(a) Construction. Fired thermal fluid heaters must meet the requirements of part 52 of this chapter, as applicable.

(b) Controls. Fired thermal fluid heaters must have a low fluid level cutout device or a low flow device. When the rate of fluid flow through the heating coils is insufficient to ensure proper heat transfer, the device must cut off the fuel supply to the burner. If the fluid temperature exceeds the designed maximum operating temperature, a high temperature limit device must cut off the fuel supply to the burner. These devices must be of the manual reset type.