Need help with PhaseChange refill

Hello,

Not sure if this is the correct subforum.

As the title suggests, I need help with SS refill.

I bought some time ago used unit from my teammate.

The SS is made by LittleDevil and is similar to this one: http://ldcooling.com/shop/ld-pc-v2/52-ld-pc-v2-phase-change.html

Maybe just a little bit older (3 years), but should be the same, minus the usb controller.

It doesn't hold the same temperatures as before, so I want to refill it.

Does anyone know what kind of gas (r507 ?), pressure and oil LD uses in these?

I tried to contact him, but have no answer to date.

Keep in mind I don't know anything about phase change, never built one myself, etc.

So I need to know what to tell the technician who will refill it.

Compressor is Danfoss NL11F which I believe is a popular one.

Any help appreciated.

In such "home-made" systems , you cant really tell , what king of gas was used.

NL11F is a small compressor , designed for R134A gas but it can tolerate an R404A gas.

R507 is a bit more brutal gas , and some people chose it , to gain 4-5C lower temps.

But you need more cooling power down to the heat exchanger.

If your problem is minor , you can give your phase-change a tiny blind zip of R404 and see if things get better.

As far as I understand, r507 is similar to r404a and also don't think it is r134a, since it has higher boling point compared to the other two.

NL11F is designed for R134a , but others builders use R404/R507 to charge it , because at lower boiled points.

also as phase change builder i´m not agree with this solution because R134a use another pressure chart compared with R404/R507 , even they use same oil ( POE- polyolester - sintetic oil).

NL11F it has only 11ccm , so it is very small compressor and very silent but to small for heavy load that used on hardware today , on my experience you can tunning this sistem up to 300W dummy load with -20 to -25* C evap temps , and remember you must change (or add another ) condensor because original is to small for 300W load .

if your unit it has a leack and you have more than few weeks , you should change also OIL , because is contaminated in contact with air , POE oil is hygroscopy , if you expose more than 30min without capped or inert gass into will have moisture and ruin hole OIL.

if recharge the unit , should change filter dryer to new one , a deep vacumm is a must till 250 -200 microns on your gauge , charge liquid refrigerant intro liquid line acces valve and then complet with vapours/gas into suction/ service port - but add refrigerant with evaporator loaded , so you will need a load tester

also i don´t know if the builder that build your SS use a suction accumulator in suction line , if not you should pay attention to NOT overcharging the sistem , reciprocating compressor are weak to liquid refrigernat flood back , and compressor will die in short time!

Yeah, accumulators are meant to prevent liquid to enter the compressor. Never done an SS before but read a lot at XS. A friend of mine built one and tested with R404a and R507c, both refrigerants are almost the same, but R507 could manage better the workloads and was a bit cheaper.

Tests were made with some rotaries designed for R410a (Panasonic 13000/9000 BTU), but as long as the gas is meant to be used with the same oil (POE in this case), there is no problem at all.

Regards

R507 is compatible with R404a and viceversa , so if you had a compressor design for R404a , you can charge it with R507 as a designed refrigerant for it!

the most powerfull single stage are made with rotaryes , because they can endure better liquid refrigerant presence( also they had from manufacture included suction accumulator) , they endure better gas temp in discharge line and more resistence and stable temps on evap at hight ambiental temps!

right rotaryes for a single stage are r407c rotaryes and charge with R507 .

R507 are the best/performant LBP( low back pressure) refrigerant to use intro SS , also R407c rotaryes accept very well R507 , because R507 works and mix very well with POE oil with visosity 56 , 68 , 72 ,100 specify for R407c and R410a that are used into AC system.

R404a works well( R507 aswell) with POE with low visosity iso 22 , 32 etc , but into rotary with hight POE viscosity R507 is better and irreplaceable.

rotaryes design for R410a refrigerant( HBP - hight back pressure) , worsks also very well with R507 , but compared vs R407c rotaryes at same btu/h they are small at cm³/rev ( ccm) .

ex: 10.000 BTU/h R407c rotary = 16,4ccm

10.000 BTU/h R410a rotary = 12 ccm

R410a rotaryes are best way when you wanted to use HBP refrigerant( R410a , R23, R1150 , R50 etc..) in 2 ,3 stage cascade in the second stage specify for hight back pressure refrigerant:)

like i did in my build´s here:

http://www.xtremesystems.org/forums/showthread.php?290110-2-stage-Rotary-Cascade-first-cascade-build

http://www.xtremesystems.org/forums/showthread.php?290159-Big-Rotary-SS-)

http://forum.lab501.ro/showthread.php?t=14259

http://forum.lab501.ro/showthread.php?t=14511

Thanks guys. The technician said the said, so it seem he knows what he's doing.

I still haven't tested it, because I gave it to a teammate and he handles the process.

Any idea how to check if we over filled system? The system I.nfraR.ed talk about have only one port and we refiled trough it with liquid refrigerant R507. SS was on low heat load on the head. Unfortunately it perform worst as before refill and temps are higher (+).

Edit: Will post some pics later, i hope they will help.

Manifolds? If system has only one port it's not good because, if you overfill you have to turn your unit off to release part of the refrigerant.

Any one know how to calculate oil quantity for our sistems if it carry 200 grams refrigerant? What will happen if we increase diameter and/or lenght of suction pipe in order to simulate suction  accumulators with ambient temps ?

what compressor we speak ? reciprocating /rotary ? rotary will have less oil issue because this design is better oil management, also endure better working temperature/pressure and much more ressistant at liquid refrigerant floodback , reciprocating has ~ 3% of total discharge volume is oil that get pumped out with  each stocke of the piston into system and them must be returned back  .. i recomanded to use an suction acummulator to prevent liquid refrigerant flood back and suction line not larger that DN10 ( 8mm inleet) to not have oil issue , and not longer than 0.8 -1.0 meter  , in specially using small displacement compressor like NL11F or ~ 10-14ccm

SS is with Danfoss NL11F. 

This was also my thinking .. to add small suction acummulator. Are you sure about suction line? There had to be vacuum so oil should not be an issue or no ?. Or there will be vacuum only if proper pipe is used as you reccomended ?

Can you please enlight me where is the end of suction line is to to the soft connection or is all up to evaporator ? Because if its theevaporator our is longer than 1meter.  I will post some pics later.

p.p lot Q form the noobs

NL11F is an R134a design , pay  attention at ratios pressure ...because R404/R507a will work at higher discharge pressure/temp than R134a.

about suction line , using so small displacement compressor and to long suction line witch will be also oil return for compressor( because in this units we use no oil separator) , compressor will work harder and will pump much more oil into sistem , using to long suctionline till amount of oil will be returned back to the compressor , that will have not enought lubrication , and temperature cranckcase will rise and will be overheated and ireparable damaged over time!

using from 0.8m to 1m ( not measured at each cm...if is 1.05 or 1.03 no matter) and inleet of pipe that suction port of the compressor have ( not larger..and also not smaller) will help you aswell to have a bit lower temp on the evaporator! theoreticly short suction line will give you  low evap temp! , but not foget for reciprocating design is a MUST to use  suction acummulator , that will separe liquid to vapour and enter intro compressor only vapour refrigerant!