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  1. #1
    Join Date
    Jun 2018
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    guidance in selecting new HVAC

    Hello. I am seeking some guidance on replacing our HVAC in our home that we purchased last year. The house is 24 years old, 2700 SQ FT, two story with 4 bedrooms on the second level. The existing/original equipment is York, and we've had issues with the condensor not starting when it should. The contacts and the capacitor have been replaced without fixing the issue. So we are trying to get some bids, and be ready to move forward when the system finally breaks for good, or when we know what system we should go with, whichever comes first! Our biggest complaint, other than the compressor does not start when it should, is the upstairs is very warm in the summer. We have been playing with closing down the 1st floor dampers, which has helped out some.

    We have met with 4 contractors so far. Over the course of those 'interviews', we have determined that we are looking for a 2 stage variable furnace 96% Eff, and a 2 stage 16+ SEER AC. They all seemed to agree that utilizing a 2 stage ac will help the system run longer, which should help the upstairs not be so hot. They all pretty much were in agreement that we should try the new system, and if we are still unhappy with the upstairs, we can then install a zoning system.

    I try to educate myself so I can be a smart consumer, and I understand that many of the units are very similar, and that brand name should not be as important as the quality of the install. However I found that it was difficult to really know which company would be the best installer. Two of the companies, I met with dedicated salesman. They both were 'polished' and sold their services well. The two others were lead techs, who knew their stuff, but were not so polished. Anyways, after meeting with them, it seems like our existing ductwork is pretty good, as none of them really said much had to be done with it. One of them said they like to 45 degree the ducting where the vertical duct joins the horizontal duct. Other than that, ducts seem ok. Some like to remove the unit from the rack that is existing and mounted about 3 foot up, and build a pad on the ground. Some said they like the unit up so grass/leaves don't get in the unit as much. Some like the 4 inch filters, some don't and say the 1" are better when changed out more often. So it seems like a pretty basic install/replacement, where they are not doing much other than replacing existing, and running the fresh air piping for the furnace. 2 of the contractors were Trane dealers, 1 was a Comfortmaker dealer, and 1 was a Carrier dealer/Coleman dealer. I don't know what the rules are for listing prices, but I'm guessing that it's forbidden, so I won't even attempt that unless someone tells me it's ok. Even though I'm not supposed to let brand steer me, I have always liked my Trane that I had at my previous house, so I am partial to that brand. If cost were not a factor, one of the two Trane dealers has stood out to me. However, the Carrier dealer is substantially cheaper than the rest of them, like 30% cheaper. So we have been having a hard time trying to decide what our next move should be. I'm hoping to get some feedback from you all here. I appreciate any and all input and thank you for your time.

  2. #2
    Join Date
    Jun 2005
    Location
    SW Wisconsin
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    The 2-stage equipment alone will not solve the 2nd floor low airflow lack of cooling problem.

    There are some things that can be done to increase the cooling to the second floor areas.

    You could add some returns from the second floor area and also add a few supply runs to the second floor area to help increase the airflow to those areas.

    Also, increase the filter rack areas to reduce the velocity through the filter areas this will reduce the pressure drops on the return side. The less resistance you have on return-side the more air that will get to the blower wheel blades and thus increase the static pressure on the supply side all the way to the diffusers.

    Also, select duct fittings with the lowest equivalent lengths so that you retain the supply-side static pressures in the ducts all the way to the 2nd floor diffusers. Closing dampers alone will not solve the problem… They need to know how to apply Manual D...

    I would also use Purolator filter's 'sized to achieve' a .16” pressure-drop @300-fpm filter velocity or 20-fpm less. This should help provide more static pressure and airflow all the way to the second floor diffusers.

    Tell us where you live; you may not need a higher cost 2-stage 16-SEER system... ?

  3. #3
    Join Date
    Jun 2018
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    Thread Starter
    Quote Originally Posted by udarrell View Post
    The 2-stage equipment alone will not solve the 2nd floor low airflow lack of cooling problem.

    There are some things that can be done to increase the cooling to the second floor areas.

    You could add some returns from the second floor area and also add a few supply runs to the second floor area to help increase the airflow to those areas.

    Also, increase the filter rack areas to reduce the velocity through the filter areas this will reduce the pressure drops on the return side. The less resistance you have on return-side the more air that will get to the blower wheel blades and thus increase the static pressure on the supply side all the way to the diffusers.

    Also, select duct fittings with the lowest equivalent lengths so that you retain the supply-side static pressures in the ducts all the way to the 2nd floor diffusers. Closing dampers alone will not solve the problem… They need to know how to apply Manual D...

    I would also use Purolator filter's 'sized to achieve' a .16” pressure-drop @300-fpm filter velocity or 20-fpm less. This should help provide more static pressure and airflow all the way to the second floor diffusers.

    Tell us where you live; you may not need a higher cost 2-stage 16-SEER system... ?
    Thank you for your reply. It seems to me that it would be difficult to install new returns/supply runs to the second floor. I'm not sure, but none of the contractors mentioned that route. That would seem ideal. One of the contractors did mention that he wanted to increase the size of the horizontal return ducting. He mentioned that the ductwork would be 2 inches lower, as he can't make it wider due to other utilities. Is this what you mean by decreasing the resistance on the return side?

    I'm not finding a Purolator filter calculator, but still looking..

    I live in St. Louis. I will also mention that we do plan to stay in this house for the long haul, and being 'green' and energy efficient is a good thing for me. However I don't want to waste money if I'm not going to see the benefit in energy savings.

  4. #4
    Join Date
    Jun 2005
    Location
    SW Wisconsin
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    Is the return he is planning to enlarge from the upstairs area?
    It could help some even if it is from the downstairs area.

    Increasing the filter size area can be extremely important toward reducing the supply-side loss of static pressure… Sufficient Available Static Pressure is essential toward delivery of adequate CFM to the 2nd floor area.

    I will look up the summer design of the St. Louis area; it is very important not to oversize the air conditioned system because you need more runtime to even out the temperatures between the first and second floor areas. Summer design is 94-dry bulb & 77-wet bulb for 46.1% RH, at 94°F that is a lot of grains of moisture.

    If none of them do a duct Manual D or a Manual J load calc; then here is a free whole house load-calc & Sizing that you can use: http://www.loadcalc.net/ get others to help you; don't cheat...!

    It is very important that you spend your money on the things that will save you energy costs while providing you with the most comfort for the dollars that you spend.

    ‘If’ you are absolutely going to do zoning then the two stage air conditioning system would be the best way to go.

  5. #5
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
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    INITIAL THOUGHTS - ACCA Manual J _Ball Park Estimate / Calc_

    Quote Originally Posted by jjwelly View Post
    Hello. I am seeking some guidance on replacing our HVAC in our home that we purchased last year.

    The house is 24 years old, 2700 SQ FT, two story with 4 bedrooms on the second level.

    The existing/original equipment is York, and we've had issues with the condensor not starting when it should.
    The contacts and the capacitor have been replaced without fixing the issue. So we are trying to get some bids,
    and be ready to move forward when the system finally breaks for good, or when we know what system we should go with, whichever comes first!

    Our biggest complaint, other than the compressor does not start when it should, is the upstairs is very warm in the summer.

    We have been playing with closing down the 1st floor dampers, which has helped out some.

    We have met with 4 contractors so far. Over the course of those 'interviews', we have determined that we are looking for a 2 stage variable furnace 96% Eff, and a 2 stage 16+ SEER AC. They all seemed to agree that utilizing a 2 stage ac will help the system run longer, which should help the upstairs not be so hot. They all pretty much were in agreement that we should try the new system, and if we are still unhappy with the upstairs, we can then install a zoning system.

    I try to educate myself so I can be a smart consumer, and I understand that many of the units are very similar, and that brand name should not be as important as the quality of the install.
    However I found that it was difficult to really know which company would be the best installer.

    Anyways, after meeting with them, it seems like our existing ductwork is pretty good, as none of them really said much had to be done with it.

    One of them said they like to 45 degree the ducting where the vertical duct joins the horizontal duct.

    Other than that, ducts seem ok.

    Some like to remove the unit from the rack that is existing and mounted about 3 foot up, and build a pad on the ground.
    Some said they like the unit up so grass/leaves don't get in the unit as much.

    Some like the 4 inch filters, some don't and say the 1" are better when changed out more often.
    So it seems like a pretty basic install/replacement, where they are not doing much other than replacing existing, and running the fresh air piping for the furnace.

    Even though I'm not supposed to let brand steer me, I have always liked my Trane that I had at my previous house, so I am partial to that brand.

    I appreciate any and all input and thank you for your time.
    1. Blower Door Test
    _______ https://www.energy.gov/energysaver/blower-door-tests
    --- ASSOCIATED SEALING

    2. Room-by-Room Load Calc - ACCA MANUAL J

    3. Air Balancing
    ____________ are needed.

    Any Air distribution ( ~ 1,400 CFM Cooling, ~ 1,200 CFM Heating ) issues for a 2,700 sq foot residence
    are DEFINITELY Not easy to resolve.

    What are the upstairs nd downstairs temperatures?
    ___________ UP ______ DOWN
    Winter ___
    Summer __

    IF the temperature difference is > 3'F _ OR _ air flow is < 360 CFM/Ton,
    your duct layout DOES NOT Seem to be O.K.

    … _ _ BALL PARK ESTIMATE _ _ ...
    Attached Images Attached Images   
    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

  6. #6
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
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    Is there an Attic?

    2 Floors 2 "Systems"

  7. #7
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Two speed a/c will do a poor job of getting the more dense cold air to the second story. Cold air is like water and prefers to get out of the duct asap and go low. My brother built a new to story home with VS a/c, lower level always colder.
    Too fix we now operate the a/c fan "on" low speed to mix the cooler lower level with the warmer parts of the upper level. This house is in a green grass climate like you. We also added a whole house dehumidifier to avoid over cooling and provide perfect humidity control during the low/no sensible cooling hours. During low/no sensible cooling and high outdoor dew points, the a/c was unable to remove moisture to maintain <50%RH.
    Go high quality a/c, Trane/Carrier/Other single speed and a whole house dehumidifier for exact temperature and %RH control. Get a VS blower and operate the a/c blower "on" low mode for slow re-circulation to quietly mix the warm/cool parts of the home 24/7. Adjust the supply vents to limit cold air to cold areas. Also include the basement in the re-circulation and humidity control. This will warm and dry the lowest level of the home. Many of finest homes being built are incorporating this technology as part of conditioning system.
    One of our site sponsors is Ultra-Aire whole house dehumidifiers made in Madison WI. The is original manufacturer of the high efficiency durable units.
    Ultra-Aire.com
    Keep us posted on what your thoughts and results are. Imagine the temperature/%RH you want throughout the home and simple durable equipment.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  8. #8
    Join Date
    Jun 2018
    Posts
    13
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    Thread Starter
    Ok thank you all for contributing! I am trying to do what I can to get up to speed with everything discussed here. One of my bids did do a quick calc when here...

    graydesigngroup.com/jeff/calc.JPG

    I don't have the exact temperature differences between the 1st and 2nd story, but it's definitely more than 3F. I have been keeping the fan on full time as I have heard this will help with the issue.

    So I'm definitely in for the 96% afue 2 stage VS blower furnace, and that doesn't seem in question. But sounds like single vs 2 stage AC unit is not so clear. All of them have stated that the existing 3.5 Ton AC unit is not sufficient, and moving up to the 4 ton is recommended. This makes sense as the house had an addition added (about 400 SF).

    Also to note, the attic insulation is still original and thought to be about R26. I have a couple of bids to bring that up to R50. I don't know if doing that will have any bearing on things other than the system working less, but thought I should mention it. There is an attic.

    @ Teddy Bear: Can you clarify what you are saying about the VS AC fan? Do you mean to buy a VS furnace/fan, or are you saying to buy a VS AC unit? Or both? None of the bids I received included an option for a VS AC unit, although they mentioned they had them. They all seem to be saying that a single or a 2 stage AC is appropriate, and to not go the VS AC route, but they all said to do the 2 stage VS furnace..

    How would I include the basement in the re-circulation? Would that be just cutting vents in the supply and return ductwork? I'd be very interested in a whole house dehumidifier. We already have a humidifier..

  9. #9
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    Jun 2018
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    Thread Starter
    still can't post links, but if you paste the address listed in the post, it will show the load calc that was done..

  10. #10
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Basements are a different heat load / loss then the rest of the structure. A dehumidifier and small Mini Split.

  11. #11
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    Jun 2018
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    Thread Starter
    Mini splits are interesting to me. I don't know why no one has even mentioned them to me. AND, not one of the contractors has even mentioned dehumidifiers. I've gotten 4 bids from what appears to be very reputable companies. Maybe I need a 5th bid..

  12. #12
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    Aug 2002
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    Southold, NY
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    Quote Originally Posted by jjwelly View Post
    Mini splits are interesting to me. I don't know why no one has even mentioned them to me. AND, not one of the contractors has even mentioned dehumidifiers. I've gotten 4 bids from what appears to be very reputable companies. Maybe I need a 5th bid..
    Maybe you need someone that knows a bit more about your comfort and less about the $’s there going to make!

  13. #13
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    Jun 2018
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Maybe you need someone that knows a bit more about your comfort and less about the $’s there going to make!
    That's the story of my life!!

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