Guidelines for Service of Units with Microchannel Condenser Coils

With the introduction of Microchannel condenser coils, some service practices have changed from traditional copper tube and aluminum fin coils. It is important to understand that Microchannel coils hold a relatively small volume of refrigerant.  First thing to remember is because of this, you cannot pump down Microchannel coils when you need to service other parts of the system like you have done in the past with tube and fin coils.

Secondly, gauge sets should be connected only when necessary for service. Again, since the systems only hold a small volume of refrigerant, every time you put your gauges on the system and fill your hoses with part of the system charge, you could be affecting the performance of the system.  A slight (ounce to a few ounces) under-charge can impact unit performance. Use your gauges sparingly. When you do have to attach a gauge set, if you have bled off the “charge” in your hoses for transport, re-charge the hoses and purge them before attaching them to the unit and make sure your low loss fittings are working.  By charging your hoses, you are keeping  both non-condensables out of the system and assuring you are not affecting the unit charge.  Keep in mind that the gauge set hoses should be considered when charging a unit. (1.5 ounces per 3 foot hose typical). Also, make sure you turn off or close the low loss fittings on your gauges before removing them from the system to avoid loss of refrigerant from the system.

(Source 1 part number for set of 36″ hoses with low loss fittings S1-CCLV-36)

If you find that you do have to adjust a unit charge, a complete recharge by weight to the nameplate lb./oz. is the best method for “charge adjustment”.   A slight (ounce to a few ounces) over-charge, or any non-condensables can cause high pressure trips, especially at times of compressor starts in higher ambient.


At the risk of being called redundant, I need to emphasize the point that because the condenser holding volume is so small, these units can be unforgiving when the refrigerant charge is not precise.

Let’s look at an example — a YCJD30 13 SEER unit’s charge.  The unit holds only 3# 14 oz. of refrigerant for the unit, coil, and 15 feet of line set.  If you add just an additional 4 oz of refrigerant (1/4 lb.), you have just over-charged the unit by 10 %.  If your line set is longer than 15 feet, be sure to calculate the “charge adder”for the size tubing you are using for the additional line length and carefully weigh it in. All the charging information is readily available on our Tabular Data Sheets that come with each unit. Also remember, that you need to charge with liquid refrigerant with R-410A.  You may want to invest in a “quick charge” adapter that turns the liquid into a saturated vapor in order to avoid “slugging” the compressor. They do work very well.

You must use a Digital Scale to weigh in, or out, the refrigerant when you are adjusting the charge. Add or remove only 2 oz. per adjustment and wait at least 15 minutes per adjustment. This allows the refrigerant in the system to circulate and equalize itself in the system.

Old practices of  charging like, “BEER CAN COLD AND SWEATING” or “OUTDOOR AMBIENT +30” need to be thrown away.  The use of “fishing scales”, “bathroom scales”, or “guessing” for weighing in charge, need to be thrown away. As mentioned above, you need to invest in a good digital scale to work on Microchannel coil systems since the charge in these systems is critical as the example above shows.  Of course, you do need to use the charging charts on the unit and set either the super-heat or sub-cooling to the proper point depending on the type of metering device in your system. You also need to make sure the indoor unit is set for the proper CFM (400 CFM / Ton).  Remember, when you add or remove charge, keep it small (2 oz. at a time) and allow 15 to 20 minutes to expire before making any further adjustments. It is a “slow” process but it will prevent recalls for over charge pressure switches tripping, or under charged and a “not enough cooling” calls.  It all goes back to  do it right the first time.

Of course, good brazing practices with a nitrogen trace running through the system and evacuation to 500 microns with a micron gauge is also critical to a properly performing system.  Since moisture is a non-condensable, and since the charge is critical, even a little bit of moisture left in a system can cause nuisance head pressure trips.

Some other points about Microchannel coils that you need to know:

  • Even though Microchannel coils are all aluminum, they can be repaired with our repair kit and solder alloy.
  • If a coil ever does need to be replaced, the coils come with copper stubs on them so you only have to make copper to copper brazed joints. (see attachment at the end of this posting)

As I have posted in a previous Blog (May 4th), cleaning of the coil is also different from conventional tube and fin coils. To re-cap, that posting:

  • the use of chemical cleaners is not recommended.
  • coils can be blown out from the inside out or vacuumed off.
  • coils can be washed out with a hose from the inside out
    • pressure should not exceed 100 psig,

If you follow these procedures and those listed in the manufacturer’s installation instructions, you will have a properly working system with few to no safety trips or problems. Microchannel coils do provide high-efficiency in a compact design but can be unforgiving if not charged and serviced properly.  Be sure to read some of my other postings on how Micro-Channel coils work so you have a better understanding of these systems. 


MicroChannel Service Coils


About yorkcentraltechtalk

I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired. One of my goals has always been to "educate" dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it. The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way. I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about. Thanks for taking the time to read my postings! Mike Bishop
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12 Responses to Guidelines for Service of Units with Microchannel Condenser Coils

  1. trachsel says:

    Well said Travis. I will be passing along this app to others!

  2. Bryan says:

    In your article it says micro channels are aluminum in can be repaired with our repair kit and Solder alloys. Who is the “our” it is referring to.

    • By “our” I was referring to York/Luxaire/Fraser Johnston/Coleman/ Guardian/ Source 1/ UPG 9(unitary products group) since I worked for YORK at the time. You can check with you local distributor for any of the brands above for information or availability of the repair kit.

  3. Ray Austin says:

    I had the pleasure of running a call in which I found a micro channel condenser (Resi split system). This is just my first impression of them up close and personal… They look cheap. Not that cheap is always a bad thing, but in the case of the one I was inspecting he wasn’t working… and he’s only a shade older than 12 months and a few days.

    You know the story from there: “We got a really good deal…” — nothing a little time will swindle you out of any conceived notions of such.

    However, it wasn’t the fault of the micro channel yet as the problem was the indoor evaporator coil was leaking refrigerant. Bad news for a poor little micro channel… you have to fix the leak as topping off of a critically charged unit will not work.

    So the cost is cheap up front, to leave you speechless and a flat wallet in no time flat.

    How do you pick an air conditioning for your home these days? By price? By guessing? By the use of a professional Licensed HVAC contractor? (notice I didn’t say AC technician.) *Spin the wheel?

    The devil is in the details. Do you really want me to blog about the decisions you made to cool your home?

  4. John jones says:

    Have 5 ton condenser coil been replaced twice unit three years old
    I personally think they are junk

    • Why were the coils replaced? Do you live in a coastal area? Has your contractor offered a ” coated” coil? Do you have a male dog that relieves himself on the unit? Coils normally do not fail that often. There are usually extenuating circumstances for the failures.

  5. Don says:

    Mike, I appreciate you sharing your knowledge and experience with others. Your blogs offer insight to those who are never too experienced to continue learning, making those in our trade better equipped to serve our customers.

    We service all brands and I am careful to refrain from being critical of any brand that my customer owns. I do have a York specific concern regarding the microchannel coils that leak. In my experience copper tube style condenser coil leaks have not been common. A recent job working on a 6 year old YCJF series condenser has left me questioning the durability of the coils. Leaking in a minimum of 3 locations, with apparent signs of general surface corrosion on all sides of the unit that cannot be traced to any external condition. The unit is located in a seasonal area of Michigan with multiple units of various brands within the complex most of which are much older and not experiencing coil failure. The condenser coils are “on national back order” which leaves me to believe there is an issue. Support for solutions has left my customer with the option of complete replacement at full cost or wait a minimum of 1 month during peak cooling season. The season here is only 4 months at best. Can you offer any insight to the durability of the aluminum condenser coils and why the backlog in production? Thank you.

    • Don, first of all, Thank You for the compliment of my blog site. It’s nice to know that the effort is appreciated.
      In all of my experience with micro channel condenser coils leaking, that there was some external/environmental cause for the failures. Since you see the corrosion on all sides, that would lead me to believe this is also the case. One other problem could be the type of coil cleaner used on them causing the problem.
      Are the units on the ground? Do they use a commercial landscape company that “sprays” fertilizer and/or weed killer? That will eat up the coils. Just another possibility?
      Anyway, the solution to coils failures due to corrosion is to order the “E” coated coils. These were developed just for this type of issue and especially for coastal (sea salt corrosion) applications.

      Now I have been retired for the past 2 years so I cannot answer why there is a wait on new replacement condenser coils. Have you looked into the E coils?

      I wish I could give you a better solution, but as I said,my experience with the coils had been very good. And those instances where we had corrosion failure issues we could trace it back to external issues but, when we changed the coil, the E coils solved the problem.

  6. Don says:

    Need troubleshooting assistance, brand new york 5 ton affinity seris micro-channel coil, of course the installers I choose have zero experience with this type of condensing coil, I have some questions, anyone available?

    • On most new installs, the refrigerant charge is critical. I would contact your local distributor for assistance. They can also work with your installer to make sure he has proper training on these units.

  7. Don says:

    Thanks for replying so quickly…I have and he is very helpful, I’m just trying to use all my resources to become a more educated consumer in the realm of HVAC, specifically, residential. Your blog got my attention, may change careers in the not to distant future. Just had a few questions. Could 60ft of 1/2″ liquid line pose a problem on a 5T York (CZF06013) 16 SEER? Suction side is 1 1/8″, I think the compressor is actually a 4T. Also, during the heat exchange process on the condenser, noticed during normal operation the front 1/2 of the air flow is hot and the back half cold, any ideas? So far I have had one HP trip on an 80F day (Houston, TX) with low humidity.

    • The only problem with an oversized liquid line is it requires more refrigerant. It should not affect operation provided the charge has been carefully weighed into the system and taking into account the larger liquid line. If you use the search box at the top of blog and enter microchannel, you can see my “primer” on this type of condenser coil. It is a “split” coil so, yes you can have more heat on a side of the condenser than the other.

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