Cant get bubbles out of sight glass

[shaka]

I can't believe boss man wants to keep chugging it with juice..

[mcewans]

Went on this call at a church, back for leak check today, but pressures where I left them. Turned the unit on and it was 76 inside and turned down to 72. Pressures were 200/75. Coil split was 18, and sweating all the way through on all u bends. Super heat was 2 to 3 and subcool was 1 to 2, with bubbles in sight glass, but very minimal, almost milky looking. T-stat satisfied in a half an hour. Went over evap coil with leak detector and nothing. Went to outdoor unit and found a leak on top of suction service valve with cap off( not shrader portion) tightened cap up and not leaking. Found a leak on true suction service port. Seemed like someone had over tightened the shrader b/c could not get core tool on shrader, so leak locked cap. My boss says to keep throwing refer to it but that goes against the grain. Indoor piston(#83) low super heat(measured at service valve), but has low subcool, and bubbles in sight glass. Added a total of 7lbs counting both visits. I knoiw it has to be overcharged, but delta t good and RH 50% db 70 wb 60. Outdoor unit Trane M# 2TWA0048A3000AB S# 3471N213F, indoor unit is 4 ton dont have numbers though. I wonder if the comp valves are bad? Should have tried to pump down. At a loss with this one, any help would be appreciated.

This is the reason for the bubbles.

[mcewans]

You are over charged.
First sight glass charging is wrong with those conditions
AC unit are designed at 95f
When it's around 70 condenser is too efficient and subcools gas faster than normal.
So sight glass will not be clear.

Go back to basic
Check superheat chart and input your conditions
I believe it's 16 SH
ignore sight glass.

If they are going to run Ac with these conditions
Then you will need a low ambient control
To prevent freeze ups

I have found the opposite to be true. If you have more subcooling, then you have more liquid and therefore fewer bubbles. Think about it, if your subcooling is low, then you won't have enough liquid to form a solid column feeding your metering device.

[shaka]

I have found the opposite to be true. If you have more subcooling, then you have more liquid and therefore fewer bubbles. Think about it, if your subcooling is low, then you won't have enough liquid to form a solid column feeding your metering device.

So your his boss..

So exactly how much sub cooling should he be trying to reach?
You really want him to clear the sight glass?

[shaka]

This the reason why you should never install a sight glass on small residential unit
Someone always trying to clear sight glass on any conditions.

[Sicofthis]

Did the OP edit his post I don't see where he said it was 70 outside.

[shaka]

My bad
I don't see it either.

Regardless sight glass should not be used to charge this unit.
Pressures and temperatures
Is all u need.

[Sicofthis]

My bad
I don't see it either.

Regardless sight glass should not be used to charge this unit.
Pressures and temperatures
Is all u need.

x2

OP is awol

[Chris_Worthington]

millertime77,

Please do not create duplicate threads on this site to discuss the same problem. I have merged the 2 that you created together.

[Tjune54]

I would have to check the piston as it looks like it is stuck in the fitting and bypassing refrigerant. Sometimes I have been able to seat them by rapping on the FCCV with the handle of a wrench.
On stubborn ones you have to pump down and open the fitting.
Being a pump the piston does move in and out of the seat and can gat stuck partially open.

[LU91Tech]

Forget about the sight glass and use your charging chart.

[WhiteSoxFan]

Agreed, forget the SG.

Get a charging chart.

I have a nifty app on my smartphone that says with those conditions ( 70 Outdoor Ambient, 60 Indoor Wet Bulb ) You should be around 23.5 Subcooling (if TXV) or 15.7 Superheat (If using a fixed orifice)

Hope that helps

[jimj]

I'm in for the SH number, Not so sure about that SC number!

[millertime77]

At 70* IDDB and 70* ODDB you should have 10* of SH. With a matched indoor unit it calls for an #83 piston. The unit calls for 8lbs 6oz for a 15' line set ( and you added 7lbs?). You started with 200/75 and then added 7lbs ( ouch)?

At 70* ODDB you should be around 65/190. See the Trane Fast Fact attachment.Attachment 305681


Your OVER CHARGED.

No thats what I ended up with. Call was unit not cooling , low suction and high superheat, so it needed refrigerant(R-22) The outdoor ambient was like 95 that day the rh,wb,db readings are from inside the conditioned space. Thats my point is this thing is working great, now, but still has bubbles in the glass, and boss kept telling me to keep adding but I didnt want to so I finally talked him into letting me leave it. As far as non-condensables being in the system, the paper is green.

[millertime77]

millertime77,

Please do not create duplicate threads on this site to discuss the same problem. I have merged the 2 that you created together.

The reason I did that is because when I first posted it didnt go through correctly and gave me some sort of passage saying to email the site administrator if this passage is shown. My thread came up on the main screen but when I clicked on it, that was what I got. So I tried again, that is why there are 2.

[SBKold]

What do you mean paper is green.

[jpsmith1cm]

As far as non-condensables being in the system, the paper is green.

The 'paper' in the sightglass is for moisture and only moisture.

It will tell you nothing about non condensibles in the system.

[ryan1088]

The 'paper' in the sightglass is for moisture and only moisture.

It will tell you nothing about non condensibles in the system.

^
X2

[WhiteSoxFan]

^
X3

FWIW, I had a similar job a month ago. SC was where it was supposed to be but the SG was not clear... I was told a TXV needed a full column of liquid to work properly so I kept adding juice. I couldn't clear the SG to save my life... After way overshhoting the SC and still seeing bubbles, I decided to forget about the SG and just focus on the SC.

Hope that helps...

[garyed]

It sounds more like a dirty evaporator coil or low air flow but I suspect dirty coil. It can still cool O.K. depending on how much demand there is in the conditioned space. A dirty coil won't necessarily show a low TD but will show low SH. I also agree with the others about no need to worry about bubbles in the sight glass, especially dealing with a piston system.