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  1. #1
    Join Date
    Feb 2013
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    25

    2 stage Amana or modulating Amana

    My load calc came in at a light 3 ton and Im going dual fuel. I going 3 ton 16 seer 2 stage Amana heat pump and Ive got different quotes on the nat gas furnace part. Ive got quotes for a 2 stage 69000 VS system and a modulating 80000 VS system both Amana. I personally think after I ran the numbers and it says 64000 or 65000 that I could probably get away with a 60000 modulating system but I want to here some of ur guys thoughts. The house is in southern il and its 1600 sq ft with a good amount of glass but they are newer windows and its a well sealed up house built in in late 80s and newly remodeled. Im kinda lost on how the Amana modulating works compared to Carrier or York.

    Thanks for any replies and you guys have been a big help that is much appreciated

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,415
    Seems like a lot of equipment for 1800 sq ft if build decently. Next door we typically would be 2.5 ton max on cooling and 60K 95%er for heat. If you are going 2 stage you have no choice but the 3 ton. Luckily low is a bit lower capacity though not that much. I sure wouldn't suggest 80K furnace though.

  3. #3
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    AMana/Goodman modulating valve only goes to 50% during normal running mode. IT does run at 35% for it appears 2 minutes initially after lighting, but steps up to 50% before modulating.

    In comparison, the Carrier unit modulates to 40% and I think Trane and York modulate to 35%.

    I agree with above, 80k sound very big for your climate. I'm further north than you and 60k should be plenty. You'll never notivce that last 4k, but you will notice if low stage is 38k instead of 29k. I think Amana also runs a 50F max temp rise, so a 80k will need a lot more air than a 60k. That could mean noisy ductwork.

    Also, a 60k BTU modulating will transition seamlessly around 25-35F from high stage of the heat pump to 28k BTU's on the furnace. So below about 35-40F, you can expect that the system would run almost continously as some level of heating. That means nice even temepratures. With dual fuel you get a system that can go from around 15k BTU to 60k BTU in heating. Only hot water hydronic systems can modulate that low.

    Get the better CTK03 controller which ever furnace you choose. It's basically a Honeywell Prestige and has some niec programability.

  4. #4
    Join Date
    Feb 2013
    Posts
    25
    I am for sure going with the CTK03 stat as I noticed the ctk02 looked emerson and the 03 looked honeywell and the price wasnt that much difference. Baldloonie do you think I should go with a RPQL030JEZ 2.5 with VS and Rheem Mod furnace with all the communicating rheem stuff instead as my contractor also deals Rheem and Armstrong. I was just really liking the Amana warranty and the 2 stage but is the amana oversized even with it being 2 stage. I have a plenty big enough RA setup and supply duct system so noise shouldnt be and issue even with 2 stage gas furnace. Im gonna be here a long time so comfort and lower bills are my concern and I do like how the rheem has hspf of 10 but the amana 3 ton 2 stage is hspf 9.75 so not much difference their. The exact words were your load comes in at a really heavy 2.5 ton like 2.8 2.9ish they said so close they would recommend a 3 ton.

  5. #5
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,415
    As I recall, you can't do dual fuel with Rheem and communicate unless you get a JEC outdoor unit. That means RPRL outside. HSPF a bit less but 16 SEER. Still think Rheem makes the best mod!

    What part of the state? Still seems high for 1600 sq ft. My cousin in Waterloo has say 2400 sq ft 2 story, lots of old windows, 100 years old. 3 ton for whole house. Been there plenty of times in 90 some degree weather.

  6. #6
    Join Date
    Feb 2013
    Posts
    25
    Southern Il in between mt. vernon and carbondale. So do you think I should consider the 15.5 seer 2.5 ton Rheem with VS instead of a 2 stage 3 ton Amana. Can you explain the Rheem modulating vs the Amana modulating. I used to go to Indy for the Super Chevy meet and to the best of my memory it was it was about a 4 hour drive.

  7. #7
    Join Date
    Feb 2013
    Posts
    25
    Im confused on one other thing, the cfm needed to get the job done for my place. The 60000 modulating is 1600 cfm with max output being 57600 btu and the 80000 modulating is 2000 cfm with max output being 76800 btu. Im wondering what kind of difference the cfm makes and the max output as far as calc goes I need 64000 and Im in the middle either way I go. It seems like either way I go Im either over or undersized. Whatcha guys think

  8. #8
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    I think in heating, when you're that close to the smaller unit, you go smaller. The actual CFM for hi heat should only be 1050 for the 60,000CFM and 1400 for the 80k at a 50F temp rise. The blower has more capacity, but you won't need to go that high. That being said, with the 80k, you need ductwork sized for 1400CFM. Pretty good chance your marginal for even the 1200CFM you need for the 3 ton heat pump, but a pro needs to evaluate that. The 60k unit on the same ductwork running at max, will use less electricity and be slightly more efficient on gas. Ideally supplies should around or under 700fpm and returns 500fpm. So if you take you cross sectional area of your plenum and seperately your branches, they need to be 2sqft for supplies and 2.8 sqft for returns for 1400 CFM. The total length and distribution/balance also matters, but that's a much more complicated calculation.

    Given your location, and the homes size, I don't think 60k is going to be undersized by any stretch. Smaller to medium sized space do swing more quickly because they have less mass, but internal heat loads warm them up quickly and solar heat gain, very significant sinec your in S IL, has a larger impact. Worst case, the dozen or so days the temps drop under 15F, use a minimal setback and you might find that in really cold weather... for your area... below 10F it could fall behind by 1F until the sun comes out. Remember most all extremely cold days are normally associated with clear skies, so that sun will warm it up quick. But I really don't think it will come to that.

  9. #9
    Join Date
    Feb 2013
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    25
    I currently have a 3 ton 12 seer heat pump that has a 4 ton air handler and I cant find the cfm its pushing now. The return duct work and supply duct work are quiet with the current setup. Im just worried that dropping to a 60k mod furnace is gonna be lacking in air flow to the registers with the lower cfm.

  10. #10
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    Quote Originally Posted by 6speedb4c View Post
    Im just worried that dropping to a 60k mod furnace is gonna be lacking in air flow to the registers with the lower cfm.
    That's a common misconception that you need some mythical minimum airflow. Besides, if you want more aiflow, you cna adjust the heating airflow settings all the way down to about 25F if you want, so the heat rise off the furnace would be as low as the heat pump, if you want a lot of airflow. Another myth is that a larger furance or unit will "push" air better. All it does is use more electricity, and if hte unit is oversized, you get shorter cycle tiems which makes temperature imbalances worse. Typically, most registers still have adequate throw even at fairly low flwo rates.

    IF register throw is an issue, you should repalce the registers with better quality ones. The cheap stamped steel units that builders throw in are like $5, while the better quality ones are maybe $10-15. So we're talking a $100-200 quick fix for comfort in many homes. They also have less resistane so they can flow more air which can aide in balancing the system room to room.

    Again, a larger unit NEVER improves comfort, unless the next smaller size would fall behind on the coldest days. Most all contractors on here will tell you that they've never ever seen an undersized furance. On rare occassion a undersized AC, but the problem is usually leaking ductwork or poor insulation or installation issues. Heat pumps do lose a little capacity over time and the compressor gets older and loses a little compression and the fins get bent or dirty.

  11. #11
    Join Date
    Feb 2013
    Posts
    25

    thanks for the insight

    Quote Originally Posted by motoguy128 View Post
    That's a common misconception that you need some mythical minimum airflow. Besides, if you want more aiflow, you cna adjust the heating airflow settings all the way down to about 25F if you want, so the heat rise off the furnace would be as low as the heat pump, if you want a lot of airflow. Another myth is that a larger furance or unit will "push" air better. All it does is use more electricity, and if hte unit is oversized, you get shorter cycle tiems which makes temperature imbalances worse. Typically, most registers still have adequate throw even at fairly low flwo rates.

    IF register throw is an issue, you should repalce the registers with better quality ones. The cheap stamped steel units that builders throw in are like $5, while the better quality ones are maybe $10-15. So we're talking a $100-200 quick fix for comfort in many homes. They also have less resistane so they can flow more air which can aide in balancing the system room to room.

    Again, a larger unit NEVER improves comfort, unless the next smaller size would fall behind on the coldest days. Most all contractors on here will tell you that they've never ever seen an undersized furance. On rare occassion a undersized AC, but the problem is usually leaking ductwork or poor insulation or installation issues. Heat pumps do lose a little capacity over time and the compressor gets older and loses a little compression and the fins get bent or dirty.

    So your saying the 60k mod furnace will be more then enough as far as airflow is concerned, I was just worried going from a 4 ton to the 60k mod that airflow would decrease too much and not be able to push enough air. Im going dual fuel so the blower in the furnace is also going to be handling the airflow from the heat pump in the summer. I really want to go 60k mod but not if it wont be able to push enough air in the summer and if that is the case then i will go 69k 2 stage furnace or 80 k mod furnace instead for the air flow. My duct work is plenty capable of pushing a 4 ton air handler so does that make it to big to supply using 60k mod.
    I really appreciate the replies from you, caincompany and baldloonie. I cant put a price on how valuable ur help has been though this process.

  12. #12
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    The 4 ton air handler shouldn't have been moving more than 3 tons of airflow (1200 CFM) if it was set-up correctly, unless you lived in Arizona where you use 450CFM/ton because humidty removal isn't needed..

    The 60k has a 3 Ton blower. Its' 1/2 HP. You 4 ton PCS motor is also probably 1/2HP. They have approx. the same capacity at the same static pressure when trying to move 1200CFM. IF you say the ductwork is quiet now with your current 3 ton unit, unless you supply and return plenums are undersized (which should alwasy be corrected during a new installation, no matter what size blower you put in).

    It's bad practice to oversize the blower (and furnace) just to compensate for undersized ductwork. That's not solving the problem. Better long term to correct the ductwork.

  13. #13
    Join Date
    Feb 2013
    Posts
    25
    So ur saying the 60 k will move enough air in ac mode and furnace mode if that's the case then I will be goin 60k modulating. Really appreciate it moto

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