I would think that the disconnect could be a dp 20 although I would use a dp 30. Never thought about using a dp 20. I use an a/c disconnect but I have had to use a switch before and it was a dp30. I know with motors the disconnect must be 115% of the load but I don't see that for water heatersGiven 4500 watt electric water heater, is it legal to install a 20 amp double pole toggle switch to serve as a disconnect? The load should only be 18.75 amps. 30 amp circuit of course. I can't find where in the code it prohibits this.
Not if the load is 18.75 amps -- unless it's a 100% rated breaker.I would think that the disconnect could be a dp 20
210.20 Overcurrent Protection. Branch-circuit conductors and equipment shall be protected by overcurrent protective devices that have a rating or setting that complies with 210.20(A) through (D).
(A) Continuous and Noncontinuous Loads. Where a branch circuit supplies continuous loads or any combination
of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load.
Exception: Where the assembly, including the overcurrent devices protecting the branch circuit(s), is listed for operation at 100 percent of its rating, the ampere rating of the overcurrent device shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load.