Aprilaire model 500 install perfectly but what about this outdoor temp sensor? Is it needed?

Friday, November 11, 2011 by Aprilaire Team
Consumer question:

I installed the 500A on our furnace this weekend without any trouble. We cannot get access for the outdoor temp sensor, due to the 100 year old brick walls, so we are running the Model 60 Controller in manual. Because there was no return duct available the Model 60 has been mounted on an interior hallway wall. As per the instructions, the foam gasket was removed. The Model 60 hygrometer seems to be reading 10% high. We happen to have two digital hygrometers here and they both read about 36% while the Model 60 is showing 45% causing humidifier not it turn on. Can the model 60 be calibrated or can I get a replacement?


Aprilaires' response:

Thank you for your email regarding your model 500A Aprilaire humidifier. The model 60 is not designed to be installed in the living space. This is because the humidity sensor on the back of the control needs airflow past it to receive an accurate reading of the humidity. When mounted to a wall the airflow is blocked. The model 60 can not be calibrated. It has an accuracy of +/- 3%. As a result if it is measuring 45%, the humidity is between 42% - 48%.

Your email indicated there was no cold air return duct, however the return is necessary to install the humidifier. Our recommendation would be to re-locate the model 60 up stream of the humidifier on the cold air return. If this is not possible you will need to obtain our manul humidistat model 4655. The 4655 can be mounted in the living space. We ask for you to please contact the place of purchase to purchase the 4655.

Thank you for giving us the opportunity to be of service.

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