Burnout Clean-Up

Question:

From William Benzenhafer Niceville, FL

What is the best agent to use to clean up a residential air-conditioning system after a compressor burnout? Requirements must be that the agent is cost-effective, safe for the system, environmentally safe, and non-hazardous to people.

Answer:

By Dallas Rohrer Aftermarket Specialties Keenesaw, GA

The best and perhaps the only agent is CF-20. It is cost effective, safe for the system, and may be purchased at most ac/r wholesalers throughout the United States and Canada.



Settling Superheat

Question:

From Brian Feather Scottsbluff, NE

I have trouble setting superheat on non-TXV systems in early spring. I use a required superheat calculator with ambient drybulb of 60% to 65% and an indoor wetbulb at the eye of the blower of 52% to 54%. But I can’t get the vapor pressure above 61 psig to set the superheat by the calculator.

Does the indoor DB need to be above a certain temperature also? Is the calculator temperature too low for this climate? Does sizing the indoor coil 1/2-ton larger for more efficiency effect this? Does the heat exchanger condenser effect this?

These are new installations, so coils, blowers, and filters are clean. The indoor flow restrictor is sized for the condenser. When indoor load conditions are higher and outdoor temperatures are higher, the superheat calculator works great.

Answer:

By Daniel Kramer, P.E. Patent Attorney, former chief engineer for Kramer-Trenton

You state that in early spring you can’t get the suction pressure above 61 psig (R-22) to set the superheat by the Carrier chart.

Does the air drybulb temperature affect this problem? Nominally, the sole driving force affecting the capacity of a dehumidifying coil is the wetbulb temperature. That’s because the theory says the capacity of a dehumidifying coil in enthalpy-driven and wetbulb temperature is the sole variable affecting air enthalpy. Therefore, the drybulb temperature should not affect the suction pressure. However, as a practical matter, warmer air (higher drybulb temperature) can carry more moisture and therefore more easily exhibit higher wetbulb temperatures.

Is the calculator temperature too low for your climate? The calculator settings are restricted by the freezing point of water. The chart does not show a pressure lower than 60 psig because 60 psig (R-22) corresponds to 34°F. If your suction pressure were even 2.5 psi lower, say 57.5 psig, you would be freezing at the coil.

Your Carrier superheat calculator was intended to provide you with the means to correctly and fully charge a capillary or restrictor-type (non-TXV) system under non-ideal conditions.

The calculator has two adjustable windows. The first provides a sliding chart that allows you to measure and input the observed wetbulb air temperature at the evaporator inlet and the drybulb temperature at the condenser air inlet. With these inputs, the slide chart indicates the correct suction superheat to which you should charge under your observed non-ideal conditions that will provide substantially correct operating conditions at design temperatures.

The second window appears to lock you into only one combination of suction pressure and suction line (the chart calls it “vapor line”) temperature to secure the desired superheat.

However, by sliding the chart up and down you can see that at any suction pressure you select within the chart range, the chart will show the suction vapor temperature you must have for the desired superheat.

Would sizing the indoor coil larger for efficiency cause your problem? No, an oversized evaporator would help in getting the suction pressure up.

If you were short of evaporator capacity, low suction line temperature and low suction superheat should accompany your low suction pressure. You would have to increase the fan speed, clean the filter, etc. However, since you have an oversized evaporator, this is unlikely.

If, on the other hand, your low suction pressure is accompanied by suction line temperature approaching the entering air drybulb temperature (high superheat), then you have any of the following three problems:

  • The orifice is too small. Pick the next larger size. A high-efficiency condenser could make it necessary for you to use the next larger size orifice.

  • You haven’t charged enough refrigerant into the system. Add some while watching the condenser subcooling (not over about 15°F).

  • If you are adding refrigerant in an effort to get the suction pressure up or to reduce the evaporator superheat and the only change you see is the head pressure going up while the liquid line gets cooler, then you have a restricted or undersized orifice.

    • The superheat slide chart appears to make everything simple. In most cases it does. But in those other cases you must understand the logic of both the chart and of the manufacturer who designed the chart. The chart is to guide you in securing a satisfactory result for your customer and to avoid nuisance callbacks that are harmful to the bottom line and your reputation.



    Refrigerant Regulations

    Question:

    From Phil Senner SennFab Industries

    Is there someplace on the web where EPA refrigerant regulations reside? Regulations seem to be ever changing. Many companies have financial interests in promoting scare tactics used in selling refrigerant usage tracking systems and software.

    Where can we get the real truth about the actual requirement? Is there information regarding actual cases of EPA enforcement?

    Our company works on no systems with more than 50 lbs. of refrigerant charge. What actual regulation states that we must track leak rates and refrigerant usage for these types of systems?

    Answer:

    By Jerry Kestenbaum Refron, Inc. Long Island City, NY

    You can find everything you want to know about ozone depletion and EPA regulations by going to the EPA’s Ozone Depletion Home Page atwww. epa.gov/docs/ozone.

    In addition to finding out about laws, regulations, and approved substitutes for ozone depleting substances, you can also find copies of easy-to-understand “fact sheets” issues by the EPA on various topics including leak repair requirements and record keeping. Fact sheets can be obtained from www.epa.gov/docs/ ozone/title6/608/608.html.

    On the home page, you can also click on “enforcement actions” for a listing of more than 50 separate enforcement actions taken by the EPA.

    All of the above information can also be obtained from the EPA Stratospheric Ozone Hotline by dialing toll free 800-296-1196.

    Specifically in answer to your leak repair question, there are currently no regulations that require tracking of leak rates and refrigerant usage for systems that contain less than 50 lb of refrigerant charge.