Helmer Scientific i.Series
®
Ultra-Low Freezer
Service and Maintenance Manual
360173-A/C
34
Problem
Possible Cause
Action
The chamber temperature
does not reach or stabilize at
setpoint.
Ambient air temperature is too high.
Confirm freezer location meets requirements.
Warm product was placed at sensor.
Move product and monitor chamber temperature. Wait to see if temperature
has stabilized or lowers.
Check remaining items.
Excessive frost has accumulated in
the chamber.
Defrost chamber.
Temperature control sensor is faulty.
Check accuracy of temperature probe.
Confirm the sensor is providing resistance in the range of 73 Ω to 110 Ω.
Replace the sensor if resistance is outside of specified range.
Install jumper across J11 on the CP board:
Display 4°C+/-1 - NO call Helmer Technical support.
Display 4°C +/-1 - YES - CP board process is good, check connections at CP
board and under connector pin, wait 8 hours to see if unit stabilizes.
Condenser filter is dirty.
Check condenser filter, clean as needed.
Condenser fan running slowly or not
at all.
Check voltage and wiring to fan motor at connector.
Check voltage output at CP board relay J42.
Replace motor.
Low stage compressor starting and
stopping after 2 to 10 minutes run
time.
Check cascade temperature - touch i.C
3
Settings (enter password) / Device
Status - Cascade temperature maintaining below -20ºC.
- NO - Contact Helmer Technical Service.
- YES - During pull down and starting at
~
-35ºC - normal behavior.
- YES - Check compressor amperage, OHMs and start components.
High Stage running: Low stage not
running.
Check cascade temperature - touch i.C
3
Settings (enter password) / Device
Status - Cascade has to reach
~
-35°C before low stage will start. Did cascade
reach
~
-35°C?
- NO - contact Helmer Technical Service.
- YES - it is normal to see the cascade heat exchanger elevate above -35°C
and could reach -20°C: if this happens the low stage will cycle off NORMALLY,
until the low stage reaches
~
-35°C and the low stage will start again. This is most
typical during pull down. At normal operation when at setpoint, this will not occur.
Check i.C
3
Control board for lit compressor LEDs (D21 and D22) to energize
compressor relays - ON, check remaining items: OFF - Contact Helmer
Technical Support.
Check i.C
3
Control board for lit compressor LEDs (D21 and D22) to energize
compressor relays - ON, check remaining items: OFF - Contact Helmer
Technical Support.
Check solid state relay - replace if control power is present but relay is not
allowing voltage to pass.
Verify operation of High pressure switch(s) control and line is not open.
Check start components.
Contact Helmer Technical Service.
Compressor(s) not running
Check power to unit.
Verify call for both compressors - touch i.C
3
settings (enter password) Device
Status - call for both on.
- NO - Reboot.
- YES - Check remaining items.
Check i.C
3
Control board lit compressor LEDs (D21 and D22) to energize
compressor relays.
- OFF - Contact Helmer Technical Support.
- ON - Check remaining items.
Check solid state relay. Replace if control power is present but relay is not
allowing voltage to pass.
Compressor buzzing or humming - replace start components.
Amperage check and OHM compressor. Contact Helmer Technical Support.
