Microchannel Unit Charging

As many of you know, we are using a condenser coil design called MICROCHANNEL in both commercial and residential. cooling products. With this technology, we have been able to decrease our equipment size while maximizing our SEER ratings on our equipment.  It is a great benefit to all.

One of the best features of our microchannel units is the smaller size of the unit, which is made possible by the size of the microchannel condenser coil used in each unit. This smaller sized condenser coil results in a refrigeration system that requires less refrigerant than a comparable unit with a tube-and-fin condenser coil. The amount of factory charge is up to 50% less than tube-and-fin units.

Because of the unique design of these coils and the fact that they use about half of the refrigerant needed for conventional “tube and fin” coils, charging of these units is critical.  It is very easy to overcharge a unit with a microchannel coil.  The flow through these coils is what is referred to as “parallel flow”, which means in the top portion of the coil, all the refrigerant flows in 1 direction to de-superheat  the refrigerant  and then enters into a header where it drops down to the bottom part of the coil where the refrigerant is subcooled providing a solid column of liquid refrigerant so the metering device can function properly.

The coil is made out of “tubes” that contain “microchannels”

and it is through these microchannels that the refrigerant flows.

So, now that you understand microchannel technology, you can see that the microchannels are quite small accounting for the lower refrigerant charge in these units. The significance of this information is that a microchannel condenser coil has less volume and cannot hold as much refrigerant as the old style tube and fin design.

The recommended procedures for charging a unit with a microchannel coil are:

1) On any NEW INSTALLATION, accurately measure the length of the correctly sized line set.

2) weigh in the charge based on coil and line set adders published in the Tabular Data sheet for the unit you are installing.

3) allow system to operate at least 15 to 20 minutes for charge to stabilize. Anytime you add or remove refrigerant, it is critical to allow this time for the refrigerant to circulate and stabilize in the system before adding or removing more refrigerant.

4) check head pressure per charging chart on unit. All residential units have this chart on the side of the unit near the data plate.

5) check superheat (for indoor orifice metering device) or subcooling (for indoor TXV metering device). This information is also on the side of the unit by the data plate.

6) When in doubt, verify operation of system per the information in the Service/Condenser Application Guide (438317-UAG-B-0409) available through your local branch.

If these procedures are followed, proper charging of a microchannel unit can be accomplished without overcharging a unit. 

One other thing of significance to note:

HVAC technicians are tempted to pump down a system that has a microchannel condenser coil. This practice can result in damage to the compressor or condenser coil. Therefore, THE PUMP DOWN OF REFRIGERANT INTO A MICROCHANNEL UNIT IS NOT APPROVED UNDER ANY CIRCUMSTANCE.

Hopefully, this information will be helpful to you and your service personnel.

One last thing, the microchannel coil can be repaired.  We have a kit for repairing a leak in the aluminum coil.  We also have a video showing how to do it.  Contact me and I’ll be glad to send you a copy of the video via email.



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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8 Responses to Microchannel Unit Charging

  1. JW Redmond says:

    Hello, I,m kind of new in the HVAC business. I have been a lab tech at ADP for five years. I have been thinking about going into the business for myself, BUT I’m afraid there is so much I don’t know.

  2. Bob says:

    I have only run across a few micro-channel units in my service area. But I have had an alarming amount of coil leaks I am in a coastal area and the coils fins corroded and they fell apart from the tubes when replaced.
    Should these be coated?

    • depending on the manufaturer’s recommendations, microchannel coils in coastal areas should be coated since the salt spray in coastal areas can be very corrosive to the all aluminum coil. York does have coils that are coated and can be ordered as replacement coils or as part of new equipment orders just for these applications.

  3. Joel says:

    Can u send me video on how to repair micro channel coils?

  4. Bruce Eckstein says:

    Please send me the video on how to repair a microchannel coil. Could you also include the repair kit part number.

  5. Don says:

    Could you also send me your information on repairing a microchannel condenser please?

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