Tag: filter drier

Courtesy of Emerson

It is important to have refrigerant that is free from debris and contaminants and we control these issues on many different fronts.

  1. Proper tubing handling preventing copper shavings, dirt and water from entering while installing
  2. Flowing nitrogen while brazing to prevent carbon build up
  3. Deep vacuum of 500 microns or less to remove air, nitrogen and moisture
  4. Installation of a liquid line filter drier to keep contaminants from hitting the metering device

But in all of this we can forget the role that suction driers can play in protecting the compressor and the compressor oil.

In air conditioning, we rarely install suction driers unless there is known acid contamination such as in the case of a compressor burnout. Interestingly Copeland actually recommends suction driers in ALL applications in bulletin AE24-1105 R5 .  While I certainly don’t think that we need to change our practices and begin installing suction line filter driers on every single installation, it does get you thinking about the role a suction drier can play in protecting a compressor.

In a typical burnout application where acid is present, it is a good practice to –

  • Remove / Flush as much contaminated oil from the system as possible considering the application including any oil traps, separators or accumulators
  • Install a high capacity acid removal suction and liquid drier or removable core(s)
  • Some contractors will add acid neutralizers such as Acid Away in certain applications
  • Return after running the system for a while and test for acid and replace high capacity filter/driers with new ones if required
  • Once acid is no longer present, return and remove the suction filter/drier and install a standard liquid line drier or core

These practices above are good, general practices to follow, but you may consider replacing the suction drier with a standard, high capacity, low-pressure drop suction drier with two pressure ports instead of just straight piping it. This will provide you an extra layer of protection for the compressor should any acid or contaminants from the burnout make their way to the compressor.

Table Courtesy of Emerson

If you do choose to LEAVE a suction drier in a system there are a few things to consider.

  • Just like with a liquid line filter drier, make sure to install a suction filter/drier that is large enough for the system capacity. Read the info on the drier or the manufacturer’s data to make sure it is large enough so you don’t start off with a restriction
  • Make sure you don’t burn the paint on the drier when installing. Because suction driers on air conditioning will often be exposed to the elements you want to make sure the paint is intact so they don’t rust.
  • Use a suction filter/drier with ports on both sides and measure the pressure drop whenever you service the unit. make sure the pressure drop does not exceed the levels shown in the chart above.

All in all, having a suction drier in the system is a good thing, so long as it isn’t contaminated, rusty or restricted.

— Bryan

P.S. – Sporlan has a great catalog of filter/driers HERE

Diagram above by Carrier 

It’s really easy to put a liquid line drier in the proper location, it’s still more common that it gets installed in the WRONG location , namely, right at the condensing unit (OK it isn’t that big of a deal but for dramatic emphasis). Installing at the indoor coil is good practice for two main reasons.

#1 – It better protects the metering device (expansion valve or piston) from anything that may be in the liquid between the outside and the inside

No matter what, when you first put a unit in Service, you are either releasing the charge on the liquid line first or adding pressure in the liquid line. This means if anything is in the liquid line it is going to hit the indoor metering device first and putting the drier inside better protects the valve.

#2 – It won’t turn into a rusty mess and start leaking after a few years

This is pretty simple, so to make this tech tip a bit more in depth here are some other drier best practices.

  • Don’t “sweat” out an old drier. When you heat an old drier the moisture it has previously absorbed is driven out of the drier and back into the system. Cut it out instead.
  • Use the right type and size. Different driers have different purposes and vary in capacity. If you have a heat pump make sure to use a “bi-flow” drier. If you are mitigating a burnout ensure you are using a burnout suction drier. Make sure the capacity of the direr matches the capacity of the system, this will take a bit of reading. However for residential systems you can use 8 cu/in on small tonnage systems only. To be safe I would generally stick with 16 cu/in liquid line driers (chart by Parker / Sporlan)

  • Don’t burn the paint on a drier when installing. Not only will it look ugly, it will be more prone to corrosion. Use a damp cloth or other heat control methods.
  • Point the arrow in the correct direction. Suction driers point towards the compressor and away from the evaporator. Liquid line driers point toward the metering device and away from the condenser.
  • A liquid line drier goe in the liquid line NOT in the discharge line. The discharge line is between the compressor and the condenser. The liquid line is between the condenser and the metering device.
  • Flow nitrogen while brazing and pull a proper vacuum. Both of these practices are more important than whether a drier is inside or outside.
  • Remove all old line driers and install a new line drier whenever the system has been open and exposed to the atmosphere. Sometimes the old ones were in the wrong place, if so, go ahead and straight pipe them and install your new filter / drier in the proper location.

— Bryan

 

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