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djkeev
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Joined: September 30, 2007
Posts: 32987
Location: Reading Pennsylvania
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Howesight
Samba Member
Joined: July 02, 2008
Posts: 3402
Location: Vancouver, B.C.
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 Posted: Thu May 07, 2015 2:57 pm Post subject: |
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Hey Dave:
You are going to use between 2 and 3.5 cans of Red Tek. The "perfect" quantity is going to be determined by adding refrigerant to a running, operating system in a stable ambient condition and watching for the lowest vent temperature. When adding RedTek no longer brings vent temps down, you are at the "sweet spot".
Obvious hint: Weigh your RedTek cans before and after to get a tare number and write the number for the weight of refrigerant installed on your compressor when you are done.
Less obvious comment: There is a conversion table for both R-12 and R134A to RedTek on the RedTek website to allow you to calculate the R134A amount if you ever go over to the Dupont Dark Side.
Here are suggested conditions:
1. Start around 12:00 noon or thereabouts so ambient temps and sun load are not changing.
2. Install the first can of RedTek into the fully-vacuumed system with the engine not running. It will all get sucked in. The RedTek instructions say not to install the refrigerant into a hard vacuumed system. IGNORE THAT.
3. Now start the engine, AC off, and allow it to get to operating temperature. See the link to my "RedTek install" comments below for precise details, but what you will now do is set the idle speed to 2,000 or 2,500 rpm, place a box fan on high speed in front of the condenser, set both AC thermostats to max cold, set evaporator fan speeds on high, and place your digital vent temp thermometer in the vent for whichever evaporator is your primary evaporator (the one designed to be used most often - - in modern minivans, this is always the front evap.).
4. Your system will likely cycle the compressor on and off. When the system is cycled on, assuming ambient temperatures of 75-80F, you are getting close to the "full" point when your low side pressure (compressor cycled on) is around 25 psi. This is the point at which you can start to pay close attention to the vent temps. After that, keep adding until vent temps no longer drop during the compressor's "on" cycle.
By the way, do both of your evaporators use a TXV, or does one use an orifice tube?
Here's the link to my (overly?  ) detailed post:
http://www.thesamba.com/vw/forum/viewtopic.php?t=562000&highlight=redtek+howesight
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'86 Syncro Westy SVX |
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Farf
Samba Member
Joined: July 12, 2009
Posts: 463
Location: Colorado
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| Posted: Thu May 07, 2015 9:36 pm Post subject: |
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Dave,
This post does not answer your question regarding how much RedTek does your system need, but it will answer different questions that you may have.
I think Howesight provided enough information to answer your original question.
First, please read the link below regarding charging systems with zeotropic refrigerant blends. As you know, RedTek falls into this catagory.
http://www.refrigerants.com/faqs.aspx
After reading the link, you now have a better understanding of what to do for your particular system. I do recommend that you charge with liquid only, it's standard practice and easier. If you are uncomfortable about using your manifold to meter liquid into the system, adapters for this are available. See link:
http://www.testequipmentdepot.com/yellow-jacket/hv.../41123.htm
This adapter would be installed on the low side manifold port (where the blue hose attaches to the manifold.)
Whatever you decide, make sure the last can is installed liquid only.
Howesight, nice write up. I'm going make some suggestions to streamline your hose attachment procedure to Dave, I hope you don't mind.
Dave, connect your gauge manifold to the system both high and low sides.
Run your vacuum pump again for whatever time you think is good. Shut off both valves at the manifold. Disconnect the vacuum pump and get it out of the way. The high and low side hoses are now under system vacuum there is no need to disconnect them until you have finished charging the system.
Attach your first can to the center hose (usually yellow). Pierce the can and purge the yellow hose only at the manifold. You are ready to charge the system.
As Howesight said, with a/c off, let the first can into the high side in liquid form. Don't be shy, let her rip. When the first can is in, shut off the high side service valve on the gauge manifold, do not disconnect the first can yet. You will not open the high side valve again for the remainder of the charging process.
Start a/c system per Howesight's directions. You may need to jump out low pressure switch. Charge any remaining refrigerant in the first can into the suction line. Once again can inverted. You are always using the low side service valve to access, meter or isolate the system from the RedTek can.
Repeat with additional cans as necessary always remembering to purge the center hose each time.
Remember, last can liquid only...Don't forget to monitor air discharge temps and of course, high and low side pressures.
Hope this info is helpful.
Mike |
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ScottShelley
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Joined: October 15, 2012
Posts: 596
Location: California
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| Posted: Sat May 09, 2015 6:44 pm Post subject: |
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| I have a question related to this. Is the receiver dryer for this set up the same as the stock vanagon unit? If not, does anyone have a part number? |
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xflyer
Samba Member
Joined: June 15, 2006
Posts: 313
Location: SOCAL
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| Posted: Sun May 10, 2015 8:58 am Post subject: |
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Scott, Yes the drier (some call it the receiver-drier) that fits your Vanagon, if you buy a new one, should be fine. All the driers manufactured for at least 20 years have a desiccant that is compatible with all current refrigerants and oils. Unless you get some alchemist brew in a back alley.
Remember to leave the new drier capped until you are ready to hook up your entire system, evacuate and charge it with the refrigerant of your choice.
If the cap(s) are removed for even a short time anywhere but the driest desert, the drier will be as good as one out of a 30 year old junker.
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1989 Campmobile, 1984 7 passenger beater Vanagon
Both with cool A/C |
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ScottShelley
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Joined: October 15, 2012
Posts: 596
Location: California
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| Posted: Sun May 10, 2015 9:53 am Post subject: |
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| Thanks for the info. I figured out, that the dual Behr unit uses the dryer used in the earlier vans up to 86. The inlet and outlet are set up a little different. It is available from Van Cafe. |
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djkeev
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Joined: September 30, 2007
Posts: 32987
Location: Reading Pennsylvania
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djkeev
Samba Moderator
Joined: September 30, 2007
Posts: 32987
Location: Reading Pennsylvania
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Howesight
Samba Member
Joined: July 02, 2008
Posts: 3402
Location: Vancouver, B.C.
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| Posted: Wed May 13, 2015 2:44 pm Post subject: |
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Hey Dave:
Your results look good. You might be able to add a bit more RedTek and get even better results. When ambient temps are in the 80 to 85 degree F range, you can check again. Once the system settles down (it takes a few minutes for heat soak to stabilize), you will want to see around 195 to 210 on the high side and 27 to 29 psi on the low side at 80 to 85 ambient, which indicates a "full" condition on refrigerant fill.
As always, however, vent temp results are king and if a refrigerant fill that produces those pressures ends up increasing vent temps, then decrease the fill by venting to atmosphere - - no smoking allowed in that operation.
Overall, if you can achieve a satisfactory vent temp at a lower high side pressure (which can be caused by refrigerant characteristics or highly- efficient condenser operation), go for it because that results in less wear to the compressor. Having said that, 40 degrees at the vent is pretty darn good, I say.
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Farf
Samba Member
Joined: July 12, 2009
Posts: 463
Location: Colorado
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| Posted: Wed May 13, 2015 6:40 pm Post subject: |
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Looks good. For a head pressure "gut check" using the rule of thumb for R-12, (close enough to HC-12A) your there.
From Vintage Air:
R-12 type:
High-side pressure: 140 to 230 PSI. NOTE: A general rule of thumb is two
times the ambient (daytime) temperature, plus 15%.
Low-side pressure: 12 to 15 PSI in a steady state.
Center duct temperature: 36 to 46° F.
Agree with Howesight, check again when its warmer, you will probably need more stored in the receiver for hotter temps.
Out of curiosity, what was the vent temp. from the rear evap.? Did you have both evap. fans on high speed? Box fan in front of condenser? |
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ScottShelley
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Joined: October 15, 2012
Posts: 596
Location: California
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| Posted: Wed May 13, 2015 7:12 pm Post subject: |
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| Good info! I'm waiting on parts to use my dual Behr with the Subie conversion. Can't wait! |
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djkeev
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Joined: September 30, 2007
Posts: 32987
Location: Reading Pennsylvania
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