Figure 6 Figure 7 Figure 8 motor speed for the proper CFM for heating is placed, in Resideo’ s drawing, Figure 7, they are using the‘ ML’ motor speed. The proper speed can be obtained from the OEMs literature or by performing a test to verify‘ temperature rise’ across the heat exchanger. Let’ s discuss‘ Continuous Air Circulation’ or‘ CAC’. Continuous low speed indoor air circulation has been around for a long time, in fact it came along with the first forced warm air furnaces of the late 1930’ s, Figure 9.
Running the system blower can make a home better in many ways. One big plus is improved temperature distribution. The blower keeps air moving, making sure every room is at a comfortable temperature. This stops hot and cold spots that happen when the blower isn’ t on.
Also, better indoor air quality is a benefit. The blower helps the air move around, which cuts down on dust and moisture. This can stop mold and bad smells. Recommending a good quality air filter, also helps clean the air more. You should do a bit more reading if you have a lot of customers with furnaces about MERV filters, Figure 10, and ratings.
In 1987, the American Society of Heating, Refrigerating, and Air Conditioning Engineers( ASHRAE) designed the MERV rating scale to give a more accurate picture of an air filter’ s
www. fueloilnews. com | FUEL OIL NEWS | JULY 2025 31