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Thread: TXV and Capillary tubing iced-up
02-12-2009, 12:39 AM #1
TXV and Capillary tubing iced-up
About 4 months ago, I recommissioned an older dormant system. It is a large walk-in freezer, set and holding at zero degrees. I stopped by today to check out it's operation. Noticed accumulator and exposed suction lines frozen over up to the suction service valve on the compressor. I know icing/frosting is common on exposed low pressure pipes and components.
After inspecting the inside evaporative coils, I found the TXV output, distributor, and cap tubes iced and frozen solid. SH is right at design specifications of 9* (at evap) with a 10*TD.
Coil is clean as a whistle and defrosting perfectly, just curious why that little section is iced solid.
What causes the icing of the TXV's distributor end and cap tubing?
Is it due to the fact that they are not in direct contact with the electric defrost elements?
02-12-2009, 12:13 PM #2Regular Guest
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- Feb 2009
There is alot that can be causing this. For example the load that is in the box could give off steam and the moisture could cause an ice build up, This could also go with opening the door to the box and what the conditions of the air outside is.
I doubt that it is a undercharge of refigerant since SH is good but better be on the safe side and check the SC.
This is an interesting topic if it isn't a undercharge because i all the systems that are freezers that i have seen electronic defrost element has not came in direct contact with the capp lines and distributor.(I could be wrong)
02-12-2009, 12:34 PM #3
hey, i'm just a new guy in this industry, so let me correct myself. I am even just a student at this point, and am just trying to get involved.
I apologize for putting my 2 cents in i realize now its beyond me if is confusing me. I thought the whole point was the exchange of ideas, and communication in general, however it seems i misinterpreted the original post entirely and really should just sit back and observe until i am more qualified to comment
Last edited by fogshat; 02-12-2009 at 05:56 PM. Reason: //
02-12-2009, 12:55 PM #4Regular Guest
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- Feb 2009
02-12-2009, 01:03 PM #5Professional Member*
- Join Date
- Dec 2008
- Dixiana, AL
If the distributor, tubes and txv are in the conditioned space and not inside the coil cabinet where they somewhat have a chance to defrost, and excessive ice becomes a problem, you may want to thaw this area, dry it off, and insulate it to keep moisture contact to a minimum.
02-12-2009, 01:23 PM #6
Doesn't really matter wh( type of refrigerant is in the system. This question would apply to any WI freezer box, no matter what the charge. Pressures really don't matter either unless the low side is extremely low, in which case, I believe that the original poster would have questioned that as well.
Most of the WI freezer boxes I work on have some degree of ice build-up on the TXV, distributor and distribution tubes.
Never gave it much thought. Really cold -23 evap. As long as the airflow areas aren't being obstructed, I leave alone.
From the explanations given, the non-contact with heaters seems to be the most logical.
Again, in the boxes that I work on, the TXV and other parts are in a seperate section of the coil, it is pretty tough to concentrate heat there while it is defrosting the coil.
02-12-2009, 02:35 PM #7
I am throwing out a basic observation, not asking for diagnosis of an issue. I am admittedly not a know it all and very green in refrigeration. I am not concerned to much with the icing/frosting of the TXV and cap tubes, just reaching out to the masters who see this everyday if this is normal occurrence.
The only concern I had was the frosting of the exposed suction components outdoors, ie; accumulator, suction filter/drier shell, exposed piping. This is what brought me inside to take a quick SH reading.
Like I stated, I was in the area and dropped by to see how things were running. Walked around back to check oil levels and saw the icing. Not pulling out the arsenal of equipment, yet. I do keep a low pressure gauge on a 6" hose and a pipe temp gauge on me for quick readings. Took 10min to check SH at evap (mfg was nice enough to install access valve in evap) against the engineering specs. Designed for -10* operation with a 10TD and 8* to 12* SH. I had a 9*SH with 8* to 10*TD.
If those of you whom want every exact little smidget of model#, compressor info, refrigerant type, temps and pressures, etc to concoct a theory then I'll get it for you. But this is a general simple question, not a cry out for diagnostic help.
P.S. R507, if it matters?
02-12-2009, 02:39 PM #8
02-12-2009, 02:43 PM #9
Thanks...jpsmith and smilie
02-12-2009, 05:05 PM #10If Guns Kill People, Do Pencils Misspell Words?
Before we work on artificial intelligence why don't we do something about natural stupidity?
02-14-2009, 08:49 PM #11
I have recently had a problem with a wif that froze back to the roof and over the accum and to the compressor head. the problem was the txv bieng stuck wide open and feeding too much, the defrosts were clearing the coil ( electric no x terminal preset for 40 min ) but eventuially blowing up the valve plate on a 3 hp coplemedic in the middle of january. changed the txv and valve plate and problem solved. just my 2 cents
02-16-2009, 11:14 AM #12
When I got back to office the other night, I brought my readings back to compare with those when system was first started up. We attached KW meters along with a few extra bells and whistles. Comparing the KW readings with those collected over the last few months showed a huge peak in usage.
Returned Friday afternoon and asked some exploratory questions. Never dawned on me at first that freezer curtains had yet to be installed since I entered off of a small second level heated service door to access a gang plank that runs along the upper back of the freezer to work on the ceiling mounted evap units.
Found out last Monday, they moved all the product out and onto trucks. During this time the large freezer door was left open and the curtains have yet to be installed by the owners.
Tuesday thru Wednesday they started restocking the freezer with all new product. Again, large 12ft x8ft door wide open a majority of the time.
By Friday, freezer was three quarters full, door closed, and systems thawed out and running/cycling properly. Hmmmmm, now I know why my poor condensing units were freezing and running so hard.
Begged the owners to get those damn curtains installed, they are killing the system. We bidded installing freezer curtains back in the beginning, but they balked at the price and said they could do it themselves for much cheaper.
Oh well, they break um...more money for me to fix um...had them sign off paperwork advising my warning and suggestions.
02-25-2009, 02:54 PM #13Professional Member
- Join Date
- Apr 2007
- Mesa, AZ
Excellent idea getting them to sign off on that curtain install (or lack thereof). I see this ALL the time with our freezers getting left open while loading/unloading product. Your preliminary checks were well done and gave an instant snapshot as to the system's condition. Moisture in the ambient air is a real headache with freezers when the users aren't (and usually don't care) to be knowledgable in thermodynamics. THESE ARE THE SAME ADULTS WHO STILL INSIST ON ASKING "WHY DOES MY COLD GLASS SWEAT ON A HUMID DAY"!