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Chunk
12-06-2008, 09:41 PM
Hello.

I have some moisture in a dual temperature rack that i cannot seem to remove.

I have done the usual stuff,pumped the rack down until it cant pump nay more.I have also shut the defrost side down for 48 hours so all refrigerant passes through driers.

After any work it disappears for a couple of days,then comes back,but only affects 3 freezer cases.

The defrost is hot gas and the stub tees in 1 metre above oil seperator then shoots off to the freezers.The condenser and reciever are on the store roof.

Normally on saturated gas defrost systems you can shut the defrost gas off from the reciever so all gas goes through driers,but i am not having any luck with the hot gas.

Any ideas would be great as this is taking up valuble sunbathing time:p

PS i`ve been told not to fit driers in the cases,so that options out. Cheers

fowlie
12-06-2008, 10:41 PM
hi chunk,
i ve found the best way to deal with this is to shut down the liquid valve for each case and allow it to run on fans and defrost any ice and maybe change tev/orifice.then allow case to run on fans for say a day or so and change the drier cores to high moisture ones for a few days but allow case to still get sat gas defrosts as this will help moisture leave evap.hope this is some help.:)

nike123
12-06-2008, 10:57 PM
Hello.

I have some moisture in a dual temperature rack that i cannot seem to remove.

I have done the usual stuff,pumped the rack down until it cant pump nay more.I have also shut the defrost side down for 48 hours so all refrigerant passes through driers.



Did you changed driers? It looks like they are saturated with moisture and giving up moisture back in system when defrosting with hot gas.

Evacuate all refrigerant thru new filter-drier. Change all system filter-driers. Evacuate system to 300 microns and be sure that it holds at 500 microns (with all valves open). Then recharge system slowly again thru new (again) filter-drier, or with new virgin refrigerant.

fowlie
12-06-2008, 11:04 PM
hi nike123,
that idea is the best but getting a supermarket in the uk to shut down shop for a day wouldnt go down well with the customer,and your boss wouldnt be to happy either

nike123
12-06-2008, 11:16 PM
hi nike123,
that idea is the best but getting a supermarket in the uk to shut down shop for a day wouldnt go down well with the customer,and your boss wouldnt be to happy either
It could be done over night with few vacuum pumps and new refrigerant!;)

Chunk
13-06-2008, 06:09 PM
Hi Guys thanks for the responses.

This pack has 48 cases and 6 coldstores running on it so getting them emptied for even a day is not going to be allowed.

We have a cabinet clean scheduled for 4 weeks time,so trying to work out if anything can be tied into doing repairs and cleaning at the same time.This gives me a window of about 18 hours at best.

As Fowlie said,getting the supermarket to empty everything is a big no no,unless it is a major catastrophe and even then they still fight you to get it fixed quick.

As for new refrigerant,this pack holds 800 kgs of r408a,so thats not going to happen either.

The driers have been replaced every time after pack has been pumped down.

chillin out
13-06-2008, 08:24 PM
After any work it disappears for a couple of days,then comes back,but only affects 3 freezer cases.
If it is only affecting 3 cases then why don't you isolate them and seal them up then vac them for a few days?
With the fans running at ambient temp it will soon get rid of the moisture.

Chillin:):)

chillin out
13-06-2008, 08:26 PM
Another thought, are you sure it's moisture?
Could it be oil logging in the suction pipe from these cases?

Chillin:):)

Chunk
13-06-2008, 08:34 PM
If it is only affecting 3 cases then why don't you isolate them and seal them up then vac them for a few days?
With the fans running at ambient temp it will soon get rid of the moisture.

Chillin:):)

Hi

These 3 cases dont break down together,i can clear the valve with hot water then a couple of days later it appears in a different case,and so on.It seems to happen on these 3 cases only.

Have asked about vaccing,but i am on the waiting list to borrow the companies only vac pump.;)

Chunk
13-06-2008, 08:38 PM
Another thought, are you sure it's moisture?
Could it be oil logging in the suction pipe from these cases?

Chillin:):)

Definately moisture.All the telltale signs were there originally,pack failed acid test big time and when these problems first arose,the driers definaltely had moisture in them.

Dodgy bottle of reclaimed gas went in,but i dont want to get into that.;)

bernard
16-06-2008, 10:33 PM
Hi

Dodgy bottle of reclaimed gas been there, gas from somewhere turns up and your told to put it in lol any thing to save a few pounds....next time one of the cases goes down then replace the valve and orifice and keep replacing the valves and orifices and drier.

I had the same problem that would take down the same coldoom every time,when I removed the valve I found ice crystals blocking it,after three new valves,numerous driers and oil changes it went.

Pouring hot water over it only moves it on.

Good luck Bernard

chillin out
16-06-2008, 11:02 PM
I am surprised that the evap has not burst yet.

Moisture likes to go into the seams of the welds expand and then rupture the pipe.

Chillin:):)

taz24
17-06-2008, 12:43 AM
Iv'e had the same a few times.
You need to put dryers infront of the 3 freezers and change them in a months time.
You need to replace the dryer filter cores at least once a week.
If you are persistant you will get the moisture out.

Cheers taz.

US Iceman
17-06-2008, 12:53 AM
Chunk,

Are these 3 freezers the only evaporators that operate below freezing on this rack system? If they are then that would explain why you are only seeing this problem on them?

If you can't vacuum the system (I understand why), what you can do is increase the filtrain/drier capacity by putting drier shells in place that hold additional cores (and changing them frequently).

I feel your pain. This can be a real pain in the a$$ to repair.

refmech
17-06-2008, 05:17 AM
i have seen this one too may times,bad day, crappie gas,or working behind someone that drags there hoses across a wet roof! dryer changes will get you there. make friends with the guy who makes coffee.

refmech
17-06-2008, 05:25 AM
another thought. vac down dryer shells with new cores. make certain they are dry.

nike123
17-06-2008, 06:12 AM
another thought. vac down dryer shells with new cores. make certain they are dry.
How are you suppose to do change of core without vacuuming shell? Blowing refrigerant is illegal and leaves non condensables and moisture in shell (there is no membrane between refrigerant and moist air, they are mixing).;)

Chunk
17-06-2008, 06:17 PM
Hello,thanks for responces.

I have 14 freezer cases on this rack,all are fitted with Danfoss AKV electronic valves,so nice and easy to strip down.

Today i changed the filter cores again and pumped the system down.Whilst the system was empty,i stripped the valves down on the offending cases then warmed the valve body up with my heat lamp then gave them a good wipe out.As Bernard says in his post,there looked to be small crystals forming near the orifice.

I physically cannot fit a drier near to these freezers,due to the pipework is run under the floor and comes up in the middle of the island where you cannot reach.

I have another few weeks until i can shut them all down properley,so i shall carry on pumping down,changing filters and cleaning valves in the mean time(it aint my money;)).

What i really need is a few yobs to set fire to the place as they have done to a couple of other stores,but i`ll keep dreaming.

P.S i did find moisture in the compressors which might explain why the filter cores are not catching it,as the discharge comes off the comps and down to the cabinets for defrost.I have done a complete oil change,but now thinking i might have to fit driers in discharge line:confused:.Why is nothing simple?

US Iceman
17-06-2008, 06:46 PM
...now thinking i might have to fit driers in discharge line.


:rolleyes::rolleyes:


Stop! Don't do that! I saw a similar attempt many years ago and the drier cores disintegrated into something that looked like sand. You can imagine what that did for the compressors?:(

If you can fit a suction drier shell back in the compressor room, that will help. In this instance what you need is a lot of drier capacity and the only way to get that is to have the larger four core drier shells with good cores. I always used the acid core driers since my thought was: if there is water then there might be acid!

Chunk
17-06-2008, 07:07 PM
:rolleyes::rolleyes:


Stop! Don't do that! I saw a similar attempt many years ago and the drier cores disintegrated into something that looked like sand. You can imagine what that did for the compressors?:(

If you can fit a suction drier shell back in the compressor room, that will help. In this instance what you need is a lot of drier capacity and the only way to get that is to have the larger four core drier shells with good cores. I always used the acid core driers since my thought was: if there is water then there might be acid!

HaHa i wouldnt really do that!!

I have core housings on the suction of all six compressors,will that do? The suction pipe is 4 1/8" so i dont really want to be cutting into that.

Peter_1
17-06-2008, 07:49 PM
Look once to my post 19 of this thread where I posted some pictures http://www.refrigeration-engineer.com/forums/showthread.php?t=13111&highlight=water

I know what you're going through :confused:

US Iceman
17-06-2008, 07:58 PM
I have core housings on the suction of all six compressors,will that do?


If you have driers on the suction and liquid lines, then that is all you can do unless you recycle the entire charge and pull a vacuum to dehydrate the piping, etc.

If this is only showing up in a small number of evaporators you have it easy.:D

I once worked on one that every TXV was freezing up. I'm here to tell you that was no fun!! But I guess you are figuring this out without me telling you it, right?;)

Peter_1
17-06-2008, 08:44 PM
We needed +/- 45 cores on a much smaller system to dry it out completely.
We reheated also some in a microwave to reduce cots.
We even shaked the copper lines of the freezer in their cable trays and we heard the ice running in the lines that came lose while shaking the lines.
We couldn't laugh at that moment.
We had to heat some T-junctions of 1 5/8 to remove the complete ice blockage.

Billy Ray
17-06-2008, 09:29 PM
Chunk,

it maybe an idea to change the oil!!

I'm not sure, but if the oil is saturated with moisture, will the refrigerant driers remove that moisture??

Billy Ray

Chunk
18-06-2008, 07:41 PM
Changed the oil,installed high capacity cores in liquid and suction,cleaned out valves.We`ll see how it goes.

Thanks again for your contributions.I`m off out for another night of finding gas leaks and sorting oil problems.Have fun.

Chunk
18-06-2008, 07:48 PM
We needed +/- 45 cores on a much smaller system to dry it out completely.
We reheated also some in a microwave to reduce cots.
We even shaked the copper lines of the freezer in their cable trays and we heard the ice running in the lines that came lose while shaking the lines.
We couldn't laugh at that moment.
We had to heat some T-junctions of 1 5/8 to remove the complete ice blockage.

I installed a banana factory in Liecester England years ago that had a 12 fan condenser that was full of water from the factory.It took 3 months to sort out and nearly 400 drier cores.We had the same problems as you had,but when you have to take apart 30 liquid solenoid valves every 2 hours to remove ice it does get a bit depressing.

US Iceman
18-06-2008, 07:58 PM
...you have to take apart 30 liquid solenoid valves every 2 hours to remove ice...


I think I would prefer to use some warm water poured over the valve to help keep it clear of ice. By taking the valves apart (and open to atmosphere) you may be creating more work for yourself.

Anyway, if you can keep the refrigerant flowing the driers will pick it up faster.

Chunk
18-06-2008, 08:07 PM
I think I would prefer to use some warm water poured over the valve to help keep it clear of ice. By taking the valves apart (and open to atmosphere) you may be creating more work for yourself.

Anyway, if you can keep the refrigerant flowing the driers will pick it up faster.

It was a building site at the time so we only had freezing cold water.And the kettle we had on site took 20 minutes to warm up.:confused: