Honeywell CONVERTASTAT TP970A2145 Replacement Data Download

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TP970 SERIES CONVERTASTAT

KITS

Changeover

TP971 and TP972 thermostats have changeover
features. The TP971 has day/night changeover and the
TP972 has summer/winter changeover. TP971 controls
direct acting at day setting with 13 psi (90 kPa) main air
pressure and direct acting at the lower night setting with
18 psi (124 kPa) main air pressure. The TP972 controls
reverse acting (RA) for summer cooling at 13 psi
(90 kPa) main air pressure and direct acting (DA) for
winter heating at 18 psi (124 kPa) main air pressure.

The branchline pressure (BLP) drops as the temperature
drops when the thermostat is operating DA. The BLP
drops as the temperature rises when the thermostat is
operating RA.

Changeover Conversion

On some systems the lower main air pressure is higher
(14 or 15 psi [97 or 103 kPa]) so the changeover point
must be raised. On these systems, turn the changeover
adjustment screw (Fig. 9) one-half turn clockwise for
each 1 psi (7 kPa) over 13 psi (90 kPa).

TP971 or TP972 thermostats used on systems having
16/21 psi (110/145 kPa) or 13/16/21 psi (90/110/145 kPa)
main air pressure require a different spring for proper
changeover operation. Change the spring as follows:

1. Remove thermostat from backplate if mounted.
2. Remove changeover adjustment screw (Fig. 9)

from thermostat back.

3. Replace gold-colored spring with silver-colored

spring furnished in TP971 kit. Order 14002373-001
Spring for TP972 conversion.

4. Reinstall changeover adjustment screw and set

flush with spring chamber top.

5. Mount thermostat on backplate again.
6. Follow procedures in Changeover Calibration

Check section and recalibrate if necessary.

FILTER COVER

THERMOSTAT
MULTISTAGE FILTER

C5411

CHANGEOVER
ADJUSTMENT SCREW

SPRING CHAMBER

DAY/AUTO LEVER
(TP971 ONLY)

Fig. 9. TP970 Series Thermostat—Back View.

Changeover Calibration Check

1. Set main air pressure to higher pressure setting

(night for TP971, winter for TP972A2192, and
summer for TP972A2200).

2. Using gage adapter, insert gage into gage tap (see

Fig. 8). If results in Steps 3 or 5 are incorrect, go to
the Changeover Calibration section.

3. TP971:

Turn day setpoint adjustment until setpoint
indicator reads approximately 10F (5.5C) degrees
above space temperature and set night setpoint
dial below space temperature. The gage should
indicate main air pressure. Push day/auto lever to
day (left) position; it should stay there and BLP

should go to 0 psi (0 kPa).
TP972:
Turn setpoint adjustment until setpoint indicator
reads approximately 10F (5.5C) degrees above
space temperature. BLP should go to 0 psi (0 kPa).

4. Set main air pressure to lower pressure setting

(day for TP971, summer for TP972A2192, and
winter for TP972A2200). Use 16 psi (110 kPa) on
13/16/21 psi (90/110/145 kPa) systems.

5. TP971:

With day setpoint indicator and night setpoint dial
set as in Step 3, BLP should go to zero. Push
day/auto lever to day (left) position, it should return
to auto position when released.
TP972:
With setpoint indicator set as in Step 3, BLP should
go to main air pressure.

Changeover Calibration

1. Remove thermostat from wall.
2. Loosen screws. Remove backplate from wall but

do not disconnect tubes from backplate.

3. Plug thermostat into backplate.
4. Use following changeover procedures for calibra

tion with or without a branch line pressure gage.

WITH BRANCHLINE PRESSURE GAGE

If thermostat changeover point was not correct at Step 3
of the Changeover Calibration Check procedure:

1. Use screwdriver end of thermostat tool to turn

changeover adjustment screw one-quarter turn
counterclockwise (see Fig. 10).

2. Make a calibration check.
3. Continue with one-quarter turn adjustments

followed by a calibration check until changeover
point is correct.

If thermostat changeover point was not correct at Step 5
of the Changeover Calibration Check procedure: