Gurgling noise at evaporator lineset connection...

[alexb]

Greetings;

I know that the lineset should have a hissing noise as the refrig. move thru, that's obvious. Also, I've been near enough systems to know what normal refrig. flow sounds like. --Now my system has a distinct gurgling noise where the lineset enters the evaporator. I've run my system for 30min straight waiting for this noise to go away, in case the presures haven't reached their 'happy-place' yet.

The noise is there more often than not, and if it goes away, it only stays away for 20 sec or so. Is this noise the sound refrig. makes if it starts evaporating to early? What will that do to efficiency & temp delta across the coil
? The liquid line makes a 180-degree bend before it enters the coil, but the bend was done with a torch & is a 'graceful' bend, no kinks at all.

This problem has *survived* an evacuation/recharge. I showed this noise to the guy who did the recharge, and he got a wrench out & tried to do something with the nut that secures the liquid line to the evap coil, but looked otherwise clueless.

Any thoughts?

[Mr Bill]

We need more info. pressures/sc/sh/td etc. can you give up equipment name and model#'s and size evaporator type and size and model, condenser model and type and size this might be a good start to really be able to help you out.

[jamieo]

System is undercharged. Have the service company return to balance charge. Gurgling noise is refrigerant vapor as it enters metering device. The smooth, hissing noise you heard before was a full liquid head being presented to device - no vapor. When a system is underchaged, there is not enough volume to maintain head and the gurgling noise results. If there were a sight glass present in the liquid line, you would see the result of an undercharge as bubbles. There is a possibility that the system may have non-condensibles but need more info. Just curious - why did the system need an evac and recharge?

[Mr Bill]

I printed out the above, thanks for the advise, now if all that was only true.


If there were a sight glass present in the liquid line, you would see the result of an undercharge as bubbles.

[alexb]

System is undercharged. Have the service company return to balance charge. Gurgling noise is refrigerant vapor as it enters metering device. The smooth, hissing noise you heard before was a full liquid head being presented to device - no vapor. When a system is underchaged, there is not enough volume to maintain head and the gurgling noise results. If there were a sight glass present in the liquid line, you would see the result of an undercharge as bubbles. There is a possibility that the system may have non-condensibles but need more info. Just curious - why did the system need an evac and recharge?

Original poster: The site-glass is on the liquid line as it exits the compressor (outside). True, it has bubbles in it that never go away [Others her have told me to paint over it, as it has no diagnostic value..] This connection has gurgled ever since it was installed in 1988. I had it evacuated & recharged just as "PM", since it'd never been evacuated in 16 years. Outside unit is 1988 Carrier 3ton, and Carrier AH inside, also 3-ton (A/C-only). I didn't see the guages when the guy re-charged last year, so I didn't see what the charge was. Is there any way that the charge can still be improper, even tho the guages indicate and OK-charge? Any quick way I can tell if there's a metering device installed? I can post a pic of the lineset connection to the evap. Lastly, the gurgling is always present, no matter what the outdoor temp is, and no matter what the indoor temp is.

[Shophound]

Any quick way I can tell if there's a metering device installed?

It's not a matter of if there's a metering device installed, it is of what type is in place. A thermostatic expansion valve (TXV) or a fixed orifice (piston) are the two most common options available. Less common is the capillary tube restrictor, which has fallen out of favor due to clogging issues and the need for a critical charge (has to be right on the button for best efficiency). What many techs may not know is that piston systems are also very close to a critical charge. A few ounces off either way and the system's performance will suffer.

The only true way to determine if the "gurgling" is indicative of an undercharge is to get the pressures, superheat and subcooling readings, and determine if the indoor and outdoor coils and air movers are clean or not. A sight glass is marginally helpful but more useful as a moisture indicator than anything.

[alexb]

It's not a matter of if there's a metering device installed, it is of what type is in place. A thermostatic expansion valve (TXV) or a fixed orifice (piston) are the two most common options available.

____________________________________________
Pretty sure I have a piston-type orifice, since I don't have one of those little bulbs strapped to any lines. From what I read, the superheat figure is the difference between a.)The boiling point of freon and b.)The temp of the low-pressure line as it leaves the evaporator. How does one calculate supercool? I couldn't find a good description on the websites I checked.

[alexb]

It's not a matter of if there's a metering device installed, it is of what type is in place. A thermostatic expansion valve (TXV) or a fixed orifice (piston) are the two most common options available.

Original poster here. The sticker by the evap coil connections says, "Unit Equiped with Piston# 67 ACCURATOR" could a badly-sized piston cause gurgling in its vicinity?

[tinknocker service tech]

the unit is sixteen years old and has made this noise since it was put in. i will assume it has cooled the house fine. you had the refrigerant removed and system evacuated and then recharged. the noise is still there. why after all these years. the noise may just be carecter of this unit and you may never get rid of it. is it still cooling your house. if it is leave it alone and save your money then in a year or replace it. this unit did its job

[madhouse]

I have a new 13 seer a/c unit with a txv that does the same thing. When I charge to proper subcooling the noise is present. If I increase the charge and raise the subcooling 2 or 3 degrees the noise stops and I get the nice hissing sound. System performs equally well either way. I kept the charge a little high figuring as the system ages and gets dirty it will need the couple of ounces of coolant. Also a txv should only see liquid.
Charging by sound! Now that’s a new one…

[dnt]

ooh I like that charging by sound I added that to the list. If the unit is properly charged it will stop gurgling most likely your service tech throwed some gauges on and got the pressures within guestimate and cut a trail. Save up your money and have someone come out and do a proper superheat/subcooling check and let your ears rest a while. Hey madhouse, just curious did you have the manufacturers information for establishing the desired subcooling value or did you use a standardized chart using outside ambient dry bulb and evaporator inlet wet bulb temps?

[alexb]

If the unit is properly charged it will stop gurgling

Any chance that a badly-sized piston can cause gurgling at the Evap. inlet? The sticker indicates that a #67 is installed. Would installing a variable restrictor do anything for me at all? I bet analyzing the SH and SC of the unit will dictate piston size...

[jdenyer]

Alexb,

I have run into this a few times. Customer complains of gurgling noise, but other than that cools great. Subcool and superheat check out fine, pressures good. System working great other than some gurgling noise. Because you are hearing the noise at the evap it's just possible that what you are hearing is the refrigerant boiling off inside the evaporator(this is normal). Have a good tech come out and check superheat, and subcooling. If all is fine stop worrying Hope this helps.