Thread: One for the fridgies

Rule of thumb:
Tighten until it goes soggy.
Back off half a turn.

Originally Posted by scarry

Did heaps of work on those H,K,Y and T Kelvies over the years,they were bloody good gear.

But they do seem to dislike R22.

After the phase out of 12 and 502,we converted quite a few to R134a,and R408a,but I can’t remember any on R404a.


We also used to run them in trawlers,driven by the old CAT3208.

I actually found an old Kelly service catalogue in the office,with all the flywheel nut torques,and a bit of other info,the other day.

22 on low temp is ****.
The compression ratio is too high = ridiculous discharge temps = cooked oil, burnt valves, etc.
A cursory look at a Pressure/Enthalpy chart will reveal all (and something I haven't done in probably twenty years!)
When 404 came out I fell in love with it because of the low discharge temps, but it does tend to fall over in high ambients.
134a is much better out west or when you are running high SST's, eg egg rooms.

I had all Dad's old engineering literature up until a house fire in '96.
It was amazing how often I'd refer to it.

Here's the current state of play with Supermarket freezer systems.
This CO2 rack chills 45 glass door upright freezer (maybe 9 modules?) and a 6x6x3.3m Freezer room. I should know how many doors to a module, I had to defrost two modules on Christmas day, I got out of the store at 5am christmas morning.....
The compressors are tiny! 20190719_123745.jpg

Lower left corner you can just see the backup condensing unit for the heat exchanger if the MT rack falls over.
Without something to cool the CO2 discharge, pressure relief valves go bang very smartly!

R22 even in medium temp isn't the best,particularly if the system superheat isn't the greatest,discharge temps don't take long to get over 100 degrees or so,a bit of spit on the discharge line is the old test...

Yes 404a is so much better,as long as the condenser is sized correctly,clean,and in good condition,and NO recirculation of hot air.Also good can be used in medium and low temp.

All gonna change soon with all these new refrigerants coming soon,we won't have any idea what gas is in what,unless its labelled properly....

Old data,often really important and hard to find,i been patching up my 2006 Heatcraft capital equipment manual for ages,i use it all the time.Yesterday the local rep tells me has a copy on email and sends it to me.

Originally Posted by rick130

Here's the current state of play with Supermarket freezer systems.
This CO2 rack chills 45 glass door upright freezer (maybe 9 modules?) and a 6x6x3.3m Freezer room. I should know how many doors to a module, I had to defrost two modules on Christmas day, I got out of the store at 5am christmas morning.....
The compressors are tiny! 20190719_123745.jpg

Ok, she said, please explain,the three bitzers are Co2?Flexible line going to pressure switches must handle some pressure if its CO2?
The Kirby unit bottom left does what?

As you can see i am a wiz at this new stuff,maybe not that new

Yep, those three tiny Bitzers are our Freezer refrig for the entire medium sized supermarket!
I'm also surprised the Gomax hose is rated for the pressures!
and the hermetic system behind is a backup for when the MT racks fall over just to provide subcooling for the CO2 heat exchanger.
They are basically a cascade. The MT rack suction plus liquid injection cools the CO2 discharge.
We've had problems recently at another store with the 134a in the CO2 heat exchanger and we've had liquid floodback to the MT rack

Originally Posted by scarry

Yes 404a is so much better,as long as the condenser is sized correctly,clean,and in good condition,and NO recirculation of hot air.Also good can be used in medium and low temp.

All gonna change soon with all these new refrigerants coming soon,we won't have any idea what gas is in what,unless its labelled properly....

Yep, recently came across a blast freezer in a kitchen using R452a???!!!

A quick google tells me it's a new R404a replacement.
Thankfully I was only doing a site audit tendering for a new client.

I love this thread.

All the different R....numbers stuff and that is all good.

Why aren't you all up in the Whitsundays where the charter yacht companies and the privates can't get reliable fridge mechs for more than a couple of weeks?

Just asking............

DL