I don't think that the RHP is too small. It's probably just not working anymore. Before tossing it, I'd run it without a thermostat for a couple days, even a week, straight to see how high you can get it. RHPs can take a while to reach the proper temperatures. If you don't reach your range, then you know that RHP just ain't cutting it. If you do reach your range, then it's just a matter of where to set the thermostat.