Demand response unit

[GAK]

I install demand response units (DRUs) for my local electric coop. Usually 2 or 3 per month. The DRU allows the utility to shed the water heater load during a peak demand period. The utility also sells the water heaters, which are a Marathon brand with 3800 watt elements.

My process is to go in, disconnect the water heater, mount DRU, connect branch circuit to line side of DRU, then connect load side back to water heater with a short piece of FMC and single strand conductors.

My question:
Is there anything that allows me to use 12 gauge wire from the DRU to the water heater in the short piece for FMC, if the branch circuit is on a 30 amp breaker? 12 gauge is sufficient for the load of 3800 watts, and the wiring I connect to in the water heater itself is 12 gauge. I would like to use 12 gauge because I always have plenty of scrap laying around.

 

[augie47]

No Code compliant way of which I am aware.

 

[LarryFine]

Use 20a breakers.

 

[don_resqcapt19]

It appears to me that a 30 amp breaker is not permitted for that load. 422.11(E) limits the OCPD rating to a 150% of the appliance rated load. The rated load is 15.8 amps and 150% is 23.75 amp making the maximum permitted OCPD the next standard size which is 25 amps.

422.13 sets the minimum branch circuit at 125% of the rated load, and that would be 19.8 amps. Since you need to install a smaller breaker, you might as well use a 20 amp breaker and 12 AWG copper.