Posted on

Problem: Will a larger blower motor help my air conditioning? My air conditioner does not seem to be blowing air very hard.

Happy AC

Problem: Will a larger blower motor help my air conditioning? My air conditioner does not seem to be blowing air very hard.

Answer: I would like to recommend checking your furnace’s blower motor capacitor to make sure the capacitor is not weak. A weak motor capacitor can cause the blower to run slow. Please click here if you would like to see the capacitors that we sell. Some small appliance shops will test capacitors free of charge. I would also recommend that you check to make sure your blower wheel (squirrel cage) and the bottom of your air conditioner evaporator coil is clean before trying a larger motor.  I would recommend checking your refrigerant charge to make sure you AC is charged up properly. If your AC system is low on charge it will cause the coil to freeze up and cause a restriction in the air flow. Rule of thumb is the blower should produce 440 CFM (cubic feet per minute) of air per ton. On a two ton system that is 880 cfm. This usually calculates out to about a 1/4 to 1/3 HP blower motor. If you get too much cfm it is hard on the air conditioner, because it robs the air conditioner of the cool gas going back to the compressor to keep it running cool and you have to over-charge the AC unit to get the cool gas going back to the compressor. I usually need to add refrigerant to a system that has too large of a blower motor. You want to charge your system so that there is cool gas going back to the compressor and the suction line feels like a cold coke can right out of the refrigerator. The air conditioner should make a 15 to 20 degree difference in the ambient air. If you home is 75 degrees inside, the air coming out of the registers should be between 55 to 60. I hope I have answered you question. I have installed oversized blower motors before to get more airflow. I would not recommend going over 1/3 horsepower in your case. You would need to check the charge after you install the new motor to make sure you are getting the needed cool gas back to the compressor. Below we have a real good YouTube video produced by hvacrepairguy which shows how to replace a blower motor. Thanks to hvacrepairguy for making this informative video! Please click here if you would like to see other DIY videos on how to test capacitors and clean AC evaporator coils. If you have any questions please email us anytime at: support@arnoldservice.com or comment in our comments section below. We would love to help you out and have your business!

16 thoughts on “Problem: Will a larger blower motor help my air conditioning? My air conditioner does not seem to be blowing air very hard.

  1. Hello Steve,

    Hope you could help me here and sorry for the write up.
    I have a few concerns about a furnace blower motor replacement.

    An HVAC contractor came to my home to do a furnace tuneup on my older Heil unit.
    The unit is under the house (crawlspace). He removed the motor, wheel and housing in order to wash it off.
    When he put everything back together, the motor burnt out and he ended up replacing it with one he had in his truck.

    I had:
    GE 1/3 HP 2.9 FLA, 2 speed Permanent Split Capacitor, 1075 RPM, 208-230 Voltage, Frame 48YZ

    He replaced it with:
    FirstChoice Direct Drive Furnace Blower Motor, 3/4HP, 3 Speed, 208-230 Volts, 1075 RPM, 5.4 Amps Frame 48Y

    He stated that I was getting an upgrade and that my old blower motor was using one speed and now the 3/4hp motor he installed will be at medium speed for heat and full speed for cold.
    He also replaced the relay and capacitor.

    I am concerned that this higher HP and almost double AMPS motor may cause some premature failure somewhere in the system as it is at least 18yrs old.
    I am also worried that the higher amps motor will consume a lot more electricity and my bills will be higher as I tend to keep the fan on circulating mode to move the air in the house.
    The motors are the same RPMs, so not sure if it is pushing more air even with a higher HP? and that will be bad for my system somehow or my ducts?

    Please let me know if I should have these concerns, expect a much higher elec bill or premature failure, or what to look out for and keep an eye on.
    Thanks a lot for your insight.

    Relevant info:
    My unit outside is a 3 Ton older Heil Heatpump NHP036AKA1 with a compressor UPKA-035jaz
    Fan motor at the Condenser unit (if this helps) is a 1/3HP 208/230 volts 1075rpm 1 speed 48Y 1.9amps

    Note: There was a sticker on the furnace from the original factory installed furnace blower motor and it reads that it once had a 1/2HP 208/230volts FLA 3.2 MODEL NUMBER BH3036SKB1 MFR NO: NBH3036SKB1 STYLE BEA36A
    This makes me think that this unit originally had a furnace 1/2 HP motor and then the previous home owner had it replaced with the 1/3hp GE motor at some point before I bought the home 15yrs ago. I never had and issue with the Furnace GE 1/3 motor even if it was less HP and 2.9 instead of 3.2amps that the originally installed motor had and lasted the full 15yrs until yesterday.

    Also, the fan motor at the condenser unit was replace about 10 years ago and it was replaced with the 1/3 HP 208/230 volts 1075rpm at 1.9amps. I am not sure if the condenser fan was chosen to match close to the 1/3HP furnace motor the previous home owner installed.

    Sorry again for the long write up!

    1. Hi Jay! Great question and concern! The furnace and air conditioner in your home are manufactured, sized and based on the amount of air flow that the furnace or air handler produces. Since you have a 3-ton air conditioner you should have a blower that produces 440 cfm (cubic feet per minute) of air per ton or 1320 cfm for a 3-ton system. I would think that installing a 3/4 horsepower motor might harm your heat pump in the air conditioning mode because with the stronger blower motor the increased airflow can boil off more refrigerant and cause the compressor to not get enough cool gas back to the compressor to keep it running cool. You would need to have your unit checked out with gauges and thermometers to make sure you are getting the proper superheat and subcooling for your unit’s design with the new blower motor. I would think that your tech would need to over-charge the unit slightly to get the proper subcooling with the larger blower motor. I would think that you would hear more noise of air flow in your home with the stronger blower. Most of the time 3/4 horsepower blower are used on 4 to 5-ton units. I usually think of 1 amp as like one 100 watt light bulb burning. So if you increase your amps by 2 then it would be like burning two 100 watt light bulbs and this would increase your electric bill to compensate for the extra power for the 3/4 horsepower motor. If you were having trouble heating and cooling your home because of poor airflow in your home, then I might consider going up to the 1/2 horsepower, but I would not recommend the 3/4 horsepower. Some of the universal motors have the speeds rated in horsepower. Like low speed is 1/3 horsepower, medium speed is 1/2 horsepower and high speed is 3/4 horsepower. If this is the case on the 3/4 horsepower motor then I would say that is great, but if you had a straight 3/4 horsepower with low, medium and high speeds then I would not recommend this. I hope I have answered your question. Hope you have a great day! Steve

  2. I have an older home that is 2200sqft + 1000sqft of basement that the central air also feeds to.
    My AC unit is from 1985. It runs and cools the air slightly, but basically stays running all the time, and never gets the house below 75 on the first floor. Upstairs is about 78. The air coming out of the vents doesn’t feel that cool and there is not a lot of air flow.

    What is the best way to address my situation? Is the cost of a new unit ($3000) really worth it? I moved into the house a few months ago so I do not know how well it was working before. The furnace is newer and seems to do a good job of heating the house, which makes me think the A/C unit is on it’s last leg and that’s why it’s not cooling the house. Plus my electric bill is over $100 a month because it runs so much.

    Thank you for the help!

    1. Hi Doran! I would like to suggest that you have the air conditioner serviced by a reputable company. You might ask your friends if they know of a good honest HVAC company to call for service. You could check with Angie’s List or the Better Business Bureau for a good company to call. I recommend calling for service because you might just need a good cleaning or a little refrigerant charge to fix your air conditioning system. If you do get a new AC system I would recommend that your installers do a heat gain and heat loss calculation (Manual J Calculation) to make sure you are getting the right size Air conditioner and duct work to cool your home. We are required to have a heat gain, heat loss calculation here in Louisville, KY before the Housing Department will give a permit to do a new heating and air conditioning install. That way you know that you are getting the right size equipment for your home. I hope that you find an easy inexpensive solution to your problem. God bless you and your family. Steve

  3. I have a 1320 sq foot mobile home, they put a 3 1/2 ton HVAC AC unit and it runs five minutes at a time it stays humid, and ,I’ve had the coil replaced then two weeks later needed it replaced again. I’m asking them to bring it down to the 2 1/2 ton that was for this home. Can I leave the same heater and blower motor and just replace the outside AC unit and the inside evaporator coil’s? AC unit and it runs five minutes at a time it stays humid and I’ve had the coil replaced and two weeks later needed it replaced again. I’m asking them to bring it down to the 2 1/2 ton that was for this home. They want to put a 3 ton on the home. Can I leave the same heater and blower motor and just replace the outside AC unit and the inside evaporator coil‘s , My home is just now one-year-old

    1. Hi Sherry! Yes, it most definitely sounds like they over-sized your air conditioning system since it is cutting off and on so much! I do not understand why they keep on having to replace the coil. That is hard to believe they had two bad evaporator coils in such a short period of time. You can leave the same blower motor in if they can lower the speed on the blower motor to produce 440 cfm (cubic feet per minute) per ton on the air flow out of your existing blower motor. So for a 3 ton unit the blower should produce 1320 cfm air flow. They would need an anemometer to measure this or many times the furnace will show in the installation instructions how to set the blower speeds to produce different air CFM’s. So if your existing furnace or blower can be run at a lower speed then yes, they could use the same blower. If the speed can not be lowered then you will need a new furnace or blower because it would be hard on your new air conditioner to have beyond the designed air flow. Thanks for asking this question. I hope you can get this fixed soon!
      Steve

      1. I want the 2 1/2 ton that’s what the house square footage requires. If they insist on putting the 3 ton, well I have the same issue with the cutting off and on. Or, will a 1/2 ton make that big a difference?

      2. Hi Sherry! If they did a heat gain and heat loss calculation and found out that your home requires a 2 1/2 ton AC then I would insist on the 2 1/2 ton because, yes you will get the same problem with the unit shutting off and on all the time and not running long enough to take the humidity out of your home. You might think about getting a thermostat that has a 2 degree difference in on off cycles. I know that some of the thermostats are real sensitive and can cause lots of cycling if not set properly. I hope you get your problem taken care of soon! Steve

  4. The back rooms in my home have always been hotter than the rest of the house. The past 2 years the whole house is hot. About 5 years ago I had to replace the furnace. I also had new ductwork done, a second air return added and a new thermostat. The AC unit is about 12 years old. 2 years ago I had the capacitator replaced. I had the insulation checked last year and it is good. They added 1 lb of refrigerant last year. Still hot. This year I had another company come out. They measured air from the vents vs air return, added another 1 lb of refrigerant, checked for leaks and everything was coming up good. Still hot. Called again and he is stumped. He is suggesting increasing the AC unit by 1/2 ton even though based on home size it should be good. However, to do that he says I would have to replace my furnace too since he feels the AC would freeze up because the furnace size would not match the AC. Is this true and could I not just install a larger blower motor on the furnace since it is relatively new?

    1. So sorry to hear that you are having all these problems getting the back rooms in your home cool. I would suggest adding at least one supply register in each room if that is possible and see if this helps. You could increase the horsepower of the blower motor and see if that helps. The motor needs to be matched with the blower wheel or if the motor is too large it will not load the motor and the motor will burn out fairly soon. The contractor maybe having trouble fitting a larger coil on your furnace due to width restrictions of the furnace. We are required to submit a heat loss, heat gain calculation for every home before Code Enforcement, the housing department will issue a permit for a new installation. If your contractor had completed the heat gain and heat loss calculation they would have know the AC was too small for your home. I hope you can get this taken care of with the least expense. Steve

  5. Hi I have twoout of 3 bedrooms 2nd floor and they do not cool or heat very well. The HVAC is in the basement and it is an electric ac and gas furnace. Unit is 18 yrs old and original from the time the townhouse was built. The ac part was replaced about 5 yrs ago. Will a new HVAC system help these rooms? One company said I should put booster fans in the duct work to push the air to those rooms.

    1. Hi Deb! You should get your contractor to do a heat gain, heat loss and duct calculation before installing the new system. Then you will know if the new furnace and air conditioner will do the job or not. More than likely you do not have the right size duct work or number of ducts to heat and cool your upstairs properly. We are required here in Louisville, KY. to submit a heat gain, heat loss calculation to our code enforcement housing department before we can start work on a new installation and get a work start permit approved. Thanks so much for asking this question. Steve

  6. I live in a 45 y/o mobile home with central air (which was installed as an afterthought). Coleman Evcon model BPCH0301BA. The 12″ diameter flexible ducting from the unit has to travel at least 6 feet before it connects with the metal ducting that delivers the conditioned air to the vents. Airflow into the house is minimal. I have to run the unit constantly and block the windows with dark curtains to achieve a modicum of cooling. Could the distance it has to travel account for the loss of pressure? Would a bigger blower help? The motor currently in the unit is 1/2 hp. Thank you.

    1. Hi Ginger! Sorry you are having trouble keeping your home cool. If your home only has one supply duct that is 12″ in diameter then this could be the problem. A 1/2 horsepower blower motor should handle 3 to 3 1/2 tons of air conditioning. Most mobile homes only have 2 to 2 1/2 tons of air conditioning not unless you have a very large mobile home. There are lots of things that can cause poor air flow and poor air conditioning such as: dirty filter, dirty evaporator coil, dirty blower wheel, dirty condensing unit, under or over charge of refrigerant, duct work too small for air conditioner, air conditioner under-sized for the heat gain of your home. The installers should have done a heat gain heat loss calculation to determine the size of the air conditioner and the size of the duct work that should be installed in your home. I am sure they did not do this 45 years ago. You might try to get some of these items checked out. A larger blower motor might help, but if you only have one supply duct it still probably will not do that much good. Sorry that I could not give you a definite answer. Steve

  7. Stumbled upon this while researching a similar issue. I have a 1700 square foot home, with a full unfinished basement that I am in the process of finishing. There are no vents in the basement. The upstairs vents put out decent air, but I’m afraid when I run vents to the two new bedrooms, bathroom and the family room it won’t be enough. Wouldn’t a larger blower solve this IF it becomes an issue? Also, how many returns should the basement have?

    1. Hi Mr. Birkemeier! A larger blower motor could harm your air conditioner since the amount of air that the blower sends out determines what tonnage Air conditioning you should have. The duct size determines the amount of air too. Too much air going through too small of duct work creates noise. Most of the time a 1/3 horsepower blower motor will handle a 2 1/2 to 3 ton AC unit and a 1/2 horse power blower motor handles a 4 ton unit and a 3/4 to 1 horsepower motor will handle 5 tons of air conditioning. The air flow should be 440 cfm per ton. You could try a larger blower motor, but test the cool gas going back to the compressor on a warm day. What usually happens is you have too much air flow and you have to over-charge the unit to get the cool gas back to keep the compressor running cool. When you have to over-charge the AC it you do not get as good cooling because it raises the evaporator temperature and it is harder on the compressor pumping more refrigerant. Just keep a watch on the pressures and super-heat going back to the compressor if you do install a larger blower motor. Rule of thumb in a basement would be one supply in every room. Probably two in the larger family room and one return that is centrally located in the basement near the floor. You probably already know this, but do not install the return in the same room as the water heater and furnace. The return should be in the largest living space if possible. Best of luck on this project. Steve

Leave a Reply

Your email address will not be published. Required fields are marked *