Originally posted by 54regcab
Doesn't it take about 10 minutes for a system to reach full efficiency? I belive the 7 minute delay just allows the coil to get cold a bit faster. I personally put a timer/relay on my A/C system to switch the blower from low to high speed @ 7 minutes and it helped a lot with dehumidification Delta T only decreases about 1 degree when high speed kicks in. Normally it won't hit the high blower speed unless it's over 95 outside or the thermostat setting has changed. Oddly enough our power bills don't seem to be any higher either.
If your system is cycling off before 7 minutes, then it's oversized.

Also, the timer approach is simply a convenience. The "better" approach is to get a dehumidistat so that the low-speed blower operation is activated on demand rather than whether it is needed or not.

Lennox makes one of these ("EfficiencyPlus") and I had one in my old house. On a damp day with low-demand, the system would run it's entire cycle (typically 12-15 minutes) at 275 CFM/ton or so and do this all day, which is what prompted my question (e.g. why is this any different than closing some registers).