Bought a whirlpool hot water heat model- N40S61-403 serial- 1413T463635, installed 4/30/14, the other day, the water was not heating, it was set on hot120deg. Moved to setting A 125deg. and is working fine, and left it on that setting. But I don't want to leave it there b/c of my kids. It's too hot if they wash there hands. Just wondering why this might have happened. Flame sensor or something? No code flashing either. Thanks.