Heavy Frosting On Suction Return Line

[sodadude]

Just a small hermetic system with R134a and a 1/3 hp compressor with captube.

Besides an overcharge, what else could cause a heavy frosting on the suction return line?

[t527ed]

bad thermostat, bad evap fan, dirty evap or condensor, overcharge thats about it unless cap tube was messed with.

[cyro]

compressor sized to big
frozen evap
blocked/clogged evap
cap tube to short
cap tube wrong size
evap motor to small (cfm)
evap to small (btu)
evap blade to small or wrong pitch (cfm again)

[MikeJ]

Someone spilled a can of Duncan Hines?

[sodadude]

Originally posted by cyro
)blocked/clogged evap
cap tube to short


I cut the captube back no more than an inch when I replaced the filter drier.

It vacuumed down really well.

I had a senior moment when I was charging system, I plugged the compressor in directly and started charging, and then when the high and low sides did not look correct, I went duh and plugged in the cooler so the evap fans could be running.

I think Monday I will reclaim and vacuum again. I think something either let go and is causing a blockage or possible moisture in the system.

Christ I cant fix coolers or computers, what the hell is my purpose in life anyways?

[sodadude]

Originally posted by MikeJ
Someone spilled a can of Duncan Hines?

Thats funny.

[primmers]

humidity

[gosteelers]

maybe im just stupid but is the suction line temp under 32 degrees Fahrenheit ? is it insulated ... moisture changes state at that temp lol but what do i know .. alot of other things may be the cause but this is the only one nobody listed .. i do large amounts of refrigeration so im not really that dumb but have a great day ... i hope the BEARS get their a$$e$ kicked

[dixie2005]

I would agree with gosteelers. Although liquid floodback is a possible cause, it's also likely that it's just humidity freezing on cold suction line.

Do you have superheat?

[icemeister]

Originally posted by sodadude
Just a small hermetic system with R134a and a 1/3 hp compressor with captube.

Besides an overcharge, what else could cause a heavy frosting on the suction return line?

I'm assuming you're dealing with a True or Beverage-Air reach-in.....you being a Coke guy. I've run across a number of these where the evap fan motor had been replaced but is rotating in the wrong direction. The greatly reduced airflow gives low suction, heavy frosting on the suction line and poor overall cooling of the box.

Just a thought.

[sodadude]

Yeah its a true cooler,dixie, what causes liquid floodback?

Ice this cooler came out of a Walmart. Tech that checked it out said it had a plugged filter drier. So friday at the shop we decided to replace the deck and change the filter drier on the old deck later.

Should have been smoooooooooth, but somewhere along the way I effed up.

So the evap fan should not be an issue at this point.

So what the hell causes liquid floodback.

[rayr]

U never said what the superheat was?????????

[air2spare]

hit it on the head. If you can give some pressures and line temps this may be a cake walk

[sodadude]

Originally posted by air2spare
hit it on the head. If you can give some pressures and line temps this may be a cake walk

Ok I will post those later after I do some more work on it today.

What causes liquid floodback?

[rayr]

Originally posted by sodadude

Originally posted by air2spare
hit it on the head. If you can give some pressures and line temps this may be a cake walk

Ok I will post those later after I do some more work on it today.

What causes liquid floodback?

Make absolutely sure that the fan is operating in the proper direction, air flow is unrestricted, other than that on a cap tube system I would say over charge. That doesn't have a liquid receiver on it does it. Don't laugh cuz I have seen it with a cap tube and trying to operate on a LPCO. Very very dumb.

[dixie2005]

Originally posted by sodadude
Yeah its a true cooler,dixie, what causes liquid floodback?

Ice this cooler came out of a Walmart. Tech that checked it out said it had a plugged filter drier. So friday at the shop we decided to replace the deck and change the filter drier on the old deck later.

Should have been smoooooooooth, but somewhere along the way I effed up.

So the evap fan should not be an issue at this point.

So what the hell causes liquid floodback.


Liquid floodback is when liquid refrigerant is coming out of the outlet of your evaporator and getting back to your compressor. This happens when the evaporator is not able to boil off all the liquid that it is being fed by the metering device (cap tube in this case).

Unless you changed the cap tube, I don't suspect that the metering device would be responsible for liquid floodback in this case. If liquid is getting back to the compressor (and I'm not saying that it is), it would be most likely be caused by something affecting the heat transfer at the evaporator (fan motor bad, dirty evap, fan shroud out of place, etc).

Liquid floodback is a condition that will cause ice or frost to accumulate on suction line although this is much more commonplace in low-temp systems. But as I said in my last post, a quick way to rule this out is to do a superheat calculation. If you have superheat at evap outlet, liquid floodback isn't an issue.

[selfemployed]

Your old enough and been around this stuff long enough to fix them in your sleep. So get those readings or it will never get fixed. ;) All in good humor ya'll.

[sodadude]

Originally posted by selfemployed
Your old enough and been around this stuff long enough to fix them in your sleep. So get those readings or it will never get fixed. ;) All in good humor ya'll.

16º on lowside, 160º on highside, could not do superheat calculation because someone stole the clamp on shop thermometer.

I think the first time I charged it without the evap fan running(senior moment) that caused me to overcharge thus leading to a low suction side reading because evap was freezing and a high head building.

Anyways it seems to be working fine now. Thanks for the help and answers.

[engine chiller]

FROST on a suction line only means that it is below 32 degrees.

If low temp you had better have frost.

Also if small selfcontained unit WEIGHT THE CHARGE IN PER NAME PLATE.

[Freezeking2000]

I would suspect the cap tube has been shortened a few inch's a few times and you need a new one.

[Wild Leg]

Originally posted by engine chiller
FROST on a suction line only means that it is below 32 degrees.

If low temp you had better have frost.


These things usually don't frost outside of the cabinet.

[sodadude]

Originally posted by engine chiller


Also if small selfcontained unit WEIGHT THE CHARGE IN PER NAME PLATE.

You are right.

[taylortech]

T-stat set correctly
Evap clean,no bent fins good airflow etc...
Condensor clean aiflow etc...
Heat,super and subcooling.
TECH method works on most refrigeration

[keywest]

check your evaporator fans make sure at right rpms

[NedFlanders]

here's some frost for ya

http://i2.photobucket.com/albums/y39/FlandersNed/frostheadr.jpg

http://i2.photobucket.com/albums/y39/FlandersNed/frostbody.jpg

http://i2.photobucket.com/albums/y39/FlandersNed/MVC-024S.jpg

From today at work

[smilies]

Originally posted by NedFlanders
here's some frost for ya



From today at work

But, today is Saturday http://hvac-talk.com/vbb/images/icons/icon10.gif

[sodadude]

Now THAT is what Im talking about!! Quick side question, do you guys do commercial refrigeration work on ice skating rinks?

I looked at a setup in the back room of a hockey rink and my mind was blown for all time.

[NedFlanders]

I have and do work with guys that do.

If you talk with them , it's just another system.
May be different methods , but all the same rules apply.
It's does seem to be true...it's all the same , just more HP and more amps.;)

When I grow up I want to learn more big stuff also.

[len]

sodadude,is that cooler one of those reach throughs?they take about 14 ozs of refrigerant,seeing that you have that pos in the shop replace the captube,pull a good vac.and weigh that stuff in,now whileyou are at it reinsulate the suction line and get a stupidheat reading,its a lot easier to do in the shop than at the acct,you dont have to wait an hour for the cooler to get near temp to do stupid heat and subcool.