My first thought was thermostats but both the upper and lower would have to not be working properly....a rare event. So, did you refill the tank with water by opening a nearby hot water faucet to let the air out? The water won't heat if it isn't in the tank.
Oh, and make sure the heating elements haven't been on before filling the tank. That could cause a serious steam event!!!
Last edited by Estacada John; 11-23-2010 at 08:57 PM.
Reason: Worried about possible exploding water heater.