A/C Subcooler Information

[Jim Sims]

I have received a request that I repost the information on the A/C subcooler I adapted and mounted on several of my 911's.

The stationary service subcoooler I adapted is made by Y/P Products, 20 Leigh Drive, York, PA 17402; Phone (717) 849-0311; www.ypproducts.com/exchangers. I used model HTX-100 based on it's size (length) and ease of attaching the appropriate flare fittings. When I bought my subcoolers, model HTX-100 cost $16.58 each in small quantities plus shipping. The subcoolors were custom adapted for their mounting locations above the splash pan in a 1973.5 911T and a 1976 911S. I silver brazed them together terminating the ends in male brass flare fittings (available at most hardware stores). The units were then pressure leaked checked, painted, insulated with "Prestite" insulation (commonly seen around the expansion valve in the evaporator) and the insulation covered with aluminum foil tape. The units cost about $30 each in parts and supplies to fabricate. The high pressure and suction refrigerant hoses had female flare fittings (cost~$12) added to allow the subcooler to be inserted in the lines. The subcooler is best fitted close to the evaporator; in the high pressure line between the receiver/drier and evaporator is the ideal location. Due to the set up the KCool systems I was upgrading I ended up putting the subcooler just before the R/D. It took some effort (silver brazing) and access to a refrigerant fitting crimping rig to adapt and fit in the subcoolers. If these services/equipment are not available one should consider buying and installing the Procooler which functions as a combined subcooler and R/D.

For the 1973.5 911T:


For the 1976 911S:

[NathanR]

Thanks Jim! Very Cool. (pun intended)

I recall you mentioning in a post a few years ago something about whether the expansion valve had to be adjusted with this application. Is that the case? Forgive me if this is a dumb question.

Regards,
Nathan

[khamul02]

Thanks for the repost. I looked long and hard for the info but the old thread came up empty, like it's contents were deleted.

[khamul02]

Also, check out this http://www.coolflow.com/Heatexech.htm
It was posted by SXSMAN in another thread. Their page suggests that their unit (pro-cooler) doesn't use a desiccant. It's that the case with your unit? I would think it is. Also, why isn't rennaire's Procooler this way? Why does it have to use a desiccant?

Obviously no desiccant means it can be reused.

[Jim Sims]

A/C subcoolers are old technology - they've been in engineering thermodynamics textbooks for at least 40 years; a subcooler is merely a heat exchanger to glean the last bit of heat of vaporization from any liquid leaving the evaporator. Some modern automotive A/C systems are now incorporating them as OEM equipment. The YP Products subcooler I adapted does not contain desiccant; it is only a heat exchanger. One of the difficulties in using an add-on subcooler with a 911 is finding a place to readily locate it close to evaporator. I will conjecture (and this is just my speculation) that is the reason for the Procooler's design with dessicant - relatively easy installation in place of the OEM R/D.

[SXSMAN]

Jim , thanks for the repost . Great info and pics .

Not sure what final route I'll take but I plan on ordering a few exchangers to play with .

SxS

[mtbguy]

I'm thinking of doing this also to learn more about my car and save money over buying the Pro-cooler.

Dumb question I know, but on the HTX-150 model, which looks like it will work for my 87 year model, what is the appropriate hose routing when its placed between the evaporator and rec/dryer?

Any responses are appreciated!

[SCWDP911]

Has anyone else done this mod that Jim has provided the info on in this thread? I was wondering about someone that might not be as familiar with it and their take on completing this mod. Thanks for the info Jim. What kind of help does it provide, I mean actual temp change?

[mtbguy]

I'm about to try this- I found the company website where they are sold, and believe that the one Jim shows in the lower picture will work for my 1987 year model. I won't have to add all of the complex tubing that he had to in the upper photos-just end fittings.

I am going to have barrier hoses made locally anyway, so I just need to get the hose length approximated.

Lastly, I need to then figure out if it is acceptable to sweat/solder the hose adapter fittings on or do I have to braze them? Ive done copper plumbing in the home before, but never brazed, only soldered. I guess I would need a mapp torch and different solder for brazing- my propane is barely hot enough for copper plumbing soldering.

The first time I saw this thread I was intrigued. I bet this heat exchanger works even better than the pro-cooler model, since it is a dedicated heat exchanger with no dessicant. I found rec/dryers on Ebay for $15 that will work, so I would really rather have a dedicated heat exchanger rather than something trying to do two things at once.

Thoughts anyone?

[Jim Sims]

A subcooler should be located as close to the evaporator as possible. Note that both the high pressure liquid line coming from the condenser(s) and the low pressure return line (going back to the compressor suction) have to go through the subcooler. I found I could mount it up above the front axle support splash pan (keep in mind that it has to fit in among the brake lines and kept clear of the steering gear). I would only recommend hard silver soldering/brazing using a mapp torch or a oxy/acetylene rig. I brazed on brass male flare fittings (available at many hardware stores) and crimped on matching female flare fittings to the hose ends. If you are going to use the reduced barrier hose (weighs less, has a smaller outside diameter and tighter bend radius) the female flare type fittings for this type of hose are difficult to come by. The regular barrier hose flare fittings can be adapted by changing out the crimping ferrules (to reduced barrier hose size ferrules) but this must be done with care.

I believe adding a subcooler made about 10 degrees F difference in the louver air temperature in my car while moving (my system has just a single 1970's style/technology engine deck lid condenser). It is not a substitute for adequate condenser area being blown by fans when driving slowly or idling in traffic. However, while cruising (75-80 mph) through 110 F desert heat and sun (car is medium blue with black interior) with two people in the car we had to turn the A/C down. I have an under dash A/C air distribution duct which IMO provides better air flow than the SC and Carrera built in dash units. I'm running R134a refrigerant. My A/C system is apart this winter while I tinker with another inexpensive condensing aid.

Cheers, Jim

[mtbguy]

Thanks for the info Jim- I am going to go ahead and buy it (and a mapp torch) and also do the mod.
Have a great day!

[rnln]

Anyone in OC, SCal already did this or going to do it? Can I come and join to learn how to?

[kuehl]

Something like this, about $85.00, 4" OD x 11" height




Something like this, $56 to $82.00



Braze on a few fittings and ......

[Hugh R]

I made one based on Jim's design a few years ago then I replaced my a/c lines. It wasn't particularly hard. You do need to have custom made lines between the R/D, the subcooler and the evaporator though. I elected to make it like you see in his last two pics. I mounted it behind (I think) the steering track. Cost me about $30. I don't think I insulated it as well as Jim did however.

Jim, I do have one question. This winter I removed my compressor to have it rebuilt due to an oil slinging leak. I had it apart about 48 hours, should I replace the R/D which was new about 2 years ago? Not a lot of money, like $30, but would value your opinion. Some people say always replace the R/D when you open the system.

[mdurbahn]

Got any pics? I am thinking of doing this but doesn't look like I have the same about of room by my rack (79 930)

[bob deluke]

Hugh:

If you left the a/c system open to atmosphere for any length of time without sealing openings, (please, duct taping openings does not qualify), you may have to replace receiver dryer. Some have a desicated "eye" that lets you know if system is dry or wet (changes color). If you have a good vacuum pump, (Robinair, Imperial Eastman) minimum 1.5 cfm, change the vacuum pump oil (every time you use it) and sweep the system, your existing dryer should work fine. By sweeping the system I mean you pull deep vacuum 29"Hg or 500 microns if you have a Torr gauge. Let system rest a few minutes, break vacuum to "0" psig with clean dry refrigerant gas, pull deep vacuum again, about 30 minutes or so. Let system rest, break vacuum to 0 psig with clean dry system refrigerant again, pull final vacuum to 29"Hg or 500 microns. Charge system as usual. This is called the double sweep, triple evacuation method of drying out a "wet" system. A heat lamp helps as well to drive moisture out of the system into the vacuum pump. For all this to work, the system needs to be leak tight, use clean dry refrigerant, have a good vacuum pump and a good set of gauges.

[mtbguy]

Anyone try to contact this Y/P Products company lately? I've made numerous attempts to phone them and they never answer the telephone and it hangs up after ten rings.......

This subcooler is the only part left I need to complete my AC project.

[mtbguy]

I found another company- Doucette Industries. I ordered their comparable 1.5 HP model- it cost ~ $30. They answered the phone and were very helpful- dimensions are identical to the other unit Jim Sims ordered from YP products.

Here is the info:
Doucette Industries
20 Leigh Dr.
York, PA
(717) 845-8746

Model is SLHE 1.5 (stands for suction line heat exchanger 1.5 HP)

Hope this helps anyone looking!

[N758BB]

Does anybody know where to get the O-ring fittings to braze onto these sub coolers. I can find the taper fittings but would like to stay with O-rings if possable. Even thread on (pipe thread) would work if those are the only ones available.

[mtbguy]

I bought some pipe thread type from local hardware store but haven't brazed them on yet. My car is being repainted presently and has been away from home for the last few weeks.

I too, would like to know where to get these if you find them....