Heat Recovery Unit (HRU) Specifications

What are BuildSmart's HRU eligibility requirements? | Recommended minimum water tank capacities

What are BuildSmart's HRU eligibility requirements?

To be eligible for BuildSmartTM certification, Heat Recovery Units (HRUs) must meet the requirements listed in the table below.

Equipment	Requirement
All systems	Must be installed: Permanently and according to manufacturer's instructions.
Size	The size must be rated to: meet or exceed the air conditioner size.
Certification	HRU certification must be: listed in the latest Directory of Certified Refrigerant Desuperheater Heat Recovery Unit Water Heaters administered by the Association of Refrigerant Desuperheater Manufacturers approved by: Underwriters Laboratories (U.L.) or another nationally recognized testing organization in accordance with U.L. standards. All HRUs not installed in the air conditioning system at the factory must be rated according to: Standard 471-80 of the Air Conditioning and Refrigeration Institute (ARI) and regulatory modifications required by the state.
Warranty	Installation must not void any warranty on the: HVAC unit or domestic water heater.
Manuals	Manuals must be given to the homebuyer for equipment: operation and maintenance.
Domestic water heating tank	The domestic water heating tank must be: at least 30 gallons (see Recommended Minimum Water Tank Capacities) and equipped with pressure relief valves. The lower element thermostat in the tank feeding directly into the dwelling must be reset to the minimum temperature.
Water piping	Length between the HRU and the domestic water heating tank must be in accordance with: manufacturer's recommendation or not exceed 70 feet in total length.
Refrigerant piping	Length between the HRU and the condensing unit must: be in accordance with manufacturer's recommendation or not exceed 25 linear ft. in total length 1-way and have a maximum vertical lift of 20 feet.
Piping insulation	All accessible piping carrying hot water or refrigerant must be: insulated and insulated joints tape sealed. Pipe insulation exposed to direct sunlight must be: protected from or highly resistant to ultraviolet radiation degradation.
Heat exchanger	The heat exchanger: must have double walls between the refrigerant and potable water should be installed within the structure where feasible and must be supplied with a freeze protection circuit if it is located in an area subject to freezing temperatures.
Water control	A control means must be provided so that the HRU: can only supply warm water to the water system and does not overcool the refrigerant loop.
Check valve or similar component	Must be installed to prevent thermosyphoning when the air conditioner is not in use.

Recommended minimum water tank capacities

Recommended minimum tank capacities by family size are shown in the table below.

Family size	Tank capacity (gallons)
1 - 2	30
3	40
4	52 - 66
5	66 - 80
6	80 - 120
7	120