John Wood Power Direct Vent (Non-ENERGY STAR qualified models) - Manual (Page 21)

In households with children, disabled or the elderly, select a
lower temperature setting. Valves for reducing point–of–use
temperature by mixing hot and cold water are available.
Consult a licensed plumber or the local plumbing authority.
Should overheating occur or the gas supply fail to shut off,
turn off the manual gas valve to the appliance.
– 21 –