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08-13-2007, 10:58 PM #1
Norlake Freezer Unit Mystery - any ideas?
Customer calls: "freezer is warm. Just needs freon. A customer checked and found out. Come and charge it up."
Get there. "it was not running - my customer he look at it - he adjust pressure - now running - no cold enough - he say needs freon"
Great pal - mind if I check for myself?
The unit and walkin are five years old. Customer says there have been no problems except a stat was replaced a few years ago. I believe it - no wrench marks on access or valve caps.
I find: R-404 system. Copey iron body (KAJB 010E CAV100) Sight glass is clear - shows dry. 111 degree condensing temp. Liquid line is 102 degrees from the receiver outlet, both side of the drier, and to the TXV. Evaporating temp is about zero. Suction line temp is about 70 degrees.
I conclude that it does not need refrigerant. I screw the TXV stem all the way out - no change in suction pressure or line temperature - TXV must be bad.
I call NorLake and ask them which valve they used. They tell me some 1/2 ton Sporlan # (EFSE-1/2-ZP) that I don't have but I locate one on the phone and go get it.
Working in a 105 degree attic, on top of the box - 11" clearance over the NorLake evap box - 12" clearance alongside - I R&R the valve along with a new Sporlan 163-S drier. Valve bound in wet strips of cloth, Stay-Brite solder joints. Propane torch. Valve barely warm to the touch the whole time.
Open the condensing unit valves, the unit starts, the evaporating temp is 19 degrees the suction line temp is 8 degrees. Frost happens right to the suction service valve. Cool - I'll wait for it to stabilize a bit and drink Gatoraide. Line temp hangs at 8 degrees for a few minutes and starts to climb. Stops at 60 degrees and remains.
Hmmmm . . . recheck: subcooling is 7 degrees. evaporating temp is 20 degrees. Suction line temp is 60. Damn - now what?
Box temp is 27 degrees. I screw the TXV stem down (open) a few turns - no change.
This evap coil is six rows deep - face about 12" by 30" Has heavy frost on first row fading to slight frost on the third pass. Nothing after that. Four distributors - all with even frost.
Can the valve really be too small with the coil temp so high? You would sure think it would be wide open with a 60 degree suction line. I am just guesstimating but I would think a 1 HP compressor at a -10 suction would be pumping about 3000-4000 BTU's tops. A 1/2 ton Sporlan with a 200+ lb. PD would flow maybe 7000 BTU's?
It has been my lifelong experience that TXV's rarely fail.
This is looking like a restriction of some kind to me at this point - and apparently at the TXV. OK maybe once - but twice? First a bad TXV and then another one right out of the box? Come on now.
Have I just just been brain-fried back into a one month apprentice? I poked around for a few minutes but at 9:30P I called it a night. Told them to let it "stabilize" and I would check it in the morning. <g>
So? What do you all suggest?PHM
08-13-2007, 11:46 PM #2
You are probably running at the MOP of your valve. It is pressure limiting and it will do what it says: pressure limit. ZP charge tells the tale. so, until you come below MOP (35i or so PSIG depending on setting) you will see high superheat. I will reread your post, but this isn't at a Subway, is it? Call Norlake for the specs on the box, it maybe a "holding" box. Not designed for any door traffic or real pulldown. Don't beat your head on this one, You have the subcooling-your valve has all of liquid it needs. You have a high suction (relatively) You are loaded. Get a compressor curve and see if she pumps. good luck.
08-14-2007, 12:03 AM #3
A Subway; yes. Why do you ask?
Were you there today? And, being smarter than me - refused to work in that nasty friggin attic? <g>PHM
08-14-2007, 12:32 AM #4
reason I ask Mikey, is that this maybe one of those holding boxes I have spoke of. If they leave that box closed all night, you might get to 0. Might. I don't have mod and ser infront of me, but I know norlake had put a box like this out for Subway and they told them it wasn't for heavy pulldown. That was the 502 machines we converted to 408a. I thought that they were going to go 3/4 horse with the 404 machines. In a nutshell, you have a chain (Subway) asking for a box to do "X" lets say HOLD a frozen product at 0 to 5 degrees. Then it gets to the jobsite and you have serious door traffic and them loading it with warm product, all the while lying to you saying "Oh yeah, it was at minus 15 degrees, always has been, oh until you guys started working onit" That is BS. Ask Norlake what this box is desuigned to do. Good luck.
08-14-2007, 01:41 PM #5Regular Guest
- Join Date
- Jan 2007
- Washington State
Look Up "ZP" on your sporlan chart
First let me say that you did an excellent job on your troubleshooting. You may or may not know what a "ZP" head is. A "ZP" head is pressure limting. This is used on systems that don't pump down during defrost. I'm guessing that originally you had a bad valve and after you changed out the valve you were experiencing excessively high suction pressures. (Relative to a freezer) This caused the "ZP" head to throttle the valve closed. Give the system some time and I bet your just fine. Good Luck!!!
08-20-2007, 12:19 PM #6Regular Member - Bad email
- Join Date
- Apr 2007
- Rossland, B.C.
These condensors are undersized especially in high ambient. I was happy to replace a condensor and comp when the originall k seized. Put on a higher btu cond and works great. Used a can.
08-20-2007, 05:57 PM #7Professional Member
So you didn't ask, what you though was a stupid question. Now how, are you going to tell the boss about your stupid screw up?
- Join Date
- Dec 2005
- South Bend, In.
08-21-2007, 07:02 AM #8Professional Member
- Join Date
- Dec 2004
I love when they tell you whats wrong with it. I always think to myself then why did you call me if you already got the answers lol.
I agree about the ZP head messing with your head on your readings. I don't know about the other stuff the above posters are saying about out of design parameters but I've been in that boat too. Tell the customer he is trying to tow a 40' boot with a 4clyc motor he will grasp that concept and then when you leave he will ignore what you told him. document it on your ticket so when it gets called back in your covered.