The ADT valve.
Using R-22 in low-temperature applications does not necessarily yield rave reviews.

It has been tried from time to time over the years. When CFCs like R-502 faced phaseouts in the mid-1980s, HCFC-22 was the first choice for commercial refrigeration. But the high discharge temperature of 22 raised concerns. Those concerns were initially offset by such technology as demand cooling and compound cooling of compressors.

At the same time, refrigerant manufacturers introduced new HFC refrigerants such as 404A and 507, so that 22 would not need to be used.

Yet amidst all this refrigerant roulette, there are those in the industry who contend that 22 can work well in low-temperature applications. They say 22 is less costly than HFCs and can be used with less costly oils than the POEs that have to be used with HFCs.

That information has R-22 low-temp advocates beating the drum for their favorite refrigerant.

One such advocate is Mark Madigan, the owner and operator of Madigan Refrigeration & Energy Systems of Waunakee, WI. His 25-person shop with a dozen techs does a range of refrigeration projects from ice machines to ultra-low-temperature research equipment. The $3.5-million-a-year company has close to 450 customers, including about 60 supermarkets.

Supermarkets have been among the first sectors to try nonCFC refrigerants, including R-22 and the newer HFCs.

Madigan said those discharge temp problems with 22 and uncertainly about aspects of the HFCs caused him to look for another angle.

Madigan theorized that if there was a way to lower discharge temperature aside from demand or compound cooling, 22 could continue to be used for many years into the future.

He then set about inventing his own solution: the automatic discharge temperature (ADT) valve.

System installation.


The ADT valve is designed for semi-hermetic, hermetic, or scroll compressors. It can be used on stationary or mobile refrigeration units, new low-temp R-22 refrigeration systems, and in converting refrigerants in low-temperature refrigeration, where the conversion would result in high compressor discharge temperatures.

Madigan said, “The valve provides the most cost-effective method of replacing R-502 compared to other alternatives, and combined with R-22, it offers the most practical solution available today.”

The problem with high discharge temperature, he said, is that it can lead to oil breakdown and compressor failure.

“With the ADT valve, discharge temperatures are controlled to acceptable levels with no adverse affect on the compressor.”

The valve is designed for new R-22 systems and retrofitting R-502 installations without the need for a compressor changeout. Madigan said the valve “can also be used in applications where long suction lines result in excessively high suction temperatures.”

The valve uses liquid refrigerant to desuperheat the compressor discharge temperatures, which in turn is designed to decrease the compressor discharge temperature.

A sensor monitors the discharge temperature and a controller activates the valve. When it is open, liquid refrigerant subcools the suction line.

Madigan said the valve “is unique in that it uses an adjustable orifice to accommodate different compressor horsepower sizes, and a controller that is fully adjustable to accommodate different load conditions.”

He said the valve has been successfully installed in hundreds of systems since 1997. Besides the retrofit of 502 systems, he said it could be used in new installations and “when new alternate refrigerants have had problems with high discharge temperature.”

He did note that the valve works best with alkylbenzene (AB) oil rather than a mineral oil, as the AB oil is said to better assist in oil return.

The inventor manufactures and ships the products out of Mad Tech LLC in Lodi, WI. He is also establishing a base of supply houses to stock the product.

Madigan plans to continue to use R-22 as long as it is available. Given present phaseout schedules, he said, “Current demand for R-22 is below the 2015 phaseout levels.” That does not even take into account the reclaimed R-22 collected for recycling.

“So by using good inventory management, that could mean going to the year 2020 or even beyond,” said Madigan. “I want to use R-22 until it’s gone. Then I’ll retire.”

For more information, contact Mad Tech at 608-592-7743.

Publication date: 08/06/2001