AC recovery/prep?

[Josh Wyatt]

Greetings all,

I'm planning to retain air conditioning for my pending conversion, and am seeking guidance on the proper approach.

Prior to removing the engine, I intend to have the AC refrigerant removed.  Then, remove the engine, dismantle/remove the AC accessory components, etc.  Then, after the drive mechanism for the compressor has been fabricated and assembled to the compressor, reconnect everything and recharge.

Surely it can't be this easy.  What am I missing?

Thanks in advance,
Josh

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[Josh Wyatt]

Josh Wyatt wrote:

> Greetings all,
>
> I'm planning to retain air conditioning for my pending conversion, and am seeking guidance on the proper approach.
>
> Prior to removing the engine, I intend to have the AC refrigerant removed.  Then, remove the engine, dismantle/remove the AC accessory components, etc.  Then, after the drive mechanism for the compressor has been fabricated and assembled to the compressor, reconnect everything and recharge.
>
> Surely it can't be this easy.  What am I missing?
>
> Thanks in advance,
> Josh

I should add:

The vehicle is a 2002 Ford Focus ZTS.

Thanks,
Josh

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[Brian Pikkula]

Hi Josh,

I'm just leaving mine all connected and not even discharging it.  Just
keeping it all supported as per the shop manual.

You will need to utilize the high and low pressure switch (and
possibly the fan switch).  My switch is located in line just after the
the condenser coils up front.  You will need the shop manual for the
pin outs.

Brian


---------- Forwarded message ----------
From: Josh Wyatt <josh.wyatt@...>
Date: Thu, Aug 7, 2008 at 8:59 AM
Subject: [EVDL] AC recovery/prep?
To: Electric Vehicle Discussion List <ev@...>


Greetings all,

I'm planning to retain air conditioning for my pending conversion, and
am seeking guidance on the proper approach.

Prior to removing the engine, I intend to have the AC refrigerant
removed.  Then, remove the engine, dismantle/remove the AC accessory
components, etc.  Then, after the drive mechanism for the compressor
has been fabricated and assembled to the compressor, reconnect
everything and recharge.

Surely it can't be this easy.  What am I missing?

Thanks in advance,
Josh

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--
Brian in TX
http://www.austinev.org/evalbum/960
http://www.evdub.blogspot.com/
It may seem like I am doing nothing, but on a cellular level I'm
really quite busy.

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[Roger Heuckeroth]

Josh,

My AC was working fine when I started my conversion, and I was able to  
unbolt the compressor before I removed the engine.  That way  
everything stays sealed. I figured that would be better than having it  
emptied and recharged.

I plan on using either a separate DC motor to direct drive the  
compressor, or use an AC motor with VFD.  Whichever one is less  
expensive is what I will end up going with.  From what I have heard on  
this list you will need about 2 HP at about 1500-2500 RPM.  Direct  
drive is better than using a belt drive as it will minimize belt  
losses and wear on the bearings.  However,  It all depends upon what  
fits.

You can us the 12V signal that was going to the compressor clutch to  
run a motor starter to turn on the motor, so it only runs when you  
need it.

Roger

On Aug 7, 2008, at 10:18 AM, Josh Wyatt wrote:

> Josh Wyatt wrote:
>> Greetings all,
>>
>> I'm planning to retain air conditioning for my pending conversion,  
>> and am seeking guidance on the proper approach.
>>
>> Prior to removing the engine, I intend to have the AC refrigerant  
>> removed.  Then, remove the engine, dismantle/remove the AC  
>> accessory components, etc.  Then, after the drive mechanism for the  
>> compressor has been fabricated and assembled to the compressor,  
>> reconnect everything and recharge.
>>
>> Surely it can't be this easy.  What am I missing?
>>
>> Thanks in advance,
>> Josh
>
> I should add:
>
> The vehicle is a 2002 Ford Focus ZTS.
>
> Thanks,
> Josh
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev

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[Neon John]

>From: Josh Wyatt <josh.wyatt@...>
>Date: Thu, Aug 7, 2008 at 8:59 AM
>Subject: [EVDL] AC recovery/prep?
>To: Electric Vehicle Discussion List <ev@...>
>
>
>Greetings all,
>
>I'm planning to retain air conditioning for my pending conversion, and
>am seeking guidance on the proper approach.
>
>Prior to removing the engine, I intend to have the AC refrigerant
>removed.  Then, remove the engine, dismantle/remove the AC accessory
>components, etc.  Then, after the drive mechanism for the compressor
>has been fabricated and assembled to the compressor, reconnect
>everything and recharge.
>
>Surely it can't be this easy.  What am I missing?

Just about that easy.  The lube used in 134a systems is hygroscopic so you'd
want to plug off each component, preferably after purging with either
refrigerant or dry nitrogen.  Replace the receiver/dryer unless you can bake
it under a vacuum to regenerate it.

If the system is a 134a system then you can in good conscience simply release
the refrigerant.  EPA still says that this is a no-no but then they say all
sorts of silly things.  134a is a common aerosol propellant and is also common
in canned air.

If you want to recover the stuff, you don't need a fancy recovery system since
you're not in a hurry.  All you need is a suitable container and something to
keep it colder than ambient.  A propane tank and an ice chest will work.

The refrigerant exists in a dormant system as a liquid and vapor in
equilibrium at the vapor pressure corresponding to the ambient temperature. If
one portion of the system is cooler than the rest then the liquid refrigerant
will collect there.  All you have to do to remove the refrigerant is provide a
cooler place outside the system.

I use propane tanks, 1 lb disposable tanks for small amounts and 5 or 10 lb
refillable tanks for larger amounts.  A common 20 lb grill tank will do the
job if you have a large enough ice box.

All you have to do is make an adapter to go from the tank to the 3/8 SAE flare
that is standard for this kind of refrigeration work.  For the 1 pounders, I
use a setup similar to this

http://www.neon-john.com/RV/Propane/Tank_drainer.jpg

except that the top fitting is a 3/8"NPT to 3/8" male flare adapter. (1/4"
flare for older systems.)

(see the photo in context here
http://www.neon-john.com/RV/Propane/propane_refill.htm )

For refillable propane tanks I take a POL (old style) or ACME fitting that
mates to the tank and attach to it a 3/8" flare adapter.  Most tank nipples
are 3/8" NPT so a female 3/8 NPT to male 3/8 flare adapter is all you need.

In addition to that you'll need a hose with the SAE snap-on service fitting on
one end and the 3/8" flare nut on the other.  A hose from a set of gauges will
work or you can buy a single hose.  I recommend gauges.  Big box auto parts
stores might even loan or rent them to you.

First purge the tank of any propane or air.  Either pull a vacuum in it or
pressurize and purge it a few times with refrigerant.  Pulling a vacuum is
preferable.  This little pump is good enough if you do a vacuum-fill-vacuum
cycle with refrigerant.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92475

Then connect the hose from the car's service fitting (I start off with the
high pressure side and if the car has an expansion valve that closes off, do
the low pressure side after that.) to the tank.  Place the tank in an ice
chest and cover it with ice and water slush.  You'll have to weight it down to
keep it submerged.  To speed things along, salt the ice.  Open the valve and
go have a beer or something.

R-134a's vapor pressure is 71 psi at 70 deg F but only 27 psi at 32 degrees
and 6.5 psi at 0 degrees, about what ice and salt will achieve.  That much
pressure differential will cause the refrigerant to flow rapidly to the cold
tank.  At least at first.  When the liquid evaporates in the car system, it
absorbs heat just like it does when the AC is operating.  Points where the
liquid collect will soon frost over.  The receiver/dryer, the bottom of the
condenser and sometimes the evaporator.  

One should watch for frost points and heat them with a hair dryer or heat gun.
NOT a friggin' propane torch, Einstein!!!!  On the other end, the refrigerant
gives up heat as it condenses in the propane tank so the ice/water/salt mix
must be in intimate contact with the cylinder or it will heat up and flow will
stop.

If you have a set of gauges or you buy a hose with an in-line gauge, you can
gauge the progress by watching the gauge.  When the gauge drops to the
pressure corresponding to the temperature in the propane cylinder and stays
there AND there are no frost spots visible, then the recovery process is
complete.  Close the valve on the propane tank, disconnect everything and
dismantle the car's AC components.  

Make sure you have a supply of Caplugs or other stoppers so that you can cap
each opening IMMEDIATELY after you break the connection.  PAG and POL are NOT
like old mineral oil.  They crave moisture from the air and will quickly
become saturated with water.  PAG in particular, is like brake fluid in that
regard.  That's because it's first cousin to brake fluid.  Wet PAG is an even
worse lube than dry PAG.

When you go back together, remove the caps or plugs and assemble as fast as
you can and then purge the system with refrigerant.  The stuff you recovered
is just fine.  Then pull a vacuum.  If you have a good mechanical vacuum pump
capable of 5 microns or better, then a few hours will do.  You can then charge
the system.

If you use that little compressed air-driven pump from above, you'd want to do
it several times.  It doesn't make a good enough vacuum to make water boil at
ambient so it takes awhile to pull moisture out of things.  With service
gauges in the line (or a gauge and valve on the hose if you go that route),
pull the vacuum as low as it will go, close the valve, turn off the compressed
air and watch the gauge.  It'll rise as absorbed air and moisture come out of
the pores.  Periodically turn the pump on, open the valve and pull the system
back down.  

When the gauge no longer moves after an hour, fill the system with refrigerant
to about atmospheric pressure and evacuate again.  Repeat this again and
you're ready to charge.

A 134a system almost HAS to be charged by weight.  Most systems don't have
sight glasses and the reason is that clearing the glass isn't enough
refrigerant.  If you change the length or size of the hoses in the process of
the conversion, weight no longer works.

The second best method is with sound.  You'll listen to the sound the
refrigerant makes as it flows through the expansion device - expansion valve
or orifice tube.  You can buy a fancy and expensive electronic listener but I
find that an ordinary mechanic's stethoscope works just as well.

What you'll do is put the stethoscope probe on or as near to the expansion
device as you can on the liquid line and listen as you start adding
refrigerant.  Pressing hard with the probe will many times dampen out the
motor and compressor noise, making the high frequency flow noise easier to
hear.

With the drive motor running, the AC on high, all the doors open and the
stethoscope probe in place, start adding refrigerant.  If you're using
blow-off cans, have the right number at hand according to the weight sticker
under the hood.  If you properly cleaned the propane tank of foreign gases as
discussed above then you can reuse that refrigerant.

Modern cars have low pressure cut-off switches so initially the compressor
won't run.  As refrigerant is added, it'll start.  You'll hear the sound of
high velocity gas through the expansion device.  As you add more refrigerant,
it'll start to sound like wet gas, progressing to foamy gas, bubbly gas and
finally the low hiss of liquid flow.

At this point, the charge is enough to provide the expansion device with a
solid head of liquid but it isn't enough.  You have to charge for the extreme
conditions.  The worst condition is a very hot day in traffic when the system
is trying to get rid of heat soak.  Therefore you want to keep the cabin
temperature at least 70 degrees and preferably hotter.  If I'm servicing a
system in mild weather, I'll put a 240 volt forced air heater in the cabin to
supply the heat load.  I really like to see 80-85 deg in the cabin.

Block the condenser with cardboard or other material until its temperature is
at 130, plus or minus a little.  Now put your probe back on the expansion
device and add refrigerant until the sound of flowing liquid returns.  This
should take AT LEAST half a pound.  If it doesn't, then you've not identified
the correct sound.  If in doubt, put an extra half pound in and be done.

I also monitor the inside air vent temperature.  As the flow to the expansion
device becomes a solid flow, the vent temperature will drop.  It may continue
to drop as you add more refrigerant or it may go up a little.  It SHOULD rise
just a little, 2-4 degrees as you add the "over-charge".  The over-charge
makes sure that there is sufficient refrigerant available even in the worst
conditions, hotter than you can simulate with cardboard and a heater.

If you're driving the existing compressor with an electric motor, be sure to
drive it fast enough.  Most car compressors need to be spinning at 3500 RPM to
achieve their rated capacity.  The compressor is overdriven from the engine.
Be sure to check the mfr's specs to be sure, as this varies.

You might consider replacing the compressor with a higher displacement, lower
speed unit to reduce the windage and frictional losses inherent in a high
speed drive.  This type of compressor is used on diesel engines, particularly
semis where the engine rarely turns over about 2500 RPM, more usually at about
1800 RPM and idles at perhaps 700 RPM.  I know that Sanden makes this kind of
compressor and I'm sure the rest do too.

You might also consider adding a larger condenser.  That's the major path to
higher EER or COP numbers.  Squeeze all the condenser in that you can and
cover it with electric fans.  Ideally, the condensing temperature as indicated
on your service gauge's high side pressure will be no higher than 10-15 deg
above ambient.  The lower the better.  With the lower condensing pressure, a
slightly larger orifice tube may be necessary.  If the system doesn't cool as
well as it did, especially if the compressor cycles often, then a larger tube
is necessary.  A thermostatic expansion valve should handle the situation
without adjustment.

So ends Neon John's "Reefer 101" brain dump.  Feel free to ask questions.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Unable to locate Coffee -- Operator Halted!

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[Tom Parker-12]

On Thu, 2008-08-07 at 20:51 -0400, Neon John wrote:

> Just about that easy.  The lube used in 134a systems is hygroscopic so you'd
> want to plug off each component, preferably after purging with either
> refrigerant or dry nitrogen.  Replace the receiver/dryer unless you can bake
> it under a vacuum to regenerate it.

Hmm. I should have asked this question a month ago. I've left my system
open to the air that long.

Air conditioning is fairly low on my list of priorities (have to get an
adapter plate made first!) but I would like to avoid any further damage
to the system. I'm only likely to use the evaporator and maybe the
condenser.

> If you want to recover the stuff, you don't need a fancy recovery system since
> you're not in a hurry.  All you need is a suitable container and something to
> keep it colder than ambient.  A propane tank and an ice chest will work.

I had mine drained by the local air conditioning shop for NZ$25. Took
about 15 minutes.

We chatted about how to make it go once the car was electric. They had
the special Prius compressor oil but I would have to find a suitable
inverter and control system for it. The masterflux compressors might be
easier to get working, especially since there is an inverter off the
shelf. Has anyone used one? I saw the discussion last week, but I
haven't heard of someone actually using one.

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[Tim Humphrey]

John,

Thank-you for writing all of that.

 I imagine it took more than just a few moments.

Stay Charged!
Hump

Neon John wrote:

So ends Neon John's "Reefer 101" brain dump.  Feel free to ask questions.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Unable to locate Coffee -- Operator Halted!

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[Neon John]

On Fri, 8 Aug 2008 10:12:46 -0700 (PDT), Tim Humphrey <hump@...> wrote:

>
>John,
>
>Thank-you for writing all of that.
>
> I imagine it took more than just a few moments.

You're welcome.  Yeah, I get carried away when I start doing a brain dump.

John

--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
No one can be right all of the time but I'm getting close.

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[Janet Plato-2]

> You're welcome.  Yeah, I get carried away when I start doing
> a brain dump.
>
> John

Having never posted a post longer than a paragraph, it's hard for
me to empathize....  ;-)  I also enjoyed the post, and several others,
including the ones about why people do things.

Cheers,

Janet


     

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