About Hot Water Temperature Maintenance


Large commercial buildings need a way to provide hot water at the tap in the most energy efficient way, without long waits or wasting water.

Hot Water Temperature Maintenance Heat Trace System

Pentair Thermal Management has a sophisticated domestic hot water temperature maintenance (HWAT) system that provides immediate hot water at the tap that is more energy efficient and saves more water than a recirculation system.

Whereas, a recirculation system:

  • Requires that you keep the water heater temperature in the system at least five degrees above the maintain temperature to compensate for the heat that is lost in the recirculation loop.
  • Requires return lines, pumps, and balancing valves as part of the system.

Pentair Thermal Management hot water temperature maintenance (HWAT) system provides a simple, reliable alternative to recirculation in commercial buildings. The HWAT system:

  • Maintains the water at a uniform temperature along the entire length of the supply pipe. Thus, it is unnecessary to heat the water above the maintain temperature.
  • Includes HWAT heat trace cables that can be installed up to the fixture, which mean that you get hot water faster and waste less water.

HWAT is a fully integrated system that includes:

  • Electric heat trace cables – the HWAT-Y2 and HWAT-R2 heat trace cables adjust their power output along the entire length of the pipe to compensate for variations in water temperature and ambient temperature. These cables are designed for installation on hot water supply pipes underneath standard pipe insulation.
  • Connection kits and accessories – items for making electrical connections and properly completing the installation, such as power connection and end seal kits.
  • Advanced control systems – electronic controllers that monitor and/or control the desired temperature maintenance of the pipes.

The HWAT-ECO and ACCS-30 electronic temperature controllers optimize the energy efficiency of the HWAT system by controlling the pipe temperature with either HWAT heat trace cable. The temperature set point can be programmed on a 24/7 schedule to suit the specific job requirements, providing the maximum water temperature control and energy savings to the end user.


Simple hot water temperature maintenance system compared to recirculation:

  • The self-regulating heating cable compensates for the heat loss of the supply pipe
  • No return pipe or pump.
  • Maintain temperature of the pipe can be programmed as required on 24/7 calendar schedule
  • Instant hot water
  • Minimal water waste
  • Supply and return pipes, fittings, insulation, etc.
  • Complicated design
  • Labor intensive
  • Balancing valves
  • Circulation pump power
  • High maintenance
  • High heat loss
  • High water waste
Complies with ASPE water delivery times and non-circulated pipe length requirements.

ASPE allows up to 50 feet of non-circulated hot water supply pipe, but requires that hot water is delivered within 30 seconds. This is only possible for high flow fixtures, not today’s 0.5 GPM. HWAT can be installed all the way to the tap to meet these ASPE requirements.

Complies with approval standards, plumbing codes and energy standards.

The HWAT system, with or without the HWAT-ECO or ACCS-30 controller, is UL Listed, CSA Certified, and FM Approved in nonhazardous locations.

The HWAT system satisfies the following international and national codes:

  • International Plumbing Code
  • International Building Code
  • International Energy Conservation Code
  • National Standard Plumbing Code
  • National Electrical Code
  • Canadian Electrical Code
  • Massachusetts Building Code
  • City of New York Construction Code
  • California Title 24 energy code
  • IAPMO Green Plumbing & Mechanical Code Supplement
Self-Regulating Technology

Raychem HWAT self-regulating electric heat trace cables automatically adjust their power output to compensate for temperature changes. Heat is generated as electric current passes through the conductive polymer core between the conductors. As the temperature drops, the number of electrical paths through the core increases and more heat is produced. Conversely, as the temperature rises, the core has fewer electrical paths and less heat is produced.

Raychem HWAT self-regulating heat trace cables:

  • Have a cross-linked, conductive polymer core forming a parallel circuit
  • Have a self-regulating core that limits the maximum temperature that the heat trace cables will maintain, making them compatible with both metal and plastic hot water distribution pipes
  • Offer HWAT-Y2 for 105°F to 125°F and HWAT-R2 for 105°F to 140°F maximum maintain temperature
  • Are protected by a tinned-copper braid encased in a durable outer jacket to withstand mechanical abuse during installation
  • Feature an aluminum barrier to protect the heating cable from plasticizers which diffuse from commonly used closed cell foam insulation

Advanced Control Systems

The HWAT system includes two different electronic controllers, the Raychem HWAT-ECO and the Raychem ACCS-30.

Raychem HWAT-ECO and Raychem ACCS-30 controllers:
  • Provide 24/7 programmable pipe temperature set points, to allow for maximum energy efficiency and the greatest user flexibility. Temperature set points include:
    • Maintain: The setting that lets you set the hot water delivery temperature set point.
    • Economy: An energy savings feature that lets you lower the temperature set point when hot water is in low demand.
    • Off: The setting that lets you turn the heating cable off when hot water is not needed, or after a heat cycle when the pipe needs to cool. Heat cycle: The setting that lets you raise the temperature above the hot water delivery set point whenever you wish to sanitize to the water in the pipe.
  • Do not require pipe temperature sensors for water temperature control, instead, the controllers provide on/off duty cycle control to the heating cables to only provide the power necessary to keep the pipes at the desired set points, saving energy and providing temperature flexibility.
  • Provide water temperature monitoring, alarm and Building Management System (BMS) integration.

In addition, the HWAT-ECO:

  • Is ideal for smaller buildings with limited hot water distribution systems
  • Can control a single heating cable circuit

In addition, Raychem ACCC-30:

  • Is ideal for large hot water distribution systems or multiple heat-tracing applications
  • Can control up to 260 heating cable circuits
Case Studies
Pentair Thermal Management Installs Heating Solutions at London Rolex Building
Key Challenges

Pentair Thermal Management was brought in to employ a variety of its heating solutions at the new Rolex Building in London, England. Rolex was looking to convert its heating to a simpler, lower cost single pipe system that required less maintenance.


Pentair Thermal Management provided hot water services using the Raychem HWAT single pipe hot water temperature maintenance system.


Pentair Thermal Management installed more than 400 meters of cable to provide hot water all the way to the point of use, 600 meters of WinterGard pipe frost protection cables, and RayClic connection devices to safeguard the chilled water supply lines from freezing.

In addition, a beautifully tiled floor at the entrance foyer now welcomes visitors with the ambient warmth of Raychem floor heating systems, with the installation of nearly 50 square meters of T2QuickNet.


The reduction of pipework left more space for the single pipe and insulation so that thicker insulation over the system could be used to increase its efficiency. The total estimated energy savings for this project will be approximately 50-60 percent. Even with the higher unit cost of electricity, the actual customer savings are expected to be 5-15 percent.

The design, supply, and installation of the Raychem systems were undertaken by Jointing Technologies, a Pentair Thermal Management distributor partner headquartered in South East England. The project was completed in October 2010. Featured Case Studies Pentair Thermal Management Installs Floor Heating at Syon Park