I have a full sub-panel and want to add a heat pump water heater next to my electric dryer. Since the water heater doesn't need to be on all the time (they hold temperature pretty well, and usually I'm not using lots of hot water while the dryer is running), I would like to use the same circuit. Is there a device that will switch load between the water heater and dryer automatically? Ideally, I would like to power the WH by default, but if the dryer demands power, disconnect the WH. I know a manual disconnect switch would work, but my wife is unlikely to tolerate that - it needs to be automatic.
You'd need something like current measurement at the dryer feeding a relay controlling this switch-over. If both devices plug in, you can probably find examples of this on the web;.if the water heater needs to be hard-wired, I think you might need expert advice to come up with a solution that meets code.– keshlamApr 1 at 19:56
2“Full” of breakers or according to load calculation?– nobodyApr 1 at 21:07
Does the heat pump water heater require a 30A/240V circuit or is it looking for smaller? Does your house have gas heat and A/C, and what breaker size is the A/C?– Harper - Reinstate MonicaApr 2 at 4:45
Dryers are usually on a 30 Amp circuit with Nema 14-30 plug
I use the NeoCharge Smart Splitter for my needs that are similar to yours.
Obviously you use a Water heater instead of EV charger but in the assumption your water heater is on 30 Amp circuit this might work.
This device will prioritize the dryer power if needed and it will only automatically switch to water heater when dryer is off. Yes it is UL certified.
I'm not associated with this company, so go ahead find other product, but make sure they are UL certified.
You might say it is expensive, but how much is the happiness of the spouse worth– RuskesApr 1 at 20:29
Good reapplication of a commercially available device.– keshlamApr 2 at 2:27
@keshlam except for putting a cord and plug on a water heater. Now, some HPWH's want that, and some even want 120V. Which would work with this actually. Apr 2 at 4:46