aswr
New Member
only one fan runs them bothIt's less than ideal to have two furnaces sharing ductwork AND running at the same time. Different static pressure will cause premature wear on the blowers if they are competing with one another. You'll also pull air backwards through the return when one furnace isn't running. I have mine set up with isolation dampers and an interlock. Flip the switch one way and the damper to the LP furnace / AC closes and the caddy is run by the home thermostats. Click it the other way and the Caddy is offline, it's damper closes and the LP furnace gets the signal. As to the intake damper on the Max Caddy, I agree. When it closes and your cruising, the secondaries die off fairly quickly and even a new call for heat 30 minutes later opening the damper back up doesn't bring them back. Now you have a slow burn until reload. For this reason, I'm considering pulling off my fresh air kit and doing a paper clip mod to prevent the intake damper from completely closing.