From: muriana@aclcb.purdue.edu (Peter M. Muriana)
Subject: Summary: -20C Cryofreezer vs. Home freezers?
Reply-To: muriana@aclcb.purdue.edu
Organization: Purdue University AIDS Center
Date: Wed, 30 Sep 1992 14:14:33 GMT


Here are a number of trimmed responses to my original post about our -20C
cryofreezer (~ $1,200) going down and would a home freezer (~ $400-$450)
suffice?
	It seems like everyone who did respond **do** use home freezers
	in their lab for the -10 to -20C range (not supercold -80C).  No
	one responed negatively to the use of these freezers for frozen
	storage of cultures, enzymes, etc., but they all mention the need
	to stay away from self-defrosting models which warm-up somewhat to
	stay defrosted.

	regards, Peter Muriana

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Responses (extraneous stuff deleted):
------------------------------------

We have been using standard freezers for our enzymes etc for many years. 
Any commercially available one should do the trick if it holds -20 degrees,
as long as it is not one of the automatic defrost types.  The cycling
defrosting will kill your enzymes.
Cheers,
Klaus Matthaei

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We have been using a standard FROST-FREE commercial freezer for years.  For
critical items like enzymes, we put them in a styrofoam box (a shipping
container from one of the enzyme companies) along with a few of the packaged
"ice" bags that sometimes come with shipments; the whole box then goes into
the freezer.  The insultation plus the residual cold in the fake ice is
adequate to hold the temperature during the defrost cycle.  (The particular
enzymes we put in the lab freezer are admittedly not particularly 
temperature-sensitive, but the -20C cold room we use for all the other enzymes 
also has a defrost cycle; we use the same system there, and seem to have no 
trouble with decreasing activity.)

Bill Melchior                                                 
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G'day Peter,

The 12 cu ft (not frost free), upright Sears model is what I use.  I bought
one in 1989, and it behaved perfectly (I defrost it once a year or so), and
I bought another three months ago.  A couple of other labs use the chest
model for strain storage, and modify it to put in an alarm system.
cheers, John

John Nash                         

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You answered you own question.  For a -20 freezer, go to your local
cheapie appliance store and buy what they have.  Your only consideration
is that you DO NOT want a frost-free model.  Which is great, because they
are the cheapest ones they make.  Should not cost more than the $400
you mentioned.  The ones we are using are Frigidaires.

BTW, the same applies to refridgerators.  I tend to get the ones with NO
bells & whistles and the _smallest_ possible freezer compartment.  This is
because refridgerators almost always come with frost-free freezers.  And,
in case you didn't realize it, frost-free freezers work because they
periodically warm up to melt the frost.  This is not a good thing for
sensitive (and precious) reagents.--
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Dave Dudley                      
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Dear Peter:

	Where are you?  I'm at Med Chem in the pharmacy building at Purdue,
and everyone in our department uses GE freezers (Purchasing has a contract)
which run about $400 for 18 cu ft.  Phys. Plant insists on explosion proofing
at some unknown additional cost.  These work fine for us, but do frost up and
can't maintain -20 with severe frostup.  I have two, one nearly 10 years old,
has never failed.

	Curt Ashendel

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Peter,

I bought a Frigidaire small (about 5 cu ft I think) chest freezer when I
started the lab 3 yrs ago.  Have had no problems, and it holds -20 deg C
just fine.

The only difficulty nowadays is finding a freezer for the home market that
is _not_ frost-free.  Hope you are aware that f.f.freezers use either a fan
or a brief warmup cycle to stay that way.  The first is not a big deal as
long as everything is tightly capped; the second (more common) way of making
a freezer f.f. is disasterous to enzymes, etc.

I can get you the model no. if you want.  I think your price is high by
2x.  I remember paying about $250 for mine, I think.
Jim

--
Jim Hutchins                 
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I have always just used a good brand of home (not frost free)
freezer. $400-500 is about right. We have some around here whihc
are 20 years old with never a repair.

 Michael Benedik		

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Subj:	Re: Cryofreezers (-20C) - any problems with yours?

I've had very good luck with a Sears model.  The key feature you
need is either a non-self defrosting model or one where you can
turn the feature off.

Eric Hugo
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Subj:	Cryofreezers (-20C) - any problems with yours?

We use use a 13 cu ft sears upright and it works fine.  Just be sure
it is ***not*** frost free because the auto defrost will damage some
enzymes.
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*  WALT LILLY                     

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Subj:	RE: Cryofreezers (-20C) - any problems with yours?

We found that any commercial freezer was good - read Consumer Reports. 
 Just make sure that you don't buy a "frost-free" variety.  
 The cycles in temp are not good for stability.
 
from HAL.HAHNEMANN.EDU 



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*  Peter M. Muriana, Ph.D.		Phone	= (317)-494-8284    *
*  Dept. of Food Science		FAX	= (317)-494-7953    *
*  Purdue University		E-mail	= muriana@aclcb.purdue.edu  *
*  W. Lafayette, IN  47907                                          *
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