Thermistors - All thermistors are identical in their tem- perature vs. resistance performance. Resistance at various temperatures are listed in Tables 15 and 16.

LOCATION - General location of thermistor sensors are shown in Fig. 13.

Cooler Leaving Water Thermistor (Tl) - Tl is located in leaving water nozzle. The probe is immersed directly in the water. All thermistor connections are made through a %-in. coupling. See Fig. 15. Actual location is shown in Fig. 13 and 14.

Cooler Entering Water Thermistor (T2) - T2 is located in cooler shell in first baffle space near tube bundle. Ther- mistor connection is made through a %-in. coupling. See Fig. 15. Actual location is shown in Fig. 13 and 14.

Compressor Suction Gas Temperature Thermistors (T7 and T8) - T7 and T8 are located in lead compressor in each circuit in suction passage between motor and cylinders, above oil pump. They are well-type thermistors on 040-210 and associated modular units, or ferrule-type on 225, 250, 280 units. See Fig. 13 and 14.

THERMISTOR REPLACEMENT (Tl , T2, T7, TS) (Com- pressor and Cooler)

Thermistors are installed directly in fluid or refrigerant circuit. Relieve all refrigerant pressure using standard refrigerant practices or drain fluid before removing.

Proceed as follows (see Fig. 15):

To replace sensors Tl, T2, T7 (225,250,280), and T8 (225,250,280)

1. Remove and discard original thermistor and coupling.

IMPORTANT: Do not disassemble new coupling.

 

Install as received.

I

 

2.Apply pipe sealant to ‘/a-in. NPT threads on replace- ment coupling and install in place of original. Do not use packing nut to tighten coupling. This damages fer- rules (see Fig. 15).

3.Insert new thermistor in coupling body to its full depth. If thermistor bottoms out before full depth is reached, pull thermistor back out I/s in, before tightening packing nut. Hand tighten packing nut to position ferrules, then finish tightening 19’4 turns with a suitable tool. Ferrules are now attached to thermistor which can be withdrawn from coupling for unit servicing.

To replace thermistors T7 and T8 (040-210 and associated modular units):

Add a small amount of thermal conductive grease to ther- mistor well. Thermistors are friction-fit thermistors, which must be slipped into receiver located in the compressor pump end.

Pressure Transducers - TW O tvpes of pressure trans- ducers are used on 30G Flotronic’” Ii*chille&: a low pres- sure transducer and a high pressure transducer. The low pressure transducer is identified by a white dot on the body of the transducer, and the high pressure transducer by a red dot. See Fig. 16.

Three pressure transducers are mounted on each lead com- pressor: 2 low-pressure transducers to monitor compressor suction pressure and oil pressure, and a high-pressure trans- ducer to monitor compressor discharge pressure (see Fig. 17 for exact locations on compressor). Each transducer is supplied with 5 vdc power from a rectifier which changes 24 vat to 5 vdc.

TROUBLESHOOTING - If transducer is suspected of be- ing faulty, first check supply voltage to transducer. Supply voltage should be 5 vdc + .2 v. If supply voltage is cor- rect, compare pressure reading displayed on keypad and dis- play module against pressure shown on a calibrated pres- sure gage. If the 2 pressure readings are not reasonably close, replace pressure transducer.

TRANSDUCER REPLACEMENT

rTransducers are installed directly in the refrigerant cir- cuit. Relieve all refrigerant pressure using standard re- frigeration practices before removing.

1.Relieve refrigerant pressure using standard refrigeration practices.

2.Disconnect transducer wiring at transducer by pulling up on locking tab while pulling weather-tight connection pfug from end of transducer. Do not pull on trans- ducer wires.

3.Unscrew transducer from !&in. male flare fitting. When installing new pressure transducer, do not use thread sealer. Thread sealer can plug transducer and render it inoperative.

4.Insert weathertight wiring plug into end of transducer until locking tab snaps in place.

5.Check for refrigerant leaks.

-75”

l/4” SAE FEMALE FLARE

WHITE DOT-LOW PRESSURE TRANSDUCER

RED DOT -HIGH PRESSURE TRANSDUCER

SAE - Society of Automotive Engineers

Fig. 16 - Pressure Transducer

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Carrier 040-420 specifications Pressure Transducer
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040-420 specifications

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