A K5 Cummins Conversion: The saga continues...

[MaxPF]

excellent timing on this - I'm in the midst of a roll-my-own ac system for my 'burb. I like what you're doing - a lot. The roll-my-own portion is divorcing the rear ac system from the front and using an electric pump for the back that I can plug in to house power when camping (a portable generator), and not having anything on the roof but still be able to run when I'm going down the road off an inverter.

Are you going to share the refrigerant circuit and condenser between the systems, or do you plan on using a separate condenser? Also, FWIW, depending on the tonnage your talking about Tecumseh makes electric AC compressors capable of 12, 24, and 48V DC operation under their Masterflux brand. I haven't used them, but they look interesting. I found them when looking for a small low temp 12V compressor for use in an on-board fridge/freezer

That looks cool, Greg

I hope it keeps me cool! It's getting hot already :sigh:

 

[SuperBuickGuy]

Are you going to share the refrigerant circuit and condenser between the systems, or do you plan on using a separate condenser? Also, FWIW, depending on the tonnage your talking about Tecumseh makes electric AC compressors capable of 12, 24, and 48V DC operation under their Masterflux brand. I haven't used them, but they look interesting. I found them when looking for a small low temp 12V compressor for use in an on-board fridge/freezer

I'm leaning towards 2 systems where one system is the stock GM system, the other one powered by electric.

I wondered who really made the purple compressor - now I know. I also didn't know there was a 24v compressor, that is quite helpful and good. Thank you for pointing it out. There's a second company as well called Danfoss that builds DC compressors.

*edit* I dug a bit more, and it all makes sense - Danfoss makes the compressor for ARB coolers, the BD35F is what's in their cooler. Masterflux is in Dometic.... but I didn't realize that they made things that were large enough to cool cars that were 24v...

 

[Mb30sdl]

Yea let me point out that TXV is just a metering device to increase efficiency of AC ( orfice is just a hole), expansion tank is there to provide extra room for freon expansion which is enevetable due to changing temperatures.

TXVs nowadays are failing very often a least in Household ACs.

 

[MaxPF]

I'm leaning towards 2 systems where one system is the stock GM system, the other one powered by electric.

I wondered who really made the purple compressor - now I know. I also didn't know there was a 24v compressor, that is quite helpful and good. Thank you for pointing it out. There's a second company as well called Danfoss that builds DC compressors.

*edit* I dug a bit more, and it all makes sense - Danfoss makes the compressor for ARB coolers, the BD35F is what's in their cooler. Masterflux is in Dometic.... but I didn't realize that they made things that were large enough to cool cars that were 24v...

I've never been a fan of Danfoss. Their TXV's are crap. Their compressors seem OK though. Tecumseh (well, Masterflux) also makes little 12V compressors, which I was going to use for the MaxPF 12V cooler. All the Dc compressors are are either split phase or (more often) 3 phase AC compressors with an inverter attached to the side. You could take a small Copeland or Embraco 115 or 230V compressor and run it off of a small inverter and it would do the exact same thing.

Yea let me point out that TXV is just a metering device to increase efficiency of AC ( orfice is just a hole), expansion tank is there to provide extra room for freon expansion which is enevetable due to changing temperatures.

TXVs nowadays are failing very often a least in Household ACs.

Technically, the TXV is a metering device designed to maintain constant superheat in the evaporator, which does increase efficiency. Orifice tube systems need the accumulator because they often run flooded, so liquid refrigerant exits the output of the evap. The accumulator is needed to prevent liquid from slugging the compressor (liquid isn't compressible, so liquid entering a compressor is A Bad Thing ™). A flooded evaporator does give the best evaporator utilization, but the systems have poor efficiency and don't work very well at idle and low speed.

The TXV failures you are referring to aren't the fault of the TXV (even the Danfoss TXV's :wink. Copeland was using a new sealant in their 410A scroll compressors, and it was breaking down and sending a sticky goo into the TXV's. Copeland has been quietly replacing the compressors under warranty if asked. Many techs just stick a filter in the liquid line to prevent the crap from making it to the TXV's, but it's not clear if the filter/drier actually captures the dissolved substance.

 

[MaxPF]

So the AC is still a work in progress. I wanted the adjustment stem on the TXV to be accessible without having to remove a bunch of crap and without mounting the TXV in the engine bay. I decided to mount the TXV with the adjustment stem poking through the bottom of the housing. I had to drill a hole for both the stem cover/body of the valve as well as the inlet fitting. This is what I ended up with:

This mounting arrangement does have the drawback that the liquid line will also exit the housing, but I will be able to make a tight u-bend and send it back up the firewall-side. Since there is a roughly 1" gap between the back of the housing and the firewall for sound insulation running the liquid line up the back of the housing presents no issues.

The next thing to do was fit the distributor/tubes and route them into the evaporator. This started with running the tubes along the bottom, then making a few judicious bends to turn them up toward the top inlet:

Then more bending and head scratching to fit the tubes into their respective circuits in the evaporator. In order for the distributor to work properly the tubes to each circuit must be equal length, so the tubes going into the lower circuits have to make u-turns and head downwards to their respective inlets. Once I got it all fitted, I hooked up my CO2 bottle, started a slow flow of purge gas, and started brazing the tubes in. I got the second one brazed up when I realized no gas was flowing. A quick check of the gauge showed my Co2 bottle was flat :gaah: I had to load it up, schlep over to the welding supply joint, and get a refilled bottle just so I could braze up the last tube. But I gotter done, and here is the result:

Here's an underside view of the finished product:

The cap covering the adjustment stem will be readily accessible but safe from being hit by errant feet. You can also see the condensate sump that I was able to mold into the bottom cover. Unfortunately, the back side of the sump got a bot thin and a couple holes developed. Rather than try to make another one (this was already attempt #2) I sealed up the holes with the urethane adhesive. I still need to drill a hole in the sump and install a suitable drain fitting. That will be a post for another day.

 

[MaxPF]

I'm leaning towards 2 systems where one system is the stock GM system, the other one powered by electric.

I wondered who really made the purple compressor - now I know. I also didn't know there was a 24v compressor, that is quite helpful and good. Thank you for pointing it out. There's a second company as well called Danfoss that builds DC compressors.

*edit* I dug a bit more, and it all makes sense - Danfoss makes the compressor for ARB coolers, the BD35F is what's in their cooler. Masterflux is in Dometic.... but I didn't realize that they made things that were large enough to cool cars that were 24v...

I was looking at the Masterflux Sierra series, and I'm not sure I would say "large enough to cool cars" unless you are talking about compact/subcompact cars. At 24V the biggest compressor in that line can only manage 9340 BTU/hr at a 45° evaporator. If you are willing to tolerate a 55° evaporator it can manage 11,494 BTU/hr, which is still a tad under one ton. By contrast, a Sanden SD15 or Seltec TM15 or similar size GM, Ford, Denso, etc engine-driven compressor can easily exceed 1.5 tons at cruise with a 35°-40° evaporator. My Seltec TM-16 or the common 170cc-200cc compressors used by GM, Ford and others can go well over 2 tons (24000 BTU/hr). The Sierra compressor might be OK for auxiliary rear air in an SUV, but if you want it to be able to cool as well as an engine-driven compressor you would probably need a pair of them. At that point I would build my own variable speed inverter and use a 1.5 or 2 ton 240V three phase hermetic reciprocating compressor.

 

[alrock]

Nice! When are you pulling the 6.2 from my Camaro and dumping it into my H3?

 

[MaxPF]

Second Tuesday of next week?

 

[MaxPF]

I was looking at the Masterflux Sierra series, and I'm not sure I would say "large enough to cool cars" unless you are talking about compact/subcompact cars. At 24V the biggest compressor in that line can only manage 9340 BTU/hr at a 45° evaporator. If you are willing to tolerate a 55° evaporator it can manage 11,494 BTU/hr, which is still a tad under one ton. By contrast, a Sanden SD15 or Seltec TM15 or similar size GM, Ford, Denso, etc engine-driven compressor can easily exceed 1.5 tons at cruise with a 35°-40° evaporator. My Seltec TM-16 or the common 170cc-200cc compressors used by GM, Ford and others can go well over 2 tons (24000 BTU/hr). The Sierra compressor might be OK for auxiliary rear air in an SUV, but if you want it to be able to cool as well as an engine-driven compressor you would probably need a pair of them. At that point I would build my own variable speed inverter and use a 1.5 or 2 ton 240V three phase hermetic reciprocating compressor.

Or, here's another thought....

That's a 24V 7.5HP DC motor hooked up to a 10ci York. I got a few of em I am going to build for OBA, but it wouldn't know the difference between compressing air or refrigerant. You would probably need to run it on 12V to limit it to about 1.5 tons. On 24V you would probably see 5 tons or more, which might be a tad excessive :whaa:

 

[SuperBuickGuy]

Or, here's another thought....

That's a 24V 7.5HP DC motor hooked up to a 10ci York. I got a few of em I am going to build for OBA, but it wouldn't know the difference between compressing air or refrigerant. You would probably need to run it on 12V to limit it to about 1.5 tons. On 24V you would probably see 5 tons or more, which might be a tad excessive :whaa:

Is it ever enough :horns:

It's cool you suggested that, I mentioned that same concept on my thread on Expo Forum. The other thought is simply get the battery pack and a/c system out of a Leaf (or a Volt).... wouldn't it just be perfect to take an electric car off the road to air condition a Suburban? I'd have Greenpeace trying to run into my 'burb while out in the wild. That would follow more along the line of what you suggested with the 3 phase 240v system. Again, more checking but I think the Volt system is 300v 3 phase, best part is it could give me electric heating too and/or a heat pump system. Some preliminary measurements that I've done of the battery pack for the Volt is the battery would fit perfect under the couch/bed.

 

[MaxPF]

I thought you wanted a 12V or 24V solution? In any case, I take back my suggestion of using a hermetic recip. I forgot that recips generally need constant crankcase heat to prevent refrigerant migration to the oil sump. That probably explains why the Masterflux compressors are rotarys. A scroll would work fine as well, but all the stationary scrolls I know of are vertical and they are quite tall, and you can't mount them horizontal due to oiling.

 

[SuperBuickGuy]

I know I get a bit annoying how I circle around the issue until I finally come to a solution. Your input helps more then you can imagine. Thank you for it.

 

[MaxPF]

I neglected to mention earlier that I have a new family member!

Her name is Freya, and she does an excellent job of holding down the floor while I work:

She is a 3-½ year old German Shepherd who was at a rescue shelter. She is great with kids and cats, and she has a good sense of people and she has definitely become protective of her new family. She is also very intelligent. I am looking forward to taking her camping with us. I think she will really like hanging out in the forest. Unfortunately, the weather is heating up fast, and when she rides in my truck her attitude is "Dude! Get me some AC goin' in this thing!"

With that said, I got the evaporator finished. I was originally going to run the suction line out the back as one piece, but I quickly realized it would be impossible go get the evaporator in or out of the housing. I ended up running a horizontal section of suction line long enough to accommodate the TXV bulb then turning it down and putting the -12 brass female o-ring fitting on the end. With the exception of the Schrader fitting, which is brazed on with 56% silver braze, all of the suction piping is soldered together with Harris Stay Brite silver solder. Stay Brite is designed for HVACR service and because it takes much less heat to melt there was no danger of accidentally melting the braze joints between the header and the three tubes exiting the evaporator. After I got it soldered and brazed, I used my pressure test fittings to plug up the inlet and outlet and pressurized the whole unit:

I found my old Imperial gauge set and chose to use it to pressure test the system. Despite being over 35 years old, the manifold doesn't leak. My JB manifold leaks, and my Yellow Jacket manifold has a broken low side gauge. They are both on my to-do list to fix. Whether they will get fixed depends on if I decide to invest in a Testo 550 or a Sporlan SMART tools setup to attach to the Imperial manifold. Anyway, I digress. Here it is holding ~190psi pressure:

The problem with this gauge set is that it was designed for a better, vanished time. It has saturated temperatures for R-12 and R-22, and the gauges start to retard after 80psi, at which point they're not very accurate or responsive. I tried running my JB manifold with brand new R-410a gauges that read to 250psi on the low side with no retarding, but then I discovered that the low side valve seal leaks. I ended up putting the Imperial set back on and pressurizing the evaporator to 75psi. It has now been a couple days and the gauge is holding pressure, so I think I can pronounce the evaporator coil leak-free.

I also got myself a new micron vacuum gauge. Back when I got into refrigeration and AC nobody had micron gauges because they were expensive. Turns out they are still expensive, but cheaper than they used to be. After having seen how different two new digital gauges from the same manufacturer can read on the same line, I chose to go with a laboratory-type instrument. If I get a cheap, compact digital gauge I can use this instrument to sanity check it.

I decided to use my new gauge to see how low of a vacuum my over-20-years-old vacuum pump can pull. Here's the gauge tube attached to the pump:

I tried initially with the oil in the pump, and was only able to pull 180 microns. I dumped the oil and filled the pump with some old (but unused in a sealed bottle) oil I had lying around. The pump holds a quart, and I had 3/4 quart of VERY high quality and very expensive Inland 45 synthetic pump oil in the cabinet. I poured it in the pump, and topped it off with ¼ quart of cheap Robinair vacuum pump oil that had been kicking around in a cabinet for 10 years. The Robinair oil is nowhere near the quality of Inland 45, but the pump still managed to pull a very respectable vacuum:

14 microns! It actually pulled down to 11 a few minutes after I snapped that pic, at which point I shut it down. For a relatively inexpensive refrigeration service pump that is an excellent vacuum. Assuming the AC system doesn't leak I should have no problems pulling down to 250 microns.

That's all for now. Hopefully the next update will be to show the evap housing mounted under the dash.

 

[SuperBuickGuy]

what a beautiful dog, thank you for rescuing her. Any idea what landed her in doggie jail?

 

[MaxPF]

what a beautiful dog, thank you for rescuing her. Any idea what landed her in doggie jail?

By the way she reacts to certain things she was definitely abused by her previous owners. She is rapidly coming to the realization that she won the doggie lottery by getting adopted by us

 

[SuperBuickGuy]

It's really cool that you got a rescue. I'm involved in K9 Search and Rescue (we train bloodhounds), my mom rescues GSDs, and part of my day job is defending dogs who have bitten. Rescues are cool, but they can have attendant problems - it's almost like dating, where people put their best foot forward then, as time progresses, cracks show through. With abused, rescue dogs you can avoid a lot of issues by doing a lot of training. Just as a tired dog is a good dog, a trained dog has a job to do and will do that job above all else - this is doubly true with GSDs (German Shepherd Dogs). My mom has rescued some very abused dogs and they have caused a few issues - probably the worst is they are obsessed-protective. The know they won the lottery and by god they're going to protect their owner from all perceived attackers.... in one case, it was a guy who was there to replace her windshield (he was an idiot because the dog was warning him and he kept walking rather then get back into his van) and got him in the balls (lol).

With all that said, I see the worst of the worst - and there are hundreds of thousands of rescues who are great dogs - so the point is simply be sure that if she's showing aggression, it is appropriate and completely under your control. If not, give her a job

 

[alrock]

Congrats on the new pup!

 

[SuperBuickGuy]

Sorry to pollute your thread, but I'd really value your opinion on this for my build
Opinion?

[h=3]Specs:[/h]

• 1/3 hp compressor motor, the most powerful in the RV industry today
• Running Watts for Cooling - 1225 to 1450 Watts
• Approximate full load amps - cooling - 11.1 amps
• Evaporator Air Delivery on high speed - 200 CFM
• Dimensions: 44 2/25" L x 32" W x 10" H
• Weight: 92 lbs
• Optional 5,600 Btuh heating element to take the chill out of cool mornings.

 

[MaxPF]

Without knowing what it is going on and the heat load it's difficult to give an opinion. On top of that, the specs for that unit don't list cooling BTU's. Typically, AC units running a 40-45° evaporator need approximately 1HP of compressor capacity per ton of refrigeration, so 1/3HP is probably around 4000BTU/hr. This is about the same as a small window AC unit.