404a high pressure cut out

Liquid line flash gas. Excessive liquid refrigerant returning to the compressor flood back. Defective compressor overload which will cause the lube oil control to time out and shut the system down.

Uses of Refrigeration Low Pressure Controls

The load is too high. Has there been a recent addition to the design load? Product, people, heat producing equipment in the refrigerated or air condition space etc. Poor insulation, doors left open, or defrost heaters running continuously. Faulty low pressure control, temperature control, hot gas bypass valve or capacity control valve. Compressor malfunctioning, possibly leaking valve. Check amp draw verses suction pressure verses condensing temperature using performance chart.

System undersized. Excessive load on the evaporator above the design conditions. Rerun the load calculation. Suction pressure high - High superheat at evaporator outlet. Excessive suction pressure beyond the limits of the compressors ability to start and run. Check the performance charts of the compressor for the maximum suction pressure. Low outside air temperature on an air cooled system. Check the low ambient control.

Excessive suction pressure beyond the limits of the compressors ability to run.

Normal Range of Operating Pressures for 404A?

Re-circulating of condenser air. This is a common occurrence when an oversized outdoor weather hood has been installed. The ambient temperature surrounding the condenser is too warm.At DrywallTalk. Knowing that many homeowners and DIYers are looking for a community to call home, we've created www.

Remember Me? Lost Password? Trade Talk. Make a Forum Post. Add a Blog Entry. Brighten Pools Custom Made Air Start a Project. Submit a Product to Review. Normal Range of Operating Pressures for A?

Send Message. Have not worked with A before and I'd like to know what the normal range of operating pressures would be for a cooler at 34 degrees with an ambient outdoor temp of 80 degrees? Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

What pressure would you expect for RA, R22, or R12 at those same conditions. Convert the pressure for those gasses to saturation temp, and use the same saturation temps on RA systems. You concure? I just punch up the refrigerant I'm working with and it automatically shows the saturation temps. More than that I can attach the included temperature clamps to the lines and get Superheat and Sub-cooling in real time.

I also picked up the wireless remote temp probes and the HG3 so I can get a full system analysis and target Superheat. No more guesswork. I couldn't be more pleased with this setup and customers are impressed with the level of efficiency I can squeeze out of their systems. Im just making sure Im doing this right so that I don't get confused. Originally Posted by Rooster.It works on the principle that there is a direct relationship between the pressure of the saturated refrigerant in the evaporator and its temperature.

A typical low-pressure control has two setpoints: its cut-in and its differential. In order for the control to work properly, both the cut-in and differential setpoints need to be set properly. Most manufacturers have stated values for the proper setpoints for their systems. However, these values usually only work well on self-contained or close-coupled systems. If the condensing unit is remotely located, the stated values may cause problems with the cooler.


Setting The Cut-In On systems where the condensing unit is located a considerable distance away from the evaporator, it is more accurate to first set the cut-in setpoint.

The cut-in setpoint should be set to a pressure temperature that will allow the evaporator to completely defrost during the off cycle. If this frost is not removed and continues to form, it will eventually completely block the airflow through the evaporator coil, causing the unit to malfunction.

The cut-in value needs to be set to a pressure temperature that will not allow the compressor to come on until the coil is completely defrosted. However, that is usually too close for comfort. This will ensure that the coil has been completely defrosted. Setting The Differential Once the cut-in pressure has been set, the differential setting must then be set.

The differential setting is used to cycle the compressor off at the lowest possible box temperature. The differential setting represents the difference between the cut-in pressure and the cut-out pressure.

The exact cut-out pressure needed to correctly cycle off the compressor may be different from unit to unit.

404a high pressure cut out

One of the reasons for this is that the pressure drop from the evaporator to the compressor may be different on each unit. Set the differential pressure to an extremely high value. This is a value the suction pressure should never reach under normal operating conditions. A psig setting should suffice. Allow the system to run while monitoring the box temperature. Once the box reaches its lowest desirable temperature, slowly adjust the differential counter-clockwise until the compressor cycles off.

Using this procedure will ensure that the cut-in and differential settings have been properly set and the system will function as intended. I want to hear from you. Tell me how we can improve. In this issue, we take a comprehensive look at the future of social media, SEO, apps, and more and how they can affect your contracting business. We also look at new home automation and zoning products and trends that will benefit your customers in terms of comfort and convenience.

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404a high pressure cut out

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At this time, we do not carry this unit. We list it on our site because we do sell replacement parts for this unit. Please contact us with any questions: We are away right now. Our Live Chat hours are:.By cycling the compressor in response to the suction low side pressure, box temperature can be controlled. This type of control is most popular in small-refrigerated boxes such as beer coolers. To control box temperature with a low-pressure control, the system must use a thermostatic expansion valve, non-bleed type.

As box temperature decreases, the evaporator temperature decreases, and a lower suction pressure results. There are some advantages to this type of system.

Short cycling, due to door openings, etc. The same is not true for a standard temperature control. Wiring is simplified and installed cost is reduced. Two settings need to be made on the LPC:. This will be the cut-in setting.

The differential is the difference between the cut-in and the cut-out pressures. Usually it is advantageous to keep the compressor on as long as possible for maximum efficiency.

Setting up low pressure contol to control temp

To set the differential, and consequently the cut-out setting, four factors need to be determined:. The TD of the evaporator coil. What all this means is that one picks cut-in and cut-out settings that should result in good temperature control, monitors the system, and then fine-tunes each specific job to achieve the desired results. Figure 1 shows the usual starting set points to set up a LPC for various applications. Figure 1. Our example of a beer cooler could be set up as follows:.

Refrigerant RA. Set the cut-in at 31 psi. Allow 2 - 3 psi for suction line D P. Set the differential at 11 psi. The compressor will now go on at 33 psi and go off at psi suction pressure. See Figure 2. Figure 2.

Depending on how well the system balance was made, that is, matching the evaporator to the compressor capacity at the selected suction temperature, the compressor run time will be long enough to give good efficiency and not short cycle. Fine-tuning the differential setting should produce the desired results.

The settings in Figure 1 are only a beginning reference. Variations in systems will probably require small corrections of the settings. Remember—too close a differential may maintain close temperature control, but cause short cycling, greatly shortening equipment life.

A wide differential will give longer running time, but may cause wide temperature swings. The final chosen differential has to be a compromise.View Full Version : setting LP control on pumpdown system.

G'day all. I was recently having a debate with a co worker on pressure control settings for a low temp walk in freezer with pump down. My argument is that if you set the cut in too high when the solenoid opens it will delay the making of the pressure switch and the unit will not cut in until the room warms enough to raise the suction pressure, therefore unit will be taken out of normal operating temps to deg C His argument is that he has set them this way for 36 years and that the suction pressure will not correspond to what the temp is in the controlled space and that the ambient temp will also raise the suction pressure somewhat.

He also states that if you get a leak that my settings will cause quick short cycling that could damage the compressor. I will get a guage and check this but was interested what other members set their pressure controls on low temp pumpdown. Thanks in advance.

Using a Low-Pressure Control to Maintain Temps

My argument is that if you set the cut in too high when the solenoid opens it will delay the making of the pressure switch and the unit will not cut in until the room warms enough to raise the suction pressure, therefore unit will be taken out of normal operating temps to deg C Thanks in advance.

I agree with you the cut in pressure is in relation to the evap temp. So the pressure temp relationship is constant. I have set systems that run on a LP switch only and they are very efficent. Cheers taz. Hi there, If you are setting the low pressure control for Pump-down then you have to set it low so the evaporator is empty when pump-down is activated.

Short cycling is very common in the water chillers because the water pump is always working and basically water brings load to the evaporator therefore if the low pressure control is set high then you will have short cycling. To avoid all these problems and discussions I suggest the following : Use two Low pressure controls: one for pump-down and the other for safety. Set the pump-down low pressure control very low and the other one higher for compressor safety. Also you have to add a relay in your electrical box to switch the controls, i.

I always use this method and there is no short cycling and also there is always low pressure safety in the system. I hope this helps. Hi Temprite I'd set the Lp switch the same as you. Setting the cut in pressure above the evaporating pressure may cause none starting problems in cold weather. I'd fit a delay timer if rapid cycling was a problem starts an hour depending on the compressor size if memory serves me correctly:. Cheers Jon. I'll go with settings Temprite, you can always install a non-recycling pumpdown control if someone is worried about it.

Temprite, you're right and also for another reason: if your colleague sets them that high, then it will take a long time until the unit will start.

But, in the meantime - while pressures slowly rises - the evaporator will fill completely with liquid refrigerant because this is a very cold spot in comparison with the warm refrigerant under pressure. The compressor will then start with liquid slugging. The same phenomena happens with cold plates. And what your colleague says is of course not true: temperature has allways a relation with pressure for any refrigerant. I agree with you also my Aussie neighbour. Too high a pressure switch cut in, will raise the freezer temp, and we dont want that eh.

Stick to what you are happy with. Thanks to all who replied, much appreciated.

404a high pressure cut out

Peter this is something that I had not thought of Temprite, you're right and also for another reason: if your colleague sets them that high, then it will take a long time until the unit will start.

I generally set the control at 0 and 15 psig. Exception to this would be a chiller which should never be pumped down for fear of freezing. All rights reserved.What should the high and low pressures be for A refrigerant on a freezer? All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply. Hottest Questions. Previously Viewed.

404a high pressure cut out

Unanswered Questions. Home Appliances. Mechanical Engineering. Wiki User I got it ,but the mention pressure of suction discharge at what temprature in centegrade it should be. Related Questions Asked in Thunderstorms and Lightning What should the high and low pressures be for A refrigerant on a walk in cooler?

Asked in Refrigerators What is the property of refrigerant A? No, refrigerants cannot be blended. Asked in Refrigerators What type of refrigerant do you need in a high temp walk in freezer?

Newer freezers compliant to efficiency standards use Ra. However an older unit may only be able to us R which will be completely phased out by Asked in Definitions Define a near-azeotropic refrigerant blend and give two examples? Asked in Science Could ra mix with r? Ra is a substitute for r refrigerant but requires the system to be charged with POE lubricant.

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No ra is not compatible with ra, ra and a use the same lubricates and are compatible but ra use a different lub making them incompatible. Trending Questions.