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Originally Posted by WhiteSoxFan

Please explain how. Not that I disagree, I just want to understand why.

With more heat to reject at the condensor there will be less liquid building up in the condensor the hot gas will take longer to change state to liquid.

Originally Posted by shaka

High indoor loads will cause bubbles too

Please explain how. Not that I disagree, I just want to understand why.

Txv or fixed orifice
Sight glass should not be used to determine the charge on small resi equipment.

Its not true that only on low ambient condition will cause bubbles on sight glass
High indoor loads will cause bubbles too
Dirty condenser
extreme outdoor temp
Long liquid line on the roof (flash gas)
Long vertical liquid line (pressure drop)
Non condensable
Blend refrigerant high temperature glide.
Restriction upstream of sight glass
Wide txv hunting
Unseated orifice
Gas heater is running the same time

Sorry that's all I could think off right now.

Sorry. I meant to say indoor WET bulb and outdoor ambient

I agree. Sight glasses can be useful on TXV systems but are worthless on fixed bore metering devices. Never use a sight glass on any refrigeration, ac, or heat pump with a fixed bore. Get back to basics and check superheat based upon the inddor dry bulb temp and the outdoor ambient temp.

Sightglasses are for TXV systems ONLY. Take it our or tape it up!

A sight glass is a useful tool on any system regardless of low temp or high temp. IMHO. Its function does not change because it is on a ac unit.

Its a nice tool meant used in conjunction with (not in leiu of) all the others.

Thanks for all of your guys help. Experience says that airconditioning should always have a solid column of liquid, and refrigeration, in low ambient, is the only time you should see bubbles. I think it could be a problem with the piston(in backwards, or moving around a little, like someone mentioned), and probably a few other possibilities, but what are you going to do. If it isn't broke don't fix it. By the way I have checked the evap coil, and it isn't dirty, and I changed the filter. I think the sight glasses should be used in medium and low temp applications only, not air conditioning. Thanks to all.

Originally Posted by 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...

Yep, had a unit early in my career that I charged by site glass, operated great when I left it, next day call for no cool, go back 30* sc, sh&@! Set sc at 10* and no call back. DO NOT CHARGE BY SG, period!!!

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.

^
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...

Originally Posted by jpsmith1cm

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

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

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X2

Originally Posted by millertime77

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.

What do you mean paper is green.

Originally Posted by 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.

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.

Originally Posted by jimj

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.

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

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

Forget about the sight glass and use your charging chart.

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.