Can a relief valve be located on a tee that also serves as the tank outlet? It is a vertical tank with the outlet at the top. The flow rate is 56 GPM and the heat exchanger connected to the tank has a capacity of 2,800 MBH.

Yes, provided the outlet is on top of the tank. The SRV must be in an upright position, with spindle verticle with no horizontal connecting piping. The connecting piping must be as short and straight as possible. All piping between the SRV and tank must be a size equal to or larger than the SRV inlet. The requirements are the same as a water heater or a hot water storage tank construted to ASME Code, Section IV, see HLW-801.2.