Unless the existing refrigerant is compromised by the mixing other refrigerants as Capz suggests, the system performance won't be significantly improved by switching to another R12 interim replacement refrigerant like R414B or R401A. There's nothing inherently bad about R409A.
I think we need to get back to some basics first...like doing a quick load calc for the box and comparing that to the expected capacity of the existing system.
What is the size of the box?
What is are the model numbers of the condensing unit and evaporator?
If the load and capacity appears to be in line, then perhaps checking the compressor performance would tell a tale. Get the suction and discharge pressures along with the amp draw and input voltage at that condition. With that info, we can go to the compressor manufacturer's performance data and determine what the amperage should be.
I may be reading the info all wrong....but it seems like you are saying the discharge air temp off the evaporator is the same, or warmer, than the box temp.
I'd also like to know what your compressor amps are compared to its rating.
We have to know if you have the right airflow and TD across the evap. Maybe they sealed and insulated that evap when they did the work on the box???
That's what I read too... Mixed gas or oil logged evap would be my vote.
Originally Posted by Russ57
Were there any other changes made during the resealing of the box? Where is the cond unit in reference to the evap? Is the TXV hunting or steady? Is there a full colum of liquid feeding the TXV?
maybe I was in to big of a hurry??
Ok, sorry on the "door" confusion, right now the door is not being opened and closed much at all, just enough to restock the beer cooler at the bar maybe once a night, not a big or busy bar, right now all they store in the cooler is case and keg beer until we are sure we can keep the temp in the 38-42 range. So the door may be opened 6-8 times a day or less at this time. There are no new racks in the cooler, just some on the outer walls of the cooler, most are empty, just some kegs sitting on the floor and case beer on the racks on the wall by the door, t-stat bulb located in the airstream going into the back of the evap, no hot foods are being placed in the cooler.
As far as I know no one else has touched this system since I started it up for them 2 or 3 years ago, at which time I evacuated the system which was out of refrigerant, vacuum held, so I charged to a clear glass, checked sh and sc, and have not done anything to it till now. To my knowledge no one has compromised the charge by mixing refrigerants, not many around here that will do refrigeration or know how, unless its a bigger commercial company from one of the bigger cities an hour away, but I am sure this customer would not be willing to pay their rates.
I have checked the back of the evap and it is 100% clean, the condenser is clean, even blew it out with air to be sure.
Didnt want to pull out the 409a and switch to 414b, I dont have 414b and have no accounts with 414b right now, but I do have a cylinder of 409a which is pricey, and thats what the cooler had in it originally.
As to the load caulc. I will need to measure the box and get the evap. and condenser info this week, and see if they are sized correctly, I have wrote the info down, but cant seem to find the condenser info right now. I don't remember what the amp draw was in relation to the nameplate amps, but my liquid pressure was 165#/108F with a liq. temp of 99F, suction was 30#/36F evap. outlet temp was 40f suction temp at the compressor was 48-51f. Ambient where the condenser sits is 80-85 (located in the basement directly below the walk-in, box temp. was 48f at the time of these readings.
Yes the evap discharge temp was 46f, and as I said i dont remember the amp draw, will re check that this week. The evap. has good airflow, only one evap. fan, coil is clean, when they resealed the box, they lowered the evap enough to slide some insulation above the evap, so the evap is wide open.
The txv is not hunting, it is nice and steady, sight glass is clear, txv is getting a steady solid column of liquid, had 6 degrees of subcooling, added some 409a brought the sc up to 8, but still evap air outlet temp at 46f.
I was set to go back and recover the charge and recharge the system now that the box is close to temp, called the bar and they said the cooler was maintaining a 38f box. Only thing I can think is maybe I was in to big of a hurry, as it was really hot this week all the beer was very warm in the cooler as they had it open while they were resealing the cooler, so when they started the system back up it had a huge load, maybe I was not patient enough for the keg beer and all of the case beer to cool off, and the system was just trying to catch up with the large load placed on it. I still plan to stop back in this week see if its maintaining temp, check amp draw, and get the condenser info and box size to see if the system is sized properly to maintain a 38f box temp.
Thank you for all of the input I greatly appreciate all of the comments, will post the amp draw and m/n of the evap. and condenser, along with the box size, still seems to me the discharge air temp. should have been cooler, I am anxious to get my gauges back on the system, and check my pressures, temps and amp draw now that it has been maintaining all weekend!!
Had a beer cooler customer that was having trouble keeping the beer cold too. Very old building with left overs from old renovations all over the place.
It was about the third or fourth recheck when I noticed an open door at the other end of the cooler. They added an extra 640 cuft. that they didn't bother telling me about and I got to trusting the customer too much. With the door closed it worked fine. Just another wake up call on customer logic vs common sense.
Been using 409 and 39 for many years and very few problems, but that said , on older/weak/ undersized systems, you can run into some issues. Both 409 and 39 run slightly higher discharge pressure/temps.
On an old r-12 based system that can cause problems - especially when ambient temps/humidity raise.
I have run into many old systems that were marginally sized using r-12 and when converted to a different ref. and in extreme temps/hum., the evap. coils tend to ice up.