Tp974a, Tp978e, Fig. 7. tp971c typical operation – Honeywell TP9600 User Manual

Page 10

TP970 AND TP9600 SERIES PNEUMATIC THERMOSTATS

75-7134—1

N.C.

N.O.

D/N

MP516C

FAN

P638

TP971

VALVE

HEATING
COIL

120V AC
50/60 HZ

AIR
STREAM
STAT

13/18 PSI
(90/124 kPa)

D/N

MSB

K H

FILTER

DISCHARGE AIR

OUTDOOR
AIR

RETURN
AIR

C3541

Fig. 7. TP971C Typical Operation.

TP972A and TP9620A

The standard TP972Aand TP9620A is RA for cooling and DA
for heating. A rise in temperature at the TP972Aand TP9620A
with main air pressure at 13 psi (90 kPa) causes the
TP972Aand TP9620A to lower BLP, opening the valve to
control the temperature with chilled water. A fall in
temperature at the TP972Aand TP9620A with main air
pressure at 18 psi (124 kPa) causes the TP972Aand
TP9620A to lower BLP, opening the valve to control the
temperature with hot water (Fig. 8).

TP972A OR
TP9620A

13 PSI
(90 kPa) RA

18 PSI
(124 kPa)
DA

N.O.

M B

S/W

HOT WATER/CHILLED
WATER SUPPLY

C3542-1

Fig. 8. TP972A and TP9620A Typical Operation with a

Normally Open Water Valve Assembly.

Models are available that limit the cooling setpoint to a
minimum of 75 or 78F, the heating setpoint to a maximum of
72 or 75F. They work with 13/18, 16/21, 25/20, 19/14, or 20/
25 psi changeover. Some models are DA for both cooling and
heating.

TP973A,B and TP9630A,B

A fall in temperature at the TP973A or TP9630A causes the
TP973A or TP9630A to lower BLP, providing proportional
control of existing load requirements for heating (Fig. 9). A
rise in temperature at the TP973B or TP9630B causes the
TP973B or TP9630B to lower BLP, providing proportional
control of existing load requirements for cooling.

Fig. 9. TP973A and TP9630A Typical Operation, One-Pipe

Using External Restriction.

TP974A

The TP974A Sensor (Fig. 10) provides a pneumatic output
signal of 3 to 15 psi (21 to 103 kPa) in direct relation to the
sensed temperature, allowing direct and remote readout of
the temperature. An RP908 or RP920 Controller is used with
the TP974A to convert the output into a usable signal to
operate a pneumatic valve, damper, or other equipment.

TP973A OR
TP9630A

N.O.

HOT WATER OR
STEAM SUPPLY

C3543-1

TP974

VALVE

TEMP
GAGE

4 8 9

2 3 1

RP920

C3544A

M B

Fig. 10. TP974 Typical Operation.

TP978E

NOTE:

To vary the ZEB between heating and cooling
operation, adjust the setpoints on the TP978E.

A fall in temperature within the cooling range at the TP978E
causes the TP978E to increase the BLP of the cooling
element. This action proportionally closes the normally open
cooling valve (Fig. 11) to maintain the temperature set on the
high range portion of the TP978E. The normally open heating
valve is held closed by the high BLP on the DA side of the
TP978E.

A continued fall in temperature, into the heating range at the
TP978E, lowers the BLP of the heating element. This action
proportionally opens the normally open heating valve to
maintain the temperature set on the low range portion of the
TP978E.

TP978E

HEATING
VALVE

COOLING
VALVE

H C

N.O.

C3545

EXTERNAL
RESTRICTORS
0.005

Fig. 11. TP978A Typical Operation.

This manual is related to the following products:

TP970