-150 Degree Lab Freezer

[coolerik]

Get to work on one of these tomorow, just wondering if anyoe knows anything about them... Im basicly going in blind, i know its made by Fisher Scientific, but thats about it.. no model number or anything
Ive worked on a few -80s but apperently this is a whole different animal. Noone else at my company or any other company in town wants to go near it, so i figured id give it a shot.
Anyone know anything about these babys?
Thanx

[Snapperhead]

Jeeeeeezus thats cold

Is this one of them deals where you walk inside one freezer , then inside another , inside another , getting colder and colder

[Pete838]

Probably a small reach in or chest freezer. Probably a microprocessor controlled cascade system with two different refrigerant circuits (possibly running two different refrigerants) and a refrigerant to refrigerant heat exchanger. Stage one cools the box on the evap side and warms the hxe, and stage two cools the hxe and discards heat at the air side condenser. Low temp side maybe 404a or 508b, warmer side 134a.

Here's a little background:
http://www.ishrae.in/journals/2000july/article05.html


...Or it's liquid nitrogen.

[grkmano]

Damn never seen these would love to put my hands on it...

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[VTP99]

Getting kinda close to cryogenics isn't it. Where do you put the dead people while your fixing it ?

[Octopus]

Ultra low temp its most likely cascade and will haveb134a and r23. The condenser from the 23 is cooled by the EVAP of the 134a. Try to rule out everything other than charge before you go jerking the 23 ckt around.

[coolerik]

Work on the -80s which are 404 on stage one and propane and 508b on 2nd stage... this one is different tho, 1 comp with a mix of about 12 diff gasses... 134,404,23,24,n2,600 etc.. they freeze human brains in it... einstiens mabey.. tomorow should be interesting

[coolerik]

Just a reachin deal, glad its not a walkin....yikes

[grkmano]

Nice good luck.. bring back a few pictures for a tease

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[coolerik]

Ill samp some pics if im allowed....or noones around

[coolerik]

Probley just needs z new a19

[cmclifton]

-150 is an autocascade. Single compressor (3HP scroll iirc) 4-5 different refrigerants in one system. The higher pressure gases act like non-condensibles in the air cooled condenser, after which liquid is dropped out through a cap tube to a heat exchanger that cools the vapor that didnt condense in the air cooled condenser, so on and so forth. At the end you have argon in a saturated vapor state going through the evaporator. I like working on them, most people run screaming. Mostly cause they don't want to do what the manufacturer says needs to be done to get it right...

[Helioson]

I work on walk-ins at Plasma Centers, only -40F though. Have worked on some -80 scientific cascades at universities, but damnit...-150...that's friggin colder than Duluth, MN! Thank goodness it's a reach-in. The worst headache (literally) I've ever had was working on -40F walk-in on a 108F day, going back and forth from evap to cond on a 38' roof top. To old for that sheet! Let us know what you find, good luck.