Indirect Water Heaters (IWH)


Program Scope

This program applies to Indirect Water Heaters having a volume (potable plus heat source) of 120 gallons or less, for which Published Ratings are available, and which are designed for installation with a hot water boiler(s) as the only heat source.

Scope Exclusion

  • Direct-fired instantaneous or storage water heaters;
  • Tankless water heaters;
  • Heat pumps water heaters, and;
  • Combination space heating and water heating appliances

Voluntary Program Scope Inclusion

Indirect Water Heaters for use with alternate heat sources meeting the scope of the Applicable Rating Standard may be included in the Program, provided that general advertising and promotional literature will not claim certification unless all models are certified or unless certification is clearly claimed only for certified models. Models listed with AHRI under the IWH certification program must always be sold as certified when they meet the scope of the certification program. These models can be found on the AHRI Directory of Certified Product Ratings.

Certified Ratings

The following certification program ratings are verified by test:

  • Standby Loss, °F/hr
  • First Draw Rating, gal/hr
  • Continuous Draw Rating, gal/hr
  • Heat Source Friction Loss, ft w.c.

The rules and procedures for obtaining and maintaining certification are detailed in the Resources section above. The specific Standard listed above details the technical requirements for rating and publishing your product performance, the AHRI General Operations Manual (OM) details the program operational rules that are generic to all of AHRI’s certification programs and lastly, the Product-specific Operations Manual provides the operational rules that are specific to this program along with the required documents and fees. Please ensure that you are familiar with the latest rules and procedures for this program.