I can't say how much space is available but totaly agree with you about the 4" pleated filter being preferred over some kind of electronic filter. 2'' pleated is certainly ample for most applications but if they arn't available localy,one shouldn't spec them. It's also important that you get 16x25 , 20x20 or best of all 20x25 and not some odd size that must be special made at 10 fold the cost.

I would want Trane's Perfect Fit 5" media filter cabinet. Changeout is easy. Filters last up to one year before replacement is required. Filters both OEM and generics are available from online filter companies. And the name has a reason. The Perfect Fit filter cabinet is made to fit Trane furnaces and air handlers like a hand should fit a glove. It is a heavy duty cabinet with industrial type seals.

IMO

This post was edited by tigerdunes on Wed, Jul 3, 13 at 5:55

I don't understand why your HVAC contractor is being so difficult. This seems like an easy decision to go with the Trane media filter cabinet.

I suggest the new return duct have no sharp 90 degree angle. Ideally it should have a curved corner. This helps the return air flow.

Thanks for the responses. It's not an easy decision to go with the Trane media cabinet. I'm sure he'll sell me one, but it's an expensive upgrade. About 50% more than my car payment. The electronic filter is about two car payments.

I just wanted to make sure there wasn't some reason we couldn't make the standard opening (not a cabinet, just the old style hole where you slide in a filter) 4" wide instead of 2". Which should be a $0 upgrade (maybe $5 in materials, no additional labor).

This post was edited by zirconx on Wed, Jul 3, 13 at 8:52

You could do what you suggested. The problem is you would be creating a big hole in the return duct. A lot of air will be sucked into this opening. Some air will by pass the filter. This will eventually cause problems with the furnace and coil. You will also be reducing the amount of air being pulled from the house. In addition you may be causing a negative air pressure condition in the basement. It could cause a dangerous condition if you have a gas hot water heater near the furnace.

What price did you get for the Trane filter cabinet?

How much air flow is required for heating & cooling?

What tonnage is the A/C?

What Btuh Output is the furnace?

3.5 ton AC, 100k btu furnace (95% eff). The media filter cabinet is a $450 option. Seems like a lot of money for a cabinet.

Yes the hole will be bigger but it will be filled by a bigger filter. So would it leak any more than a 1" hole plugged by a 1" filter?

Also when the blower is running the filter is sucked tight to the ductwork. So any air leakage will be on the other side of the filter - in other words the gap will be on the "input" side of the filter so the air will be filtered.

Also I think I could rig up a "lid" to place against this opening pretty easy. A piece of magnetic strip should do it.

When I bought my house there was a heat pump with a pleated paper filter in it. It seems to be about 6" thick, but I found that the medium let enough dust through that I got dust everywhere just as though it was not filtering. The tech said I had the low cost pleated paper and they had one much better. I put one in but still had dust. It was because as the filter got a bit dusty it was easier for the air to leak around the edges than to pass through it. I would go for the "expensive" Trane system rather than have a useless filter.

The electronic is a good filter, but I would go with the 4" media filter. Compare the pressure drop in both systems and see what the affects on air flows will be before going one way or another.

Media filters are rated on a MERV basis. Prior to this system coming out there was no better example of the "figures don't lie but liars figure". Everyone spoke of effectiveness and efficiency and it was all just wrong.

The lower the MERV number, the lower the efficiency. A 5 is less efficient than an 11. I would suggest over 10, but again, to tight a filter will affect air flow and static pressures must be calculated. I used to represent Purolator and saw many people throw a MERV 13 in a system and Kaboom...no air flow.

Discuss this with your contractor and don't let him soft peddle this. Make sure you understand what you are getting and how it will work on your duct system. I am surprised that a media filter cabinet is more than an electronic. All the media filter is, is a frame to hold the filter.

I also recommend a duct leakage test prior to replacement of any equipment. Keep in mind that the DOE says that the average residential system looses between 18 and 42% of its energy due to duct leakage. Saying that it is lost to the building envelop is not correct thinking. It is the ultimate rationalization. My system in the home we purchased 4 yrs ago was so poor that I eliminated all the duct (and found closets;), and went mini-split heat pumps and Rinnai Energysavers. All "net to the space" zoned H&C.