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User Guide | Danfoss troubleshooting guide for supermarket electronics
2. AK-SM 800
4 | BC337731384771en-000301
Compressors not coming on with high suction
1. Check status screen of rack to see if any warnings are listed (i.e. phase loss, high discharge pressure,
oil fail, etc)
a. For high discharge pressure, check settings tab to confirm cutin/cutout values for "Disch
pressure safety" are appropriate (cutout should be higher than cutin)
b. For phase loss, oil fail, see if the device sending Danfoss a signal is tripped (i.e. phase loss
monitor, oil sensor). If so, that device needs to be investigated.
c. If the device is not tripped, check wiring and polarity in program (under Addresses on-off inputs
tab) to ensure proper config (i.e open/closed/voltage/no voltage).
2. If no warnings are listed, check staging pattern of controller (auto/manual) under Settings
a. If set to manual, # of steps should be greater than 0, and individual steps should show
compressors selected with capacity increases from one step to the next.
b. Reset the controller after reviewing this section (even if no changes made). Staging pattern
changes do not take effect until after a reset.
3. Check Address section to ensure relay address for compressor still exists, polarity correct.
4. Under status screen for rack, select "Service" and confirm no manual overrides on compressors
Keypad not Responsive
1. Reset unit
2. Remove keypad from AK-SM 800 and reconnect
3. Ensure excessive wiring does not exist behind keypad
a. If so, shorten cables where possible
4. Replace AK-SM 800
IO Offline
1. Verify Power to modules, Complete rescan
a. Power supply to comm modules should be 24 V AC/DC
2. Verify 'Channel Lonworks' enabled on Network Nodes screen
a. If not, enable and rescan afterwards
3. Verify term resistor switch position at AK-SM 800 is correct
a. If 1 loop from plug, switch = 'On' position
b. If 2 loops from plug, switch = 'Off' position
4. Verify EOL resistor in place at end of loop(s)
a. 120 Ω resistor or term switch in On position
b. If term switches exist on modules in middle of loop, need to be in Off position
5. Verify comm module addresses via rotary switches
6. Verify that there are no hairline shorts on the comm loop terminal
7. Verify comm loop is run as point-to-point daisy chain (no branches, etc)
8. Verify comm cable type
a. EIA RS 485 (max. 4000') for Modbus and LON RS485 devices
b. 120 Ω impedance, 42– 75.5 pF/m capacitance, typically 22-24 AWG
9. Isolate loop in sections, rescan
a. Identifies where comm problem may be introduced
Database will not load via USB
1. Verify filename ends in ' . s55' extension
2. Verify filename is 8 characters or less, no special characters
3. Verify file is on root drive of USB, not subfolder
4. Verify controller firmware version equal or higher than database version
a. Database version can be verified in RMT
b. If database is 255 database being converted, must be v2.191 or higher.
5. Reset AK-SM 800 and attempt to load again
Case Controller 'Mismatch' Issue
1. Go to Network Nodes → Scan Status → Controllers
a. Locate address in list
b. Note controller version, part #, type shown
2. Go to Configuration → Control → Refrigeration → Circuits → Type
a. Confirm type matches info from #1 above
b. If not, change selection in list to proper choice
c. Rescan after updating
© Danfoss | Climate Solutions | 2022.02
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