What is one method of preventing ice build-up on the recovery coil of a runaround heat recovery system during cold weather?
a) by using electric heating elements on the coil
b) by the use of a pre-heat coil
c) by using a steam to glycol heat exchanger
d) by using a three-way mixing valve to mix cold and warm glycol
e) by throttling the air inlet dampers to restrict the airflow
Answer: D