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Re: Could you detail your 'fridge pump vacuum pump set up please?
Let me try to explain a few things before I answer your question. I'll
answer it but first I'd like to explain what happens and why.
1. Oil located in the base of the pump gets circulated with the freon.
that is the only thing that cools (lubricates) compressor. Without the oil
the compressor would burn up due to lack of lubrication as such with any
motor. The freon itself doesn't cool it at all. The time it takes for a
motor to burn up depends on the amount of oil in the base of the compressor
and how good of a motor it is. It could take minutes or days depending on
that.
Here's why freon doesn't aid in cooling ....
A compressor such as those used in freezers, A/C's and refrigerators are
very much alike with the exception of the type of oil, freon and volume they
can handle. The oil is determined by the type freon that is used. R-12 for
instance uses alka-benzine oil and the compressor gets hot mostly by the
changing of pressures and the heat that gets transferred and replaced by
cool air. This is how the compressor gets hot. It has a low side and a
high side. When the pressure of freon is lowered it gets very cold and
turns to a liquid. Hence the fact that when a A/C or refrigerator doesn't
have enough freon but is not completely out it gets so cold that it actually
blocks the evaporator up with ice. and as the freon rises in pressure it
boils and turns to gas.
The common concept of a cooling unit is to take out the hot air and
replace it with cold air. The low pressured (cold) freon gets pumped from
the compressor and then flows from to a "Cap tube" which is a smaller tube
that compresses the freon even further. When it flows from the cap tube to
a larger tube thats when the freon is at its coldest state and flows into
the evaporator where it removes all the heat. (Heat is attracted to cold)
and the heat is absorbed into the evaporator (liquid freon) replacing the
heat that was in the box with coldness and that makes that cold freon hot
enough to boil. Therefore the freon takes the heat that has collected to
the condenser (a type of radiator) when the heat gets dissipated in the
coils and is accompanied by a fan that cools the coils and compressor.
(Water from the evaporator coils also aids in cooling down the compressor.)
>From there the freon has lost some heat and returns it's liquid state to the
compressor to be circulated once more and the cycle continues. The
compressor is more or less a pump. The heat generated on the compressor is
a result of the heat dissipation in the condenser and since its made of
metal and the condenser is hooked to the compressor heat flows along the
metal and heats it.
Therefore a compressor is simply a motor and if the condenser was cool it
would only have the warmth that an electric motor generates. Freon doesn't
make a difference in the effect of cooling. In all actuality it makes the
compressor hotter from the conversion of gas to liquid. The fan and water
from the evaporator is what cools it. Unplug the condenser fan in your
fridge and run it. The compressor will eventually shutdown using the
overload system built on or near the relay because it gets too hot. A
failed compressor may generate too much heat (faulty motor or loss of oil)
and do the same after running for a sec or for a few minutes due to either
by drawing too much amperage upon startup (Lots of heat) or burnt windings
in the sealed motor (Lots of heat also). Or Both.
Running a compressor all the time can reduce the pumping ability as in a
form of advanced aging. With different motors if they are run all the time
they can burn out more quickly. A Refrigeration unit goes into defrost
every 8-12 hours and gives the compressor a 20-45 min rest. Also a temp.
control does the same thing when the temp control is satisfied by the
coolness of the fresh food.
The low side is where the pressure is coldest and lowest. It's cool to the
touch and forms a frost pattern on the evaporator coils. The high side is
where the heat is dissipated. This is very HOT so dont touch it. Theres a
lot more including ambient temp of the outside and the temp of what its
trying to cool.
Why chest type freezers dont have condenser fans to aid in cooling......
A freezer compressor is pretty much the same as one found in a domestic
refrigerator with the exception of the design. If you were to aid
additional condenser coils in a refrigerator a fan would not then be needed.
This is due to the fact that the further HOT freon travels through the coils
the more heat it gets rid of before returning to the compressor. And since
it does that the compressor doesn't get as hot.
1.)I'm told that refrigerator pumps are designed in a manner that they don't
cool themselves all that well without freon flowing through them and that
continuous use is not advisable. ------No and Yes (see above about oil)
2.) I'm also told that freezer pumps will stand continuous duty well because
they are designed differently. ------------- Yes but, the pump is the same
just a different design of the evaporator and condenser.
3.) A\C pumps like those used in home systems naturally move a LOT of
volume, but I'm told they need freon flow for cooling worse than fridge
pumps and are not at all well suited to continuous duty. -------------Again
no, because theres a big condenser fan that helps the heat dissipate but a
different design in coils for the evaporator and condenser.
I hope this has answered your questions. If you have any more or dont
understand something just let me know. I'd be glad to help. BTW what are
you planning to do with one?
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Tuesday, August 31, 1999 7:25 AM
Subject: Re: Could you detail your 'fridge pump vacuum pump set up please?
>Original Poster: Terry Greene <xray-at-cstel-dot-net>
>
>Tesla List wrote:
>>
>
>>
>> Just reading the email real quick I noticed the talk about refrigeration.
I
>> happen to own a business doing just that and if you have any questions
>> please feel free to email me. I'll read the rest of the mail to get the
>> scope of what youre trying to do but I just thought I'd let you know.
>
>
>
>Could you shed a bit of light on the following. It was hear say and I'd
>like to hear the opinion of someone in the business.
>Thanks,
>Terry
>
>
>
>
>
>> > I'm told that refrigerator pumps are designed in a manner that they
>> >don't cool themselves all that well without freon flowing through them
>> >and that continuous use is not advisable. I'm also told that freezer
>> >pumps will stand continuous duty well because they are designed
>> >differently. Don't know myself, but in practice I've pumped down A\C
>> >systems and left my fridge pump running for hours and never had a
>> >problem. However, if you have the option the freezer pump might be the
>> >better way to go. A\C pumps like those used in home systems naturally
>> >move a LOT of volume, but I'm told they need freon flow for cooling
>> >worse than fridge pumps and are not at all well suited to continuous
>> >duty. Again here say. Either way, these pumps generally wind up in a
>> >land fill so if you don't salvage them, so you don't have much to loose
>> >if you toast one.
>
>