I recently noticed that when my furnace was on, there was air being drawn in from the garage through open vents on the return end of the furnace. This is a York furnace that was installed as downflow, which isn't the default configuration. I believe these vents were intended for the supply side combustion air and either should have been blocked off for the downflow configuration or the panel should have been moved to the supply end. I don't understand how the original installer or the subsequent installer who added air conditioning didn't notice this. Luckily we have carbon monoxide detectors throughout the house.
Should I now be concerned that the supply end doesn't have adequate combustion air since it doesn't have these vents? As far as I can tell, the only source for combustion air is the gap around the exhaust vent.
How much did these open vents on the return end affect the efficiency of the furnace and A/C? I assume the amount of return air from inside of the house would have been reduced by the amount pulled in from the garage.
Should I now be concerned that the supply end doesn't have adequate combustion air since it doesn't have these vents? As far as I can tell, the only source for combustion air is the gap around the exhaust vent.
How much did these open vents on the return end affect the efficiency of the furnace and A/C? I assume the amount of return air from inside of the house would have been reduced by the amount pulled in from the garage.