miniscule.

    In my case recently I chose a "13" SEER heat pump over a "17" SEER heat pump because the heating and cooling efficiency ratings were almost identical, despite the big price difference. In other setups, though, the difference between those two lines could have been as large or larger than what the nameplate ratings suggested. You can really only know by looking up the ARI rating of the exact model numbers of the indoor and outdoor equipment you're considering.

  7. #7
    Join Date
    Feb 2006
    Posts
    103
    My thanks to all the postings. My contractor was pretty clear that the 16 seer would be more efficient than the 14 seer, but that the increased efficiencies probably didn't warrant the cost. His reasons for pushing the 16 seer were:

    1. 401a works better than 22 when in heat mode. He says the installer originally thought the heat strips were kicking in until they realized it was the higher pressures, etc. resulting from the use of 401a. About 10-15 degrees hotter output. He said it was an unintended by-product, benefit of 401a. Sort of a nice surprise.

    2. 16 seer has a better warranty (it's an Amana lifetime, etc.), and I plan to stay in the house for the foreseeable future.

    3. The two stage heat pump would be more comfortable in the winter and summer. (Although I admit I didn't understand what wasn't being achieved by the variable speed blower).

    4. Some increased efficiency in the summer (more than the winter), but only enough to buy a couple of pizzas per month.

    5. 22 is being phased out and might as well invest in the new technology given the potential life of the system.

    Also, he was suggesting the Honeywell Vision Pro thermostat.

  8. #8
    Join Date
    Feb 2006
    Posts
    103
    I should add the thermostat is the Vision Pro 8000 series if that helps.

    Also, I need to look at the electric heat strip concept, but I have to say I like being able to "flip" between gas and electric. I suppose gas would have to fall to pre-2000 levels to make sense (or electric rates would have to double), but who know what will happen and it's nice not to be totally tied to one utility source. Also, if a go with a backup electric generator I suspect it's easier to power a furnace vs heat strips.

  9. #9
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,271

    Gas Fireplace for Emergency?

    Originally posted by georgiaguy
    I should add the thermostat is the Vision Pro 8000 series if that helps.

    , but who know what will happen and it's nice not to be totally tied to one utility source. Also, if a go with a backup electric generator I suspect it's easier to power a furnace vs heat strips.
    Just a suggestion so you are aware of alternatives
    Now instead of later

    http://www.aireone.com/Majestic_NaturalVent.htm

    IF you need real assistance on heat pump/electric strip sizing, e-mail house plans & specs.

    Best of luck!

    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  10. #10
    Join Date
    Feb 2006
    Posts
    103

    themostat and blower question

    So does a variable speed blower on a furnace serve the same "comfort" functions as the two stage heat pump, with the two stage heat pump being just an efficiency issue?

    Also what themostats will control the variable speed blower and a two heat pump with a two stage backup furnace?

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