Air Conditioning Diagnosis, Service & Repair
Replacement CondensersCharge Level Adjustment May be Necessary1Replacement CondensersMost Vehicles Use Flat Macro or Micro Tube, Multi-pass, CondensersVirtually Impossible to Flush After Compressor FailureWill Need to be Replaced.
Sub-Cooling CondenserMultiple Passages In Header TanksMultiple Passages In Header Tanks2Due to their extremely small internal passages, most multipass condensers cannot be flushed following a catastrophic compressor failure and will need to be replaced.
This section deals with an issue that is becoming increasingly common where the replacement condenser may have a significantly different internal volume than the original unit. Although the heat exchange efficiency of the replacement condenser may be equal to or even better than the original unit, an adjustment to the final refrigerant charge level may be necessary to take account of the different physical volume of of the replacement condenser.If the charge level is not fine-tuned to optimize system performance the system may never blow cold enough air..In extreme cases, if the replacement condenser is of a smaller capacity that the original, the compressor could suffer from liquid slugging especially on vehicles with low mount scroll compressors. If the replacement condenser is larger than the original, the system would in effect be undercharged. This could lead to oil dropping out in the evaporator and cause a lack of compressor lubrication.2Replacing the Condenser?Condenser Technology Has AdvancedReplacement Condenser May be More Efficient (or Less) than the Original UnitReplacement (Including OE) May not be an Exact Match for the Original UnitTube & Fin May be Replaced by Flat Tube Multi-pass Micro Tube UnitFlat Tube Multi-pass Macro-Tube Might be Replaced with Thinner Micro-Tube Unit.System Capacity May be Affected3
Flat Micro-TubeFlat Macro-TubeCondenser technology has evolved dramatically over the past 10-15 years. Designs have evolved from large tube and fin to smaller tube and fin, to flat macro tube multi pass to micro tube multi pass. There are also flat tube single pass serpentine flow condensers available. Many condensers are now sub-cooling units where the receiver drier is integral to the condenser header tank. The integral receiver drier is used to improve liquid/vapor separation in the condenser to improve its efficiency. Condenser vendors therefore have a wide choice of basic condenser designs to choose from when manufacturing a replacement condenser.As a result, a replacement condenser today may not always be an exact physical match for the original unit that is being removed from the vehicle. Although the heat exchange efficiency of the replacement condenser may be equal to or even better than the original unit, an adjustment to the final refrigerant charge level may be necessary to take account of the different physical volume of the replacement condenser. Even a replacement condenser from the O.E. dealer may not be an exact match for the original unit. Since condenser designs have, in general, become more efficient, replacement condensers will usually have a smaller internal volume that the original unit. However in some cases the reverse could be true especially if the vehicle itself is relatively new.3Condenser Tube Comparisons4
16 x 1 mm, 15 Passages, .4 x .8 mm16 x 1.75 mm, 16 Passages, .7 x 1 mm
18 x 2 mm, 10 Passages, 1.24 x 1.35 mm22 x 2 mm, 10 Passages, 1.24 x 1.75 mm22 x 2 mm, 13 Passages, 1 x 1 mm22 x 1 mm, 18 Passages, .4 x .9 mm26 x 2 mm, 10 Passages, 2.15 x 1.26 mmActual Size!The illustration above shows a variety of condenser flat tubes that are available this is just a representative sample. not a complete list by any means. You can see that even though tubes might look similar upon casual inspection, there are significant variations between tubes - width and depth of tubes, # and size of internal passages etc. These differences can affect the internal volume and the heat exchange efficiency of the condenser.. The small picture in the top left shows the actual relative size of these tubes.In addition to tube design variations other consideration are the total # of tubes in the condenser, the cooling fins per inch, whether single, multi pass or serpentine flow etc.
4F150 - Condenser 15
Replacement Condenser 1 - Muti-pass Tube & Fin (Piccolo) Design Older TechnologyPpTo illustrate this problem we purchased three condensers from different vendors for a 2001 Ford F150 we have here at the training center.The condenser in this slide is the O.E. design tube and fin (Piccolo), parallel flow.. Relatively old technology compared to the micro tube condensers we see on most modern vehicles.
5F150 - Condenser 26
Replacement Condenser 2 - Very Large Flat Tube, Single Pass, Serpentine Flow Older TechnologyPpThis condenser is a large flat tube, single pass, serpentine flow design. The flat tube is just one open tube it is not broken up into individual passages. This is also fairly old technology, relatively inefficient compared to newer flat tube, multi-pass, micro tube sub-cooling designs.6F150 - Condenser 37
Replacement Condenser 3 - Flat Micro-Tube, Multi-pass Flow New Technology Very EfficientPpThis condenser incorporates current technology it is a flat micro tube, multi-pass flow, design very efficient but does not hold as much liquid as the previous two condensers.7Compare8
1. Tube & Fin Piccolo3. Flat Micro-Tube, Multi-pass Flow2. Very Large Flat Tube, Serpentine FlowPpFor a quick visual comparison we have laid one condenser atop the other.8Condenser CapacityWe Evacuated Each Condenser & Charged it with Liquid RefrigerantThey Held:1. Piccolo = 47 oz. (Matches O.E.)2. Serpentine = 43 oz.3. Micro-Tube = 26 oz.We Need to AdjustOriginal ChargeAmount
Piccolo Condenser Held 47 oz.PpTo illustrate the significant difference in volume between the different designs we evacuated each condenser and charged it with liquid refrigerant. As you can see the micro tube design held only just over half of the original design (Piccolo) condenser.The original refrigerant charge specification for this F150 is 33 oz. If we use the serpentine flow or especially the micro tube design condenser we will need to reduce the original charge level in order for the system to perform efficiently.Any of these alternative designs may perform perfectly well in the system. However, an adjustment to the system charge level will almost certainly be necessary to optimize system performance. In most cases we have seen so far, the replacement condenser required reducing the system charge level to optimize performance.However it the replacement condenser was of a larger capacity than the original, then the final charge level would need to be increased.Any adjustment to system charge level needs to be done with extreme caution given how critical precise charge level is to ensure proper compressor lubrication (undercharge) and avoid slugging (overcharge).9How to Handle?Compare Original and Replacement Unit DimensionsBasic Design Flat (Micro or Macro) Tube, Serpentine or Multi-pass, Tube & Fin?Compare # of TubesSize of Header TanksConnection Line Diameter# of Cooling Fins/InchCondenserThickness10
PpHow to Handle this IssueA side by side, apples to apples comparison of the old and new condensers should be performed before installing the new unit . The technician should compare the basic design tube and fin, (large or small), macro tube or micro tube, multi-pass or serpentine flow, sub-cooling or not (integral drier), # of cooling fins per inch etc.
10Confirm Charge LevelPerform Temperature Test to Validate Charge LevelStart at 80% of Original ChargeAdd 1-2 oz. IncrementsMonitor the Three DeesCondenser Drop 20-50 Deg FAmbient to Duct More that 30 Deg. DifferenceFinal Charge May be More or Less than OriginalWhen Evaporator Inlet/Outlet Difference = 0 Deg. F Charge Level Correct11
PpUltimately, the most effective way to optimize the system charge level is to use temperature testing.The temperature test should be performed in the normal way . The charge level should be adjusted in increments until the three Ds (differences Condenser inlet/outlet, evaporator inlet/outlet, and ambient/center duct ) are all in the acceptable range. Refer to the section starting on page 63 of the Air Conditioning Diagnosis, Service & Repair book for the complete procedure on how to perform a Maximum Heat Load Temperature Test.Begin by charging the system to 80% of the original charge. This is a good starting point. With the vehicle set up to perform a maximum heat load temperature test (doors open, ambient above 80 F etc) add an ounce or two at a time and monitor the temperature drops until they are in the normal range. Allow the system to stabilize for several minutes as each refrigerant increment is added. On an orifice tube system the ideal temperature difference across the evaporator is 0F (+/- 5 F). Of course the ambient to duct and condenser differences must also be in range. For TXV systems use either the Direct or Indirect methods, described on pages 67-70 of the book, to measure evaporator superheat.It is very important to keep track of the total amount of refrigerant in the system. If the system does not respond normally as refrigerant is added (or removed) the system could end up grossly over or undercharged. In most cases the final charge level will not differ by more that 20% from the original charge amount.
Click here to load reader