5
requires prior selection of heat pump (DIP switch 1 ON), and
must be selected in Hybrid Heat installations. It prevents
simultaneous operation of both furnace and heat pump, and
prevents direct transition from heat pump to furnace operation.
When system is Hybrid Heat (heat pump and furnace), set to ON.
When system contains fan coil, set to OF. Factory default is OF
(off).
TO SELECT:
1. Enter configuration mode if not already there. See Step 4
“To Enter Configuration Mode.” Use up and down
buttons to make small (now flashing) display indicate 10.
2. Press SET TIME/TEMP button once to flash large display.
3. Use up or down buttons to alternate between OF and ON
on large display. Factory default is OF.
4. Press SET TIME/TEMP button again to flash upper small
display for selection of another option, or press END to
exit configuration mode.
Option 11—Balance Point Setting
This option is for Hybrid Heat installations only. It requires prior
selection of heat pump (DIP switch 1 ON) and Hybrid Heat
equipment (Option 10 ON). It allows selection of an outdoor
temperature of 5
_
F through 55
_
F (or equivalent values in C), or
OF (off). Heat pump is prevented from operating for outdoor
temperatures below selected temperature. If OF (off) is selected,
heat pump operation is allowed at all outdoor temperatures.
Factory default is OF (off). This setting can only be equal to or
below the setting choice made for Option 8. Moving the setting
higher may push Option 8 setting upward. If the outdoor
temperature is above the “balance point setting”, the heat pump
will energize first to try to satisfy the indoor temperature demand.
If the heat pump does not make a sufficient improvement within a
reasonable time period (i.e. 15 minutes), then the gas furnace will
come on to satisfy the indoor temperature demand. If the outdoor
temperature is below the “balance point setting” the heat pump
will not be allowed to operate (i.e. locked out), and the gas
furnace will be used to satisfy the indoor temperature.
There are three separate concepts which are related to selecting
the final “balance point setting”. Read each of the following
carefully to determine the best “balance point setting” in a Hybrid
Heat installation:
CAPACITY BALANCE TEMPERATURE:
This is the point where the heat pump cannot provide sufficient
capacity to keep up with the indoor temperature demand because
of declining outdoor temperature. At or below this point, the
furnace is needed to maintain proper indoor temperature.
ECONOMIC BALANCE TEMPERATURE:
Above this point, the heat pump is the most cost efficient to
operate, and below this point, the furnace is the most cost efficient
to operate. This can be somewhat complicated to determine and it
involves knowing the cost of gas and electricity, as well as the
efficiency of the furnace and heat pump. For the most economical
operation, the heat pump should operate above this temperature
(assuming it has sufficient capacity), and the furnace should
operate below this temperature.
COMFORT BALANCE TEMPERATURE:
When the heat pump is operating below this point, the indoor
supply air feels uncomfortable (i.e. too cool). This is purely
subjective and will depend on the homeowner’s idea of comfort.
Below this temperature, the gas furnace should operate in order to
satisfy the desire of indoor comfort.
TO SELECT:
1. Enter configuration mode if not already there. See Step 4
“To Enter Configuration Mode.” Use up and down
buttons to make small (now flashing) display indicate 11.
2. Press SET TIME/TEMP button once to flash large display.
3. Use up or down buttons to move between OF, 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, or 55 on large display. Factory
default is OF.
4. Press SET TIME/TEMP button again to flash upper small
display for selection of another option, or press END to
exit configuration mode.
Option 12—Defrost Heat Select
This option allows installer to select the amount of heat provided
by Thermidistat Control during a heat pump defrost cycle. This
can be very helpful in maintaining a comfortable leaving air
temperature during defrost. The Thermidistat Control senses
when defrost is in progress by monitoring voltage placed on the
O line by the heat pump while defrosting. It responds by turning
on selected combination of W1 and W2 during defrost. Note that
this is very different from the operation of an ordinary thermostat,
which cannot sense defrost in progress and only turns on its W
outputs in response to a temperature demand. Combinations of
W1 and W2 are selected via the following:
Table 1—W1/W2 Outputs
Selection
Definition
0
W1 nor W2 is turned on. This is factory default.
1
Only W1 is turned on.
2
Both W1 and W2 turned on.
3
Only W2 turned on (available only if 3---stage
heat is selected.
The selection procedure is given below. If 0 is selected, operation
is like that of an ordinary thermostat, and a wire is required
between W2 of outdoor unit and a selected W on indoor unit.
When selection 1, 2, or 3 is made, no wire should be connected
from outdoor W2 because this connection may override selection
made. Obviously the heater must be in 2 sections, and fan coil
jumper must be removed between W1 and W2 for there to be a
difference between selections 1, 2, and 3. For most heaters, W1 is
lower wattage heater, and W2 is higher, although some have
equal elements for W1 and W2. Consult fan coil/heater
combination for the actual wattage connected to each of W1 and
W2.
In Hybrid Heat applications, above selection choices apply and
can be used to select low or high heat if furnace is 2 stage. W1
will produce low heat. W1 and W2 together produce high heat.
This option provides no value with single--stage furnaces because
only 1 value of heat is available.
The selection choices guarantee selected outputs will be on
during defrost. If room temperature demand requires additional
heat, it will be supplied, resulting in additional outputs being
turned on. If room overheats, specified outputs will not turn off,
guaranteeing a sufficiently warm leaving air temperature during
defrost. Temperature overshoot during defrost can occur, but is
almost never noticeable because of the short duration of the
defrost cycle (4 minutes typical, 10 minutes maximum).
An additional feature of Thermidistat Control defrost is that it
always allows defrost cycle to run to completion. The
Thermidistat Control leaves the Y output on as long as outdoor
unit holds voltage on the O line, even if it is satisfied. This
prevents premature termination of defrost cycles, which occur
with normal thermostats.
TO SELECT:
1. Enter configuration mode if not already there. See Step 4
“To Enter Configuration Mode.” Use up and down
buttons to make small (now flashing) display indicate 12.
2. Press SET TIME/TEMP button once to flash large display.
TST
AT
