Heat pump installations for plumbing

Purpose

The purpose of this advisory note is to inform the plumbing industry of some common non-compliances found when Building Commission NSW inspectors conduct inspections of Heat Pump Hot Water installations.

Issue

Heat pump hot water installation

Reference

AS/NZS 3500.4:2021 - Plumbing and drainage, Part 4: Heated water services

Details of non-compliance 1

The termination of the temperature pressure relief drain

The TPR valve pipework terminated not as required in AS/NZS 3500.4:2021 – Clause 5.11.3.  In some cases, the location of the discharge point could potentially scold the user, in others, the installation was detrimental to the system itself and the immediate surrounding building elements, adding possible financial burden to the property owner for repairs or replacement.

How to comply

Refers to AS/NZS 3500.4:2021 - Clause 5.11.3 Installation

Drain lines from temperature/pressure-relief valves, expansion control valves and tundishes shall be installed as follows:

• There shall be no tap, valve or other restrictions in any line.
• Each line shall fall continuously from the valve to the point of discharge.
• Drain lines from expansion control or temperature/pressure-relief valves shall not discharge into a safe tray.
• The point of discharge from each drain line shall be located so that the release of steam or hot water does not cause a nuisance, is readily discernible and incurs no risk of damage to the building or injury to persons.
• Where a drain line terminates outside a building, the end of the line shall be:
  • not lower than 75 mm or higher than 300 mm above an overflow relief gully or disconnector gully;
  • not lower than 75 mm or higher than 300 mm above a gravel pit not less than 100 mm in diameter;
  • over a tundish in accordance with Item (h) below; or

  • not lower than 200 mm or higher than 300 mm above an unpaved surface.

    Note: Where discharges from valves may adversely affect slabs and footings of buildings, the drain lines should discharge away from the building. Further guidance is provided in the National Construction Code (NCC).

• Where the drain line from the expansion control valve on a heat exchange water heater is directed into the water storage container, there shall be a minimum air gap of 20 mm, except where the valve and associated drain lines are supplied as an integral part of the water heater.
• Where a water heater is externally located, the drain line from the relief valve shall be terminated so as to discharge water away from the operator during operation of the valve.
• Where discharging over a tundish or gully, drain lines shall have an air gap of a size at least twice the diameter of the drain line.
• Where installed, plastics drain lines shall be:
  • continuously supported;
  • fixed and secured in accordance with Clause 4.5 - Support and fixing above ground;
  • protected from UV if exposed to direct sunlight; and

  • installed with a suitable allowance for thermal movement.

    Note 1: Typical installations of drain lines are illustrated in Figures 5.11.3(A) and 5.11.3(B). 

    Note 2: Ponding should be avoided. 

    Note 3: As the function of the temperature/pressure-relief valve on the water heater is to discharge high temperature water under certain conditions, the pipework downstream of the relief valve should be capable of carrying water exceeding 93 °C. Failure to observe this precaution may result in damage to pipework and property.

Details of non-compliance 2

The Heat Pump Hot Water system was not protected with a pressure limiting device.

Installations did not have pressure limiting valves (PLV) fitted. AS/NZS 3500.4:2021 - Clause 5.9.2 requires the installers to test inlet pressure and ensure a PLV is installed when required. When the inlet pressure requires a PLV however one is not installed, excess pressure may cause the TPR valve to fail and/or the tank itself to leak, this may be detrimental to the system itself and the immediate surrounding building elements also resulting in possible financial burden to the property owner for repairs or replacement.

How to comply

Refers to AS/NZS 3500.4:2021 - Clause 5.9.2 Required set pressure of valves (for unvented water heaters) 

The required set pressure of expansion control valves, expansion vessels and inlet-pressure-control valves shall be determined from the set pressure of the temperature and pressure-relief valve supplied with the water heater with reference to Table 5.9.1(B).

Table 5.9.1 (B) - Set pressures for valves

Note: Where the maximum mains pressure is likely to be exceeded, inlet pressure-control valve shall be used.

Details of non-compliance 3

The hot, cold and TPR pipework was not insulated as required.

Installations had incorrectly fitted or no insulation installed. AS/NZS 3500.4:2021 - Clause 8.2.1 requires the pipework to be thermally insulated to help ensure the installed Hot Water Unit works as efficiently as possible.

How to comply

Refers to AS/NZS 3500.4:2021 - Clause 8.2.1 Piping associated with storage water heaters.

Piping shall be thermally insulated to achieve a minimum R-value as given in Table 8.2.1 for the climate regions identified in Appendix K for Australia and Appendix L for New Zealand, as follows:

• The inlet and outlet pipes, including valves, for a storage water heater, for at least the first 500 mm or, where an external heat trap is fitted, to a point 150 mm down the heat trap vertical leg closest to the water heater.
• All relief valves fitted directly to a storage water heater.
• The primary flow and return pipes, including valves, between an auxiliary heater and a storage water heater.
• All vent pipes to 300 mm above the maximum operating water level of the heated water system.
• On multiple installations, the whole heated water manifold, including valves, to a point at least 500 mm past the heated water outlet branch from the last water heater.
• On a solar water heater installation, the pipework between a solar pre-heater and an in-line supplementary water heater. The insulation installed in accordance with the above shall be installed so as not to impede the operation of the valves.
  
  Note 1: Care should be taken to ensure the continuity of insulation at wall and roof penetrations. Insulation should be carried through roof penetrations into the ceiling area.
  
  Note 2: In New Zealand, refer to NZBC Acceptable Solution H1/AS1 and NZS 4305.
  
  Note 3: All exposed heated and cold-water piping to and from externally mounted water heaters in frost-prone areas may require additional insulation to prevent freezing.

Details of non-compliance 4

The hot water tank was installed not on a level, stable base as required.

Several instances were identified where the hot water tank was installed directly onto the dirt or not adequately supported. There were also instances where it had been installed leaning either sideways or forward off the wall due to the base and therefore the tank not being installed level.

How to comply

Refers to AS/NZS 3500.4:2021 - Clause 5.5.3 Support of water heaters or water storage tanks installed other than in a roof space or above a roof 

Storage water heaters and cold-water storage tanks installed other than in a roof space or above a roof shall be floor-mounted or supported as follows:

• By brackets or hangers, designed to withstand the applied load.
• On a level, stable and impervious base designed and located to avoid ponding and made of:
  • bonded brick or concrete cast in situ, having a thickness of not less than 75 mm; or
  • pre-cast concrete having a thickness of not less than 50 mm.
• On a platform of timber, or other suitable and not less durable material.
  
  Where such a platform is located at or near ground level, it shall be supported so that a clearance of not less than 100 mm is maintained from the surrounding ground.
  
  Note: A typical platform construction is shown in Figure 5.5.3. 
   
• In a recess in a wall structure able to withstand the applied load.

Important information for hot water systems installers in NSW

Below is key information for installers of hot water units, including heat pump types identified during Building Commission NSW heat pump inspections.

When installing hot water systems in NSW ensure you are referencing the current Australian Standards - AS/NZS 3500.1 and AS/NZS 3500.4 and the current Plumbing Code of Australia.

Where the hot water tank is to be installed internally whether concealed or not, refer to:

• AS/NZS 3500.4:2021 - 5.4.1 - Concealed water storage tanks
• AS/NZS 3500.4 2021 - 5.4.2 - Unconcealed water storage tanks

When installing two or more hot water tanks as a bank of storage heaters, refer to:

• AS/NZS 3500.4: 2021 - 5.10 - Multiple installations of pressure-type storage water heaters