Danfoss AKS 41 Liquid Level Transmitter
Section 9
Publication 9-45
Issue 1 : 10/11
Page 13 of 18
If the system uses R717 (ammonia) refrigerant, oil may tend to collect at
the bottom of the level column and eventually interfere with the correct
operation of the transmitter. Check for oil logging and if necessary drain
off the oil using the apparatus and method illustrated and described in
Pumping Down, Recovering Ammonia Refrigerant Charge in publication
5-20 in Section 5.
9.
Faults and Remedies
If the 4 to 20 mA output signal does not match the actual measured liquid
level, it is important to establish if the problem is due to the AKS 41/AKS
41U and not to the liquid level controller the 4 to 20 mA output signal is
connected to. Carry out the following checks:
Dismantle the cap on the DIN connecting plug and pull it back a little on
the cable to gain access to the four screw terminals inside the plug where
the four wires are connected.
Measure the resistance in the outer current loop between terminals 2 and
3 (the plug must not be mounted on the transmitter when carrying out this
check). If the resistance exceeds 500
Ω
, check for disconnections or
excessive resistance in the level controller connected to the liquid level
transmitter.
Refit the inner part of the DIN plug to reconnect the level transmitter to
the level controller. Measure the supply voltage on the plug’s screw
terminals marked 1 and earth. Check that the voltage is between 20 and
30 V ac (18 and 48 V dc). If not ok, look for the cause in the transformer
and its connections.
Disconnect the wires from plug terminals 2 and 3 so that any errors in
wires or external equipment will not interfere with the measurement of
signal current. Measure the signal current directly between plug
terminals 2 and 3. If the measured current does not correspond to the
observed liquid level, proceed to the 5 fault descriptions in Table 2.
