Jim wrote:
Presently we are having very warm and humid days. The central air
conditioning handles this properly. Then late at night as the outside
temperature drops the system doesn't call for cooling as often. Once
again this is normal operation.
But during this time the humidity indoors rises

you mention (not quoted above) every 15 min for 1 min which others have
already pointed out is a bad idea. however let me add that as an idea it is
not bad at all with proper timelimits.

I've seen several installations in s.florida where the thermostat maintained
a temp setpoint (as you mentioned) but humidity behaved erratically and it
was solved with a thermostat calling separately for low speed (variable
speed blowers) and stage1 (multi-stage system) for a given duration in
programmable timelimits

one such example was a dual compressor (2 ton & 4 ton) system where the VS
blower at very low speeds initiated the 2 ton compressor when humidity
setpoint (54%) was reached and it ran the system for 30 minutes and then
shut down. this was accomplished with a 24vac macromatic relay (timer
On/Off) tied into the stage1 (Y1) circuit from the thermostat RH% sensor
(DH). every time the DH 24vac relay opened, it sent a signal to the
macromatic On and this in turn ran to Y1 which activated the 2 ton
compressor, after 30 min (adjustable dial on the macromatic) the relay shut
down.

there are other types of macromatic relays, my personal favorites are the
interval On, interval Off where you can program the time duration on and
time duration off and the cycle repeats. thus you could have indoor temp at
77F while maintaining a precise 50% humidity and if the time interval
results in too little or too much cooling (likely not a problem with
variable speed blower and small stage1 compressor), it's simple and easy to
adjust

hope that helps