Question about Ruud Central System Air Conditioner

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Not enough air flow coming from the vents on the second floor.

I would like to increase the air flow on the second floor of this two story house as there is only a trickle of air coming through the vents. The temperature is a good 4°C to 5°C cooler in the upstairs rooms than on the ground floor level (this is in Mid January).

I have checked the round disc plate inside the ducting on all the vents and they are all fully open. I have checked the loft insulation and that appears more than adequate. I just don't think that the air flow coming from the furnace is enough to reach the upper level of the house.

I am a new owner of this 30 year old house and confused about the performance of the furnace which is a RUUD 90 PLUS ACHIEVER, it appears to be about 10 years old.

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  • Ken Harrison Jan 13, 2009

    It is an electronic filter and was just recently cleaned about a month ago.

    The further away from the furnace, the slower the air speed, until air movement from the outlets (registers) on the second floor is practically none existent.

    Thanks, Ken

  • Ken Harrison Jan 13, 2009

    I have tried to do that. I shut down 3 vents on the ground level, 2 in the basement (it is a completely finished basement) but no difference.

    The house is about 1850 ft² not including the basement, which could be another 1000ft²

    There are
    4 - vents in basement;
    10 - vents on ground level and
    6 - vents upstairs

    I also don't know the furnace btu rating; there is a blower performance chart inside the unit giving blower speeds vs Btu's and all models have 4 blower speeds, but it says it is for up-flow units only and I'm not sure which unit I have......documentation is practically none existant.

    Based on previous houses I have lived in this unit is either very quiet (which is an advertised feature) or it is running too slow.

    Thanks, Ken

  • mperez84 May 04, 2009

    I have a problem. I just installed a new 12 SEER Grandair 3 ton unit in my house. I have a zone system which has a thermostat in the main floor, and another thermostat in the upstairs bonus room. I have the main level thermostat set on cool at 73 degrees. I have the upstairs thermostat set at 76 degrees. The system freezes up completely. I know it is an air flow problem. I suggested to take out the doors from the zone system and have only one thermostat control the whole house to keep the unit from freezing up. Do you have a better suggestion??? ---HELP---

  • Ken Bledsoe May 11, 2010

    Have you changed the air filter on your furnace? ken

  • Ken Bledsoe May 11, 2010

    You might be able to shut down couple of vents that go to rooms you don't need that much heat in like kitchens. and maybe spare bedroom. That would give you more pressure to the open vents.

    Also how many vents do you have not counting return vents and how many square feet is your house?


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If you feel like increasing your blower motor speed you can do this. Go to the air handler take the cover off to expose the blower motor. You will see a circuit board that has the blower motor wires going to it. Using your flash light look at the board and locate the terminals that read Cool Heat Park ... Now the Cool terminal should have black colored wire going to that one. Now locate the Heat terminal if it has red going to it and maybe blue sitting on the park terminal then swap the two around, blue is like med speed on the blower. Where Red is low speed. This will increase the blower about 50 rpms. You can even read your blower motor and get the speeds more detailed. You have a big house your unit is I bet a 4 ton A/C and 125,000 btu furnace. Probably has 1600 rpm motor. This is one solution. You have a up flow model and when you open the furnace cabinet up you will be able to see the specs. on the furnace. Let me know how that goes ken here in Kansas

Posted on Jan 13, 2009

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Keeping your whole home cool with central air.

Sometimes it is difficult to keep your home cool in the hot summer months. Also, some areas of your home may still be hot where other areas are too cool. Try this method to keep your home cool evenly throughout. Before you get started make sure your furnace filter is new. This will allow for maximum air flow.

If your living space is a single floor plan:

  1. Turn the air conditioning on
  2. Switch the furnace fan from auto to on.
  3. Measure the temperature in each room.
  4. Close the vents by about half in the cooler rooms
  5. This will force more cool air into the warmer rooms.
  6. Keep adjusting the vents until all the rooms have the same temp.

If your living space is on more than one level:

  1. Turn on the air conditioning.
  2. Switch the furnace fan from auto to on.
  3. On the lowest level of the house close half of the vents that are the closest to the stairs.
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  5. Cool air will sink from the upper floors which will keep the area near the stairs cool.
  6. Measure the temperature in all the rooms.
  7. Keep adjusting the vents until you have a nice even temperature throughout the house.
I found that leaving the furnace fan on all the time will keep your home evenly cool and comfortable. You may have to replace your furnace filter once a month due to the increased air flow. It will be well worth it in a cooler, more comfortable, and more energy efficient home.

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