HVAC Journeyman Practice Exam 2025 - Free HVAC Practice Questions and Study Guide

The installation of a manual shutoff valve for a gas-fired boiler should be done upstream of all control devices. This configuration is essential for safety and operational efficiency. By positioning the shutoff valve upstream, it ensures that the entire system, including any control devices such as regulators or safety switches, can be isolated from the gas supply in the event of maintenance or an emergency.

Having the valve upstream allows for immediate access to shut off the gas flow, which is critical in case of a leak or malfunction. It prevents the control devices from being exposed to gas when the system is being serviced, thereby reducing the risk of accidents. Additionally, this positioning complies with most building codes and safety standards, which emphasize the importance of being able to quickly and safely shut off the gas supply.

In contrast, placing the shutoff valve downstream could leave the control devices energized and at risk during maintenance or emergencies. This practice would not only be potentially hazardous but could also violate safety regulations. Thus, the correct placement of the shutoff valve serves both as a safety measure and a proper adherence to recommended industry practices.