Ice Build Up After TXV To Coil Connections

JUGHNE

Just about every walk in freezer box I have ever seen has the problem of the distributor and its tubes building up layers of ice in the end box of the coil. Over time enough ice will build enough to distort or crack tube end returns and if neglected will eventually push the cover off the end box. I am always advising owners to defrost ends of the coils or pay me to do it. The larger the system and colder temps the worse it is. Is this a standard procedure or is there a remedy to this??
This seldom happens on the other end of the coil where only the tube returns are.

The picture is typical of what I am speaking of. This has had 2/3 of the iceberg manually defrosted from it and the dist tubes were bare, then system turned for one hour and you see the frost build up in that time. The defrost heaters are all working, the time clock functions 2 X a day, the defrost time clock will kick out on high coil temp....not sure if there is a fan delay after defrost. This box maintains 0 degree air temp. Any ideas? Thanks

njtommy

That's normal for any freezer nothing you can do about it. It freezes because you don't have any air flow there. Your refrigerant temp is going to be -5 to -20 degrees in a zero degree box.

aircooled81

Nature of the beast. If your box temp is -0, then your evap coil is likely -10*f or lower. Adding the heat from the box, moving air across the evap will likely frost there too, but the fins hide some of that frost. And the defrost helps get rid of that.
Adding heat tape, or defrosting distributors is fairly uncommon. Hot gas defrost can remove this though, but requires extra piping and valves.
Nj tommy is right, its normal.
If you have accessive moisture in the box, you can try to remove it more rapidly or prefent it from getting in. Is their a ptrap outside the box for condensate? Is condensate drain sloped very steep leaving the box (wrapped with heat tape), electrical conduit air tight (i fill these with a bit of silicone), wall seams sealed up, door seals tight (i check 'em with a dollar bill), they using a swamp cooler or heavy hummidity outside the entry door to the box (many ice boxes inside the fridge).
http://www.colmaccoil.com/Literature/TechnicalBulletins/OptimizingHotGas Defrost.pdf

Techman

What is the normal running suction press? What is SH for the evap and at the comp?
If that frost /ice builds up on the TXV body,TXV Power Assembly, or the TXV thermal bulb or the t-bulb cap tube then you can develop problems.
What comp and Evap coil?

pecmsg

Why is there a box of product under the drain pan? That can cause much lower evaporator temps. Nothing should be with in 12" of the blower.
On a few occasions i've remounted the DTFD klixon higher to give defrost 5 more mins.

Techman

pecmsg, that is exactly where I was headed!
I do not find "icebergs" as being normal! Well, it is normal for a "something is wrong" system.

pecmsg

Techman said:

pecmsg, that is exactly where I was headed!
I do not find "icebergs" as being normal! Well, it is normal for a "something is wrong" system.

Great minds think alike

JUGHNE

So thanks for responses:
2 vote normal....nature of the beast
2 vote normal for something is wrong, (probably is common)

This box is always overloaded. I couldn't get to the far end of the coil for a month until things got organized. That was after the threat of requiring the entire box to be unloaded to some other freezer...not available.

The air flow IMO is not obstructed. It is a pull thru coil with 2 large evp fans.

Today I have to replace the leaking LLSV you see in the coil picture. Barring rain as this is an outside covered box.
If I get back to this I can provide more details & pictures.
Thanks again.

njtommy

As long as your superheat at the evap generally is 10f is good and at the compressor 15-20f superheat is good or with in range you have no problems. With the refrigeration cycle.
You could have other problems with defrost cycles leaking doors or even doors being left open all the time. It adds moisture to the box and that's not good

pecmsg

JUGHNE said:

This box is always overloaded.
I couldn't get to the far end of the coil for a month until things got organized.
That was after the threat of requiring the entire box to be unloaded to some other freezer...not available.
.

Overloaded creates a air flow issue.

Pages and pages in the install manuals concerning return air clearances, Discharge air obstructions, properly loading and stacking (allowing air between product)

Techman

JUGHNE, not for nothing(with respect cause I've read your "stuff"for a long time) you are "missing " a sure as hell symptom and calling it normal! Does the Living Room couch get pushed back against the AC return duct? And the resulting suction press of 52psig w/ r22 is considered as normal ?

The TXV will "try" to maintain that 10*SH under almost EVERY condition.

ChrisJ

Techman said:

JUGHNE, not for nothing(with respect cause I've read your "stuff"for a long time) you are "missing " a sure as hell symptom and calling it normal! Does the Living Room couch get pushed back against the AC return duct? And the resulting suction press of 52psig w/ r22 is considered as normal ?

The TXV will "try" to maintain that 10*SH under almost EVERY condition.

Techman,
I believe this is a freezer?

Don't think there's a couch or a livingroom.

Techman

ChrisJ, LOL my friend. I was only giving one of those "analogy's". The normal AC suction press is(R22) 62psig(36*f)(KindaSorta) w/ normal proper air flow,so, blocking the AC return air ( with the couch)lowers the suction press down to 52psi (28*f),causing problems. The same applies to Refrigeration and Freezers as well. So, less than proper air flow causes lower than normal suction press and lower than normal temps. The lower the temp the more frost/ice builds up. Kinda like in the picture. There is a little known "trick" to help overcome those over packed freezers/refrigerators and you would have to be of the Polish persuasion in order for me to tell you ! If your name is Chris Jski then I could tell you, no problem!

ChrisJ

Techman said:

ChrisJ, LOL my friend. I was only giving one of those "analogy's". The normal AC suction press is(R22) 62psig(36*f)(KindaSorta) w/ normal proper air flow,so, blocking the AC return air ( with the couch)lowers the suction press down to 52psi (28*f),causing problems. The same applies to Refrigeration and Freezers as well. So, less than proper air flow causes lower than normal suction press and lower than normal temps. The lower the temp the more frost/ice builds up. Kinda like in the picture. There is a little known "trick" to help overcome those over packed freezers/refrigerators and you would have to be of the Polish persuasion in order for me to tell you ! If your name is Chris Jski then I could tell you, no problem!

I'm Danish, German, English and Polish.
Does that count?

I'm a bit confused though.
If an evaporator is running at well below zero temperatures why would the suction line ever be above freezing except when the unit is off assuming ambient is above freezing?

Then again,
I run my chest freezer at -20F and I've never seen any water on the floor...........

aircooled81

JUGHNE said:

So thanks for responses:
2 vote normal....nature of the beast
2 vote normal for something is wrong, (probably is common)

This box is always overloaded. I couldn't get to the far end of the coil for a month until things got organized. That was after the threat of requiring the entire box to be unloaded to some other freezer...not available.

The air flow IMO is not obstructed. It is a pull thru coil with 2 large evp fans.

Today I have to replace the leaking LLSV you see in the coil picture. Barring rain as this is an outside covered box.
If I get back to this I can provide more details & pictures.
Thanks again.

Glad i looked back at this post. I never opened the pic, just glannced from the small image. That big iceball is not normal, i mispoke. The wallies were right, that is indicative of another problem. But i still hold my same opinion, certainly not uncommon to frost up the cap tubes to the distributor, especially in a humid freezer.
That being said, looks like you have a lot of moisture to ring out, or stop the moisture from getting in.
Regarding low suction temps and superheat, does colder ice make more snowball? I think the defrost just not running long enough to keep up with ice accumulation, all providing your basics are covered. Sc, sh (10*f mentioned earlier sounds fare), coil clean (everyone got so upset about blocking the air, lol), condensate drain not plugged, infiltration, fans spinning right direction, etc.

JUGHNE

Worked on this unit today. External service valve would not allow pump down. Valve on receiver and compressor discharge would close completely. Changed out leaking LLSV, while testing at 200 PSI nitrogen found second leak. 1/4" tap into 1/2" LL for compressor suction cooler. Was a real bird dropping solder job, line almost on the floor of CU cabinet, took 5 tries but finally got it to test at 215 PSI of N2 for 40 minutes. Feel good about that as this has been a constant leaker.

This box, evp coil, sol valve, TXV is from 1975 or so.
It was re-installed with a new cond unit 10-12 years ago.
Box is 11'6" long 11'4" wide and 7'4" high. Two full sections were left out of the length because of limited room. This is outside and covered with metal siding and has a gable roof.
The original coil for the larger box is in use.

Thinking the evp coil may not be repairable, I gave all know parameters to supplier. They quoted a Russell AE46-164B,
that is a 1600BTUH unit with 2 ton TXV.

The old coil has 2 ton TXV, 2 X 1/5 HP 1075 motors with 18" blades that will take your hat right off.
There is at least 16" from back of box to coil inlet.

The CU is a Heatcraft 3.5 HP scroll, full outside unit with Headmaster Etc. R404A

Old box door seems sprung with crack at top, heated drain line runs directly outside without trap and it is an air sucker. Panel gaskets are probably in question also. "But is was cheap" and probably erected by volunteers.

This is just something I inherited. It for our hard strapped public school's lunch program. They order cheap USDA commodities and never know when they arrive, that is part of the reason of overstocking. I did locate more shelving for the center as this used to be a wall of solid boxes.

So all of you have made me more aware of the problems and will attempt to correct them. (actually knew most of the causes but for many old boxes this is the abnormal "normal".)

More pictures for your viewing pleasure.

Thanks a lot.

Techman

Morning JUGHNE, those shelves directly in front of the evap will cause a "short circuiting" of the cold supply air.
The evap btu is 1600btu? Maybe 16,000btu ? Coat the outside seams with some kind of sealant!!!!!!!!!, Put in a drain trap w/ heat tape unless your ambients NEVER go below freezing.
Tks for the pic's. Nice seeing an evap properly spaced off of the wall!

ChrisJ-SKI, I'll let you know "the trick" later when everyone else is at work. Unless JUGHNE is really JUGHNE-SKI
Your chest freezer does not have a defrost cycle.

Then, I am not aware of too many "high humidity" WIF, for typical kitchens! That is unless there are lots of air infiltration leaks, like an un-trapped drain.

pecmsg

That condensing unit matches up fine with the box. 15,800 BTUh @ -10*f and the Russell evaporator is a good match for that condensing unit. Do you have any #'s on the existing evaporator?

See page #4 concerning Clearances and Page #20 Concerning Air Flow.

unclejohn

If your super heat is 10* There nothing you can do. As for the box it is over loaded you can't fix what ain't broke. Run away from that customer and you will glad you did.