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Thermo Fisher Scientific

Lo P1 Error on Thermoflex 900/1400/2500 Chiller



  • ThermoFlex 900
  • ThermoFlex 1400
  • ThermoFlex 2500


Prerequisite: It has been confirmed that the correct voltage is applied: 115V for a ThermoFlex 900 or 1400; 220V for a ThermoFlex 2500 chiller.
If the Thermoflex 900/1400/2500 chillers displays a “Lo P1” error on the front LCD display, it is possible that air is trapped at the pressure sensor or the pump is cavitating.

Observe if water flows into the reservoir before the ‘Lo P1” error is displayed.

If water is flowing into the reservoir, follow steps 1-4 to release the trapped air in the pressure transducer.

If NO water is flowing into the reservoir, follow steps 5-8 to remove trapped air in the pump head or prime the pump.

Water is Flowing into the Reservoir
1) Remove the Side Panels. The pressure transducer will be accessible from the right side of the chiller.
    a) Use a Philips head screwdriver to remove the eleven #6-32 x 1/4" screws indicated in the illustrations below.

Themoflex Chiller Cover Removal.jpg

    b) Slide the right panel back approximately one inch, then lift slightly from the rear to disengage the panel's two tabs from their slots.
    c) Then remove the left side

2) Detach the Pressure Transducer

Detaching Pressure Transducer.png
3) Unscrew the Pressure Transducer receptacle and clean the connector of any debris that may have accumulated.

Unscrewing pressure transducer.png
4) Power on the chiller and with the water flowing, press on the valve stem until water is flowing out of the valve.

Pressing valve stem.png
5) Reconnect the Pressure Transducer receptacle followed by the Pressure Transducer itself and confirm that the “Lo P1” error no longer occurs. If the problem is not resolved, then replace the Pressure Transducer.

Water is NOT Flowing into the Reservoir
It is possible that the pump is still functional, but air is trapped in the pump head itself or that the pump is cavitating. To remove potentially trapped air in the pump head or to prime the pump, follow these steps.

1) Disconnect the “PROCESS OUT” tube from the Quick Disconnect (QD) fitting at the back of the chiller and in its stead connect an ~1 ft long piece of tube.
Note: If you don’t have any spare tubing and the lines between the chiller and instrument has sufficient excess, a 1 ft piece can be cut from the return or supply line.

Process Out.png
2) Point the 1 ft section of tubing connected to the Process Out  into a bucket.

3) Turn the chiller on long enough to allow the pump to engage and purge water. This will typically take 2-3 second. Then power off the chiller. The goal is to get the chiller powered off before the P1 interlock occurs.
Note: This action may need to be repeated more than once to clear trapped air.

4) Once water is pumping into the bucket, turn off chiller and reconnect supply line to instrument to the Process Outlet on chiller for normal operation.



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