DIY Mini-Split Heat Pump Installation Guide: Complete How-To for 2021

Installing an Ultra Efficient 38 SEER Heat Pump: A Comprehensive Guide


As the world prioritizes energy efficiency and moves towards renewable energy, the heat pump technology stands out as a groundbreaking innovation. Recently, I had the pleasure of receiving a remarkable heat pump kit from Signature Solar that boasts a staggering 38 SEER (Seasonal Energy Efficiency Ratio). While this high SEER rating initially seemed unbelievable, it implies unparalleled efficiency in both heating and air conditioning. In this article, I’ll walk you through my journey as I installed this cutting-edge equipment in my garage, replacing an inefficient 9 SEER window AC and an electric resistance heater. I hope to inspire you to make similar energy-efficient upgrades.

Unboxing and Initial Impressions

Upon unboxing, I noticed the heat pump kit included several essential components: the indoor unit (head unit), outdoor unit (compressor), copper tubing for refrigerant, a condensate line, mounting hardware, and a remote control. One immediate concern was the outdoor unit, arriving slightly damaged with a bent foot and a ding to one side. However, closer inspection revealed that the functionality was intact, and there were no leaks in the refrigerant tubes.

I took extra care to examine the components closely to ensure there were no critical flaws. The mounting plates, copper tubing, and condensate lines were in good condition. The electronics inside, although not my expertise, seemed well-organized and potentially well-assembled. I hoped the audience could provide feedback in the comments regarding the electronics’ setup.

Preparing for Installation

The first step involved positioning the head unit and deciding the best route for the copper tubing and condensate line. Since I wanted to sleeve the wall to prevent exposure and stop critters from entering, I opted for three-inch Schedule 40 PVC for a broader opening. This would provide more room to maneuver and reduce the hassle during installation.

I started by measuring down one foot from the ceiling and marking the position. I also accounted for the need to connect the head unit to a stud for stability and to ensure the condensate line had a slight slope for efficient drainage.

Drilling Holes and Prepping Lines

With the position marked, I drilled holes using a shop vac to reduce cleanup. The first hole was for the refrigerant and condensate lines, the second for the electrical conduit. Using a long drill bit, I made initial pilot holes before switching to hole saws to achieve the final size. The shop vac proved invaluable, preventing a potential mess.

To sleeve the hole and prevent the lines from exposure, I measured and cut the PVC pipe, ensuring it was longer than the wall’s thickness. Consequently, it fit snugly into the drilled hole, providing a clean pathway for the refrigerant and condensate lines.

Installing the Indoor Unit

With the PVC sleeve secured, I mounted the head unit on the wall brackets, ensuring a slight tilt for the condensate to drain correctly. I took care to route the electrical wires through the appropriate ports in the head unit, securing them firmly. This setup simplifies the job, preventing the hassle of threading wires through a bit more complicated parts of the unit when it’s on the wall.

Setting Up the Outdoor Unit

The outdoor unit required a sturdy base to ensure stability and proper function. I chose to pour a concrete base using a simple wooden frame, vapor barrier, and cinder blocks to elevate the unit above potential snowfall. The vapor barrier prevents concrete from escaping the formwork, conserving material.

I allowed the concrete to cure briefly before placing the cinder blocks. These blocks were positioned upright to ensure strength and durability despite freeze-thaw cycles that could otherwise crack weaker concrete bases.

Fine-tuning the Refrigerant Lines

With the outdoor unit secured, it was time to connect the refrigerant lines, known as the line set, which consists of a quarter-inch and a half-inch copper tube. The tubes came with flare fittings, and I utilized a sealant called Nylog, designed for r410a refrigerant systems.

To ensure a leak-free connection, I referred to the manual for the correct torque settings – between 33 to 40 foot-pounds for a half-inch tube and appropriate settings for the quarter-inch. The flare connections were tightened using a torque wrench adjusted to the specified values.

Pressure Testing and Vacuuming

Ensuring the line set was moisture-free and securely sealed is a critical step. Using a vacuum pump and gauge set, I removed any existing moisture from the lines. This is crucial because moisture mixing with r410a can create acids that deteriorate the system.

Nitrogen pressure testing followed to ensure the connections were leak-free up to a critical pressure of 500 psi. However, my nitrogen tank’s limitation capped my test at 410 psi, which held steady for over two hours, indicating a satisfactory seal.

Final Hookups and Electrical Setup

After verifying the line integrity, I finalized the refrigerant setup by cautiously releasing the factory-prescribed refrigerant. The connection caps were then securely replaced.

For the electrical wiring, I ran a conduit from the outdoor unit to a disconnect switch, protecting the wires with liquid tight flexible conduit. Inside my garage, I ran metal-clad (MC) wire from a dedicated junction box to my off-grid system’s circuit breaker panel. Here, I installed a suitable circuit breaker as specified by the heat pump manufacturer.

Testing the Installation

With the mechanical and electrical hookups complete, I programmed the remote control for cooling mode. Within the first minute, the temperature of the air exiting the unit fell dramatically, confirming the system was operational. I used a thermal camera to visualize the cooling effect, showing temperatures below freezing inside the unit as it adjusted accordingly.

Monitoring Performance

Over the next 48 hours, I monitored the heat pump’s performance. Impressively, it maintained a steady 63°F using only 131 watts, a testament to its efficiency given its 38 SEER rating. Prior to this, the system drew around 800 watts at maximum capacity, which is still remarkably efficient compared to traditional units.

Practical Insights and Future Prospects

The Signature Solar heat pump proved its worth, not only in terms of cooling efficiency but also flexibility in its application:

  1. Dedicated Load Center: The unit integrates seamlessly with my off-grid system, allowing isolated operation even when the house switches to grid power. This flexibility is crucial for managing energy loads effectively.
  2. Energy Savings: Transitioning from a 9 SEER window AC and an electric resistance heater to the 38 SEER heat pump should yield substantial energy savings year-round.
  3. Inverter Compatibility: This setup bypassed the need for an auto transformer, simplifying installation and reducing costs, demonstrating compatibility with various inverter types.

This experience highlights the potential for incremental system upgrades, adding dedicated load centers for specific applications in renewable energy projects. This ensures legacy systems with limited parallelling capabilities can be extended by integrating efficient dedicated loads.


The installation process of the 38 SEER heat pump was meticulous but rewarding. With the assurance of enhanced energy efficiency, lower operational costs, and comprehensive climate control, the Signature Solar heat pump is transformative. It offers a practical solution for both heating and cooling needs, paving the way for energy-conscious home improvements.

If you have any questions, please leave them in the comments below. Stay tuned for a follow-up video exploring the system’s performance over a month. Don’t forget to like, comment, and subscribe for more insights on sustainable energy solutions.

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