I have an Apollo HydroHeat MA45H (45000 BTU) system connected to a bradfordwhite water heater (75gal / 76000 BTU input). We have a 2 story 1450 sf house (1000 dn, 450 up), 1 zone. Water heater was just replaced this last summer. Water heater and HydroHeat system are separated by 25'. Heat Exchange water lines run in the crawlspace but are insulated with pipe foam. Duct system for the lower story runs in the crawlspace via insulated flex duct. Air filter is brand new. Floor joists in crawlspace are insulated. Duct vent perimeter is sealed from colder crawlspace air where it comes up through the floor. The issue I am having is very little air flow coming out of the vents - nothing like other forced air systems I've had in the past. I've inspected the crawl space and find no gaps, disconnected or kinked duct lines. All of the ducts have about the same amount of air flow which seems to suggest the fan just isn't very good at moving the air. Fan motor is rated at 1/2 hp. Temporarily removing the air filter made no difference in air flow at the vents. It took about 4 hours today to move the temp from 65 to 68 with an outside temp between 38 & 44 during that same period. When outside temp is below freezing it really struggles to keep the house at 68. It's an older home so I'm sure I have insufficient insulation but regardless of that my question is more directed at the amount of air flow (or lack thereof). Is the air flow typically lower on these types of systems? Is there anything I can look at to help identify why I have such low air flow? Thanks in advance
