There might be some cases in which the user doesn't feel any difference in the room temperature after the installation. There are only 2 situations that can cause this problem:
1- The device is not properly installed/ placed in the vent.
Please kindly note that airflow generated by the device when you turn it on freely outside of the vent should be almost equal to the flow you get once installed in the vent. Also, note that the device needs some room under it to be able to suck the air from the ducting system properly. In some cases, after the installation, the bottom of the device is very close to the body of the vent or it is not fully exposed to the air coming from the vent. This will significantly reduce the flow which is pushed out from the device. We recommend a minimum clearance of 2 inches from the bottom of the device to the body of the vent. This usually won't be an issue if the vent is the same as shown in the picture.
But for shallow vents or some of the wall vents, this can be problematic. Also, if the boot installed in your house is one of those asymmetrical ones as shown below.
In this case, please make sure to place the device on the deep side of the vent as much as possible and preferably use the hangers for that side to make sure the device is floating and has enough room to breathe.
2- The airflow is already strong enough before the installation.
In some cases, although more than enough airflow is already coming from the vent, the room still does not get to the desired temperature. Please kindly note that our device, like any other booster fan has been designed to fix the problem of having bad (weak) flow. They can generate more than enough flow for a regular size room but if the vent is already getting good flow, the device cannot help. In these cases, you need to look for the problem elsewhere such as bad insulation or a faulty main unit.