The variable speed core blowers in the system are used to circulate air through and extract heat from the brick core. A heat call from the thermostat energizes the supply air blower which begins to circulate air through the duct work. A discharge air sensor monitors the current discharge air temperature and determines whether or not the discharge air temperature is warm enough (determined by value set in L048 and L049). If the discharge air temperature is too cool, the core blower are energized to draw heat off the brick core until the desired discharge air temperature is satisfied.
In the 4100 Series, one core blower is energized and attempts to satisfy the heating requirements. If unable to maintain the desired output temperature, the other core blower will be energized. If one core blower is sufficient, the system will alternate between core blower #1 and #2.
Power is sent to the core blowers from the Base I/O relay board through the blower (core blower #1) and the damper (core blower #2) terminals. The amount of power sent to the blowers depends on the current blower speed as indicated in Location 120 and L121. The variable speeds range from zero to 255. For example, a speed of 255 in Location 120 would indicate that 240VAC should be present between the L2 240 terminal and the blower terminal on the Base I/O relay board.