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Heat Pump System Installation Process from Start to Finish

An in-depth heat pump installation process guide. Learn how installation procedures dramatically affect the lifespan and effectiveness of your heat pump.

Heat Pump System Installation Process from Start to Finish

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Joshua Rodriguez


January 17th, 2022

The installation process for a new heat pump is complicated. It’s not a case where HVAC contractors can disconnect some wires from your old unit, put a new one in its place, reattach the wires and be on their way.

What’s disturbing is the fact that many HVAC contractors don’t know all the steps that should be part of a good installation. It’s easy to cut corners so that a heat pump runs “good enough.” But “good enough” often means losing thousands of dollars in energy costs over the life of your system, frequent service calls, and decreased comfort for you and your family. It may also mean a shorter lifespan for your heat pump.

All told, 90% of all HVAC systems are installed incorrectly. That means the odds are good that your shiny new heat pump is either the wrong size or the wiring is haphazard.

In this article, we are going to cover the entire heat pump installation process in detail, from start to finish. If you’re committed to getting the most from your heat pump, read on. By the end, you’ll have the peace of mind that comes with understanding each step. It will also allow you to pick a company whose installation process is up to snuff.

(This is not a DIY guide. Heap pump installation should always be handled by a licensed professional. Once you read each step involved, it should be easy to see why.)

At the Beginning of the Buying Process

First things first: When you’re talking to HVAC sales representatives, you should make certain that they’re not out to make a quick buck by selling you something that doesn’t suit your needs.

A Manual J Load Calculation should be performed to get the properly sized equipment. It’s a series of measurements that include the different parameters of your home. This is not the square footage of a home. Unfortunately, square footage alone was the old way of doing things, and some still subscribe to it.

So what is included in the calculation? Parameters include the following:

Thickness of insulation; number and size of windows; number and type of doors; total square footage; square footage of the floor over the crawl space; square footage of the floor over the basement; the number of occupants; rooms that lack ductwork but need heating/cooling; the height of the ceilings; whether the home has a basement or is on a slab; and so on.

There’s a huge variance in heating and cooling needs based on those parameters. If an HVAC contractor takes into account only square footage, there’s a very real chance you’ll end up with a system that does not meet your comfort needs.

Heat Pump Installation Day

Before your installation team arrives, you should receive a call or text letting you know they’re on their way.

Good HVAC companies will also send pictures accompanied by bios of the installation team that will be working at your home ahead of time. This is an additional safety and comfort factor before a stranger enters your home.

Once they arrive, the lead installer will share and review the job information with you. This packet contains the equipment information, accessories to be installed, and any special instructions given by you to the estimator before the sale.

While you are reviewing the job details with the lead installer, the other member(s) on the team will use this time to start laying down floor protection and getting tools and equipment in place.

Disconnecting the Old Heat Pump

Your existing heat pump contains a refrigerant that needs to be removed before a new one can be installed. According to the EPA standards, it is unlawful to openly vent this refrigerant into the atmosphere. A device known as a recovery machine must be used, along with a recovery tank, to safely and legally remove the refrigerant in the existing heat pump.

Once the refrigerant is recovered, electrical wiring is disconnected from the existing unit. A “whip” (flexible electric conduit) carries the power to the heat pump from the disconnect box. Good HVAC companies replace the disconnect and the whip when replacing a heat pump, to ensure system safety.

In cases where an old system lacks a disconnect box, a new one is required by safety codes to be installed with the new heat pump. Once all the existing connections are safely removed, the existing heat pump is ready to be removed.

Preparing the Area

In most cases, the existing location of the heat pump will require some prep work before the replacement can be set in place. This prep work includes replacing the pad that the new heat pump will sit on.

Before the new pad can be set, the ground must be leveled. Good HVAC companies use a gravel base to level out or build up the area where the new heat pump will be placed. A composite pad is recommended. The composite pad is designed to be outside and last the lifetime of the new heat pump.

Unlike an AC, the heat pump has to be elevated above ground level to keep coils clear of snow and ice and to allow for proper drainage. Here in Ohio, we elevate the heat pump to about 9 inches above the pad. That takes into account that we’ll have 6-8 inches of anticipated snow. The snow would have to be 10” or more for it to affect the heat pump. And even then, it’s only one inch into the coil. We raise the heat pump so the snow doesn’t build up against the outdoor coil and freeze it or block it.

Removing the Existing Indoor Evaporator Coil

The indoor evaporator coil is the other half of your heat pump system. It usually sits above the furnace, though in some cases it will sit below the furnace. This is what the other end of the refrigerant lines are connected to.

The indoor evaporator coil has two variations. One is cased and the other is uncased. In either application, the sheet metal plenum must be disconnected before the new coil can be installed. This process can be complicated when access to the coil is restricted.

Next, the existing refrigerant line set can be removed. This is a set of two copper lines through which the refrigerant travels from the outdoor condenser, then back into the indoor evaporator coil.

There are two options when installing a new evaporator coil for any new heat pump: cased and uncased. The preferred option is a cased coil because it comes in an insulated cabinet with removable panels on the front that allow access to the coil inside.

The cased coil is also designed to sit on top of the furnace without any modifications, which makes repairs and modifications easy. The biggest benefit of using a cased coil is that it comes pre-cased by the manufacturer. This makes failure from an improper installation unlikely.

When using a cased coil, it is already “installed” by the manufacturer and merely needs to be placed on the top of the furnace. The final step at that point is to connect and seal it to the existing sheet metal plenum.

An uncased coil is a coil without an insulated cabinet. It has more installation requirements and a longer preparation time. However, an uncased coil will provide the same comfort and be just as efficient as a cased coil when installed properly.

Line Sets and Additional Wiring

Next, the existing refrigerant line set can be removed. This is a set of two copper lines through which the refrigerant travels from the outdoor condenser, then back into the indoor evaporator coil.

The bigger line is called the suction line, and the little one is called the liquid line. They come packaged together, rolled in a coil. The line set will run from the heat pump outside to the new indoor evaporator coil on top of the furnace.

There will also be a small, low-voltage control wire that runs from the furnace along the line set to the heat pump. The small existing wire coming from the thermostat to the furnace sends a low voltage signal to the heat pump to turn on and off when a call for cooling or heating is needed or has been satisfied.

Heat pumps have a reversing valve that switches back and forth from heating to cooling. An outdoor sensor has to be installed - unless the thermostat is programmed to do it -  because the heat pump has to know when to switch.

There’s extra wiring to disable the heat pump and only use heat strips, and then it’s all in the set-up on the thermostat. The heat pump needs to know the outdoor temperature at some point.

The line set is then formed and fitted to the appropriate service valve on the heat pump. After the line set is fitted to the service valves, they must be brazed in. Brazing, a form of welding, is a process using two gases (oxygen and acetylene) and a filler rod made of an alloy metal and silver to join the copper line set and service valves. The valves are heated to a minimum of 1200 degrees Fahrenheit or until the filler rod will flow to weld the connection.

If this process is completed properly, the copper line set, the filler rod, and the service valve are all melted together for a tight, leak-free connection.

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Installation of the New High- and Low-Voltage Wiring

For the heat pump system to operate, the high- and low-voltage wiring must be reconnected. Using the existing power supply from the electrical panel inside the home, the installer will mount a new service disconnect box. The disconnect is mounted securely to the side of the house using appropriate fasteners, based on the type of surface it is being mounted to.

The low-voltage control wire is connected directly into the heat pump condenser at the proper locations according to the condenser installation instructions. This is the “signal” from the control board in the furnace sent through the wire to the heat pump when the thermostat calls for cooling. The low-voltage control wire is what allows the heat pump to cycle according to the parameters set regarding temperature and humidity inside the home. The low voltage wiring is connected to the control board inside the furnace on designated terminals.

The installer will start with the low-voltage connection outside then set up the thermostat. Depending on the system, they can set various parameters. The heat pump can be programmed to operate until the temperature dips to 35 degrees. Then the heat strips in the furnace or air handler will come on. When the temperature is below a certain point, the heat pump can’t do its job. It almost literally freezes. The heat pump has to be told when to go into defrost mode. Otherwise, it will continue to run. When the heat pump is in defrost mode, that’s when the call goes out to fire up the heat strips.

Commissioning Process for a Heat Pump

The startup and commissioning (testing) process is done after the system is completely installed and ready to operate. The system is turned on and must run for 15-20 minutes. This will allow the refrigerant to flow through the system.

Commissioning a heat pump will take anywhere from 45 minutes to 2 hours plus, which is 15-45 minutes longer than an AC. An HVAC contractor will have to test the heating side. And the cooling side. And the defrost. And the emergency heat. Complete testing of all of the functions will ensure that the system will function at its best. It will also satisfy the requirements to get the unit under warranty.

A good installer will check the thermostat operation, system sequence of operation, and multiple other functions as well. Proper commissioning requires training and special equipment to perform the process correctly. It also requires additional time and labor on a job site. Commissioning is the only way to know for sure exactly how well your system is operating.

Clean Up and Closing Process

The cleanup process is comparatively simple. All material and old equipment should be loaded up and taken away from the home. The floor protection should be rolled up last, keeping all debris from the installation inside the drop cloth and out of your home.

All areas should be swept and free of any materials or debris. You should expect to see the area in the same condition in which it was found.

A walkthrough of what was done during the installation should be completed with you. Going over safety, maintenance, warranty, and all special instructions are expected. Finally, a review of the commissioning and thermostat operation. The customer needs to understand how to toggle their thermostat between regular heat and emergency heat (aka auxiliary heat).

How Long Will an Installation Take?

We anticipate that a typical installation will last eight hours, starting in the morning and lasting until the late afternoon. Factors that could make the installation take longer include inclement weather (our techs can work inside a portable tent), air duct alterations, unforeseen electrical complications, and any other accessories that may have been added.

Find the Best HVAC Company in Columbus, OH

Are you looking for a good HVAC company to install your new heat pump? We hope this article has given you some tools to assist in selecting one that meets your needs.

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At Fire & Ice, we take pride in our installation process and hold our technicians to high standards to ensure the performance of your system. We believe in doing everything right the first time.

Are you in the Columbus area and ready to take the next step with one of our experienced professionals? Call us today or schedule an estimate. We’d love to be the ones to install your next system, and we offer next-day installation.

Read more:

How Much Does a Heat Pump Cost to Replace in 2022?

Should You Repair or Replace Your Heat Pump?

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