Installation Instructions

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Document No. 129-166

March 17, 2022

POWERS

™

Controls

TH 356 and TH 357 LIMITEM

Thermostats (Model 6)

Item Number 129-166-04, Rev. DA Page 1 of 6

Product Description

The TH 356 Rigid Bulb LIMITEM and the TH 357

Remote Bulb Direct Acting LIMITEM are pneumatic

thermostats with a variety of uses in unit ventilators

and other air handling systems.

The TH 356 Rigid Bulb LIMITEM is available in

either direct acting or reverse acting models. The

TH 357 Remote Bulb LIMITEM is available in direct

acting only.

Product Numbers

TH 356 LIMITEM

Table 1. Rigid Bulbs.

Product No.

Action

Operating Range

356-0750

Direct

Acting

30 to 180°F (-1 to 82°C)

356-0012

0 to 100°F (-18 to 38°C)

356-1005

Reverse

Acting

30 to 180°F (-1 to 82°C)

356-0013

0 to 100°F (-18 to 38°C)

TH 357 LIMITEM

Table 2. Remote and Averaging Bulbs.

Product

No.

Operating

Range

Sensing

Element

Bulb

Inches (mm)

Capillary

Ft (M)

357-0003

20 to 100°F

Remote

3/8 × 4 in.

(-7 to 38°C)

Bulb

(9.5 × (102)

(2.4)

357-0004

35 to 145°F

Averaging

3/32 × 15 ft.

(2 to 63°C)

Bulb

(2.4 × 4570)

(12.2)

357-0001

35 to 145°F

Averaging

3/32 × 8 ft.

0.5

(2 to 63°C)

Bulb

(2.4 × 2440)

(0.15)

Required Tools

• Drill and 1/4-inch (6.3 mm) and 5/8-inch

(16 mm) drill bits

3/16-inch (4.8 mm) and 9/16-inch (14 mm)

drill bits for the mounting of the 808-412

mounting flange of kit 163-172

• Flat-blade screwdriver

• Test gauge and test thermometer

Prerequisites

• Inspect the sensing tube for damage.

• Read the instructions to determine if any

accessories are needed.

• The use of supply and return (output

pressure) air gauges and tees is

recommended. Order Kit No. 142-0425 for

gauge and tee for 1/8-inch NPT

(two required).

• Provide adequate clearance for the sensing

tube.

Troubleshooting

If the limitem fails to operate properly, use Table 3

as a troubleshooting guide. Ensure that the

thermostat receives 18 to 30 psi (124 to 207 kPa) of

clean, dry, oil-free supply air. Also, use a test gauge

with a length of 3/16-inch ID rubber hose to measure

the return pressure at the test port if permanent

gauges are not available.

Summary of content (6 pages)

PAGE 1
Installation Instructions Document No. 129-166 March 17, 2022 POWERS™ Controls TH 356 and TH 357 LIMITEM® Thermostats (Model 6) Required Tools Product Description The TH 356 Rigid Bulb LIMITEM and the TH 357 Remote Bulb Direct Acting LIMITEM are pneumatic thermostats with a variety of uses in unit ventilators and other air handling systems. The TH 356 Rigid Bulb LIMITEM is available in either direct acting or reverse acting models. The TH 357 Remote Bulb LIMITEM is available in direct acting only.
PAGE 2
Document No. 129-166 Installation Instructions March 17, 2022 Troubleshooting, continued Table 3. Troubleshooting Chart. Complaint Check Supply Air Pressure If return is still zero psi Return Line pressure stays at approx. zero Press down exhaust valve Return Line pressure stays at approx. supply pressure Using a screwdriver, rotate the setpoint dial counterclockwise to the limit stop Probable Cause Low Pressure Defective valve assembly Corrective Action As Required Replace thermostat 1.
PAGE 3
Document No. 129-166 Installation Instructions March 17, 2022 Installation, continued • The mounting bracket, furnished with the thermostat, may be attached to any flat surface and the thermostat body threaded onto the protruding pipe nipple. • When metal tubing is used for the supply and return air lines, this tubing may also serve to support the body of the thermostat. Mounting the TH 357 LIMITEM Bulb • Figure 2. Swivel Flange Mounting Kit Part Number 356-090.
PAGE 4
Document No. 129-166 Installation Instructions March 17, 2022 Installation, continued Averaging Bulb Mounting Averaging bulbs require some means of support for the bulb and capillary. • • Use a coil clip, Part Number 356-115 (Figures 6 and 7) or a capillary clip, Part Number 7421700060 (Figure 4), to support the bulb if there is easy access to the coil. Figure 5. Clip Mounted on Coil. For duct mounting where access to the coil is limited, see Figure 8.
PAGE 5
Document No. 129-166 Installation Instructions March 17, 2022 Calibration Change setpoint 1. Remove the cover. 2. With a screwdriver, turn the dial adjustment screw to change to the desired setpoint. See Figure 8. 5. If the return pressure does not read 7 to 8 psi (48-55 kPa), turn the dial adjustment screw with a screwdriver until pressure is 7 to 8 psi (48-55 kPa). 6. Loosen the dial screws and turn dial until the temperature at the bulb and dial is identical. Tighten the screws. 7.
PAGE 6
Document No. 129-166 Installation Instructions March 17, 2022 Figure 10. Sensitivity Spring Setting. 5. Ensure that the dial adjustment screw point touches the sensitivity spring. 6. Recalibrate the unit. Table 5. Cross Reference Chart. * Non-relay (one-pipe) requires external restrictor. ** Direct or reverse acting-reversible. References Technical Instructions TH 356-1 LIMITEM® Rigid Bulb Thermostat, Document No. 155-070P25 TH357-1 LIMITEM® Remote Bulb Thermostat, Document No.