Trying to get verification on water heater wire size

[drbubba1995]

We had a new house built in AZ and moved into it in January. There is a backyard casita that has a 19 gallon 120 volt Bradford White water heater installed. It does not provide sufficient hot water for showering. The builder has told us he will replace it with a Bradford White model RE230L6 28 gallon tank. That model has an upper and lower element. The faceplate states both upper & lower elements as 4500/3500 Watts and 240 volts.

The current circuit breaker for the 120 volt model is 20 amp with 12 AWG from the circuit breaker to the tank. We are being told that the new tank will require a 30 amp breaker and that the 12 AWG is sufficient rather than 10 awg.

Can someone verify that this wire size will be okay for the increased voltage and larger breaker? My wife is concerned there may be a fire hazard.

Thanks very much.

 

[hj]

#12 wire should NOT be conneced to a 30 amp breaker. Use a 20 amp breaker and see it is adequate, because it would be on the cusp of a 20 amp load. you could replace the elements with 240v/3600 watt ones if necessary to reduce the load.

 

[Sponsor]

 

[Jadnashua]

FWIW, you may find that tank too small as well. Admittedly, in many places in AZ, the ground temp and water temperature may be high enough so that the recovery rate is adequate, but not if you try to use a lot of water fast; there is just not all that much in there! A typical shower head uses 2.5gpm, but not all of that is coming from the hot side. But say even 2gpm, considering that you cannot use all of the water in the tank before it cools off too much from the incoming cold water, maybe 15g, or about 7-8 minutes of a shower. Forget about filling a tub, and if you use hot water from clothes on occasion, it will not be all hot. It's probably adequate for a typical dishwasher load, though.

COde requires a maximum of 20A on 12g wire. That is unlikely what is called for on that WH, so it would be a code violation to use a 30A breaker OR even if it were restricted to 20A since in most cases, code requires following the manufacturer's instructions AND the code.

 

[drbubba1995]

Jadnashua & HJ - Thanks for the replies. The casita I refer to is about 300 sq ft with a full bath , bedroom & small wet bar area. We built it so I could use it an office (still working over the internet) and so that guests could have privacy when visiting. The water heater is only there for the shower stall (no bathtub) and at most there would be 2 people staying in the casita so I don't see more than back to back showers on any given day.

My (and my wife's) major concern is the AWG of the current feed from the outside panel. There is a 20 amp two-pole circuit breaker feeding the current 120V 1500W single element water heater (19 gallon) and 12 AWG. I posted a picture of the 120V WH plate below. I've also posted a picture of the 240V WH plate for information.

The builders customer service rep has been told by their electrical contractor the current wiring (12 AWG) is sufficient for the 240V water heater. I am just looking for verification that this is not sufficient and you have given me some information to present to the customer service rep. I know little about electricity and plumbing and want to be able to speak to the customer rep with sound info regarding this situation. The simplest thing to me would be to run 10AWG from the panel to the water heater but I need some facts to show the customer rep in order to do that.

Finally, the space where this water heater will be located is about 27 3/4 inch wide with plenty of depth from front to back. The current 120 V water heater is sitting in a drain pan. The customer rep tells us that due to the extra width of the 28 gal water heater there will not be a pan under the tank. He told me that code did not require a pan - even though there is a pan under the current 120V tank. Can anyone comment on this issue?

Thanks very much.

 

[JerryR]

drbubba1995,

I am not an electrician but I've wired and installed 4 water heaters in my homes, and all with permits and inspections.

Your picture of the water heater plate shows at 240 volts the elements are rated at 4500 watts. That's for both top and bottom elements. Only one element is active at any one time.

The way I read the plate, the installed elements are only rated for 3500 watts with 208 volts which I doubt you have in your home.

Now a constant resistive load of 4500 watts at 240 volts will draw 18.75 amps (4500/240). Per code 240.4(d), constant loads require that the circuit load not exceed 80% of wire and breaker rating. Therefore a 12 guage circuit with a 20 amp breaker is illegal per code 240.4(d) connected to a water heater with a 4500 watt elements. It would be legal if the elements were 3500 or 3800 watts max at 240 volts. Bradford white can supply a 28 gallon 3500/3500 240vac heater. They may also authorize converting the one you have and provide a new data plate for legality. That way you would be legal and safe with 20 gauge and 20 amp breaker.

For a WH with 4500 watt elements you would need at least 10 gauge wire and either a 25 amp or 30 amp breaker, depending on local code. My local inspector in west coast Florida required a 25 amp breaker where the inspector at my east coast Florida home was fine with a 30 amp breaker with 4500 watt elements.

If you actually have 208 vac and not a 240 volt supply then that changes things.

 

[Dj2]

'We are being told that the new tank will require a 30 amp breaker and that the 12 AWG is sufficient rather than 10 awg."

It's simple to verify with your local bldg dept. What they'll tell you is what is required in your town.

In my area it's 10 gauge.

 

[hj]

I doubt that he has three phase power which would be necessary to have 208 volts.