Francis G is right, with one other note. The assumption is that you only have one return air grille. If you have multiple return airs, you would need a filter in each one. That's why you usually find the filter in the unit, because it will filter all of the return air, including any outside air that might be brought in through the ductwork (not common in residential though).
The filter is in the return, already, just not on the "grill" cause it looks better, not "showing"
The only repercussions would be twice the cost when replacing them.
You can use a return air grill filter instead of the furnas filter. You can also use both and change the return air filter regular and the furnas filter only when completely dirty.
Comment by former ebayer — June 28, 2009 @ 4:58 pm
both would be too much air restriction. air movement is a huge part of heating and cooling , so do one or the other, not boaf. .
Francis G is right, with one other note. The assumption is that you only have one return air grille. If you have multiple return airs, you would need a filter in each one. That's why you usually find the filter in the unit, because it will filter all of the return air, including any outside air that might be brought in through the ductwork (not common in residential though).
Comment by Papa C — June 28, 2009 @ 4:58 pm
The filter is in the return, already, just not on the "grill" cause it looks better, not "showing"
The only repercussions would be twice the cost when replacing them.
Comment by Joe Banana — June 28, 2009 @ 4:58 pm
You can use a return air grill filter instead of the furnas filter. You can also use both and change the return air filter regular and the furnas filter only when completely dirty.
Comment by former ebayer — June 28, 2009 @ 4:58 pm
both would be too much air restriction. air movement is a huge part of heating and cooling , so do one or the other, not boaf. .
Comment by francis g — June 28, 2009 @ 4:58 pm