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#### Samart

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Hi guys,

I have couple of questions.
1)The pressure values listed on this chart are suction pressure or discharge pressure?
2)Is the temperature listed is ambient temperature.

Sam

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#### Samart

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yuri said:
I got the chart but what to understand the following:
1)The pressure values listed on this chart are suction pressure or discharge pressure?
2)Is the temperature listed is ambient temperature.

Sam

#### JJboy

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The temperature is related to the pressure. When the temperature changes the pressure increase or decrease.

#### Samart

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JJboy said:
The temperature is related to the pressure. When the temperature changes the pressure increase or decrease.
Thanks for the reply. I understand that, but not sure if the pressure values listed on the pressure temperature chart are suction pressure values or discharge pressure.

#### Marty S.

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So long as there's a saturated mix of both liquid and gas present it covers everything. Look at your chart and tell me what the R22 temp shows with a suction pressure of 60. Now look at the chart and tell me what it is on a 180 psig liquid line. How about a R22 tank with vapor and liquid in it at a room temp of 70 degrees?

#### Samart

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Marty S. said:
So long as there's a saturated mix of both liquid and gas present it covers everything. Look at your chart and tell me what the R22 temp shows with a suction pressure of 60. Now look at the chart and tell me what it is on a 180 psig liquid line. How about a R22 tank with vapor and liquid in it at a room temp of 70 degrees?
R22 shows 34 F at 60psi and 93F at 180psi. At 70F the pressur is showing around 120psi.
Thanks

#### Samart

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Marty S. said:
So long as there's a saturated mix of both liquid and gas present it covers everything. Look at your chart and tell me what the R22 temp shows with a suction pressure of 60. Now look at the chart and tell me what it is on a 180 psig liquid line. How about a R22 tank with vapor and liquid in it at a room temp of 70 degrees?
I will wait for your response.
Thanks a lot

#### JJboy

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1)The pressure values listed on this chart are suction pressure or discharge pressure?

Compressor does the change low pressure to high pressure. So the temp changes low to high temp..... What is your question?

#### Marty S.

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That's all there is to it,a relationship between pressure and temp for a given refrigerant. You have a system running 60/180. The suction line measures 50 degrees so how much is the refrigerant super heated ? The liquid line measures 80 which means you have what for subcool?

#### Samart

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JJboy said:
1)The pressure values listed on this chart are suction pressure or discharge pressure?

Compressor does the change low pressure to high pressure. So the temp changes low to high temp..... What is your question?
I mean when to compare the pressure values on the PT chart with the actual suction pressure reading on the ac and when to compare with the actual discharge pressure reading

#### Samart

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Marty S. said:
That's all there is to it,a relationship between pressure and temp for a given refrigerant. You have a system running 60/180. The suction line measures 50 degrees so how much is the refrigerant super heated ? The liquid line measures 80 which means you have what for subcool?
I mean when to compare the pressure values on the PT chart with the actual suction pressure reading on the air conditioner and when to compare with the actual discharge pressure reading

#### JJboy

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The difference between the temps that you are ​​measuring with a thermometer and the values ​​of PT chart are due to the SH and SC

#### Samart

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JJboy said:
The difference between the temps that you are ​​measuring with a thermometer and the values ​​of PT chart are due to the SH and SC
Does the temperatures on the PT chart indicate the ambient temperature or the pipe temperature?

#### JJboy

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PT chart indicate the temp of the environment where is the refrigerant. The pipe temperature it's the measured temp

#### Samart

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JJboy said:
PT chart indicate the temp of the environment where is the refrigerant. The pipe temperature it's the measured temp
I think technicians check the suction pressure on the system and compare it with the pressure on the PT chart to see if their actual reading on the system is off and they do the same thing with the discharge pressure. Am I right sir?
I mean for example at 72F ambient/environment temperature the PT chart for R22 shows the pressure as 125 but when the tech actual reading is way below 125, this means that the suction pressure in the system is low. May be there is some restriction in the system. Please correct me if I am wrong. Again, thanks for all ur help.

#### JJboy

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Yes, with these values ​​we can determine if the unit is undercharge, overcharge, with restrictions, contaminated. etc

#### beenthere

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The pressure and temps on the PT charts are saturation pressures and temps. They are not suction or discharge temps or pressure. this is the pressure the refrigerant will exert at X degrees provided that both liquid and vapor are in the container(as said earlier).

The chart is used to determine the amount of subcool or superheat the system is operating at. Not what it should be operating at.

Take a new cylinder of R22, at 32°F it will have 58PSIG in it. At 83°F the same tank with the same amount of refrigerant in it will have a PSIG of 180. The reason is that it is a saturated refrigerant. Meaning that the refrigerant is existing in the cylinder as both liquid and vapor. As the refrigerant warmed up, more of the liquid boiled off to vapor, and the vapor takes up more space then the liquid did, so the pressure increased. But the total mass in the cylinder remained the same.

You may want to read up on "saturation".

#### Samart

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beenthere said:
The pressure and temps on the PT charts are saturation pressures and temps. They are not suction or discharge temps or pressure. this is the pressure the refrigerant will exert at X degrees provided that both liquid and vapor are in the container(as said earlier).

The chart is used to determine the amount of subcool or superheat the system is operating at. Not what it should be operating at.

Take a new cylinder of R22, at 32°F it will have 58PSIG in it. At 83°F the same tank with the same amount of refrigerant in it will have a PSIG of 180. The reason is that it is a saturated refrigerant. Meaning that the refrigerant is existing in the cylinder as both liquid and vapor. As the refrigerant warmed up, more of the liquid boiled off to vapor, and the vapor takes up more space then the liquid did, so the pressure increased. But the total mass in the cylinder remained the same.

You may want to read up on "saturation".
Thanks beenthere for the detailed explanation. One question: when does the ambient temperature used on the PT chart? I mean for an ac system in a room.

#### Hubcap626

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Samart said:
Thanks beenthere for the detailed explanation. One question: when does the ambient temperature used on the PT chart? I mean for an ac system in a room.
Ambient temperature has nothing to do with a PT chart. It has to do with the refrigeration pressure and temperature.

The only real reason I use a PT chart for is when my gauges are on a circuit and it's a refrigerant that my gauges don't give me a temperature for. Say 407c. I get my pressure because that will always be the same on any Gage. I then go to my PT chart and find the corresponding temperature for that pressure under that refrigerant.

You may be talking about a psychometric chart? Where you have dry bulb, wet bulb, enthalpy and other items on the chart.

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