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Then plot thickens. I got in touch with the factory rep. to confirm some information. Turns out the tecumseh compressor that got shipped is made in France. The part number that was ordered was correct, but the wrong was shipped. They are sending another compressor under warranty, but the labor and materials will be a total loss. I will keep the board posted as the progress goes. Thanks for everyone's help and thoughts and feedback.

You've got a 70 pound suction pressure with 404a.

THERE'S your problem.

got the unit running today. Added the correct amount of refrigerant via digital scale, adding the correct additional amount for the over-sized filter/drier. It only got the temp down to 37 degrees. Still have some bubbles going by in the sight glass, but not as bad. I have started to adjust the new txv, slowly to see the change. Super heat is only 3.5 degrees. High side was 210 PSIG at startup, suction side at 70PSIG at startup. After running for about 45 minutes it was at 190PSIG high side and 75PSIG suction side. I didn't get amp load reading, but will first thing in the morning. I am hoping to get some good feed back from you guys. Thanks in advance

I did add additional refrigerent to compensate for the oversizing of the new filter/dryer. To answer ivan, I never did reach anything close to desigh temp.

Tomorrow I will put in a new filter/drier. I'll check for leaks with nitrogen. Then I will pull vacuum, check for leaks again and then pull another vacuum using my jb micron gauge. If all goes well, I will just have to play with the txv to get the super heat right. I'll post results tomorrow or the next day.

When did you take your superheat reading? Was it close to or at design temperature?

You installed an oversized filter drier.

This modified the actual system charge. It would depend on how much you oversized the drier how much additional refrigerant it would require to clear the glass.

Originally Posted by 85goldwing

This unit for sure was not short on refrigerant. I took out just short of 4 lbs on a system that calls for 3.3 lbs of 404a. So I am still wondering about the air in the sight glass. Could a over-sized filter/drier produce these bubbles in the sight glass?

You don't have "air" in the sight glass - what you're seeing is refrigerant in a vapor state. You have to remember that refrigerant coming out of a receiver is not subcooled, it's saturated (unless you want to get into some very heavy theory about refrigerant dynamics). Thus, if you have anything that throws the heat balance off in the system, e.g.; non-condensables, dirty condenser, recirculated air on the condenser, etc, it may create the condition that you describe. A restricted filter/drier of any size can and will create what you're seeing.

This unit for sure was not short on refrigerant. I took out just short of 4 lbs on a system that calls for 3.3 lbs of 404a. So I am still wondering about the air in the sight glass. Could a over-sized filter/drier produce these bubbles in the sight glass?

You are correct in your description of how a receiver works (well, except for the part where it draws liquid from the mid-point. It actually draws from very near the bottom where the liquid sits.)

You've answered your own question and don't quite know it yet.

If there are bubbles in the sightglass, the most common problem would be that you do not have enough gas.

wondering

How does a system with a receiver get air bubbles going by the sight glass down stream of the receiver. Maybe a dumb question, but I thought that condensed high pressure liquid went in to the receiver on the bottom and liquid refrigerant was taken from the mid point of the receiver. Thus ensuring the high pressure liquid stayed liquid up to the txv where it changes state to a low pressure liquid. Ok so now beat me up on this but teach this old dog a thing or two in the process.

Post a complete set of readings and findings (such as "clear liquid line sight glass") and anything else you know about the operation even if you think it's not pertinent. Everyone is guessing.

You also don't need to test superheat with a two thermometer set, 'cause you can't account for pressure drop in the evaporator. Do it with one thermometer and an accurate suction gauge w/ temp scale (or call jp and let him bring his digitals over so you don't have to do any cipherin' in your head).

It is for sure not low on charge. I'm thinking that there is obstruction in one of the lines or the txv is bad?

Still a bit low on charge I would say. Subcooling?

suoerheat was 35 degrees

What was the superheat readings?

it didn't reach temp in either a chill 34 degrees or a freeze mode -10 degrees. it wouldn't go any lower then 48 degrees.

Did you let it reach temp before you messed with the TXV?

the plot thickens

Well today I worked on my pet project and ran into a stumbling block. Hoses are fixed, vacuum is good. Used a brand new JB DV-40 micron gauge, pulled down to a 220 micron vacuum. It sat at this for about 30 minutes when i decided it was good enough. I added the 3.3 lbs. of 404a plus 2 more oz for consumption by the hoses. This thing has a good sized receiver so i wasn't to worried about going over a bit on the Freon. I checked for superheat about 8-10 inches from the txv before the evap. coil and about 3-5 inches from the suction return on the compressor. The book I have on this thing says about 20 degrees superheat is good. Now the problem. No matter where i set the adjustment screw for the txv. I can't get much of any chance on the superheat. So I asking to confirm my suspicion that the txv is bad. Let know what you all think. Other comments or ideas welcome as well

they also make vacuum hoses or you can use soft copper with flares.