Waterfurnace Geothermal 28x36x2 MERV 11 Airguard Air Filter (4PK)

The 59P509-05 is manufactured by Airguard for WaterFurnace and is considered by WaterFurnace to be the OEM replacement MERV 11 air filter for all their Geothermal Comfort Systems that use a 28 x 36 x 2 pre-filter.  

The replacement filters used with WaterFurnace units that use a 28 x 36 x 2 pre-filter must use a filter that is a full 28" x 36".  If you use a smaller filter, such as many of the 27 1/2" x 35 3/4" filters sold by other manufacturers, your filter will not seal properly, and you could get unfiltered air leaking around the edge of the filter, this is called bypass. The 59P509-05 MERV 11 air filter is approximately 28" x 36" x 1 3/4" and is the size recommended by WaterFurnace for a proper fit. 

Common WaterFurnace Geothermal Heat Pump Models that use the 59P509-05 28 x 36 x 2 MERV 11 pre-filter:

Envision Series:
Single Speed Vertical Units: NLV080, NLV095, NLV120

The 59P509-05 is made of 100% synthetic fibers that are needled together and then electrostatically charged.  The needled fibers create a dense mat that produces a MERV 11 rating and higher mechanical efficiency at a lower air resistance than other pleated filters. For more information on the construction of the 59P509-05 replacement air filter, please review the Airguard PowerGuard Air Filter Specifications.

WaterFurnace Premier Series units have an air filter rack that can be set for 1" or 2" when the units are installed. In most situations, you will not be able to change your units filter rack size without altering your ductwork, so please make sure your unit's filter rack is set for 2" filters. If your unit's filter rack is set for 1" filters, please get in touch with us for a quote on the exact filter you need.

All WaterFurnace units that use a 28 x 36 x 2 air filter actually use two 18 x 28 x 2 filters stacked. The 59P509-05 filter is made of two 18 x 28 x 2 air filters taped together. If your unit has an "H" channel between its air filters, remove or cut the tape to separate the two filters.

The manufacturer suggested replacement interval is 4 to 6 months, depending upon conditions and lifestyle.

For instructions on changing your furnace's air filter, please refer to your unit's Owner's Manual.