pressure charge

[rc_pancha]

Brod,

i have some questions, i presently work here in riyadh ksa. our outside temp is 46-49deg celsius. my question is what is the max low press and high press charge of aircon, we are using york brand, 5tr. r-22

[sedgy]

the gas charge is by weight not by pressure

[RefrigNoob]

As per sedgy. You can't alter the charge to get the unit to operate outside it's design ambient conditions.

Best you can do it try to keep the condenser cool. Simple things like a small roof over the condenser to give it some shade is a simple start to see if the unit operates better.

[Tesla]

I think differant through experience and here it is - rule of thumb for R22 condensing pressure should be 19K to 22K above ambiant temp equivalent pressure (aircooled). And when I worked on units when the amiant went above 44C I could remove 5 - 10% weight of gas to achieve an improved cooling effect, but this gas had to go back in when the temp droped down again.

[Toosh]

Hi RC, i used to work in Dhahran, !st question is the unit sitting on concrete or directly on a roof is so you will have to raise it up. The 2nd thing you will need some sort of sunshade not to close to the condensor air discharge,if you trim the charge you will end up with the compressor over heating, it needs the refrigerant to cool the windings.

Norm

[Gary]

Brod,

i have some questions, i presently work here in riyadh ksa. our outside temp is 46-49deg celsius. my question is what is the max low press and high press charge of aircon, we are using york brand, 5tr. r-22

Are we talking about a TEV or fixed orifice system?

What are the temperatures of the air entering and leaving the evaporator?

What are the temperatures of the air entering and leaving the condenser?

[Gary]

I think differant through experience and here it is - rule of thumb for R22 condensing pressure should be 19K to 22K above ambiant temp equivalent pressure (aircooled). And when I worked on units when the amiant went above 44C I could remove 5 - 10% weight of gas to achieve an improved cooling effect, but this gas had to go back in when the temp droped down again.

I can see where this would reduce the high side pressure, but how would it improve the cooling effect?

[rc_pancha]

ah ok. in maintenance, how can you check the unit if it is ok using gauge manifold

[rc_pancha]

ah ok.tnx. in maintenance, how can you check the unit if it is ok using gauge manifold

[rc_pancha]

As per sedgy. You can't alter the charge to get the unit to operate outside it's design ambient conditions.

Best you can do it try to keep the condenser cool. Simple things like a small roof over the condenser to give it some shade is a simple start to see if the unit operates better.


ah.ok. tnx. how can you check a unit if it is ok using gauge manifold

[mad fridgie]

You got your gauges on "yes"
Discharge should be Tc (pressure temp ratio on gauge) This should be about 10C (15f) above the air entering the cond Evap te should be some what colder than the air entering the evap can not give a number, the pipe leaveing the evap should be cool and warming slightly as it reaches the comp. You NEED to check the comp motor current, it should be less than the FLA rating, but I would suggest in your conditions it would be close.
If Tc is low and moter current is low and the suction is warm going into the comp then you need more refrigerant.
Another good test is :
?
?
?
?
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It is doing the job, if it is leave it alone.

[nike123]

This should be about 10C (15f)

1°F= 5/9°C (temperature interval)
1°C=9/5°F (temperature interval)

How you got this 10°C=15°F?
It should be 10°C=10x9/5=18°F

[mad fridgie]

1°F= 5/9°C (temperature interval)
1°C=9/5°F (temperature interval)

How you got this 10°C=15°F?
It should be 10°C=10x9/5=18°F
Just nice round numbers off the top of my head, :D

[Tesla]

Hi Gary
This is only used when ambiant temps are excessive, it improves the cooling by preventing the unit from tripping out on HP safety and draws less current. This is used durring a heatwave when we get real busy and have to go around putting on band aids till we have time to fix properly. Your right it does't technicly improve the cooling it just keeps it going.

[Gary]

Hi Gary
This is only used when ambiant temps are excessive, it improves the cooling by preventing the unit from tripping out on HP safety and draws less current. This is used durring a heatwave when we get real busy and have to go around putting on band aids till we have time to fix properly. Your right it does't technicly improve the cooling it just keeps it going.


I think differant through experience and here it is - rule of thumb for R22 condensing pressure should be 19K to 22K above ambiant temp equivalent pressure (aircooled). And when I worked on units when the amiant went above 44C I could remove 5 - 10% weight of gas to achieve an improved cooling effect, but this gas had to go back in when the temp droped down again.

I would think that 19K above ambient (19K TD) would be the maximum, and higher efficiency systems would be lower than this.

If this TD is exceeded, I would suspect that the system is overcharged or the evap is oversized for the condensing unit or the evap fan speed is too high.

The fact that the refrigerant would need to be added back in after the hot weather is past seems to indicate that the load is too high (oversized evap and/or excessive evap fan speed).

Assuming all else is working properly, near the end of the cycle the air temp exiting the evap coil should be 11K lower than the air at the thermostat. If it is less than 11K below the stat temp, then there is too much airflow. Reducing this airflow reduces the heat absorbed in the evaporator and therefore reduces the heat the condenser needs to reject, which means lower high side pressure.

[momo]

Reducing the charge of gas is not the best way especially if your day/night temperature swings (as in desert conditions) are great. First wash/blow out the condenser... efficiency at rejecting heat from the system becomes critical in the described conditions when even R22 units start giving up (non condensing or hissing) and dust build up will cause this. Also what is the state of the finning: good, pitted or flakeing to pieces ? Marine exposed areas with dust lead to degradation of heat transfer because the condensers mnay be rotted.

[Gary]

Reducing the charge of gas is not the best way especially if your day/night temperature swings (as in desert conditions) are great. First wash/blow out the condenser... efficiency at rejecting heat from the system becomes critical in the described conditions when even R22 units start giving up (non condensing or hissing) and dust build up will cause this. Also what is the state of the finning: good, pitted or flakeing to pieces ? Marine exposed areas with dust lead to degradation of heat transfer because the condensers mnay be rotted.

I agree with all of the above. Good advice.