If I put a basement dehumidifier next to the furnace/AC blower, will it help reduce the humidity on the main floor of the house? Humidity in the basement is around 60% - 65%. This is the same as the main floor. This is a 2 story house with partial basement of 500 square feet. There are cold air returns in the basement.
You should not need a dehumidifer on the main floor if the air conditioning system is sized correctly and operating at peak performance. The job of the air conditioning equipment is to remove (dehumidify) the air for comfort levels. A dehumidifer may help in the basement since A/C's are not normally sized to cool the basement unless it is a finished basement.