Evaporator Distributors

Hi All,

I am having a few problem with a brand new freezer room not working properly. There is a bit of a story to this so bear with me. The freezer coil was originally install on a job a about six months ago, I didn't commission it but after two week of operation and the client stocking the room it wouldn't drop past -12C. After many trips by numerous techs and replacing TEV, upsizing orifice etc. it still didn't work. I was sent to replace the evaporator on this job, I could see by the way that the bottom of the coil was iced the top clear that the refrigerant was feeding properly. It was decided to replace the evap with a model of the same capacity from a different manufacturer. I put it in and it work perfect the room pulled down quickly, all was good.

The offending evaporator was sent back to the manufacturer for warranty. Warranty was denied the said that there was nothing wrong with it, that all pass were correct and it was distributing evenly. We requested that the distributor was replaced which was done before we got it back. So having a brand new second hand evaporator sitting there that has nothing 'wrong with it', it was decided that it would be put it at the next job that calls for a evap of its size.

So it's in at a brand new job, commissioning today job to open on Friday and what do you know this coil is doing exactly what it was doing at the last job. The room is taking forever to come down to temperature. A new room empty from start up to -18C will take three hours max. After 3 it was only down to -8C. The TEV is hunting all over the place I played around adjusting super heat to no avail. I can see the problem the refrigerant isn't being distributed properly. The vapour and the liquid are separating, the bottom of the coil is flooded with liquid the top is getting mainly vapour. This is why the TEV is hunting all over the place because TEV senses the bottom circuit flooded with liquid refrigerant, 0K of superheat, and forces the TEV to close. This causes the top circuits already starved of refrigerant to operate at an even higher superheat. Once the bottom circuit is no longer flooding with liquid, the TEV senses the high superheat from the upper circuits and it open quickly, only to once again flood the bottom circuit and start the cycle all over again.

I am familiar with nozzle type distributors and this manufacturer use to use them they worked fine provided you selected the right orifice. But they have moved to a venturi type distributor, does anyone have any information about this type of distributor? How does it work?

I think there is a fault with their distributor, and I've got the manufacturer coming out tomorrow to show them. But I'm worried if they do replace the coil with a new one under warranty I'll have the same problem. Any thoughts or help would be appreciated.

Had one do the same thing, think was Friga-bohn but don't quote me on that. Basically the distributor was two 3/16ish sized cap tubes poked into a 1/2" thing with a flare nut to suit the tev. One 3/16 was at 12 o'clock and the other at 6 o'clock as the distributor was horizontal.
Gravity made all the liquid go through the lower one and had same symptoms you describe, out with the spanners, turn distributor so outlets were at 3 and 9 o'clock and it worked fine.

Thanks for the reply monkey spanners, But the TEV is mounted vertically feeding in to the distributor in this instance so I believe that it can be eliminated. But you are correct in what you are saying, as nozzle type distributors are required to be mounted vertical to work properly. This distributor is a venturi type as mention in post and can supposedly be mounted in any direction.

Any how an update on the days preceding. Manufacturers engineer came out to have a look at wat was going on. I was asked to put a larger orifice in the TEV so I did, the existing orifice was the correct size. The result to my eyes was exactly the same except the TEV was hunting even more. The suction line to the compressor quickly turned to a block of ice. But according to their so called engineer this was just cold vapour. What tish I know the difference between cold vapour and liquid lucky it has an accumulator. Anyway was room was still wasn't pulling temp so I was asked to open up the TEV superheat even more. At this point I stopped and ask the engineer are they going to warrant the compressor when the valve plate is annihilated from slugging liquid. No. Well I'm not opening it any more. So we agreed to disagree. The manufacturer says there is nothing wrong even though there clearly is.

So after discussion it was decide bite the bullet and that we replace the evaporator with a new one from another manufacturer at our cost. As if we left it the way it was it was only going to cause another 5 service calls under warranty. As a reputable company we can't have this, so tomorrow it is getting replaced I let you know how I go!

Fridgey. Can you send a picture or two of the distributor and feed to your evap?

is the tev correctly fitted, sized correctly and for the correct application- sensing bulb lower than the tev head, bulb insulated? correctly mounted on the suction line at 9 o clock?

New evaporator coil went in today, similar capacity to the evaporator being pulled out. I used the same TEV but went back to the original sized orifice and reset to factory setting. Of course pipes, electrical's and mountings are never the same, but after some rejigging the new evap was in and connected. After a vac out all was ready to go, and what do you know it ran like a dream. It pulled the room down from 20C to -18C in under two hours, the TEV superheat across the coil was 7K and was steady and not hunting, suction superheat was 14K, a massive difference to the previous coil.

What I know is that I would never use another evaporator from the original manufacturer again. Although I won't name names, previously I thought they had a good product but since manufacturing has been moved out of Australia obviously the product quality has slipped. Their lack of acknowledgment of even a problem to me is shear arrogance, but the proof is in pudding as the new coil works perfectly!