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QUESTION:My son had me install a digital thermostat (Ritetemp 8022) several
months ago, and apparently I miswired the heater control. On this
thermostat (which has numerous connections) there is a terminal "B"
called "Damper or Changeover Valve (Powered in Heat)." Instead of
attaching the wire for heater control to "R" (heater transformer), I
attached the wire to location "B." I turned the thermostat up to a
level where the furnace would light and when I heard the gas ignite and
the blower fan start, I assumed I had left him with the furnace (as well
as the AC) working. I should have allowed the furnace to shut down
normally and I would have known something was wrong. Such is life!
This all took place early in the year and he had been using the AC, but
recently he turned on the heat for the first time and discovered that
although the heat came on, the blower would not turn off as long as the
thermostat was set to HEAT position. Once the room temperature attained
the temperature set, the gas turned off and the blower continued
endlessly. To make a long story short, the solution was to move the
heater control wire to the "R" terminal (heater transformer).
What puzzles me is why the blower fan continued to run after the gas
valve had opened when the thermostat reached the selected temperature?
(It is of course normal to run a short time to cool the furnace after
the gas is turned off.) The problem occurs in the incorrect wiring but
NOT in the proper wiring. I checked the schematic for my furnace, and
there is a Fan Limit Control that turns on and off the blower
independent of the voltage controlling the gas valve. What puzzles me
is why his blower stayed on when wired to the wrong terminal (even
though the gas turns on and off), but behaves correctly when wired to
terminal R?
Now I realize that I made a mistake, and it has since been corrected.
The reason I am posting is I can't visualize what the difference could
be since the gas came on and turned off even when miswired. The comment
" Powered in Heat" sort of implies there is little difference in the two
terminals with respect to the voltage applied. There is obviously a
difference I cannot see.
ANSWER: the thermostat you described is for a HeatPump system and from your
description your son has a standard gas heat /split system a/c system. In
case you doubt it the B terminal you desctibed as "Damper or Changeover
Valve (Powered in Heat)" is for the valve that switches a heat-pump from
cooling to heating. I won't go into it further but if you want to do what
your signature line says (as well as your son) I suggest you let someone
who knows these things look at it or who knows what will happen when the a/c
system kicks on next season.
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