New home Lennox residential HVAC. What is too much filtration for a residential system to handle. A HVAC friend of mine said you shouldn’t use anything bigger than the standard fiberglass filters because residential units can’t handle the resistance and eventually makes them not cool as effectively. Builder had installed MERV 8/MPR 600. Thoughts?
2018 21 PHX/Verado 250 Pro
I modified my filter grates to take 5” filters. The surface area is so large that I can go to higher MERV ratings without causing a pressure drop.
2022 Ranger Z520R, 2022 Mercury 250 ProXS 4s
Dual 16” Lowrance Live’s at console, 12” Live with Active Target, Garmin 8612 and Livescope, and Humminbird 12” Mega 360 at the bow
Lowrance Ghost TM
My units call for up to MERV 11, so I use 11's. Helps me with allergies.
'05 Stratos 200 ProXL, '05 Evinrude 225HO
I've done a lot of research on this, and my finding is MERV 8 or equivalent and replace every 1 to 3 months. I personally by the cheap Merve 8 from HD and change out the first of the month, works for me.
I'd want to hear from the Lennox dealer for your particular model. My carrier has one of those stupid constant torque X13 ECM motors so I think in my case if I go too high on the MERV rating the motor will drop speed and I lose CFM. A constant speed motor or variable ECM will probably be fine for the higher efficiency filters but you don't want to go nuts and use your HVAC as an air filtration unit. Filter out stuff to protect your coils and ductwork, if you have allergies perhaps consider other methods.
This is the correct answer. To go to a higher MERV rating the surface area of the filter must be increased to allow the same amount of CFM to pass through it for proper air flow. Getting too thick of a filter in a small size will decrease your air flow. If your system was designed with the allowance for this your good if not it will require some modifications.Originally Posted by DoctorJJ
The constant torque motor should do the exact opposite of what you're thinking. With a normal PSC motor in HVAC systems if the restriction goes up it won't move as much air so torque and current/power draw go down. The motor speed will stay the same though.
With a constant torque motor, if the air restriction goes up the motor controller should spin the motor faster to keep the air resistance on the blower fins constant (thus constant torque motor), however they usually only built to have a handful of motor speeds they can run at (maybe 5 different speeds or so), and they will draw higher amperage/power to do that.
A variable speed motor does the same thing but with much greater range of speeds it can run at to truly keep air flow constant.
IIRC there are 5 speed taps on the X13 but the installer has to select one based on their initial TAB. Or maybe the manufacturer specs it. When I replaced both of mine I just used the middle tap and it's been fine. Point is at some point the motor won't be able to push past that larger restriction based on the tap that is selected (I think).
On a PSC I guess I was thinking that you could always select a higher speed based on your filter selection. But thinking about it now since I have the 5 taps on the X13 I presumably could do the same.
MERV 8 is pretty universal. Whatever you choose look at the R&R interval. You could go up to 13, but have to replace at half the interval of the 8.
2017 Phoenix 819
2016 200ProXS, s/n 2B359849, Mod 1200P73BD
Or it will shut down when air flow is restricted too much. I found out! A Little MERV is Good, More MERV is Better and Too Much MERV it's Shuts Down!
If professionals who's careers depend on catching fish use FFS then that's what I'm using. Might be too simple of a philosophy but makes sense to me.
Filteet 1900 has great filtration and low static pressure thanks to the high number of pleats in the filter
Most residential systems will only handle an approximate merv 8. Filter sizes have to be increased to have more area. The ahu/fcu/furnace isn't designed for the TSP (total static pressure) needed to overcome the resistance of all the return air, equipment, and supply air. All these including the types or styles of grilles and filters have static. It's about pressure drop (resistance). The higher the air flow thru a fixed area the higher the static. Residential systems operate from .5" to 1" of static.
If you use too high of efficiency filter can cause low air flow. Low air flow can cause low evaporator temperature or icing. This can lead to a potential mechanical issues. The most ECM motors will lock out with an error code if overloaded as well. A psc (permanent split capacitor) motor you may not know until an issue or failure happens.
Ask a WELL trained tech what filter your system will handle! Every system (equipment and duct) is different.
FYI quick tutorial: PSC motors have run capacitors. A lot of people on BBC refer to these as start capacitors, they are not start capacitors. While a motor will not start with a defective one, it is a run capacitor. Start capacitor is only for starting a via a relay or switch kicks out of the circuit immediately after the motor starts. The run capacitor stays in the motor circuit it's entire run cycle. For instance a compressor can a run capacitor or both.
2014 Phoenix 721XP, 250 SHO, Bobs Action Jack, Dual Blades, 112 Ultrex, 2019 Lariat FX4 F150 Supercrew 4x4
Do not use a fiberglass filter. They barely capture anything. If your filter rack in the system is only 1", then put in a Merv8 pleat and change every 3-4 months unless you notice it loading up quickly.
I would highly recommend buying an Ionizer and putting in your system. Larger particulate in the air will get too heavy and fall and what doesn't fall, will get pulled through the return. This unit will handle most all residential size systems. You will appreciate it if you do it. https://gpsair.com/products/gps-fc24-ac
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