Liquid Line Driers

Do the liquid line driers for the new Puron® R-410A (AZ-20) systems have the same desiccants as the ¿freon¿ driers? My understanding is that the only difference is the shell is rated for the higher pressures. Am I wrong? I was told not to use freon driers on a Puron system at the Puron training. What¿s the difference between the two? Answer: By Carrier Corp. Syracuse, NY

You are correct in not using freon driers on a Puron system. The current filter-drier (Parker Hannifin) is the only drier we approve because it meets our moisture-capturing requirements. This filter would be ¿backwards-compatible¿ with other refrigerants.

In the past, the freon or mineral oil refrigerants used an activated alumina as the filtering media. The new filter-drier manufacturers have pretty much gone to a molecular sieve that absorbs many times more water than the activated alumina. This is very important when dealing with any polyolester (POE) oil.

There were also concerns that the alumina would react to the higher pressures and POE oils by breaking down and creating an acidic oil. Most manufacturers have also raised or tested their burst strengths (3,000 psi) to handle the Puron R-410A refrigerant. Use of unapproved filter-driers on the Puron systems could potentially harm the system.

Vent Residue

I have noticed over the years that ceiling grilles, and especially the ceiling immediately around the discharge area of the grilles, many times collect a dirty, streaking residue. It will be noticed even on new installations that although the duct and grille are apparently clean, the ceiling keeps getting dirty. The customers always blame the filters and say they aren¿t getting changed often enough. If normal service and filter changing is being performed, what is causing this situation? This is usually found in commercial applications, but it is also observed in residential. Answer: By Jack Bartells York International Baltimore, MD

Discoloration around supply diffusers has always been a problem. Even though your question states you perform regular maintenance, including filter changes for your commercial customers, you have to take into account the efficiency rating of the filter you¿re using.

As an example, most standard 2-in. fiber glass filters used in commercial applications have an efficiency rating of about 20%. Of course, that number goes up or down slightly depending on the filter manufacturer, air velocity, cfm, and the size of the particulate you¿re attempting to filter. However, for purposes of this discussion, 20% is a good estimate.

Assuming the filter is removing 20% of the contaminants, that leaves 80% of all contaminants to pass through the filter and be carried through the duct system. It also stands to reason that the area around the diffuser is the first place this so-called ¿filtered¿ air comes into contact with. The amount of discoloration will vary based on the quality of the air being diffused.

As you know, indoor air quality is an issue being increasingly scrutinized, not only by our industry, but by regulating agencies as well. For instance, the quality of air in urban areas with high concentrations of smog will be lower than the air in rural areas with little traffic or industry.

The simplest way you can reduce the amount of discoloration would be to increase the efficiency rating of the filters you use. However, you can¿t overlook the negative side of using high-efficiency filters. The most obvious downside is the higher initial cost of the filter itself. Also, these filters have a much greater pressure drop that may reduce the cfm in your system. This could lead to reduced comfort for the building occupants and shorter equipment life tied to high temperature rise in heating or low temperature rise in cooling.

Before making a change in your filter type, make sure you discuss these issues with the equipment owners, to ensure they fully understand their options.