Ten Keys To Successful Mini-Split Installations

June 14, 2003
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For many contractors and consumers, ductless mini-splits are becoming more than just an alternative heating and cooling solution in unique applications. Mini-splits are gaining prominence as a choice for those who want more control over indoor comfort. But for some contractors and technicians, the proper installation of a ductless mini-split is still a confusing and muddy process.

The more you know about proper installation procedures and the benefits a ductless system can provide, the sooner you can provide better comfort to homeowners and building owners. In order to get contractors started, Samsung has put together the top 10 things you need to remember when installing a mini-split. Some of the following tips are specific to Samsung products, while others will help with all your future ductless installations.

10. Liquid And Suction Lines

You must ensure that both “liquid” and suction lines are insulated. When using Samsung mini-splits, the expansion device(s) are located in the outdoor unit. Therefore, in the cooling mode, the liquid line actually contains an expanded gas and will sweat. To prevent this from happening and, more importantly, to control the quality of the return suction gas to the compressor, it must be insulated. Also, because of this, the installation of filter-driers and sight glasses is not recommended.

9. Control Voltage

When using Samsung mini-splits, the control voltage is either 115 V – 1 Ph – 60 Hz (AS07 and AS/AQ09) or 208/230 V – 1 Ph – 60 Hz (all other units).

With this information in mind, “thermostat” wire cannot be used to connect the indoor compressor/condenser fan or reversing valve signal to the outdoor unit. The use of multi-connector 14 AWG wire, as supplied with the Samsung line set option, is recommended.

8. Control Wiring

This is simple. Wire the terminals labeled exactly the same directly together, outdoor to indoor. For example, connect:

  • N1 to N1

  • L1 to L1

  • 1 to 1

  • 2 to 2

  • 3 to 3

  • 4 to 4

    Polarity is very important when wiring a Samsung mini-split, as they are designed and built for a world market, where all voltage is polarity sensitive. Therefore, wiring the N1 terminal to the L1 terminal and vice versa will allow the indoor unit to operate, but not the outdoor, as we switch one leg of the power wiring for our control wiring.

    7. Power Supply

    The outdoor unit of a Samsung mini-split will provide the power for the indoor unit, 115 V – 1 Ph – 60 Hz (AS07 and AS/AQ09) or 208/230 V – 1 Ph – 60 Hz (all other units except the AP500). Therefore, wire the power supply to the indoor unit directly from the outdoor unit without using a junction box or an indoor disconnect switch.

    6. Filter Cleaning

    Samsung mini-splits feature triple filtration, including additional deodorizing and electrostatic filters. Make sure that your customers know the importance of regularly replacing these filters (every six to eight weeks, depending on the application), together with washing the permanent filters in the unit.

    This simple maintenance act will keep the conditioned air clean and free of odors and contaminants, in addition to ensuring the correct airflow for unit operation.

    5. Unit Location

    The wall-hung mini-splits are designed for high wall mounting, a minimum of six feet from the floor. Air comes in at the top and front of the unit, and is supplied via the discharge vane at the bottom of the unit.

    Based on this information, why is it that in many applications the unit is installed 18 inches from the floor? When this happens, the manufacturer is sometimes blamed when the unit is not working correctly or reliably.

    Also, because the air is designed to circulate to and from the unit, do not put any obstacles to airflow in front of the unit, for a minimum of 15 to 20 feet away from the unit. Otherwise, the flow of air will be impeded and also the temperature sensing of the return will not be accurate.

    4. Line Sets

    Samsung publishes the maximum line set runs and lifts. These are a maximum and not a suggested starting point. Do not exceed them. Move the outdoor unit closer to the indoor unit. Also, don’t forget the pipe lengths include bend allowance, so no street elbows.

    The same applies to the pipe sizes. Stick to the published line set sizing from Samsung, which is the optimum line set size.

    3. Application Requirements

    Be aware that the standard minimum ambient for the Samsung mini-split is 67 degrees F. Operation of the standard unit below that ambient can cause compressor problems. If you think that there is a possibility of operating below that ambient, you must fit a low ambient control. We recommend the ICM326H and crankcase heater (a crankcase heater is standard on a heat pump). This will help to provide low ambient operation down to 32 degrees F.

    2. Weigh In The Charge

    Make sure to weigh in the charge dependent on the line set length. The Samsung mini-splits are charged for a certain length of interconnect from the factory. For the lengths above that, additional refrigerant must be charged into the system. This additional charge must be calculated and weighed into the unit (preferably using a digital scale). To assist this process, Samsung publishes the calculated charge for its units and can be obtained from the factory.

    1. Unit Capacity

    The No. 1 thing to keep in mind when installing a mini-split is the unit capacity and room size. It is amazing the number of 24,000-Btuh mini-splits that are installed in rooms that are less than 100 square feet in size. When this happens, the unit cannot operate for more than five minutes before the cold return air satisfies the air temperature sensor. Three minutes later, it is back operating and the short cycling scenario begins again.

    For optimum operation, Samsung provides the following rules of thumb. Remember that these are just simple approximations. However, in our experience, they have proved to be true. These are not a substitute for performing a Manual J or other accurate heat load calculation.

  • Commercial settings (shops, offices, etc.) — 400 square feet per 12,000 Btuh.

  • Computer rooms and telephone servers — 250 square feet per 12,000 Btuh.

  • Residential settings — 600 square feet per 12,000 Btuh.

    Do not forget that a computer room will operate all year round. The load may be slightly higher in July, but the unit will be still producing its same Btuh capacity (or more) in the deepest freeze of winter.

    Also, Samsung mini-splits are designed to satisfy the sensible heat load, and they are exceptional at removing humidity. Therefore, it is always best to slightly undersize the unit to allow it to operate for extended periods of time.

    Remember, following these 10 simple tips will make your mini-split applications and installations quick, profitable, and painless.

    Miles is director of engineering and technical support for Samsung, Whittier, Calif. He can be contacted by e-mail at johnm@quietside.com. Taylor is manager of the Samsung technical department. He can be contacted by e-mail at stut@quietside.com.

    Publication date: 06/16/2003

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