Moisture Detection

By Loy Lobo
Via E-mail

Is there a device that will detect moisture in a refrigeration system, which would act as a relay to trip off the system if the moisture level rose above a specific set value?

As refrigeration systems get older, the heat exchangers are prone to leak in the tubes or at tube sheets, especially when the water quality is not maintained. In this scenario, if a device was installed to detect this moisture, it could trip off the system, thus raising an alarm indicating that the system needs to be checked, which would save further damage to the system.

From Dan Kramer, P.E.
Specialist Grade Member of RSES

There is a panel-mount dewpoint monitor/alarm by Mitchell Instruments. I would note that the sensor is aluminum oxide and could have a short life span in a wet environment with CFC, HCFC, or HFC refrigerants, which would hydrolyze to strong acids. If you want more help, call Mitchell Instruments at 888-270-2690.

Superheat Settings

From Bill Blackwell
Diboll, Texas

I have a couple of questions about superheat settings on thermostatic expansion valves and subcooling in condensers. I can't seem to find out if the superheat setting on the valve is the same for a residential unit (8 degrees to 12 degrees F) and a walk-in freezer. I recently had to work on a reach-in unit and the valve superheat was about 18 degrees. The heat load wasn't high and airflow was good. The system pressures were OK.

Does the superheat setting for a valve change when you go from residential to commercial cooling? What about from commercial to refrigeration and from refrigeration to ice machines? Or does 8 degrees to 12 degrees apply to all of these applications?

My subcooling question is similar. Does the 5 degrees to 15 degrees subcooling for residential applications apply to commercial refrigeration and ice machine condensing units? Are these ranges (8 degrees to 12 degrees, and 5 degrees to 15 degrees) die-hard rules, or can you be plus or minus 3 degrees to 4 degrees?

By Don McClanahan
Technical Engineer
Emerson Flow Controls
St. Louis

The proper superheat would change based on the particular evaporator temperature. Take a look at the following examples:

Air conditioning at 40 degrees should be 10 degrees superheat.

Refrigeration at 35 degrees should be 8 degrees superheat.

Freezer at 0 degrees should be 4 degrees superheat.

Blower Motor

By Richard Hawkins
Via E-mail

A while ago I had a flood in my basement. I had it cleaned up, but now my blower motor is not working. It does put out heat, but not enough. The furnace does turn on, but also shuts off after a minute or two. It does put out heat upstairs, but not downstairs.

From Dave Anderlik

It is not unusual for a furnace blower motor to fail due to a flooded basement. With a failed blower motor, you are seeing your furnace cycling on the high-limit control. This control is to prevent damage to your furnace from overheating and protect your property. The furnace blower motor needs to be replaced as soon as possible and the furnace should not be used until it is replaced. The reason you are getting some heat upstairs is because hot air is less dense (lighter), which causes it to rise.

I strongly encourage you not to use the furnace until the proper repair is made.

‘Dirty Sock' Syndrome

From John Moorefield
Via E-Mail

I am looking for more information regarding the UVC solutions for the dreaded "Dirty Sock Syndrome." Specifically, how much does this cost? Can our local service dealer install the unit? How long does the UVC solution last?

By Dan Kramer P.E.
Specialist Grade Member of RSES

Dirty Sock Syndrome is a disgusting occurrence when it affects air conditioners. It is caused by the growth of molds on and around the evaporator. It frequently arises when the drain pan is badly pitched or when organic matter accumulates on or near the evaporator, sometimes because the air filter has been (temporarily?) removed to improve the cooling effect.

The way to cope with this syndrome is to get at both sides of the evaporator and the drain pan and drain. I would spray the entire surface with a cleaner/oxidizer such as Clorox's "Cleanup" cleanser with bleach.

I wear a nose mask and goggles when using this stuff. It's fierce. Then I would wash everything down with a bristle brush and a detergent (like dishwasher detergent) to be sure that all of the solid remnants of the mold and the dirt on which it has been growing have been removed. Then I would rinse everything thoroughly since some of these chemicals may attack aluminum and/or copper over periods of time. If there is any sign that water has been collecting in the drain pan, the pan pitch must be corrected and the drain cleaned and enlarged, if necessary.

While I agree that UV may prevent further occurrences, I would not try to correct an existing situation using UV only. I believe that manual cleaning is the only sure fix, maybe then followed by UV lamps.

Another option to consider is replacing the evaporator with a new one.

Do-It-Yourself Installation

Name Withheld by Request

What does the law state about the do-it-yourselfer market and the installation of residential split systems? To be more specific: If a contractor sells an A coil, line set, and a condensing unit to a homeowner who wants to install his/her own central air system in his/her own home, is the contractor in violation of any EPA refrigerant-handling laws? Is the homeowner required to have EPA-approved certification for refrigerant handling or transportation?

From Julius Banks
US EPA Global Programs Division
Stratospheric Protection Implementation Branch

EPA regulations are not specific to the DIY market but apply to any person who maintains, services, repairs, or disposes of any refrigeration or air conditioning equipment containing an ODS refrigerant, as well as those who purchase or sell an ODS refrigerant. This holds for the sale and installation of split systems.

The refrigerant sales restriction discussed in great detail at does not include the sale of split systems containing an ODS refrigerant. However, the installation of such systems is restricted to technicians certified under Section 608 of the Clean Air Act. So, a homeowner would not be able to legally install such a system unless the homeowner was properly certified.

Wholesalers (or in this case the contractor) may sell different components of precharged split systems at different times to uncertified individuals as long as the contractor has reason to believe that these will be assembled into new split systems. This does not sound like the case in the scenario outlined. It appears that the contractor has knowledge or reason to believe that a certified technician will not install the system.

I encourage readers to visit our Web page for information concerning EPA refrigerant regulations at

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Publication date: 07/05/2004