240V outlet on water heater feed

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2663999

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I'm an engineer working on a technology demonstration project involving water heaters. It would be super beneficial if we could install a 240V outlet near the water heater on the existing water heater 240V 30A circuit. The dozen or so of these that we're doing are residential retrofits which will be signed off on by a PE, the city inspector, and performed by licensed electricians. I proposed removing the wire to the water, bringing it back to the wall in a junction box, installing an outlet in the box, and then installing a new length of 10AWG wire from the junction box to the water heater (not as a plug-and-cord, but hardwired). One electrician said it was against code (NEC 2014). I've looked a bunch and can't find what piece of the code it violates.

Is this against code? If so, which section? If not, is there any section I can reference to show that it is allowed?

I found the following in my search of the code for "water heater":

220.56 refers to kitchen equipment
220.82(B)(3)d refers to calculating the total dwelling load and proper service
220.83(A)(3)d refers to calculating the total dwelling load and proper service
220.83(B)(3)d refers to calculating the total dwelling load and proper service
220.84(C)(3)d refers to calculating the total dwelling load and proper service
230.23(B) excludes some water heaters from needing 8AWG overhead service conductors
230.31(B) excludes some water heaters from needing 8AWG underground service conductors
230.93 allows the locking of overcurrent devices to prevent tampering
422.11(F)(3) allows subdivision of circuits up to 120 amps
422.13 when calculating the load of an up-to-120gal water heater, it should be considered a continuous load
422.47 water heaters need temperature-limiting disconnects in addition to their thermostats (they are all manufactured that way) (exceptions for >180F, >60kW, or instantaneous-type water heaters)

550.12(D)(1) would prevent an outlet being installed on a water heater feed if the water heater was greater than 50% the circuit rating (18amp on 30amp is the most common, for instance) AND it was in a mobile home. It appears that it is within code to install an outlet on the same feed as a water heater, provided it is NOT a mobile home?

550.17(B)(2) excepts water heaters from continuity/operational/polarity tests
550.18(B)(4) refers to calculating total mobile home load and proper service
551.42(C) only two 120v thermostatically-controlled appliances can be install in an RV without energy management
552.46(A) only two 120v thermostatically-controlled appliances can be install in an RV without energy management
552.46(B)(3) refers to calculating total RV load and proper service
552.47(B)(4) refers to calculating total RV load and proper service
680.9 refers to electric pool water heaters680.26(B)(6)(b) refers to bonding/ground of electric pool water heaters > 50amps
Annex C has some example service calculations which include water heaters


Thank you very much for any and all help!
 
What do you want to do?

You want to unwire the water heater and hardwire it back in so that you can add a receptacle to the water heater circuit?
 
iwire said:
What do you want to do?

You want to unwire the water heater and hardwire it back in so that you can add a receptacle to the water heater circuit?
Click to expand...

That appears to be,what he wants to do.
What are you plugging in to the outlet?
 
Sounds like you want to install a junction box for splices next to the unit. That's not a violation. If you doing so for test purposes, I'd recommend putting in a properly-sized disconnect that can be locked out for when you're working on it (upstream of the j-box).

Point of clarification: "Outlet" here does not automatically mean "receptacle".
 
what the outlet is for

what the outlet is for

The outlet will be for powering a smart device (2 watts peak) that connects to the internet and monitors the water heater. We just need an outlet, but have run into struggles with getting a 120V outlet installed next to the water heater (most would require a new circuit be run from the breaker panel). 120V or 240V outlet doesn't bother me, as we can source the appropriate UL-listed power supply once we have the outlet.

EDIT: Sorry, a NEMA 6-15 receptacle is what I was thinking would be installed next to the heater.
 
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Welcome. Why not eliminate the need for an outlet by powering the device straight off the water heater? I suppose you are past that design stage at the moment.... tho if you are still in the prototype stage/early, production, I'd change that asap. You're going to kill your potential sales if every one of your water heaters requires a 30A 250V receptacle for a 2W load.
 
Putting a 15a receptacle on a 30a circuit IS a violation. Maybe tap off the 30a circuit, install 15a overcurrent devices, then use that to feed the 6-15R.

So what do you need a 120v receptacle for?
 
This is a super early demonstration product that will be installed for less than 6 months. The actual, final product does just as you suggest (tap power off directly), but hasn't been through UL yet.

The 120V outlet was to power this sensing device (as 120V power supplies are more common than 240V).

It would be within code to install a NEMA L6-30 receptacle though? Reducing the install complexity is fairly high on the list right now.
 
2663999 said:
This is a super early demonstration product that will be installed for less than 6 months. The actual, final product does just as you suggest (tap power off directly), but hasn't been through UL yet.

The 120V outlet was to power this sensing device (as 120V power supplies are more common than 240V).

It would be within code to install a NEMA L6-30 receptacle though? Reducing the install complexity is fairly high on the list right now.
Click to expand...

Gotcha. I assume this new device you are testing connects directly to the heater, and you'd need an appropriate receptacle (120 or 240V) within 6' of it.

The best way to reduce install complexity is a site survey. For example, my water heater already has an unused 250V 6-30R right next to it, and a 120V within 6'. Unless it's newer tract housing or apartments where every single install will be virtually identical. If all of your water heaters are typical 250V electric, no gas, no on demand units installed, (nothing different), then you can start thinking up how to wire your unit the best. In this house, it would be plug in and leave.

Are you designing the water heaters too or just a unit to monitor them?

To answer your question (finally!), I cannot come up with a code section that would disallow putting a 6-30R in the run that feeds the typical 250V water heater to run a 2W load. 120V receptacles will more than likely need GFCI or AFCI (or both) protection depending on where that water heater is and the Code cycle you are on, and I've never seen a tank water heater in a residence fed with 4 wire, so trying to tap off and install a 120V receptacle when there is no neutral isnt really an option except on paper.
 
OK, cool. We're just doing the monitoring, not the entire heater. All site surveys have been done. They are all resistance storage water heaters, and none had an outlet nearby (and I don't believe any were 4-wire, so installing a 120V receptacle would require new runs from the panel).

Thank you very much for your feedback. Do you know of any specific code I can reference to show a 6-30R receptacle on the heater circuit is OK? Perhaps something in Article 210?
 
2663999 said:
OK, cool. We're just doing the monitoring, not the entire heater. All site surveys have been done. They are all resistance storage water heaters, and none had an outlet nearby (and I don't believe any were 4-wire, so installing a 120V receptacle would require new runs from the panel).

Thank you very much for your feedback. Do you know of any specific code I can reference to show a 6-30R receptacle on the heater circuit is OK? Perhaps something in Article 210?
Click to expand...

The NEC is a permissive document, so no, I cannot show you where anything is allowed. If it isnt specifically forbidden, then it's allowed. I, too, was looking in 210 trying to find something re: individual branch circuits not used for any other equipment (even a 2W one), and came up blanks. I'm far from a code guru, so there may very well be something else in newer editions or other sections that forbid this.

Modifying the circuit may require you to install a disconnecting means to the water heater if there is none existing or it's not within sight of the panel. Check your state building codes and with the AHJ. Good luck with your product!
 
When you add that receptacle to the circuit you change it from a single outlet circuit to a multi-outlet circuit. But you still only have 4500 VA on one outlet and minimal (likely less then 10 VA) load on the other outlet.

Sounds fine to me as long as you either use a 30 amp receptacle or supplement whatever you use with additional overcurrent protection.
 
Your looking for 210.23 (B), there is a table TABLE 210.24 Summary of Branch-Circuit Requirements.

If your running cat5 ethernet to it could you use PoE to power it?
 
IMO, this violate 210.23(A)(2)

(2) Utilization Equipment Fastened in Place. The total rating
of utilization equipment fastened in place, other than luminaires,
shall not exceed 50 percent of the branch-circuit ampere
rating where lighting units, cord-and-plug-connected utilization
equipment not fastened in place, or both, are also supplied.
Click to expand...
 
He could provide a enclosure with terminal blocks to connect to his power supply and hard wire. That would make more sense than installing a welder outlet to power a wall wart.
It sounds like he just needs to power some small electronics and feed data back to a network so power over ethernet would probably be his best bet.
 
Dennis Alwon said:
IMO, this violate 210.23(A)(2)
Click to expand...

tortuga said:
He could provide a enclosure with terminal blocks to connect to his power supply and hard wire. That would make more sense than installing a welder outlet to power a wall wart.
It sounds like he just needs to power some small electronics and feed data back to a network so power over ethernet would probably be his best bet.
Click to expand...
I agree, and don't really see the need for a receptacle for this equipment in the first place.
 
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