Frezzer Room Problems ..With super heat

[Makanic]

Hi all New here ,Ive got a few questions hopfully some one can clear up for me..
For starters my Knowledge regarding Coolrooms & frezzer rooms is as about as much as you write on the back of a postage stamp...not a great deal:(
Anyway here goes
I refitted /reasembled a old frezer room
whick was pulled down a few years ago,,
It used R404 Refrigerant before as that is what was marked on the compresor ..
Instead of using r404 I thought i would give Hydrocarbon a go (Minus 50) as the Pressure temp charts are very simular/close to R404
After charging the system the best super heat i could get was 10 to 12 k & when I kept trying to add more refrigerant the system would not go over 300kpa ??? But at the same time i could hear the compresor loading up???
Is there a By Pass valve or something simular?? what would cause this to happen???
The frezer did run cold but i wasnt happy with the out come, So thinking ..I thought it must have something to do with the Hydrocarbon refrigerant & because of my lack of knowledge with cool rooms/freezer rooms,
I thought i would call someone that had experiance in them, So.. The guy charged the system with R404
& said its working fine & took off
after he left I put my guages on to see what presures the unit was running & the super heat That I worked out was 14 to 16k ???? far worse than what i had with Minus50 Hydrocarbon..
Has he under charged the Unit Or am i doing the readings from the wrong location?
like I said Commercial frezzer rooms i have very little knowledge
Is the super heat ment to be the same as Air Conditioners running R22 5 to 6k ?
Or could the Unit just be designed incorrectly??
Any advice or answers would be great...:)

Oh yeh forgot to mention..using Kpa & superheat 5- 6k etc is im C Not F

[lana]

Hi Makanic,

Welcome to the RE.

Nice Avatar bytheway:D .

First of all what refrigerant did you charge in the system?

Is your freezer supposed to work at -50°C? Is your compressor double stage?

Having 10°C super heat is not very bad. You have to adjust the super heat by the TEV not the amount of gas. When you are sure that the charge is nearly good (by measuring LP, HP, sub cooling and super heat), then you have to adjust the TEV.

Give more info, may be we can help.
Cheers

[setrad7791]

hi there! Firstly... refrigeration is a fickle thing, there can be many factors that can produce such problems... although 12k superheat would not be regarded as an excessive superheat. The first thing to check before looking into detail would be the load in the room, i.e is there a large amount of product in the room? is the condensing unit matched to the evaporator? is the tx valve correct/bulb location correct, and lastly is the unit sized correctly to cope with the heat load. If you could tell me Room size and model numbers of outdoor and indoor unit it would make it easier to determine if there was an actual problem with the refrigeration process, also room temp/ambient temp and suction and discharge pressures would help... and is the sight glass clear?

[Sledge]

Hi

12k SH=20F. I target 10-12F SH measured at the outlet of the evap. I would view 12k/20F SH as being too high, but not excessive. Means that a larger amount of the evap is cooling at a lessor rate, and the comp will be a bit warmer. To answer your question, I target SH the same with all refrigerants. My priniciple experience is with the old refrigerants R22,R12,R502. I measure SH at the exit of the evap, as close as possible to evap, right at the TX bulb. Higher SH means less work being done.

The SH could be excessive if the unit is undercharged. If the space temp is too high, the sight glass could be bubbly even if the charge is adequate.

Need more info to help.

Need to know size of evap, condensor, compressor, tx, ambient, space temp etc just to start

[Makanic]

HI all thanks for the advice & comments
SO the SH is to high Just as i expected..
The Frezer room was Operational before all I did is reasemble it back to how it was before.
same parts & components (besides a New Filter)
& I used a different refrigerant Minus50 Hydrocarbon
Instead of what it used before which was R404

For Some of the Questions asked

The frezer room is completely empty..
& i checked The suction line tempreture almost next to the compressor , its about 2 meters from the evap
I will Have to Cut the insulation & Check it closer to the evap

Also the frezer room is set at -20 Max
which I checked today & it did get to that tempreture over night & seems to be working Ok
It was Bucketing rain down so I didnt geta chance to recheck the presures & SH

The frezer was completely empty & not down to tempreture when I check the SH ,I think it would make a difference now that is not under load?
Is this correct or am i way off?

Anyway Thanks again guys :) Will play abit more with it

[Sledge]

If you are measuring SH that far from the evap, you may be getting a bad reading. You need to read it at the outlet of the evap, as close as possible.

If the room is not down to temp, then the system is under load. I try to let the system run for a few minutes, prior to measuring SH, but if the system is calling, and it is running, then you should be able to measure SH.

[Makanic]

Thanks again
I thought it might of been measuring the Suction temp to far away ..
Im more Used to Air Conditioners /Split Sysytems
2 way valve is miles away from the Evap
Anyway will check it again & see how it looks

[Samarjit Sen]

As Lana had asked, you have not as yet stated if the compressor is double stage or not. To get -50 C as room temperature you should use a double stage compressor.

[Makanic]

Its a single stage Compressor
& I did state -20

[Brian_UK]

The "Minus 50" Makanic is referring to is the trade name of an Ethane/Propane mix made by HyChill of Aurstralia.

One thing that I would ask is, is the equipment suitable/safe to use with a HC mix?

[Makanic]

The "Minus 50" Makanic is referring to is the trade name of an Ethane/Propane mix made by HyChill of Aurstralia.

One thing that I would ask is, is the equipment suitable/safe to use with a HC mix?

Good Question :)
Safe??
Well my evaluation is not of the Freezer room equipment itself but possible leakage flame risk
Although a dry nitogen test was done to check for leaks
I looked at if there was a leak in the future where would the gas go ,Being heavyer than air..
Roof top unit ,would have lots of air movement to disperse the gas ,& even if it did consentrate down hill from the roof, it would go down the gutter & possible a small amount could go into the storm water pipe ..very little flame risk if any!!!!!!

Indoor unit the placment of the freezer is no where near anything that can cause a flame risk

On top of that Just because I am paranoid..
I was going to install a gas leak detector placed just near the outside of the freezer door (much like a Smoke detector) Same type of unit thas is used for detecting gas leaks in Motor homes & caravans..

The other Thing people dont realise,Using Hydrocarbon YOu use about 1/3 of the original refrigerant charge..so this freezer would of had around 1Kg give or take of Hydrocarbon

Anyway is runnung on R404 at the moment :)

[Sledge]

The "Minus 50" Makanic is referring to is the trade name of an Ethane/Propane mix made by HyChill of Aurstralia.

One thing that I would ask is, is the equipment suitable/safe to use with a HC mix?

I havent seen that refrigerant in Canada, and I sure hope they dont allow it. That has got to be dangerous. There are too many other options, that dont have explosion hazards. I hate ammonia, but would prefer to work that stinky stuff, over working on a bomb.

[Makanic]

I havent seen that refrigerant in Canada, and I sure hope they dont allow it. That has got to be dangerous. There are too many other options, that dont have explosion hazards. I hate ammonia, but would prefer to work that stinky stuff, over working on a bomb.

Many different Name same stuff ..
you guys dont run cars on LPG (Liquid petrolium Gas)
As your Petrol (gas)there is cheap
Theres Thousands & thousounds of cars running around here on LPG .. Bombs on wheel??

Whats realy funny here not many Fridge Techs using this refrigerant as well..

THe main sales for the local manufacturer for the Refrigerant is in Europe ..where they say the stats are that about 80% of new EU domestic sold fridges are using it...

Also R22 not explosive?? Funny that just read a article about that today
http://www.alder.co.za/blowup.htm

Hydrocarbon Links of interest
http://www.care-refrigerants.co.uk/hmpg/hmpgdisplaylev1.asp?catid=4&idofuser=

http://www.hychill.com.au/tech/

[Sledge]

Many different Name same stuff ..
you guys dont run cars on LPG (Liquid petrolium Gas)
As your Petrol (gas)there is cheap
Theres Thousands & thousounds of cars running around here on LPG .. Bombs on wheel??


There was a big push for LPG in the 80's, dont see much of it here, some commercial taxi fleets. The most spectacular explosion I have seen was with a gas station that also filled propane.

There are many situations where propane or natural gas is present indoors. To repair those systems, it is seldom standard practice to apply a flame to the pipe.
It is standard practice to braze refrigerant pipe. There are way too many technicians in this vast industry, who are still learning their trade. Too many 16 hour days for senior technicians, on a hot busy day. Too easy to make a mistake.
Refrigerants are present in residences under high pressures, where open flame can be present in stoves, furnaces, candles, fireplaces, smoking etc. small leak, big problem.
I have read about the use of sulphur dioxide in residential refrigeration systems in the 1950's, They stopped using it because too many people were killed when it leaked.

If this was the only refrigerant available, then we would have to deal with it in the same way that we deal with the challenges of ammonia. This isnt our only option.
Too much risk, not enough benefit IMO.

[Peter_1]

Also R22 not explosive?? Funny that just read a article about that today
http://www.alder.co.za/blowup.htm

http://www.hychill.com.au/tech/

Makanic, that's not quite correct what you're saying here: USIceman and I co-authored this article for Geoff.
It was a friend of US Iceman who came withh the theory of the possible cause of the explosion.
R22 is not explosive on its own, the article is not saying this.
The Dutch version of this article which I wrote was also published here in Belgium.
For those interested in it, I can upload it via Megaupload (5Mb). See it's gone already on their server.

You did say indeed -20°C but after Lana asked if your freezer was running on -50°C.


The other Thing people dont realise,Using Hydrocarbon YOu use about 1/3 of the original refrigerant charge..so this freezer would of had around 1Kg give or take of Hydrocarbon

This need some more clarification, why 1/3? Is the enthalpy 300% larger. No it isn't, so...???

[The MG Pony]

I havent seen that refrigerant in Canada, and I sure hope they dont allow it. That has got to be dangerous. There are too many other options, that dont have explosion hazards. I hate ammonia, but would prefer to work that stinky stuff, over working on a bomb.

This is a verry sad statement. All refrigerants are a bomb when in a system mixed with oil. HC refrigerants tend to be superior to HCFC or HFCs. I greatly look forward to when we have more HC grade refrigerants to choos from.

It is only a bomb in care-less or incompitant hands.