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Normal operating pressures

I have a victory 2 door freezer. r-404a freon, cap tube system.
what is normal pressures

thanx steve

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Re: normal operating pressures

Normal operating pressures will change as the freezer reaches the selected temperatures on the inside. Normals of minus 14 degrees on the inside would be around minus 4 psi on the suction and 150 pis on discharge. Now checking the pressure will require a set of guages that have been purged with the same freon before connecting with the suction line on freezer. If not purged the suction line will draw outside air into the system and cause freezing of air and moisture inside the capillary tube rendering the freezer inoperative, Hope this helps, Sea Breeze

Posted on Nov 02, 2007

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What is the normal operational pressure in lo/hi side at the compressor of commercial freezer like dispaly case, reach in cabinet or other any low temp refrigeration uses 502 or408A/404a. is there any rule...

why yes there is. Generally speaking, the head pressure should be around the "ambient +30" rule.
That is, measure the entering air temp to the condenser, say 75 degrees. Now add 30 to that and get 105 degrees. Look at a P/T chart and see what the pressure is for that temp which is about 253 for R-404-A.
The evap on a freezer leads the load so, as a general rule, the evap temp is going to be around minus 10 degrees to get a 0 degree box. Coolers are different. So, the pressure for a minus 10 evap is around 25 or so. But the unit has to be close to operating temp. If the box is warm, naturally the pressure is higher. And what influences the pressure is whether or not it's a TXV or a cap tube system.
If a TXV and no receiver, charge by subcooling. If a receiver, fill by sight glass. If Cap tube, charge by superheat.
Hope that answers your question.

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Delfield 6000xl: what is the 404a freon charge?
this web site has a table of units and their respective charging amounts.
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Delfield 6000xl: what is the 404a freon charge?
this is for their web site. It has all the manuals and charging tables. There is no 6000xl. Need exact model number as the amount varies.
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Need to know the design superheat also normal pressures on this unit with 404A refrigerant

The McCall web site has nothing easily found on the 7-7045FT unit.
In answer to you questions, first, what is the expansion device. TXV, Cap Tube, or something else?
Low site pressure will be dictated by the super heat. The high side, in many cases, is usually ambient plus 30, then convert to psi.

Let me know if you need more info. And please double check the model number/ serial numbers.

good luck

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I have a ice maker that keep freezing up. the pressures are 50/280 its a 404a system. what are the normal pressures

For a 404 system pressures should be about 60/350 Remember when you recharged always with the freon drum upsidedown so liquid gas is going in to the system.But if it's freezing up could be the thermostat or the timer or the heaters.

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Normal Operating pressure for true 2 door Freezer R404A Room Under 80 degrees F Box at -10 degrees F

The pressures depend, somewhat, on the expansion device,i.e. a TXV or Cap Tube. Take a pressure reading, then convert it to a temperature. The evap temp should be right at 10 colder than the box temp. Remember, heat flows to cold so the evap has to "Lead the Load" in order to cool. In many cases, the condensing pressure is usually ambient temp, plus 30, then convert to a pressure. These are general accepted practices that have been used for many years.

Hope this helps

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1 Answer

My freezer will not hold temperature. Only a year

If what you say is accurate, I would look at either a weak compressor or and issue with the expansion device. (Cap tube, TXV)
What are your pressures and what freon are you using? Does the door(s) seal tight?

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1 Answer

Evaporator unit keeps on building ice. question what is the nornal operating pressure on low side and on the high side for truee freezer using 404 refrigerant

I'll try to give you the "Readers Digest" version.
First, make sure there is no ice build up on the evap. Light frost is O.K. as long as it does not effect air flow. (Very Important). All fans need to be running. Again, an air flow thing. There should be some product in the box but not too close to the evap. Again, an air flow thing.
The expansion device can effect your pressures to some degree i.e. Cap tube vs. TXV.
As a general rule of thumb, which I use almost everyday when it comes to pressures:
Low side is based on the temp difference between evap temp and condition space in the box. In freezers, it is almost always 10 degrees. If the box is 0 degrees then the evap needs to be at a minus 10 degrees. That is a pressure for R-404A of 24.5 psi. This only holds true when the temp in the box is approching set temp. I would say, about +10 degrees. 0 Degrees for the evap for R-404A is 33.5 psi.
High side should be ambient temp +30 degrees and then convert to a pressure for the refrigerant.
Example: 75 degrees in the room, +30 degrees equals 105 degrees. Now 105 degrees converted to a R-404A pressure is 253 psi. This will get you very close to the desired high side pressure.
I would look at low side first to see if it is within reason. Don't let the high side get too high. Increases the compression ratio and overworks the compressor.
Your icing problem could be a defrost issue and not a refrigerant charge issue.

Good Luck and hope this gets you started.

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Errattic temperatures in Freezer

Check out "" for manuals, diagrams, etc.
Cap tube systems are "critical charge systems". Can be difficult to get right. You did not mention pressures that you had. The split on the evap temp is almost always 10 degrees for freezers. If you want a -10 box, your evap needs to be -20. As a general rule of thumb, you want the high side to be "ambient +30". This seems to work most every time. Your problem might be operations related. Them leaving the door open alot and so on. It could also be a problem with the evap fan or the control to it. It could also be that since there had been a problem with the unit, they are now constantly checking it. Could be checking during a defrost cycle. When your box is at 0 degrees, your pressure should be about a -10 and no less that a -15 degree for the evap. You may have to babysit this thing and see how far it will pull down. You may have a weak compressor. Also, I have had many Hobart freezers fail due to dirty condensers. This causes the oil in cap tube systems to gel and clog up the cap tubes. The only fix is replacing the cap tube. There are alot of variables here so be patient, it's not going to be a quick fix. One last thing, since R404A can fractionate, you really need to pull the charge out and weigh in the correct charge with virgin refrigerant. This will eliminate 2 things. 1, it will ensure the correct amount of refrigerant and, 2 no chance of having a poor mixture of refrigerant in the system causing inconsistant readings and performance.
Hope this helps. And remember, cap tube systems are performance measured by the amount of superheat just prior to the unit making temp and cutting off.

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Low suction pressure high head pressure

That system has a restriction. Most common at TXV valve or capillary tube. Will need to be replaced by Refrigeration company. In this video I replaced TXV valve and filter drier due to the same issue You have. Its Ice Machine, Low side was at 5 PSI, High at 250PSI : 404A; should be around 55-65 Low; 250 -275 High. Replaced drier and TXV, machine works proper.

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