UHA S TANDARD U NIT H EATER I NSTALLATION O PERATION AND SERVICE MANUAL32 of 59Figure 15: Modulating Gas Valve for Models UHA[M][X][S] 150 - 400Description Part NumberGas Valve 150 - 250 NG 90032505Gas Valve 150 - 250 LP 90032506Gas Valve 300 - 400 NG 90032520Gas Valve 300 - 400 LP 900325211/2" Exa Valve 150-250 900325503/4" Exa Valve 300-400 90032551