I recently changed my HVAC filter and followed the same airflow direction (pointed arrow direction) as was on the previous filter. Almost immediately after replacing it, I keep hearing a whistling sound come from the HVAC whenever it's on. Is it because I chose a too-small pore size? I put in filters with MERV 11, which is much smaller than was there before, but we have a baby at home and I want clean air!
Picture below if that helps.
Best Answer
Yes changing to a finer filter can cause serious damage to your system. I try to always mention this. Each system is set up for a fairly narrow range of back-pressure.
By putting in a a filter that takes smaller particles out it increases the back pressure on the system and can even cause motor failure. How can this cause motor failure motors cool themselves with internal fans if the load it out of range the motor will star overheating once the motor gets to about 180 external temp the internal temps are much higher and they usually start shorting out 1 coil to the next more heat and soon you see and smell the magic smoke that is escaping.
The other thing that can happen is overheating the fire box lucky there is a safety to prevent a meltdown but it can shorten the furnace life if used for heat while the higher rated filter is in place.
Last the air exchanges are reduced so less air is getting filtered, so not only is size important but also what the system was designed for. High MERV filters require a little more beefy baffle to hold the filter securely or they buckle and air goes around them.