Possible Reasons for Temperature Issues With Your Lab Incubator

By Aimee O'Driscoll, 23 January 2019

If you need a lab incubator for your application, then you’ll no doubt be frustrated if it’s not doing its job properly. If your unit won’t heat up or cool down at all, or won’t reach its setpoint temperature, there could be a host of factors at play.

In this post, we’ll help you troubleshoot by looking at some possible reasons for temperature issues with your lab incubator, including those providing refrigeration.

1. There Has Been a Mechanical Failure

If your unit won’t heat or cool at all, it could spell a serious issue. You may have a broken element or controller, both of which would require service, and you may need to buy replacement parts. You might even need to think about purchasing a new machine.

If your lab incubator comes with a refrigeration function, but isn’t cooling at all, one of the most likely reasons is that the compressor has failed. In this case, you’ll need to have the machine serviced or even replaced.

Before you start shopping around, read on to find out about other possible issues that could be causing your temperature woes.

2. The Temperature Protection Is Set Too Low or Too High

Over-Temperature Protection (OTP) is a handy feature in many lab incubators. It acts as a backup by shutting off the heat (and sometimes activating a visual or audible alarm) in case the temperature spikes for some reason. This helps to ensure that the integrity and stability of your samples won’t be compromised by a too-high temperature.

Some units have automatic protection, such that the unit will shut down and activate alarms if the temperature deviates from the setpoint by a certain amount (often by 1°C).

For other models, the user sets an independent OTP controller to a specific temperature (about 1°C above the setpoint temperature is often advised). If this temperature is reached (according to a sensor in the chamber), power will be routed away from the heating elements.


Incubators with over-temperature controls.

ILP Personal-Sized Low Temperature Incubators and SCO Air Jacket CO2 Incubators come with over-temperature controls.

However, if you’re changing applications and using a new temperature, it’s easy to forget to increase the OTP. If this is set too low, your unit won’t heat up to the new setpoint.

Most temperature control devices that have this kind of functionality utilize both over- and under-temperature alarms. Under-Temperature Protection (UTP) is – predictably – the opposite to OTP. You set a minimum temperature to avoid your samples being exposed to a too-cold environment. If this is set higher than the setpoint, your unit won’t cool to the desired temperature.

3. The Temperature Needs to Stabilize

Some units, such as the SSI3 Benchtop Shaking Incubator and SSI5 Floor Model Shaking Incubator, include a reference thermometer to help with calibration. In certain cases, your machine may appear to be heating up or cooling down, but the temperature on the reference thermometer doesn’t match the main temperature control reading.


Incubated shakers with reference thermometers.

An SSI3 Benchtop Shaking Incubator (left) and an SSI5 Floor Model Shaking Incubator (right).

One of the most likely reasons for this is that the temperature hasn’t stabilized yet. If the door has recently been opened, the unit has been turned off, or the temperature has been reset, there may not have been enough time for the internal temperature to stabilize.

4. It’s Not Calibrated Properly

In the case above, if there has been ample time for the temperature to stabilize, the problem may be with calibration. If one of the thermometers isn’t calibrated properly, then their readings simply won’t match.

It’s recommended that the unit is calibrated at a similar temperature to your process temperature and that it is calibrated each time you change to a new temperature.

5. The Door Seal Is Broken

For both incubated and refrigerated machines, if the unit isn’t reaching temperature, the door seal could be an issue. If the seal isn’t working properly, air exchange between the unit and its environment will take place, letting warm air escape (in incubated units) or enter (in refrigerated units).


Incubators with door seals.


Whether it’s a compact unit like the Mini Incubator by Jeio Tech (above left) or a larger one like Sheldon Manufacturing’s SCO Large Capacity CO2 Incubator (above right), issues with the door seal can occur for a host of reasons. These include a broken gasket, loose latch bolts, or misadjusted hinges. The door may have even been twisted or damaged such that is isn’t fitting correctly. Check all of these issues and make repairs where necessary and possible.

6. There’s Not Enough Free Airflow

For these units to work properly, you do need to ensure there is enough free airflow around the machine. While you don’t need a ton of space, it’s not a good idea to have units pushed right up against walls or other pieces of equipment. A couple of inches of “breathing room” for the sides and rear of the unit will help ensure enough free airflow for it to function properly.

For refrigerated machines, the unit may not cool sufficiently if there is ice buildup on the evaporator. This causes insulation and makes it more difficult for the compressor to do its job. You can remove the ice and try to limit door openings to avoid moisture entering the unit.

7. More Power Is Required

Power is unlikely to be an issue with machines that are in an existing setup, but might be the problem in a new installation. If it’s the first time you’re using the unit or you've moved it to a new location, you should check that the power source’s amperage and voltage meets the unit’s requirements. You should be able to view these figures on the data plate of the machine.