Refrigerant Gas R600a Gas

2 CN.60.E2.02 November 2000

Refrigerant R 600a, or isobutane, is a possible replacement for other refrigerants, which

have high impact on the environment, in domestic refrigerators. It has zero ozone depletion

potential ODP and a neglectible global warming potential GWP. Furthermore it is a sub-

stance which is a part of petrol gases from natural sources. The refrigerant R 600a has

been in use in the past, in refrigerators up to the 40’es, and has now again found a wide use

in do-mestic refrigerators and freezers in Europe, especially in Germany, where more than

90% of refrigerators are manufactured using R 600a as refrigerant. Because of the avail-

ability of isobutane all over the world it has been discussed widely for CFC replacement.

Isobutane R 600a is a possible refrigerant for this application, with good energy efficiency,

but with a very different characteristic in several points, which implies the design to be

made or adopted for this refrigerant. Special care has to be taken to the flammability of

isobutane.

The properties of R 600a differ from other refrigerants commonly used in household appli-

cations, as shown in table 1. This leads to a different design of details in many cases.

R 600a would be charged into an unchanged refrigeration system, charge amount counted

in grams would be much lower. However, if you calculate in cm

3

, you would have to charge

roughly the same liquid volume into the system. This gives charges of approx. 45 % of

R 134a charge or approx. 40 % of R 12 charge in grams, according to the data from table

1, which also corresponds with emperical values. Additionally experience has shown a

higher sensitivity of the systems to charge deviations. Especially undercharging tends to

give higher energy consumption. This means that charging accuracy has to improve, in

cm

3

and even more in grams. On charges of approx. 20 g, which are found on small larder

refrigerators, accuracy has to be within 1 g. Maximum charge according to safety regula-

tions is 150 g for household refrigerators and similar appliances, which corresponds to

approx. 360 g of R 12 or 340 g of R 134a.

Refrigerant R 600a specification is not found in international standards. Some data are en-

closed in a German standard DIN 8960 of 1998, which is an extended version of ISO 916.

The purity of the refrigerant has to be judged from chemical and stability side, for compres-

sor and system lifetime, and from thermodynamic side regarding refrigeration system

behaviour and controllability.

The specification in DIN 8960 is a safe general hydrocarbons refrigerant specification,

adopted from other refrigerants criteria catalogue and covering normal butane, propane

and others. Some points can possibly be accepted a little less narrow for specific refriger-

ants and impurities combinations after extensive evaluation.

For the time being no refrigerant quality according to an official standard is on the market.

The specifications of possible qualities have to be checked with the supplier in details.

Liquified petrol gas LPG for fuel applications or technical grade 95 % purity is normally not

sufficient for hermetic refrigeration. Water, sulfur and reactive compounds contents has to

be on a lower level than guaranteed for those products