Cold & Air conditioning 

For some time now, there has been an obligation to carry out regular leak tests on refrigeration systems, air conditioning systems and heat pumps. These leakage tests must be carried out by certified refrigeration and air conditioning specialists and serve to ensure that no environmentally harmful refrigerants escape from the system. In most cases, nitrogen is pumped into the pipes up to a certain pressure and then monitored over a longer period of time (stability of the pressure is checked). This is the indirect measurement method to determine if there are leaks in the system.

A direct measurement method consists of finding actual leaks. To do this, the pipes are also filled with gas and then inspected for leaks using gas detection equipment.

On this page we only explain the indirect measuring method.

 

Procedure

At the beginning of a leak test, they should find out the test pressure prescribed for the system and know it exactly. If you set the pressure too high, this can lead to damage to the pipe system and the system - and if it is set too low again, it is not possible to determine with certainty whether the system is really leakproof.

If the test pressure is known, connect a nitrogen gas cylinder with pressure reducer (or optionally ALbee Cool with integrated pressure reducer) to the system and fill it to the desired test pressure. Now wait a few minutes and observe the pressure display.

Please note that due to temperature fluctuations there may be slight changes in the measurement at the beginning. Nitrogen is a flexible medium that reacts easily to changes. Therefore, wait until the gas has "settled" in the pipes.

 

Have you found a leak?

Any leaks found must be repaired immediately. After the repair, the operator must ensure that a leak test is carried out with oxygen-free nitrogen.

 

How full should a nitrogen gas cylinder be for a leak test?

A lot of pressure is needed for a leak test. Therefore, sometimes opened cylinders with little residual pressure are not sufficient. It is advisable to use opened nitrogen cylinders with little residual content for less pressure-intensive applications, such as rinsing.

 

Applications

refrigeration plants

air conditioners

heat pumps

 
Regular leak tests are required by law

In order to prevent greenhouse effects caused by escaping coolant, regular leakage tests are prescribed by law.

Depending on the weight of the greenhouse gas used in the plant, this test had to be carried out annually, semi-annually or even every quarter until 1 January 2015.

Since 01.01.2015 the legal situation has changed and the frequency of the tests now results from the greenhouse gas potential of the various coolants.

The following table explains how often tests are necessary:

Refrigerant GWP* value annual check from semi-annual check from quarterly check from

R-134a 1430 3,5 kg 34,9 kg 349 kg

R-404A 3922 1.3 kg 12.7 kg 127 kg

R-407C 1774 2,8 kg 28,2 kg 282 kg

R-410A 2088 2.4 kg 23.9 kg 239 kg

 

Definitions:

*GWP value = Global Warming Potential, this value describes the global warming potential of the refrigerant used in relation to CO2. For example, a GWP of 1000 means that 1 kg of the refrigerant used has the same effect as 1,000 kg of CO2.

 

Evacuation (vacuum pulling)

To remove moisture or residual gases from the circuit of an air conditioner or heat pump, it is evacuated before commissioning or after maintenance. A previous or subsequent flushing with nitrogen can additionally ensure that all residual moisture and residual gases are removed.

In addition to removing moisture, evacuation also serves as an alternative leak test to a leak test with nitrogen: In a leak test with dry nitrogen, filling generates an overpressure in the pipeline; the aim is to determine whether gas is leaking and whether the overpressure is maintained. In a leak test by evacuation, a negative pressure is generated; one wants to see whether the negative pressure remains or whether the pressure increases again due to leaks.

No nitrogen is required for a pure leak test by evacuation. However, as a final application after evacuation (or before evacuation), it is worth flushing the system with nitrogen to remove any residual moisture from the system.

If refrigerant is already in the system, it is often sucked out during evacuation and either reintroduced into the system after cleaning or replaced by new refrigerant.

If this is not done, the system can be replaced after a short time.

 

Proceedings

Connect a vacuum pump to the line to be evacuated and switch it on. As soon as a vacuum of approx. -1 bar is reached (may vary depending on the system), wait a few minutes and observe the pressure display. If the pressure is constant, let the vacuum pump run a little longer for dehumidification, unless the line was previously pressed with nitrogen. In this case it is not absolutely necessary.

 

Applications

refrigeration plants

air conditioners

heat pumps

 

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