I work on some old equipment (ice chests, from Leer). The
older R-12 units used to run about 150 to 170 discharge
pressure. The R-134a units run more like 225 to 250 or so.
Anyone else seen this?
Some online checking shows that's about normal. Seems a bit
unusual, after working with R-12 all these years. For the
first few degrees, the temp F and the PSIG are about the
same. But when it gets hot, the pressure takes off.
I can tell that getting used to 410a is going to take a
R410a is like any other refrigerant... it has to be charged by superheat and
subcooling. The only real difference is that the pressures are
approximately 1.6 times higher than R-22..... other than that, there isn't
any "gettin used to". But if you had gone to any of the R410a classes put on
by manufacturers and supply houses, you would know this.
I think it may be because 134a was developed to work
most effectively in higher temperature applications.
I can't wait for HFO-1234yf to replace 134a. I'm
going to have problems remembering all those darn
numbers and letters. Sir, I'm sorry to inform you that
your refrigerator needs 2,3,3,3-Tetrafluoropropene.
Let me get my environmental suit and breathing air
tank. Hey, I get to charge more!
I'm sure 134a works a LOT better at medium and high temp
applications. Well, it keeps ice cubes cold enough. Sure was
simpler when we only had four or five common gasses. Now,
we've got a real nightmare.
Not seen those. Never know, might be a good idea. Or, more
gadgets to haul around. Offhand, I think it's bad idea for
techs like me.
Thinking some more about 134a. When I start up the box, the
inside can be 70F or hotter. The system is designed for
evaporator temps more like 30F. So, the supeheat is way off
the charts. Helps explain the high discharge temps.
In hot kitchens or in older stressed equipment, I
charge them with R-416a. It runs a lower head
pressure than R-12 or R-134a and can be used in
place of either. I've had very good luck with it.
Thanks for the ideas, and information. One parts house near
me has that. I've used 409a with great success. Advertised
as a direct drop in for R12, with same mineral oil. But the
416a is noticably cheaper. I'll try that next time.
Johnstone stocks it in 25lb cylinders and in the small 9.6oz
cans. The screw on can adapter has left hand threads if I'm
remembering correctly. I have a 25lb cylinder and haven't
used the small cans in a long while.
I used a small can of one of the R12 replacements that was specifically
sold for use in household ref/freezer applications. I'm thinking it was
414A, but I wouldn't swear to it. Anyway, I just used a side puncture
can tap and it worked fine. If you bought a jug of every single R12
supposedly drop-in that is on the market, you'd be hard pressed to fit
them all in an empty service van-- definitely wouldn't fit in a Pinto,
even a wagon. Larry
I do kind of wonder why you are in HVAC in the first place. If you are a
locksmith, there can't be much time for HVAC. 3 or 4 hours in rekeying
cars in a Repo lot should net you around a $1000. One car opening would
bring in $85 and upward. Nose opening safe deposit boxes for the bank is
about 3 minutes each and $35 a box with a minimum of $350. a 5 minute
job of impressioning a lock is $75. Recombinating
safes for businesses is $150 each and takes about 6 minutes. Opening
a home file/fire safe is $300. Opening a large Diebold would run about
$1,000 to $2,500 each You can start at $10 grand for a full vault. Home
openings run about $85.00 upward. You don't need the investment in
equipment that you have for HVAC and you can haul most of the tools
around in your pocket Or Pinto glovebox. Insurance and certification at
ALOHA is very cheap in comparison to what we pay. Nobody cares how you
got to the job. You can actually do calls on a bicycle. Locks don't
change much and the Feds are not dictating your business and licensing
For whatever reason, the locksmith biz doesn't make the
phone ring enough to keep me alive. But, the ad under
refrigerators repair helps keep me busy. I think your price
schedule is a bit more than what I can get around here.
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