# What belongs on a heat pump installation checklist?

> The readings and checks that prove a heat pump went in right: pressure test, vacuum, charge, airflow, static pressure, defrost, backup heat and paperwork.

URL: https://blufflinememphisheatpumps.com/guide/heat-pump-commissioning-checklist/

Learn

The tests during installation and the readings at start-up that separate a heat pump that reaches its rating from one that never will.

Last Updated: November 12, 2026

The short answer

Ask for the readings. A correct installation shows a line set pressure test held under nitrogen, a vacuum below 500 microns that holds, refrigerant charged by weight and checked by subcooling or superheat, airflow and static pressure within the maker's range, a forced defrost, tested backup heat, and the thermostat set up for a heat pump. All of it written down.

Key takeaways

- Installation quality affects efficiency and lifespan as much as the equipment.
- The line set should be brazed under nitrogen, pressure-tested and evacuated below 500 microns.
- Charge goes in by weight and is checked by subcooling or superheat against the maker's numbers.
- Airflow and static pressure decide whether the system reaches its rating.
- You should leave with the readings in writing.

## Installation decides the result

Two identical heat pumps can perform very differently depending on how they went in. Field studies have long found that installation faults, especially charge and airflow, cost a meaningful share of a system’s rated efficiency.

[Bluffline Memphis Heat Pumps](https://blufflinememphisheatpumps.com/) works through the checks below on every installation and leaves the readings with you in writing.

### The checklist at a glance

| Stage | Check | Good result |
| --- | --- | --- |
| Before | Load calculation | Size matched to the house |
| Before | Static pressure on the ducts | Near the blower’s design, about 0.5 |
| Install | Brazing under flowing nitrogen | Clean joints, no internal scale |
| Install | Pressure test | Holds with no drop |
| Install | Evacuation | Below 500 microns and holding |
| Start-up | Charge by weight | Maker’s charge plus line set adjustment |
| Start-up | Subcooling or superheat | Within the maker’s target |
| Start-up | Airflow and static | Within the maker’s range |
| Start-up | Defrost and backup heat | Tested and working |
| Start-up | Thermostat | Configured as a heat pump with lockouts set |
| After | Paperwork | Readings, model numbers, settings in writing |

## Before the install

### Sizing

The heat pump should be sized from a room-by-room load calculation for Shelby County’s 95-degree summer and 20-degree winter, not copied from the old nameplate. The [sizing guide](https://blufflinememphisheatpumps.com/guide/heat-pump-sizing-manual-j/) covers the method.

### Matched equipment

The outdoor unit and the indoor coil or air handler should be a listed, matched pair, so the system’s SEER2 and HSPF2 ratings actually apply. The model numbers belong on the estimate.

### The ducts

A static pressure reading on the existing ducts shows whether they can carry the new system’s air. If not, the duct work goes on the estimate. The [crawl space ductwork guide](https://blufflinememphisheatpumps.com/guide/crawl-space-ductwork-heat-pump/) explains the fixes.

## During the install

### Brazing under nitrogen

When copper is brazed, the inside of the pipe oxidizes and flakes unless dry nitrogen flows through it. Those flakes travel through the system and can clog metering devices and damage the compressor.

### Pressure test

After brazing, the line set and coils are pressurized with dry nitrogen and watched for any drop. A drop means a leak, found and fixed before refrigerant goes in.

### Evacuation

A vacuum pump pulls air and moisture out of the lines until a micron gauge reads below 500 microns. Then the pump is isolated and the reading watched. If it rises quickly, there is a leak or moisture still in the system.

## At start-up

### Charge

New heat pumps come with refrigerant for a standard line set length. Longer line sets need more, added by weight with a scale. Then the charge is checked against the maker’s target:

- **Subcooling** for systems with a thermostatic or electronic expansion valve.
- **Superheat** for fixed-orifice systems.

Charge checks in cooling mode are most reliable in warm weather; in winter, weighing in the charge is the main method, with a check later if needed.

### Airflow and static pressure

The blower is set for the system’s size, usually about 350 to 400 cubic feet per minute per ton, and static pressure is measured with the system running. The temperature drop across the indoor coil in cooling, or rise in heating, gives a second check.

### Defrost

A forced defrost cycle confirms the reversing valve shifts, the outdoor fan stops, the coil clears and the backup heat covers the cycle. The [defrost guide](https://blufflinememphisheatpumps.com/guide/heat-pump-defrost-ice/) explains what normal looks like.

### Backup heat

Each stage of the strips, or the gas furnace on dual fuel, is called and confirmed. On dual fuel, the changeover between heat pump and furnace is tested.

### Thermostat

The thermostat is configured as a heat pump, the outdoor sensor checked against a thermometer, the strip lockout or dual fuel switchover set with you, and the fan and dehumidify settings chosen. The [thermostat setup guide](https://blufflinememphisheatpumps.com/guide/heat-pump-thermostat-setup/) walks through each.

### Condensate and safety

The condensate drain is tested with water. On attic units, the float switch on the secondary pan is tripped to confirm it shuts the system off.

## The inspection is not the commissioning

Your town’s mechanical inspection checks code items: the permit, the disconnect, the pad, clearances, the condensate disposal and the electrical connections. It doesn’t measure charge, airflow or vacuum. Those are the installer’s job, which is why the readings matter.

### Where to find the permit

Memphis, Germantown and unincorporated Shelby County permits go through the joint Office of Construction Code Enforcement; Bartlett and Collierville run their own offices. The [service areas page](https://blufflinememphisheatpumps.com/service-areas/) lists the office for each town.

## What goes wrong when steps are skipped

Each step exists because skipping it causes a known problem:

| Skipped step | What can follow |
| --- | --- |
| Load calculation | Oversizing, short cycles, a clammy house |
| Nitrogen while brazing | Oxide flakes clogging the metering device or harming the compressor |
| Pressure test | A slow leak that shows up months later as weak cooling |
| Deep vacuum | Moisture in the system, acids, compressor damage |
| Charge by weight and check | Over- or undercharge, lost efficiency, compressor stress |
| Airflow and static | Noise, a frozen coil, lost capacity, poor humidity control |
| Defrost test | Ice that never clears on winter mornings |
| Backup heat test | A cold house when the strips or furnace are needed |
| Thermostat setup | Strips running on mild days, a high winter bill |

## A sample start-up sheet

A completed sheet for a 3-ton heat pump might read like this. The numbers show the format; your system’s targets come from the maker’s data, and a reading outside the target is a reason to adjust before anyone leaves, not a note for later.

| Item | Reading |
| --- | --- |
| Pressure test | Held with no drop |
| Final vacuum | 380 microns, held |
| Refrigerant added for line length | Weighed in per the maker’s chart |
| Subcooling | Within the maker’s target range |
| Total external static | 0.48 inches of water column |
| Temperature drop across the coil | About 18 degrees |
| Defrost | Forced and cleared; backup heat on |
| Strip lockout | 32 degrees |

## Readings in a Memphis season

Some checks depend on the weather. A charge check by subcooling is most reliable on a warm day in cooling mode. A system installed in January is charged by weight, and a cooling check on the first warm day confirms it.

Defrost can be forced in any weather. The start-up sheet should note which checks were done in which mode, so a later visit knows what to confirm.

## What to keep

At the end you should have:

- **Model and serial numbers** for both halves.
- **The load calculation result.**
- **Pressure test and vacuum readings.**
- **Charge added** and the subcooling or superheat reading.
- **Static pressure** before and after any duct work.
- **Thermostat settings**: lockout or switchover, recovery, fan.
- **The permit** and inspection result.

Keep them with the warranty registration. They make future service faster and answer rebate questions. The [TVA rebate guide](https://blufflinememphisheatpumps.com/guide/tva-energyright-heat-pump-rebate/) explains how the participating contractor submits the rebate.

## Questions to ask before you sign

Whoever installs your system, ask:

- Will you run a load calculation, and will I see the result?
- Will you braze under nitrogen and pull a vacuum below 500 microns?
- How will you set the charge?
- Will you measure static pressure before and after?
- Will I get the start-up readings in writing?

The [replacement page](https://blufflinememphisheatpumps.com/heat-pump-replacement/) covers what a replacement includes, the [cost page](https://blufflinememphisheatpumps.com/heat-pump-installation-cost/) lists the typical ranges, and the [Memphis buying guide](https://blufflinememphisheatpumps.com/guide/memphis-heat-pump-buying-guide/) puts the decision in order.

## Questions about this guide

### What is a good vacuum reading for a heat pump installation?

Below 500 microns, and holding there with the pump isolated for several minutes. A reading that rises quickly points to a leak or moisture in the lines, which has to be fixed before the system is charged.

### Why is static pressure on a start-up sheet?

It shows whether the ducts let the blower move the air the heat pump needs. Most residential blowers are built for about 0.5 inches of water column; much higher means restricted airflow and lost efficiency.

### Should I get a copy of the start-up readings?

Yes. They show the system was set up correctly, help with warranty and rebate questions, and give a baseline for any future service visit to compare against.

## Related service

- [Service**Heat pump replacement** Your heat pump is near the end and you want the next one to last. We size it from the house and match both halves.](https://blufflinememphisheatpumps.com/heat-pump-replacement/)

## More guides

- [Learn**How should a heat pump be sized for a Memphis house?** What a load calculation measures, the design temperatures it uses here, and why the right answer is often smaller than the old unit.](https://blufflinememphisheatpumps.com/guide/heat-pump-sizing-manual-j/)
- [Learn**How do crawl space ducts affect a heat pump in Memphis?** Humid air under the floor, cold ducts, failed tape and small returns, and what to fix before a new heat pump goes on them.](https://blufflinememphisheatpumps.com/guide/crawl-space-ductwork-heat-pump/)
- [Learn**How should a heat pump thermostat be set up in Memphis?** The handful of settings that decide whether a heat pump saves money: the equipment type, the outdoor sensor, the lockout, setbacks and the fan.](https://blufflinememphisheatpumps.com/guide/heat-pump-thermostat-setup/)
- [Decision Guide**How do you buy the right heat pump for a Memphis house?** The whole decision in the order you meet it, from the system you have now to the readings you should get at start-up.](https://blufflinememphisheatpumps.com/guide/memphis-heat-pump-buying-guide/)

## Get an estimate for your house

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