Walk-in freezer, won't pull below 4

[MwTechInc]

Hello

First post , tho I read as a guest.

Like to run this problem past other techs, I must be missing something.

New customer, about 6 mths, no work on this unit till last week

Walk-in freezer 10x10 system approx 6 years old

2 fan Evap facing door

Cond on roof, 38' run with 10' being vertical,trapped at evap.

Cond has suction filter and accumlator

Copeland 3ABA series

404A gas(assume no other, assume pure charge)

Condition found:

Suction line solid ice(up to 1.5'" thick) at evap-anywhere line exposed and at condensor. Where insulation stopped at condensor everything from the suction filter to the compressor service valve was solid heavy ice.

Box temps over 0

Unit in school so had the option to shut off unit and allow a thaw.

Went back and pulled insulation scraps from evap output, NO txv bulb???

Pulled side cover and "someone" had put the bulb on the mainifold. Now this manifold is made where the vertical pipe enters the horiz line like a Tee.
The bulb was actually mounted behind the vertical pipe in the stub.!!
Maybe 1/2 " of the bulb ever saw actual freon flow.

Needless to say I moved the bulb out on the line at 4 o'clock, insulated it, and then reinsulated or repaired the entire suction line using 7/8x 3/4 wall.

Figured all OK, started unit, pulled down fairly quick to 36 deg, was at end of day went home.

This morning went back, box at 4, figured I needed to adjust thermostat, did and left. Went back tonight, 4 deg.,comp running good ice buildup on lines.

Here are measured specs with box at 4 deg, outside air 88 deg, unit running.

Suction 27psi
Head 265 psi

evap 29psi at 5 deg

discharge line temp 132 deg
liquid line at drier 97 deg

comp RLA 10.0 measured 7.2

Coils 95% clean.

No ice build up on evap anywhere.

Distribution lines all "frosted" the same

compressor runs quiet, no pounding-knocking

clear sight glass, no flashing or bubbles

headmaster shows no sign of bleeding thru(although haven't ruled it out)

unit will defrost with no errors, fan delay etc OK.

Both cond and evap fans appear to be correct rpm's


I think I listed everything .

I won't put my ideas on the table yet.
School starts in 2 weeks so I got to figure this thing out.

Thanks for any help

Andy

[Dchappa21]

Temps right for your suction pressure.. What is the SH at the txv....

That 5* you listed is the box temp when you took suction pressure and not the suction line temp right?

[Dchappa21]

Wouldn't be a bad idea to pump it down or close the suction valve and see if the valves are good.

[MwTechInc]

measured psi at evap was 29

5 deg temp was suction line 10" away from pressure port on the vertical.

Used my new Fluke clamp probe on a reliable meter.

I don't think there was insulation etc under clamp

There was a bit of up/down on meter 3,4,5, all showed up.

Pt chart in van( too tired to go get it) but this morning figured a 5 deg SH

Did check for pressure rise when forced the thermostat, held 10psi with very slow increase.

Andy

[jpsmith1cm]

27# is too high for a freezer box on 404a.

[Poodle Head Mikey]

Attach a suction gauge and front-seat the suction service valve. If the suction pressure isn't 15" in a few seconds - the compressor valves are defective.

Welded hermetic? Or iron-body hermetic?

PHM
--------

Hello

First post , tho I read as a guest.

Like to run this problem past other techs, I must be missing something.

New customer, about 6 mths, no work on this unit till last week

Walk-in freezer 10x10 system approx 6 years old

2 fan Evap facing door

Cond on roof, 38' run with 10' being vertical,trapped at evap.

Cond has suction filter and accumlator

Copeland 3ABA series

404A gas(assume no other, assume pure charge)

Condition found:

Suction line solid ice(up to 1.5'" thick) at evap-anywhere line exposed and at condensor. Where insulation stopped at condensor everything from the suction filter to the compressor service valve was solid heavy ice.

Box temps over 0

Unit in school so had the option to shut off unit and allow a thaw.

Went back and pulled insulation scraps from evap output, NO txv bulb???

Pulled side cover and "someone" had put the bulb on the mainifold. Now this manifold is made where the vertical pipe enters the horiz line like a Tee.
The bulb was actually mounted behind the vertical pipe in the stub.!!
Maybe 1/2 " of the bulb ever saw actual freon flow.

Needless to say I moved the bulb out on the line at 4 o'clock, insulated it, and then reinsulated or repaired the entire suction line using 7/8x 3/4 wall.

Figured all OK, started unit, pulled down fairly quick to 36 deg, was at end of day went home.

This morning went back, box at 4, figured I needed to adjust thermostat, did and left. Went back tonight, 4 deg.,comp running good ice buildup on lines.

Here are measured specs with box at 4 deg, outside air 88 deg, unit running.

Suction 27psi
Head 265 psi

evap 29psi at 5 deg

discharge line temp 132 deg
liquid line at drier 97 deg

comp RLA 10.0 measured 7.2

Coils 95% clean.

No ice build up on evap anywhere.

Distribution lines all "frosted" the same

compressor runs quiet, no pounding-knocking

clear sight glass, no flashing or bubbles

headmaster shows no sign of bleeding thru(although haven't ruled it out)

unit will defrost with no errors, fan delay etc OK.

Both cond and evap fans appear to be correct rpm's


I think I listed everything .

I won't put my ideas on the table yet.
School starts in 2 weeks so I got to figure this thing out.

Thanks for any help

Andy

[itsiceman]

measured psi at evap was 29

5 deg temp was suction line 10" away from pressure port on the vertical.

Used my new Fluke clamp probe on a reliable meter.

I don't think there was insulation etc under clamp

There was a bit of up/down on meter 3,4,5, all showed up.

Pt chart in van( too tired to go get it) but this morning figured a 5 deg SH

Did check for pressure rise when forced the thermostat, held 10psi with very slow increase.

Andy

http://www.fridgetech.com/calculators/

I get twice that SH with those #'s

Was there any product in the freezer.

[MwTechInc]

Compressor is semi hermetic 3ABA-031E-TAC-222

No product in freezer

I may have messed up this morning doing the super heat, was in a rush.
May have picked up the wrong number on the old chart.

I'll go down tomorrow,check the valves, do another "superheat pressure/ temp" check to verify I've got good numbers.

Andy

[Poodle Head Mikey]

Start the compressor.

Suction gauge hose on the suction service valve's access port.

Front seat the suction service valve.

Suction pressure should immediately head south to 15" of vacuum or more.

If not - order a valve plate and gasket set and get it on there.

Or - that's what I would do. <g>

PHM
--------

Compressor is semi hermetic 3ABA-031E-TAC-222

No product in freezer

I may have messed up this morning doing the super heat, was in a rush.
May have picked up the wrong number on the old chart.

I'll go down tomorrow,check the valves, do another "superheat pressure/ temp" check to verify I've got good numbers.

Andy

[luskys a/c]

I'm with stonewall. I like to run R-22 a little colder than other equipment due to the oil problems, but there is no logical reason that R-404 couldn't be used at a 2-3 degree superheat just as R-22 is. quote by jpsmith.
--
Jp...you were right . when i got the box temp down past 10*f my super heat settled to 2-3 deg f at the evap and 24*f at the compressor . I did achieve -10* f in the box and then set my t-stat at -5*f . MwTech...I still had ice build up at the compressor so your ok there.

[MwTechInc]

Ok......

Did a pump down..............after about 30 sec the ol compressor finally pulled down to about 2"

So needless to say a kit will be here tomorrow.

I guess a pump down just never clicked in my brain as the gauge dropped quick when the solenoid closed.

But in the back of my mind it seemed like the thing just couldn't pump any more

So......we will install kit, run box, do another SH check and see what happens.

Thanks for the help guys.

Will update .

Andy

[Poodle Head Mikey]

Try to scrap away from the cylinders but when you are done scraping - just bump the contactor in and all the little bits will fly out of there. Look away while you are doing this. <g>

PHM
--------

Ok......

Did a pump down..............after about 30 sec the ol compressor finally pulled down to about 2"

So needless to say a kit will be here tomorrow.

I guess a pump down just never clicked in my brain as the gauge dropped quick when the solenoid closed.

But in the back of my mind it seemed like the thing just couldn't pump any more

So......we will install kit, run box, do another SH check and see what happens.

Thanks for the help guys.

Will update .

Andy

[MwTechInc]

Been many years since I put a valve kit on.
Are the torque specs included?

[jpsmith1cm]

Been many years since I put a valve kit on.
Are the torque specs included?

Yes, they are normally included.

Copeland specs theirs in Inch/pounds.

If I remember correctly, spec for a 3D compressor is 525 in/lb or 43 ft/lb

[MwTechInc]

Installed valve kit and fired her back up.

Sounded different, picked up discharge temp to 148.

Down to the box for a SH check(after running a while)

SH was 12 so a little adjusting went on and the results are:

SH 5 , box at -2


Will follow up next time I'm at the school to do fine tuning if necessary.

Thanks for the help

Andy

[crackertech]

Glad to hear that the valve plate kit worked.

[MwTechInc]

Checked in on the freezer yesterday and found the box at -4 with the compressor cycling.

I lkie things to be right on so let me pose a question.

Still have ice formation at the condensor, now just includes the suction filter and 60 % of the accumlator.

No ice on output of accumlator, vibration dampner or compressor.

So things are better, however 5 miles away I just replaced the same HP Copeland on a freezer, corrected a lot of problems(other companies) and it runs perfect at 0/-2 with no ice on suction.

Something is just not quite right.

Now it's down to me and this system. It's only one mile from the shop so I can mess with it a lot.

The school will be stocking the unit this week, will do a SH and check once full.

All for now

[Phase Loss]

You will still be able to maintain box temperature with high compressor superheat...its just that compressor will thank you if you run it with a little ice to keep it cool.

and of course it makes for a more efficient system IE: cooler vapor is more dense than warmer vapor...so your compressor would actually be doing more work per stoke.

look at the picture in my profile...that is one happy pump.

[KLEINman]

im kinda new to the real refrigeration part of the trade, but bein in ac my brain tells me that icing at the inlet of the compressor is bad.............im guessing that with refer its ok.......

[Phase Loss]

that is because most compressor manufactures recommend no less than 20* compressor superheat. Now in A/C world...you do not really run below a 35* SST, so Ice back to the compressor would mean flooding. But in Refer world..we deal with much lower SST's such as -25,-20,-15,-10...while running such low SST's and trying to maintain that minimum 20* compressor superheat, it becomes obvious why we would expect to see ice back to a compressor. I will go out on a limb and say that if you are running a -25SST and do not have ice on the compressor...you have a problem.