View Full Version : RETURN AIR FILTER GRILLE QUESTION ?
08-04-2009, 07:38 AM
I just had a new 30 x 24 return air filter grille installed (airmate 170ff). It seems to be very flimsy and does not seem to close properly. I'm sure it is going to rattle eventually. My question is, who makes the best (sturdy) grille today in that size that is more heavy duty and will last, and are there any out there still made in the US. Thanks
That's a large return ,what size system??
Shouldn't be a issue up to5 tons.
08-05-2009, 08:52 PM
Filter rack sizing is very important to efficient airflow & system performance.
RETURN AIR FILTER RACKS
Recommended filter velocity is 300-350-fpm, lower is better.
Velocities higher than 500 fpm will decrease filter performance; increase flow resistance, and depending on the type of filter, possibly blow off collections of debris. Measure Velocity 1” from RA grille face.
Estimated average Free-Air-Area of most Return-Air grilles is about 75%.
Most 4 & 5-Ton systems require two filter racks exterior of the airhandler to achieve a low enough air velocity through those filters.
Most 4 & 5-Ton systems nearly always have too much air velocity through initial clean filters, let alone when they begin loading.
Divide the rated CFM the duct is carrying by the free area sq.ft. of the Return Air grille for airflow velocity in FPM without a filter in the rack.
The filter will reduce the sq.ft. free-air-area, thus increasing the fpm velocity, as it loads. Never worry about having too much filter area.
Don't worry about oversizing the Return Air ducts, where the air-handler furnace is over a Return Chamber there is many times, no Return ducting.
If you wanted to, in some situations a large filter-rack grille could go on two sides of the chamber providing low velocity, low pressure drops, & excellent air filtration.
There is no need to be concerned about not enough velocity or THROW.;):D:rolleyes:
08-05-2009, 09:44 PM
Seems like people are responding to something other than your question. Crown Products make good sturdy grilles. I use MetalAire which are standard aluminum. I would call your installer back and see what they can offer for an upgraded grille. There are many grille mfg out there and people usually use what is stocked locally and economical for the job. If they know you are will to pay a few dollars more they should be able to assist you. I have replaced a lot of grilles in multi-million dollar homes because the builder did not specify with the contractor and when the home was bought the people wanted something different. There are always options and upgrades. :-)
08-06-2009, 05:24 PM
I like Crown, too.
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.