How do i convert a 'INT69 Thermistor to a 'Robertshaw Sensor'?

Internal Motor Overload Protection & INT69 Thermistor Module

Internal Motor Overload Protection Installation of INT69 Thermistor module Motor Protection Mode Most compressors that use Thermistors as a means of Thermal Overload Protection utilise Positive Temperature Co-efficient Resistance type Sensors (PTCR). These are effectively a small bead like component which will increase in resistance as it’s temperature increases. Their design is such that they will rise to infinite resistance at the chosen trip temperature, typically 120 - 140 oC.

At normal running temperature their resistance is only a fraction of the trip value, hence several (up to 8) may be used by connecting in series. Discharge Gas Temperature Protection Mode Operating in a similar mode to above but utilising a single thermistor probe mounted into the discharge gas vicinity where normal upper discharge temperatures will be achieved, e.g. cylinder head, discharge pipe, etc. Temperature settings are generally higher than embedded sensors at around 200oC. Isolation Module Mode Again operating in a similar mode to above but utilising embedded Micro klixons within the motor assembly. Used in this way the module acts to prevent stray EMFs affecting the control circuit, provides a ‘reset required’ device in the event of trip, and in the event of a motor burnout prevents burn out short circuit currents passing back into the control circuit. This can be vital is electronic controls are used. INT69 Module These sensors are used in conjunction with an electronic INT69 module which continuously monitors the resistance of the thermistor group, chain or probe. Should any of the beads in the chain exceed the set point, 1500 ?, then the control module will break the control circuit.

By using PTCR sensors, they are fail safe, i.e. should the circuit be broken then the module will sense this as infinite resistance and trip the machine. This is also the manner of operation when used with Micro klixons. It should be noted that in order to operate then the bead must warm up, and this requires it is correctly embedded in the motor windings. In tripping the motor it will rely on the contactor opening when the control circuit is broken, therefore protection is lost if the contactor has welded, a common cause of motor single phasing. Connection The INT 69 control module has a strip of connections along its upper edge. R & Mp or L & N AC power supply Live & Neutral T1 & T2 or 1 & 2 Connection to series linked Thermistors or 1 off head Thermistor 11 & 14 Normally Open connections for control cct 11 & 12 Normally Closed connections for optional fault indication 1 Connect Power supply feed to R & Mp or L & N. 2 Connect T1 & T2 to Thermistor terminals on compressor or to Head Probe. Note Certain models are fitted with 2 chains, i.e all Copeland’s over 4 cylinders. In this case simply link the centre pair of the 4 terminal overload pins, to produce a longer Series chain. 3 Connect Control Circuit feed to 11 & 14 (NO). 4 Shut down alarm circuit is available on connections 11 & 12 if required (NC). Top view of INT69 module ????????????????????? R Mp T1 T2 11 12 14 |--- NC ---| | or L N 1 2 |------------ NO -------| | | | | | | Power supply Thermistors Control Circuit Module variants INT69 Basic module with auto reset INT69TM As above with power off to reset feature INT69VS As above used on Bitzer compressors including head thermistors The module has 2 power ratings. 1st is the supply voltage required to operate the module itself and this must match the control voltage upon the associated unit, typically 240v, 110v & 24v ac. The 2nd is the switching capacity of the internal relay contacts, typically max. 250 vac 3a. Testing Operate the compressor normally then using an insulated screwdriver disconnect one sense lead from T1 or T2, the compressor should stop immediately. To reset re-connect and temporarily interrupt power supply (TM & VS versions).