Which code contains rules for the construction of low-pressure hot water supply boilers?

The correct choice is indeed associated with the specific guidelines for the construction of low-pressure hot water supply boilers, which are found in ASME Section IV. This section of the ASME Boiler and Pressure Vessel Code is dedicated to rules governing the design, fabrication, and inspection of heating boilers, specifically those that generate hot water for heating purposes.

ASME Section IV outlines the requirements for materials, design, construction, and testing for these types of boilers, ensuring they operate safely and efficiently under low-pressure conditions. This code serves to protect not only the equipment itself but also the safety of personnel and the environment by setting a standard for workmanship and quality.

In contrast, other sections of the ASME code serve different purposes. For instance, ASME Section III primarily deals with nuclear components, Section I pertains to high-pressure steam boilers, and Section VII provides guidelines for the care and maintenance of power boilers. Thus, the specific focus of ASME Section IV on low-pressure hot water supply boilers makes it the correct reference for this question.