Danfoss SH485, Application Manuallines

20

AB243586442172en-001401

Electrical data, connections and wiring

Motor protection

Compressor models SH090-105-120-140-161-184 
have been provided with an internal overload 
motor protection to prevent  against excessive 
current and temperature caused by overloading, 
low refrigerant flow or phase loss. The cutout 
current is the MCC value listed in section “Three 
phase electrical characteristics”.

The protector is located in the star point of the 
motor and, should it be activated, will cut out all 
three phases. It will be reset automatically. 

While not compulsory, an additional external 
overload is still advisable for either alarm or 
manual reset. 

Then it must be set below MCC value (at max 
operating current:
•  when the motor temperature is too high, then 

the internal protector will trip

•  when the current is too high the external 

overload protection will trip before the internal 
protection therefore offering possibility of 
manual reset.

Compressor models SH180-240-295-380-485 are 
delivered with a pre installed motor protection 
module inside the terminal box. This device 
provides for efficient and reliable protection 
against overheating and overloading as well as 
phase loss/reversal.

The motor protector comprises a control module 
and PTC sensors embedded in the motor 
winding. The close contact between thermistors 
and windings ensures a very low level of thermal 
inertia.

The motor temperature is being constantly 
measured by a PTC thermistor loop connected 
on S1-S2. If any thermistor exceeds its response 
temperature, its resistance increases above the 
trip level (4,500 Ω) and the output relay then 
trips – i.e. contacts M1-M2 are open. After cooling 
to below the response temperature (resistance 
< 2,750 Ω), a 5-minute time delay is activated. 

After this delay has elapsed, the relay is once 
again pulled in – i.e. contacts M1-M2 are closed. 
The time delay may be cancelled by means 
of resetting the mains (L-N -disconnect) for 
approximately 5 sec.

A red/green twin LED is visible on the module. 
A solid green LED denotes a fault free condition. 
A blinking red LED indicates an identifiable fault 
condition:

PTC overheat

Delay timer active (after PTC over temp.)

Use a phase meter to establish the phase 
orders and connect line phases L1, L2 and L3 
to terminals T1, T2 and T3, respectively. The 
compressor will only operate properly in a single 

direction, and the motor is wound so that if the 
connections are correct, the rotation will also be 
correct.

Phase sequence and reverse 
rotation protection

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Compressor model

Overheating 

protection

Over current 

protection

Locked rotor 

protection

Phase reversal protection

SH 090 - 105 - 120 - 140- 161 

- 184

Internal motor protection

Internal reverse vent

SH 180 

Electronic module located in terminal box

Internal reverse vent

SH240 - 295 - 380-485

Electronic module located in terminal box

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Appr. 1 second

40ms

40ms

460ms

460ms

Appr. 1 second

920ms

80ms

Application Guidelines