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Johnny Walker
08-06-2012, 05:43 PM
Hi,

Can someone please give me advice on a walk-in freezer troubleshooting?
I have just installed a second hand cabinet with the equipment and its not working properly (I have seen it working and I dismantled it myself...)

First when I regassed I couldn't reach the desired superheat (It was nearly 20C), but with time it had pulled down the cabinet to -22C because it was empty (probably).
The day after they filled it up with food and now it never goes below -13C.

The readings are:
Suction pressure: 1.6 bar
Suction line temp: -1C
Discharge press: 16.2 bar
Discharge line temp: 32 C

The pipe temperature before the condenser is 68C.
Ambient 24C, Air off condenser 33C.
Air on evaporator -13, air off -17 on one side, -12 the other.

It seemed like the evaporator starving, but charging more refrigerant doesn't make any difference. (except the discharge pressure and line temperature increasing a bit.

Any idea would help, thanks.

monkey spanners
08-06-2012, 05:59 PM
How cold is the food?

If its a holding freezer and not a freezing warm things freezer it may take days to get the product down to temperature.

Don't see how air off can be warmer than air on unless defrost heaters stuck on???

Guessing its on R404A?

jdunc2301
08-06-2012, 06:04 PM
you say air on evaporator -13, and off on one side is -17 and the other is -12.......... are you sure?

If so, think about it, wheres that 1'C coming from, possible defrost heater stuck on

Johnny Walker
08-06-2012, 07:06 PM
Yes, sorry, thats probably just mistake with measuring... Probably its just the same temperature on and off.

What I was thinking to switch off the evap fans to see how the temperatures and pressures become... Suction went down to 0.6bar and line temp was -13C... R404a at 0.6bar has really low temp, so the pipe should be like really low as well, isn't it?

I was thinking about stuck defrost heater as well, but its not, I checked.

cold.man
08-06-2012, 09:33 PM
16.2 bar sounds as the discharge is a little high are you sure you havent over charged it slightly?

FreezerGeezer
09-06-2012, 01:05 AM
I hope this doesn't come across as rude, but are you happy with your basics:
Nitrogen purge during brazing & triple vac of the system before recharging. Have you checked all valves are in the correct position? Any swarf in the solenoid valves (if it has them)? Are the condenser & evaporator coils clean & clear? No possibility of air recirculation? All seams sealed, door sealing properly?
How long did you take for the initial pull down? Iirc for a new cold room with concrete floor the pull down takes about 2 weeks to avoid moisture/ice pockets forming.
What are the air ingress loads like? Butchers in particular had a bad habit of leaving the doors open.

Monkey Spanners makes a useful point. If the new use profile is very different from it's designed use profile, the cold room is never going to work properly.

sedgy
09-06-2012, 01:24 PM
hi johnny walker , just to get a fix on your job , lets start from the beggining , you say you regassed the system ? tell me did you pump down the system and valve it off ? = sedgy .

Johnny Walker
11-06-2012, 06:17 AM
Hi.
Thanks for all the helping answers.
I am beginner and not english but I'm trying to make everything properly. I've done everything as it is written in the books and all the chillers and walk ins are working nice what I have fixed/installed so far, that's why I don't understand what is going on with this freezer.
The room temperature is actually moving down slowly, I am just waiting now and tonight I will measure it again.
Thanks again

Johnny Walker
11-06-2012, 07:45 PM
Actually it has really high superheat, about 10-11C and thats it.
Its moving down slowly.
Someone was playing already with the TXV settings because the screwcap is missing.
Interesting that this is my second negative experience with Kobol brand evaporator...
Thanks for all advice I will keep it in mind.

install monkey
11-06-2012, 08:04 PM
was the food added to the coldroom at room temp or delivered at -18?- is there an air balancing valve not closed properly- is the door seal air tight?
check the tev valve adjusting screw isnt leaking as you mentioned the cap was missing.

Rob White
12-06-2012, 09:00 AM
.

It has been said earlier.

You need to go back to basics.

If it was working ok before and if all you have done is dismantle
and rebuild it then you need to find out what is differant.

Was the product frozen when it was put into the room?
Was the TEV adjuster cap missing before the rebuild or after?
Did you pump down the original refrigerant charge or did you replace it?
Is the room air tight?

If you have been adding R404a to the system you might need to look
towards the gas fractulising (seperating out).

Go back to basics.
Set valve to factory settings (screw all the way in and then back out 3.5 turns),
remove all refrigerant and vac to less than 2 torr,
Recharge with pure liquid.

Regards

Rob

.

chillerman2006
18-06-2012, 07:37 PM
Johnny

will give you a buzz with my new number & we can run through it when your on site next

R's chillerman

Airconjon
30-11-2012, 10:13 PM
Just to confirm did you pump the unit down when it was removed ? Also when you recharged the unit was the refrigerant added as a liquid or a vapour ?

Airconjon
30-11-2012, 10:14 PM
As needs to be a liquid .. It's a blend

Airconjon
30-11-2012, 10:15 PM
Also just a thought Are all fans running (evap) ie not 2 running and one being pulled around ie good ir flow ?