Which wiring method is best for tankless water heater??

[Little Bill]

Don't have my book handy but you can't have heater loads above 60A. They have to be divided.
This is from memory so the 60 may be wrong but do know you have to split up heavy heater loads.

I know there is wording like you mentioned, mostly applies to electric space heating from recollection. Might still be some instances where it doesn't apply.

Sometimes you run into a unit with a large supply circuit but still gets subdivided within appliance to circuits of 60 amps or less.

Not sure if this applies here but this is what I was thinking of...

(F) Electric Heating Appliances Employing Resistance-
Type Heating Elements Rated More Than 48 Amperes.
(1) Electric Heating Appliances. Electric heating appliances
employing resistance-type heating elements rated
more than 48 amperes, other than household appliances
with surface heating elements covered by 422.11(B), and
commercial-type heating appliances covered by 422.11(D),
shall have the heating elements subdivided. Each subdivided
load shall not exceed 48 amperes and shall be protected
at not more than 60 amperes.

It was 60A but the load can't be more than 48A because of the continuous load.
48 x 125% = 60

 

[jumper]

Not sure if this applies here but this is what I was thinking of...


It was 60A but the load can't be more than 48A because of the continuous load.
48 x 125% = 60

I think water heaters are F(3).

 

[Little Bill]

I think water heaters are F(3).

I think the secret is in the type of elements, either submersible or surface. But aren't most tankless elements the type that water flows through? So I don't see that option, so IDK!

 

[jumper]

I think the secret is in the type of elements, either submersible or surface. But aren't most tankless elements the type that water flows through? So I don't see that option, so IDK!

Immersion (submersible) would apply if the water was stationary in a tank or flowing past in a tube. In both cases the elements are immersed in water.

Section (2) specifically cites instantaneous water heaters.

 

[kwired]

Not sure if this applies here but this is what I was thinking of...


It was 60A but the load can't be more than 48A because of the continuous load.
48 x 125% = 60

That sub division into 48 amp sections can take place within the appliance and you supply a single circuit to the appliance rated over 60 amps.

Seems to be more common to see the appliance requiring multiple supply circuits though, sometimes they may have optional combining kit for a single supply.