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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017
1.7
Checking pressures with pressure
gauge
⇒ “1.7.1 Display on pressure gauges”, page 126
⇒ “1.7.2 Pressure gauges enable the following tesand meas‐
uremenwork”, page 126
1.7.1
Display on pressure gauges
1 - Temperature scale for R1234yf refrigeran(CF CF = CH )
3
2
in °C
lk
2 - Pressure scale in bar overpressure
Note
♦ Pressure is indicated in various units: 1 MPa (Mega-Pascal)
is equal to 10 bar or 145 psi; 1 bar absolute pressure is equal
to 0 bar, which is abouthe same as ambienpressure (at‐
mospheric pressure).
♦ This diagram shows a pressure gauge displaying pressure on
the low pressure side. The display here is shown in bar over‐
pressure (noticeable by “-1” in the display).
In addition to the pressure scale, the pressure gauges can have
one or more temperature scales. The scale values for R1234yf
are assigned according to the vapour pressure table. Because
differenrefrigerants have differenvapour pressures athe same
temperature, each temperature scale is labelled for the respective
refrigerant.
♦ Pressure gauges enable the following testing and measuring
measures
⇒ “1.7.2 Pressure gauges enable the following tesand meas‐
uremenwork”, page 126 .
1.7.2
Pressure gauges enable the following
tesand measuremenwork
Pressure and temperature measuremenin refrigerancircui
♦ The high pressure gauge allows the pressure (and tempera‐
ture) to be measured with the air conditioning system switched
on irrespective of whether this is athe outleof the air condi‐
tioner compressor through the condenser up to the restriction
(restrictor or expansion valve).
♦ The low pressure gauge facilitates measuremenof the pres‐
sure (and temperature) thaspreads evenly from the restric‐
tion (restrictor or expansion valve) through the evaporator up
to the inleof the air conditioner compressor with the air con‐
ditioning system switched on.
Note
The relationship between pressure and temperature shown on
the pressure gauges is valid only where the refrigeranin the cir‐
cuiis liquid or vapour, bunowhen iis gas. In the gaseous state,
the temperature is approx. 10°C to 30°C higher than indicated on
the pressure gauge.
Evidence of refrigeranin a closed container
R1234yf refrigeranis presenin a closed container or refrigeran
circuiif the temperature indicated on the pressure gauge corre‐
126
Rep. gr.87 - Air conditioning system
th
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