Thread: HVAC Drier Filter

Gentlemen (and Ladies, of course)

Typically - and I understand both best practice and manuf. recommendations, drier filters are installed as close as possible to the compressor. As can be seen, this one is as far away as it could be, save for a few more inches. The drier shown is for the compressor on the left, at least 60' away.

1. Does the placement make a significant difference and why? (I have never seen one installed anywhere else other than at the compressor)
2. Is the corrosion shown on the furnace casing due to its placement and caused by sweating and dripping condensation?
3. Could this filter be a replacement from a previous defective filter and the corrosion caused from a refrigerant leak, now resolved? Either way, any original install would still apply to Question 1
.
Your observations are appreciated. The defect was one of several issues. A full service and repairs were recommended.

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That is common practice along the coast for condo buildings with the condenser units on the roof as it keeps the drier from rusting out from the salt spray ... doesn't stop the condenser unit from rusting out ...

Otherwise, I've usually seen them at the condenser unit like you.

Originally Posted by Ian Page

Gentlemen (and Ladies, of course)

Typically - and I understand both best practice and manuf. recommendations, drier filters are installed as close as possible to the compressor. As can be seen, this one is as far away as it could be, save for a few more inches. The drier shown is for the compressor on the left, at least 60' away.

1. Does the placement make a significant difference and why? (I have never seen one installed anywhere else other than at the compressor)
2. Is the corrosion shown on the furnace casing due to its placement and caused by sweating and dripping condensation?
3. Could this filter be a replacement from a previous defective filter and the corrosion caused from a refrigerant leak, now resolved? Either way, any original install would still apply to Question 1
.
Your observations are appreciated. The defect was one of several issues. A full service and repairs were recommended.

Actually that filter is closer than normal to the compressor... that is in the liquid line that flows refrigerant away from the outdoor unit to the indoor coil.
Contrary to common practice but I can think of no reason why it should be a problem.
The filter/dryer does not sweat and cause condensation unless it is severely clogged (which would prevent the unit from cooling properly.) So, no it would not cause rusting on the furnace.

Originally Posted by Jim Luttrall

Actually that filter is closer than normal to the compressor...

Jim,

I am confused ... the drier is shown at the air handler, not the condenser unit, which would not make it close to the compressor ...

Originally Posted by Jerry Peck

Jim,

I am confused ... the drier is shown at the air handler, not the condenser unit, which would not make it close to the compressor ...

Think refrigerant flow... one installed at the condenser is the furthest point from a path of flow possible for a liquid line dryer. Yes it is physically closer when installed at the condenser but it is actually further away when looking at refrigerant path.

Also, don't forget on some systems there will be both a suction line filter/dryer as well as liquid line filter/dryer. This is typically seen only when there is a bad compressor burnout.

Originally Posted by Jim Luttrall

Think refrigerant flow... one installed at the condenser is the furthest point from a path of flow possible for a liquid line dryer. Yes it is physically closer when installed at the condenser but it is actually further away when looking at refrigerant path.

Also, don't forget on some systems there will be both a suction line filter/dryer as well as liquid line filter/dryer. This is typically seen only when there is a bad compressor burnout.

Jim
For clarification...The property had two independent A/C systems. Only one drier installed (nothing for the smaller 3 ton compressor and nothing on the suction sides of either).
I'm wondering if the line had leaked, as evidenced by the corrosion, and the drier filter was installed as a line repair and to remove possible contamination - killing two birds etc. It didn't look like any active be leak. Does that sound feasible?

Every diagram, recommendation and previous installs I have seen, place the drier at the compressor. I assume that would be the lowest point for moisture collection?

I see plenty of dryers on AHU's, although not as common as at the condensing unit.

Dom.

Originally Posted by Ian Page

Jim
For clarification...The property had two independent A/C systems. Only one drier installed (nothing for the smaller 3 ton compressor and nothing on the suction sides of either).
I'm wondering if the line had leaked, as evidenced by the corrosion, and the drier filter was installed as a line repair and to remove possible contamination - killing two birds etc. It didn't look like any active be leak. Does that sound feasible?

Every diagram, recommendation and previous installs I have seen, place the drier at the compressor. I assume that would be the lowest point for moisture collection?

I think your corrosion is coming from the lack of air seal and insulation at the suction line, and has nothing to do with the liquid line at all. The drier placement is always just a personal choice of the installer.

Lowest point is all relative and has nothing to do with the function of the filter/drier. The drying action is a chemical attraction to moisture vapor, it is a chemical desiccant that dries the moisture as if flows through.

I am confused but that may be nothing new.
There appears to be more here than meets the eye.

For one, I thought the desiccant, moisture filter, works better at "removing and holding moisture" when it is placed in a refrigerant line?
Where the refrigerant is in the liquid state and close to compressor?

Here is the image enlarged.
enlarged filter.jpg


1: I see an insulated line on the opposite side of the desiccant container, moisture filter.
2: If you look at the image I have enlarged the corrosion is upstream and above the piping and filter.
3: The top of the container is tarnished as well.
Could the source of liquid be from above the pan and filter?

Robert
The 'tarnishing' you describe is actually rodent tracking. Tracks are also seen on the edge of the casing and on the light colored cabinet to the right. It might seem logical, therefore, that the corrosion could be from rat urine but unlike other areas, no feces underneath the drier. Not to say they couldn't just use the area as a urinal but not likely.

My first thought was something overhead was dripping but nothing above except unstained trusses and decking.

Ian, much thanks for the clarification.
I am with Jim on this.