Need to know the low side of r404a psi at all time that is good

First you will need the Freon,
then a charging valve to attache to your low side of compressor line
a set of gauges to monitor pressure and a amp meter to see what amps its pulling when charging if charge is low then it has to be a leak can be a micro leak and may work for a while but not fix may need a Freon leak detector to find 90% of units end up with evaporator leaks or in condenser cooling drain pan line rusted out

Hello;

My name is Peter. I am a retired field service refrigeration technician.

You do not know how dangerous this is. You have a high pressure side 160 PSI liquid and a low pressure side 60 PSI vapor.

You can get burned from the liquid or the vapor will burn your lungs.

Only a certified technician such as I can do this.

Depends what freon you are using.......... For R12 6 to10 PSI
For R502 25 to 30 About the same for R404A

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

If this is a commercial unit, you're too low on refrigerant (freon). Freezer should be about a minus 10 degrees for the evap and high side is ambient converted to a psi for the type of refrigerant that is in the system plus 25-30 psi.
The evap fans will not come on because the evap is not cold enough.
Hope this helps and good luck.

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.

most units are on a timed defrost that occurs at different times so finding the exact time will be hard but defrost times are about 30 minutes. from the pressures you posted I'm thinking that the condenser fan is not running or the condenser itself is plugged up with dust. (i'm not very familiar with r404 but for most other refrigerants the hi side pressure is really hi). if its still in warranty you would be better off to call your service company after your sure the condenser itself is clean to prevent a charge for impproper maintanence. thanks peyton

The 3 beeps indicates that the freeze cycle is longer than 60 minutes. with the suction pressure at 20, it sounds like low on charge (freon). I believe this is an R 404-A unit. Other things to look for are: Stuck float switch (in the up position), Water valve leaking, hot gas valve leaking, txv not feeding properly, weak compressor. Look at high side pressure too. It should not go below 210 psi during the freeze cycle. Low pressure should be in the middle to upper 40's psi.

Let me know if you need more.

what is your superheat and is defrost cycle working

the amount of coolant is not the issue, its strictly a thermostat issue,WOW -40 though i dont know where youd geta thermo to go that low. def not in ANY residential/local appliance outlet