Air Source Heat Pump (Installation) Best Practice - Viva Training Centre

This air source heat pump guide is aimed to give ASHP installers a better understanding from design to installation.

Start With a Good Design

There are a lot of technical considerations to focus on during any installation. The wrong design and the customer can end up with an inefficient system.. Taking the time to work on the system design beforehand will make the installation easier and guarantee a great outcome.

Select the Right Size

Sizing the heat pump correctly is of paramount importance. Unlike combustion systems, you cannot make a rough calculation based on a home’s floor plan size. Instead, you need to take the time to calculate heat loss through windows, flooring, walls, roofs, and ventilation. Using a calculator such as the MCS standard heat loss calculator lets you determine heating capacity which you can then use to determine your heat pump sizing. The goal is to pick a unit size that can manage 100% of the duty when external temperature conditions are exceeded for at least 99.6% of the year. You’ll also need to properly size components such as heat emitters and pipework. Check all manufacturer performance guidelines to ensure appropriate sizes are used.

Locations for Indoor and Outdoor Units

For any air source heat pump, the location of the units has a huge impact on performance. Of course, you should always check and follow manufacturer instructions. General industry standards emphasize the importance of finding a space for outdoor units where there is unimpeded airflow. Ideally, outdoor units should be protected from harsh wind and in a position that gets full sun. Indoor units also need plenty of clearance, but you also need to ensure they are placed in areas that allow clear airflow throughout the home.

Customer Communication Throughout the Installation

Don’t forget that installation is about more than just putting parts together in the right order. You are also providing a service for a customer. To ensure that the installation goes smoothly, ASHP installers must take the time to discuss things with customers. Industry standards aren’t necessarily about being polite and friendly, though that always helps.

Instead, best practices are about making sure the customer is safe and fully informed. It is your duty to fully explain how air source heat pumps work and make them aware of any potential safety hazards. You also need to discuss the customer’s heating needs and daily routines, so you can ensure you don’t place any components in ineffective locations. Make sure to provide the customer with information on regular maintenance schedules, potential damage to look out for, and how to adjust the system.

Caution During Refrigerant Installation

Refrigerant line creation and location are typically some of the first things to consider. Heat pumps often use more refrigerant than traditional heaters, so this part of the installation must be handled with care. Getting the system running correctly requires a lot of focus and attention to detail.

Place Pipelines Carefully to Reduce Breakage

Ideally, all refrigerant pipelines should be as short as possible and have as few joints or bends as possible. This helps reduce the risk of leaks. For further protection, industry standards recommend covering the entire length in insulation and protecting outdoor insulation with a code-approved cover. All pipework also needs to be properly supported and clipped. To prevent issues, make sure that the slope of the line travels in the proper direction. You can further reduce the risk of leaks by always using new flare fittings and using the proper gasketed press or crimp for your tubing type.

Check for Leakage While Adding Refrigerant

Once it is time to add the refrigerant, ensure all MIS 3005 standards are met. Make sure to pressure test the lines with dry nitrogen and hold the vacuum at 500 microns or less for at least 15 minutes. Only once the lines have been tested can you charge them with refrigerant. While adding refrigerant, follow industry standards for calculating amounts and weigh the substance with electronic scales. Once the refrigerant is in the system, check for leaks with a bubble test and make sure all lines are appropriately labelled with refrigerant type, charge amount, and date of service.



Ensure Condensate Has a Clear Drainage Pathway

Managing this condensation thoughtfully will prevent leaks and other hassles from occurring later on. To follow industry guidelines, you need to check slope levels and for drain lines that do not have enough of a downward angle, installing a pump may be required. MIS 3005 guidelines also specify that condensate cannot be drained in an area where it will cause problematic ice build-up. All drain lines need to be redirected to a suitable drain away from public pathways.

When installing condensate drain lines, a few simple steps can prevent leaks or ice build-up. Avoid using flexible piping in internal spaces, because it can cause water to sit in the lower points. Make sure you use mechanical connectors, such as jubilee clips, to connect the hoses. If manufacturer specifications mention it, use pipe traps to reduce the risk of negative pressure. Finally, keep drainage well away from electrical conduits to prevent electrocution.

Follow All Manufacturer Instructions

When you’re installing the indoor and outdoor units of a heat pump, always start with the manufacturer’s instructions. Heat pumps aren’t always standardized, so different equipment has different needs. Check carefully to learn things like minimum clearance requirements and support needs. In addition to unit-specific requirements, make sure you keep in mind general heat pump installation standards. You’ll need to follow many best practices, such as:

  • Fix the outdoor unit on a firm, level surface.
  • Use anti-vibration isolators when mounting in a situation where vibration is unavoidable.
  • Only mount on roofs specifically designed to accommodate the unit’s weight and movement.
  • Leave clearance underneath the outdoor unit to allow for snow and debris removal.
  • Make sure surge suppressors are installed at either a circuit breaker box or a service disconnect.
  • Use proper hardware for the material the unit is being mounted on.
  • Confirm walls are structurally sound before mourning any units on them.
  • Check to make sure the wall behind the unit doesn’t contain plumbing, electrical cables, or cross spacing.
  • Provide enough clearance around indoor units to allow for maintenance and airflow.

Always Use the Right Materials and Placement for Ducting

Not all heat pump systems require ducting. Especially in smaller and older homes, residents often prefer ductless systems. However, it is still essential to understand best practices for ductwork in case you encounter systems that require it.

The main thing to keep in mind for ductwork is placement and sealing. Duct systems have to be carefully designed to meet industry guidelines. NHBC standards emphasize the importance of routing ductwork through practicable spaces. Routing through insulated areas is preferred. If going through an uninsulated area, the ductwork needs to be sealed with duct mastic and insulated.

It is necessary to take into account placement when selecting duct materials. Flexible ducting should not run more than 300 millimetres in length or be used around bends. Rigid or semi-rigid ductwork is ideal for most situations, and it should be sized to accommodate your unit’s airflow requirements.

Electrical Wiring and Thermostat Setup

Heat pump installers need to be up to date on all local building codes for handling electrical wiring. During the course of installation, there can be a lot of electrical aspects to work on. You have to supply electricity to heat pump fans, pumps, and auxiliary heaters. It is also typically necessary to run wiring from the heat pump to the thermostat or other controls.

It is important to make sure the building’s existing electrical system is able to handle the load of the heat pump. In some cases, it may be necessary to add new dedicated circuits. With every piece of equipment you install, you need to make sure that the equipment gets the right voltage and has a properly sized overcurrent protection.

Use industry-approved cables and connectors that are properly labelled and colour-coded. Het heat pumps also have some unique considerations, like avoid letting the wiring contact your refrigerant pipework or running the heat pump system cable and main power cable together.

When working with heat pump electrical systems, it’s important to realize they aren’t always compatible with other HVAC products. A lot of smart thermostats cannot run ductless heat pump systems.

Use Checklists

Even the best technician can end up forgetting tiny details, so it is helpful to have a checklist to go over. Of course, your exact checklist will vary depending on which equipment you use, but it can be helpful to ask yourself the following questions.

  • Have you used industry-standard guidelines to calculate the heating load, design temperature, and system capacity?
  • Does the outdoor unit have enough clearance according to manufacturer specifications?
  • Is the outdoor unit protected from rain, ice, and snow?
  • Have you fastened the outdoor unit to the structure or a mechanical pad with the appropriate hardware?
  • Is the outdoor unit level?
  • Are all indoor units located in an area with enough clearance?
  • Have you fastened all indoor units securely?
  • Did you check to ensure the duct system was adequately sized for the heat pump system’s flow of air?
  • Are all ducts sealed and tested for leakage?
  • Are any ducts outside of the conditioned space properly insulated?
  • Did you use the manufacture-specified line sets and lengths when creating the refrigerant system?
  • Were all flare connections tightened to the manufacturer’s suggested torque setting?
  • Are all refrigerant lines insulated and tightly sealed?
  • Did you test the refrigerant system with a pressure test according to manufacturer instructions?
  • Was all electrical work performed by a licensed electrician who followed all relevant government guidelines?
  • Did you operate the units in both cooling and heating mode to verify everything was working correctly?
  • Did you provide the homeowner with the owner’s manual and a recommended maintenance schedule?
  • Did you teach the homeowner how to control the system and explain what it will look like if the system breaks?

Interested in learning more about air source heat pump installation? VIVA training offers a range of renewable energy training courses, give us a call today.


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