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Which TXV for custom build?

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    Which TXV for custom build?

    Building an AC system for my 47 Chevy pickup. Going custom heater case because I insist only having a fresh air system. Dirt roads don't work well with recirc systems.
    Compressor a Sanden 508
    Condenser is a 16x19 parallel
    evaporator core in looking at is ev0024atc
    ​​​​​​I know the expansion valve can make or brake a system. Is there an adjustable one that fits the -6 o-ring inlet? Ones I should avoid?
    ​​​​​​​Thanks Nick

    Welcome Nick. OMG a custom made system for a '47 anything. A tech here Cornbinder89 will have some much better suggestions than I could for this will be by I'm sure. It's late so just wait.

    Please say which refrigerant you plan to use presumably 134a - right?

    MetroWest, Boston


      My 1st thought is if it is set up for a block type or not. I think I found a picture of what you are looking at on Summit's website. if that is the one, it is not used with block type
      Tx valves are sized by the evaporator they control. Nothing gained and something lost by using a 2 ton Tx on a 1.5 ton evaporator.
      From what I saw that evaporator doesn't have a provision for a equalizer tube connection, so unless you are going to add one in some way, you can not use an external equalized Tx valve.
      You are going to want the thermal bulb as close to the outlet as possible. and may have to adjust the "superheat" so that the refrigerant all boils and absorbs heat before leaving the finned area. Liquid refrigerant doesn't absorb (much) heat, it is the phase change from liquid to gas that needs the heat input. Not boiling all the liquid to gas reduces the overall effectiveness of the system.
      A quick look on the .net and I couldn't find any spec's for tonnage and not even the size of the fittings. Inlet should -8 as that is what the outlet of most Tx valves are (remote style). The outlet of the evap only matters for your plumbing.
      If I had to guess at tonnage, I would go with a 1.5 ton Tx, based on surface area of the evaporator. I would leave the superheat as set when you get the Tx and only if there is a big problem try making adjustments. You can do more harm than good easily.
      Good luck with your build, and I agree and commend you for going the fresh air route.


        Something else comes to mind, before you "pull the trigger" on that Evap.
        Red Dot makes many pre-packaged heat and A/C units that are quite compact and designed to be ducted. Many Semi's use Red Dot units for main and/or bunk climate control.
        New or used, one could cut the fab time and effort to inlet and outlet duct work.
        They have heater Evaporator, Tx valve and blower (with speed resistor) already in one small package. Add a water valve for heat temp and run your hoses and your done.
        Something to look into.
        If you have any big truck junkyards in your area, you could be money ahead with a sleeper Red Dot unit.


          Thank you for the replies. Sorry it wasn't sooner. For some reason I'm not getting notifications.

          Planning on 134 in the system.
          I'm pretty sure the inlet on the evaporator core I was thinking about is -8 and not -6. I knew those were usually -6 going to the valve. I forgot they bump up a size coming out of the TXV.

          I need to do some more reading on txv and super heat. I hadn't heard of that term previously which is why I wanted to ask questions before I ordered parts. Just off of this page there are plenty of options.

          I did look into the Red Dot systems. They look good but for the price and space that I have to work I think I would be better off building my own case. One of the customer vehicles at work is a 51 Chevy extended panel that has front and rear air. For the rear unit I took a universal unit and made it fit under the floor. But the time I built the enclosure to seal it from the outside and modified the case to be able to duct it outlets to both sides it would have been easier to gut the unit and build a case with everything exactly where I needed it to point.
          It just got out of paint so I'll find out sometime next month if it works or not.

          On my 47 the space I'm looking at is the huge empty area behind the right front tire in the fender. There is plenty of room there for heat and evaporator core and the blower motor. From there duct it up through the passenger kick panel with the internal ducting passing through the original heater box just for looks. Plan is to pick the components, put them where they fit best and then build the enclosure. Benefits being noise from the motor is not in the cab. No space taken up behind the dash except for the ducting. Easier to service because the guy designing it will also be the guy working on it. Ask anybody in a dealership how that usually works out. Also, leaks from heat or ac will not end up inside the vehicle. Seen that several times with vintage air.
          It's ambitious but I enjoy the challenge and the fabrication part.
          Is there anything I should keep in mind when running the lines? Oil circulation being the main concern. The compressor is the lowest part. It's mounted on it's own crossmember in front of the engine below the radiator with the pulley facing back with a spring loaded tensioner. From what I have read the smaller Sanden compressors can be run backwards being it's a swashplate design.
          V-belt deep Grove pulleys, poly mounts on the engine and compressor crossmember. It seems like it should work. I'll find out I guess. Like I said, ambitious lol.

          On the evaporator, does it make a difference in operation with the fittings on the top or bottom?

          Thanks again Nick


            Just quick. Site doesn't send notices to some devices despite you asked it to. IDK why, Tom
            MetroWest, Boston


              Some Sanden can turn either way some can't. Check before you assume. It likely has to do with a built in lube pump or channel being set up for one direction.
              I went through this with my Truck APU build. York (old 2cyl recip) can turn "backwards" and some of the smaller Sanden can. The A-6 at one time was made in reverse rotation, but I haven't see them anywhere for years. They weren't "either" but could be bought for "reverse".
              As far as oil return to the compressor, If you look at what mfg do these days, it seams anything goes. As long as the compressor isn't starved for lube, a little in a low spot somewhere isn't a deal killer. Oil dissolves in refrigerant, which is why you can't use mineral oil in everything, so will be carried back to the compressor even if some is left behind in a low spot.
              As far as location, I'd be worried if not protected from wheel spray, other than that, it is up to you. The evaporator you chose earlier looks to be a generic "under dash" type replacement. My guess stands at 1.5 ton for the Tx valve.
              I thought if I wanted to add A/C to something that couldn't or didn't want to change the stock heater core, make a "water chiller" and use an electric pump to circulate coolant from the heat exchanger (tube and shell type, refrigerant on one side, coolant on the other. Same heater core could be used to blow cool or warm air depending on season.
              Some of the old heater had too small a core for this to be very effective but others it might work well. Need a condensate drain for the heater core added.
              I have a real neat Motorola gas heater that might end up in one of my old trucks. It is from the 40's so period correct. There were some real nice looking "Art Deco" heaters made in the 30's and 40's when heaters were not often a factory item but a dealer installed extra.
              Yes, do read up on Superheat, it can be a confusing thing to understand, but the basic is this:
              to get the most cooling out of the finned surface area, all the refirgerant that the Tx lets in the eveaporator must boil by the time it reaches the outlet of the finned part of the evaporator. ANy liquid that remains means heat that didn't get used in the phase change, so reduces that capacity of the system. Conversely if it all boils before the end of the finned part, again the evaporator is not being used to its best ability. Since the thermal bulb from the Tx is not attached right at the outlet, but a little way away, and/or the equalizer tube connection the same thing. Superheat is the setting that adjusts for the difference between what is happening at the fins and what is happening at where it is being sensed. The longer that distance the more "superheat" you want. It is the temp above boiling point the exiting refrigerant is Once the refringent all has boiled it still absorbs heat but instead of remaining at the same temp, it begins to rise.
              Put another way, when you boil water, the water stays at 212 until it has all turned to steam, then the temp begins to rise again (superheat). Sensing the "super heat" is sensing when all the refrigerant has boiled, In most cases you don't adjust from factory setting. With Block type Tx valves the inlet and outlet from the evaporator are the same distance so they generally aren't adjustable for Superheat, as it can be figured out when building the block.
              Adjust too far one way or the other and you will reduce the amount heat the evaporator can transfer to the refrigerant.
              Last edited by Cornbinder89; 11-21-2022, 08:43 PM.


                Thanks for the input. I appreciate it. Parts are finally starting to show up so I can keep making progress.

                Another question. For heat control what are the pros and cons of going with a full flow heater core and an air door vs no door and an electronic valve in the hose?

                Thanks again.


                  Air door reacts to input changes mush faster than a water valve, also make blending temps more accurate when you want to run A/C to dehumidify but don't want air that cold, like when running a defroster on a cold day.
                  Drawbacks of air door is they can be hard to seal so not heat enters the ducts when heat is not wanted, it also puts a heat source right next to the evaporator box, and heat can leak into the cooled space.
                  An air door with the option of an "on/off" water valve give you the best of both. You can cut water flow to the heater when in the dead of summer and still retain the ability to blend with an air door in cool weather. If I were building from scratch, that is the way I'd go.


                    I agree with Cornbinder about hot coolant being there year round. Old reason was a heater was also an acting by-pass of coolant keeping inside of engines a uniform temp. Some if you just pinched it off engine would be hot at the back never moving much or enough coolant around engine or blow gaskets, overheat not near common use of near thermostats. Note: "Water pumps" are always pumping (most) cold or hot weather it gets below zero F. where a lot of things/cars are no problems I/we still drive in whatever.

                    IMO the use of A/C to dehumidify air is mostly BS when that cold humidity is already low and tons of vehicles made without A/C at all costly for some with a short season can't bust year round you wouldn't know.

                    Engine vacuum or plain cable runs the ducts or used to stayed put didn't wear out or lose sealing as designed - metal not plastic with felt like ends IDK everything ever made?

                    Electric actuators are used another problem in wait long term but easier to design I guess?

                    At least use what's popular enough so it can be fixed later if need be,

                    MetroWest, Boston


                      I can say for a fact that A/C on defrost makes a big difference in trucks. The large windshield area, can fog up badly without the A/C on. A/C and aux fans mounted above the windshield are common on big trucks to help keep the windshield clear.
                      Cars may be less susceptible to this, but it does help.
                      Not so much at temps well below freezing, but there is a lot of moisture closer to the freezing mark and temps above.
                      Just your breathing at temps in the -20 to -30 deg range can ice over side windows, requiring stopping and scrapping.


                        Thank you for the input everybody. I appreciate it. Those were all the same points I was thinking, just wanted to make sure I wasn't missing anything.
                        Heat requirements for this aren't super critical. It's a 3 1/2 season truck. I plan on driving it as far in the winter as I can until they salt the roads and then it's parked until spring when we've had enough rain to wash it off. The truck is sealed up well so it won't take much to heat it. From the very beginning this truck was built to be a daily driver. S10 frame, overdrive, four wheel disc, hydroboost, power steering tilt Cruise air.
                        A while back a friend of mine was parting out an 05 Chevy suburban and I got the front and rear auxiliary control heads, the overhead consoles they mount in, the complete headliner wiring harness which runs back and down the last pillar to the heater box and all of the wiring plus the complete rear heater case assembly and the ductwork. Somewhere I've got a picture of it but the rear overhead console, the little 12 in one, with the front auxiliary control head actually fits really well up in the ceiling of the 47. And at the right height my truck sits at even if you're leaning over to look in the windows you have to consciously lean over farther to look up enough to see it so to everybody outside it's out of sight. Even walking by. And from the inside it doesn't bother me to reach up to the ceiling to run the temp controls. I've got a 10 mm stainless latching push button with a blue LED for my compressor control to the relay. I can fit that somewhere up in the console where it'll look okay. The rear heater core is a decent size that I think it'll work and they are priced reasonable. I figured I've got the case, borrow the temp actuator and the door and build that into my new housing and then it's just one less thing I have to fab.
                        With the actuator and door I've got full flow through the heater core and the extra circulation will probably help the 400 that I have sitting under the hood. It shouldn't be too hard to keep some space in between the heater core and the evaporator so I don't have any heat cross over. The other option if the door is just going to be a pain is like I said I have one of those in line electronic temp valves it came with another dash AC unit that we installed on a customer's car. I got lucky in this one is 0 to 12 volts which is the same according to Mitchell as the rear temp actuator for the Yukon setup so on paper my GM control head should work with that actuator. It's just going to be a matter of doesn't go the right direction which I'll cross that when I get there.
                        If I do run the temp valve I know there's a couple companies that sell pre-made h fittings to plumbing the heater hoses specifically for the purpose of getting circulation back to the motor. The downfall there is if you do end up in cold weather and need full heat some of it is going to be bypassing I would think.


                          Side note and can't help it. Damn road salt (imported no less) is as corrosive as batter acid so I too have lots of 3+1/2 year vehicles INCLUDING a truck to plow snow. DANG PLOW RUSTED OUT had to find one from a no-salt state as it's old.

                          Just North of me is New Hampshire uses salt too sparingly and sand where appropriate works well but too much just clean that up end of season.

                          Just bitching - asked why if used and swept up isn't that re-used was told is a hazmat then pay to get rid of it.

                          Sticker on one vehicle says "YOU CAN'T FIX STUPID"- trust me no shortage of it!
                          MetroWest, Boston


                            Got the AC compressor mounted yesterday. Inner fenders still need painted yet.


                              Everything is still in mock-up stage yet. One I know it is gonna work it will get taken apart and finished.