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High head pressure ac unit

Have a Liebert unit for a data center that is tripping on high head. Coils are clean. Suction and Liquid readings are good, and it will run until we hit cold weather (Logs show it usually happens on a cold night) ... Tested electrical and everything is good there as well. Thinking it may be a problem masking an even bigger problem...

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  • 151 Answers

Two things come to mind, either it's icing and liquid coolant is causing spikes when it reaches the hot compressor, which would point to low gas or the need of a pre-heater. The second would be icing allowing the oil to get overcooled and it starts to gel at the head, same solution for both.
A more distant third would be moisture in the system, the trap could need replacing if it's been serviced a decent amount.

Posted on Apr 01, 2014

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Posted on Jan 02, 2017

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SOURCE: My central ac system occasionally

I have seen this is many digital thermostats. The worst problems usually come from the touchscreen thermostats. I would suggest installing a new thermostat. Make sure that you read the instructions before you even remove the old one.

Posted on Jul 03, 2008

  • 127 Answers

SOURCE: AC roof unit stops cooling after rain

No, the units are sealed and the rain should not have affected the system at all. I would remove the outer cover of the unit and access the capacitors. Your start capacitor may be bad. You can visually inspect this and tell if there is a problem. Small black relay on top of capacitor often burns out, if so, replace capacitor and relay. If this looks fine, then we need to start at the thermostat and work our way forward.

Thanks,

Jeff

Posted on Jul 05, 2009

t1m130
  • 86 Answers

SOURCE: unit tripping on high head pressure but has bad pump down selenoi

high head pressure can be a result of a dirty coil have you tried flushing the coil?

Posted on Jul 09, 2009

thompsonds20
  • 53 Answers

SOURCE: AC not cooling during the day

Your AC cooling efficiency is low when he ambient temperature is high and naturally it cools well when the outside temperature drops.

Please remove the filter on the grill and try to clean it under the tap water and after removing all the dust fix it back to the unit. This would increase the cooling efficiency of the unit.

Your AC is also five years old. Please avoid frequent opening of doors or windows.

Ensure that the exhaust fan and the blower of your unit are functioning normal.

The technician might not have done a proper job in fixing the area where the refrigerant would have leaked out. Please check the refrigerant pressure to ensure that no further refrigerant leak has taken place. Or even servicing your unit he would have punchered the tubes resulting in very slow leak of refrigerant resulting in no cooling or less cooling. It takes around a month to feel the pinch of it and the refrigerant. One fine morning after sometime the unit will run and it would start throwing hot air instead of cool breeze!

Posted on Jul 13, 2009

  • 901 Answers

SOURCE: It runs cold briefly for about 4 to 5 minutes then

Check the compressor capacitor. It would have gone weak. Replace with the identical value and type.

Posted on May 27, 2010

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2 Answers

How do you put in 410a into Ac unit


You turn system on to cool setting and run temp down until outside unit comes on. Then you connect your suction side of your gauges to the suction side of your outdoor unit. Next you connect the liquid(high)side of your gauges to the liquid line on your outside unit(the little copper line). Connect the middle hose of your gauges to the 410a drum of refrigerant. Before opening the suction or low pressure side of the gauges you need to turn the drum upside down and turn drum of 410a on. Then you need a temp reading meter and clamp to read the temp of your liquid line(small line). While charging you want to make sure to release refrigerant slowly. The unit should call for a specified subcooling on unit plate. 7 to 10 degrees. You take the liquid line temp and subtract it from saturation temp on the high side of your gauges.(it'll be the pink numbers on the right side of your gauge.

Jun 05, 2013 | Heating & Cooling

Tip

Charging an air conditioner by superheat or subcooling


Charging AC by superheat and subcool
First charging a unit by superheat, this is only for Acs with an orifice or capillary tube.
Optimum superheat is 12° to 15° at the compressor or suction line outside the unit.
Hook up your gages and put a thermometer on suction line (large line), start the AC. Measure the temperature of the suction line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant, (you can also use a temperature pressure chart), now read the thermometer, let’s say the suction temperature( the thermometer) is 67° and the saturation temperature (the gages or temp. press. Chart), is 55°, subtract the saturation temperature from the suction temperature, 67°- 55° = 12° superheat.
Charging by Subcooling, this is for Acs with a thermostatic expansion valve, it’s common to see a sight glass on the liquid line (on these units with a sight glass just clear it, when, indoor room is at approximate set point of the thermostat). If there is no sight glass then the Optimum sub cooling is 12° to 15° at the outdoor unit.
Hook up your gages and put a thermometer on liquid line (small line), start the AC. Measure the temperature of the liquid line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant,(you can also use a temperature pressure chart), now read the thermometer, let’s say the liquid temperature( the thermometer) is 100° and the saturation temperature (the gages or temp. press. Chart), is 114°, subtract the liquid temperature from the saturation temperature, 114°- 100° = 14° subcool.

This is also the only way to know if your a/c has the proper charge.

on Dec 28, 2009 | Heating & Cooling

1 Answer

Heat pump with High head pressure


HFC-134a ? Critical pressure is 588.9 a . With a 93 LL temp and 575 head, I would suspect 1. Air in system or 2. Ref. has gone critical.
With a 110 psig suction/85 deg.F and a LL temp of 93 deg.F/125 psig

Jan 13, 2013 | Ruud Heating & Cooling

1 Answer

How to refill gas in home spli a/c, advise presure details as wel


Charging AC by superheat and subcool
First charging a unit by superheat, this is only for Acs with an orifice or capillary tube.
Optimum superheat is 12° to 15° at the compressor or suction line outside the unit.
Hook up your gages and put a thermometer on suction line (large line), start the AC. Measure the temperature of the suction line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant, (you can also use a temperature pressure chart), now read the thermometer, let’s say the suction temperature( the thermometer) is 67° and the saturation temperature (the gages or temp. press. Chart), is 55°, subtract the saturation temperature from the suction temperature, 67°- 55° = 12° superheat.
Charging by Subcooling, this is for Acs with a thermostatic expansion valve, it’s common to see a sight glass on the liquid line (on these units with a sight glass just clear it, when, indoor room is at approximate set point of the thermostat). Optimum sub cooling is 12° to 15° at the outdoor unit.
Hook up your gages and put a thermometer on liquid line (small line), start the AC. Measure the temperature of the liquid line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant,(you can also use a temperature pressure chart), now read the thermometer, let’s say the liquid temperature( the thermometer) is 100° and the saturation temperature (the gages or temp. press. Chart), is 114°, subtract the liquid temperature from the saturation temperature, 114°- 100° = 14° subcool.

Mar 19, 2010 | Panasonic CW-1006FU Air Conditioner

1 Answer

Gas pressure


It depends on the indoor and outdoor temperature and humidity. The low side pressure can be in the area of 135# to 145# with an indoor temperature of 80° and 50% relative humidity, and the outdoor pressure can be in the area of 300# to 330# on a 95° day depending on effeciency rating.
If your asking this to charge your a/c this is not how to charge your a/c.
Charging AC by superheat and subcool
First charging a unit by superheat, this is only for Acs with an orifice or capillary tube.
Optimum superheat is 12° to 15° at the compressor or suction line outside the unit.
Hook up your gages and put a thermometer on suction line (large line), start the AC. Measure the temperature of the suction line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant, (you can also use a temperature pressure chart), now read the thermometer, let’s say the suction temperature( the thermometer) is 67° and the saturation temperature (the gages or temp. press. Chart), is 55°, subtract the saturation temperature from the suction temperature, 67°- 55° = 12° superheat.
Charging by Subcooling, this is for Acs with a thermostatic expansion valve, it’s common to see a sight glass on the liquid line (on these units with a sight glass just clear it, when, indoor room is at approximate set point of the thermostat). Optimum sub cooling is 12° to 15° at the outdoor unit.
Hook up your gages and put a thermometer on liquid line (small line), start the AC. Measure the temperature of the liquid line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant,(you can also use a temperature pressure chart), now read the thermometer, let’s say the liquid temperature( the thermometer) is 100° and the saturation temperature (the gages or temp. press. Chart), is 114°, subtract the liquid temperature from the saturation temperature, 114°- 100° = 14° subcool.

Dec 25, 2009 | Heating & Cooling

1 Answer

When i was fixed a problem in central ac trane i found decreased in freon r22 and the suctione line was freezed, i charged the ac with froen gas r 22 then i found that the suctione line changed and begin...


You are still low on freon. Charging AC by superheat and subcool
First charging a unit by superheat, this is only for Acs with an orifice or capillary tube.
Optimum superheat is 12° to 15° at the compressor or suction line outside the unit.
Hook up your gages and put a thermometer on suction line (large line), start the AC. Measure the temperature of the suction line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant, (you can also use a temperature pressure chart), now read the thermometer, let’s say the suction temperature( the thermometer) is 67° and the saturation temperature (the gages or temp. press. Chart), is 55°, subtract the saturation temperature from the suction temperature, 67°- 55° = 12° superheat.
Charging by Subcooling, this is for Acs with a thermostatic expansion valve, it’s common to see a sight glass on the liquid line (on these units with a sight glass just clear it, when, indoor room is at approximate set point of the thermostat). Optimum sub cooling is 12° to 15° at the outdoor unit.
Hook up your gages and put a thermometer on liquid line (small line), start the AC. Measure the temperature of the liquid line and read the pressure on your gages. Theres a temperature scale on your gages for R-22 or R-410A the needle will show you the pressure on the outer scale and if you follow it down to the R-22 or R-410a inner scale that is the saturation temperature for that refrigerant,(you can also use a temperature pressure chart), now read the thermometer, let’s say the liquid temperature( the thermometer) is 100° and the saturation temperature (the gages or temp. press. Chart), is 114°, subtract the liquid temperature from the saturation temperature, 114°- 100° = 14° subcool.

Oct 05, 2009 | Heating & Cooling

1 Answer

Have goodman unit, ac unit running 55 suction, 210 high side. cleaned condenser coils and charge to 10 degrees supercool. suction at 65, discharge 245, why did my discharge go so high


You should have liquid line filter/dryer that maybe restricted or there is a restriction in the orfice inside the evap coil normal operating pressures are 68/ 180

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1 Answer

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Jul 29, 2008 | Heating & Cooling

1 Answer

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It sounds like the head pressure is to high. This is sometimes do to overcharging. The hissing noise that you hear is the liquid refrigerant dumping into the suction side. This is what a compressor does when the Head pressure is way too high. The fact that it is tripping the breaker may be to a broken suction valve in the compressor. I think it might be time for a new unit.

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1 Answer

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