77 amps on #8?

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nyerinfl

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Broward Co.
Have a customer who wanted to upgrade his current tankless water heater. He selects a Titan model, one which has a dataplate that says "2 40A breaker - (2 hots, 1 ground)" with an amperage reading for "77". Doesn't make much sense. I assumed it was only asking for basically one 8/2 romex on a 40 amp breaker. So we call the manufacturer to find out what's going on with this and the guy on the phone tells me I'm supposed to parallel 2 sets of #8 for 4 #8s altogether, and each cable should be on a seperate 40 amp breaker.

At this point I begin to explain to both the customer and the guy on the phone that there's a major problem here with what they're asking me to do, parallel (2) 40 amp breakers to create 80 and that it doesn't make any sense and violates all kinds of codes, 310.4 for starters. So I told my client to upgrade to the 60 amp instead of this mess.

If you know any other codes this violates post em.
 
nyerinfl said:
Have a customer who wanted to upgrade his current tankless water heater. He selects a Titan model, one which has a dataplate that says "2 40A breaker - (2 hots, 1 ground)" with an amperage reading for "77". Doesn't make much sense. I assumed it was only asking for basically one 8/2 romex on a 40 amp breaker. So we call the manufacturer to find out what's going on with this and the guy on the phone tells me I'm supposed to parallel 2 sets of #8 for 4 #8s altogether, and each cable should be on a seperate 40 amp breaker.

At this point I begin to explain to both the customer and the guy on the phone that there's a major problem here with what they're asking me to do, parallel (2) 40 amp breakers to create 80 and that it doesn't make any sense and violates all kinds of codes, 310.4 for starters. So I told my client to upgrade to the 60 amp instead of this mess.

If you know any other codes this violates post em.
Click to expand...

No code violations. There explanation was not really clear. You are to run 2 40amp circ. to the unit. I installed one that requried 3 50amp circ. about six months later was called back to wire in a gas unit. The elect one sucked. Burn you up in the shower at first and then freeze you in about two minuets.
 
I have seen electric furnaces that require 2 40amp breakers being fed from 2 branch circuits. But the furnace has 2 40 amp breakers in it to feed from your panel. Im assuming the water heater doesnt have breakers on it so this doesnt make any sense.:confused:
 
I just was speaking with the customer and got the unit and it has 4 leads coming out of it. I'm suprised never seen a tankless that was set up this way but first time for everything I suppose.
 
You should just have to handle tie all the breakers together and you are good to go. I've seen a sub panel fed similar to this due to limitations of how large a breaker you could place in the panel. It was originally designed as a MLO, but due to building design changing, it has to become sub fed.
 
ceb58 said:
I feel I have won the lottery:grin:
Click to expand...

Not exactly big money. :grin::grin:



Correct, the unit has 2 separate heating elements.
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I think they break it up to comply with

422.11(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.

These supplementary overcurrent protective devices
shall be (1) factory-installed within or on the heater enclosure
or provided as a separate assembly by the heater
manufacturer; (2) accessible; and (3) suitable for branchcircuit
protection.
The main conductors supplying these overcurrent protective
devices shall be considered branch-circuit conductors.
Click to expand...
 
I have given several prices to people wanting them. Once they found out they needed a service upgrade to use an electric one they go with the gas models.
 
bluesmoke...oops said:
The feeder was from 2 100A 240V 2 pole breakers. What would be the bare minimum code compliant way to do it? I'm just wondering for future knowledge.
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It is very possible the install you are talking about is not compliant. Were you able to find handle ties for 2 DP breakers --- not sure how you would do that. Doesn't sound right.
 
Last edited:
iwire said:
Not exactly big money. :grin::grin:





I think they break it up to comply with
422.11(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.

These supplementary overcurrent protective devices
shall be (1) factory-installed within or on the heater enclosure
or provided as a separate assembly by the heater
manufacturer; (2) accessible; and (3) suitable for branchcircuit
protection.
The main conductors supplying these overcurrent protective
devices shall be considered branch-circuit conductors.
Click to expand...
Click to expand...

Bob,

Can you explain to simple ole me why? Would the unit not be considered a UL listed assemply and not be required to comply with that?

Also, do theses really have a resistive element? I am asking...
 
mikeames said:
Can you explain to simple ole me why? Would the unit not be considered a UL listed assemply and not be required to comply with that?
Click to expand...

No I cannot. :)

There are a number of NEC sections that specify how equipment will be built.

For example.


422.44 Cord-and-Plug-Connected Immersion Heaters.
Electric heaters of the cord-and-plug-connected immersion
type shall be constructed and installed so that currentcarrying
parts are effectively insulated from electrical contact
with the substance in which they are immersed.


422.45 Stands for Cord-and-Plug-Connected Appliances.
Each smoothing iron and other cord-and-plugconnected
electrically heated appliance intended to be applied
to combustible material shall be equipped with an
approved stand, which shall be permitted to be a separate
piece of equipment or a part of the appliance.


422.46 Flatirons. Electrically heated smoothing irons shall
be equipped with an identified temperature-limiting means.


422.47 Water Heater Controls. All storage or
instantaneous-type water heaters shall be equipped with a
temperature-limiting means in addition to its control thermostat
to disconnect all ungrounded conductors. Such
means shall comply with both of the following:

(1) Installed to sense maximum water temperature.

(2) Be either a trip-free, manually reset type or a type having
a replacement element. Such water heaters shall be
marked to require the installation of a temperature and
pressure relief valve.
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I can't explain them but I know they are there.:)


do theses really have a resistive element?
Click to expand...

Pretty sure yes.
 
nyerinfl said:
Have a customer who wanted to upgrade his current tankless water heater. He selects a Titan model, one which has a dataplate that says "2 40A breaker - (2 hots, 1 ground)" with an amperage reading for "77". Doesn't make much sense. I assumed it was only asking for basically one 8/2 romex on a 40 amp breaker. So we call the manufacturer to find out what's going on with this and the guy on the phone tells me I'm supposed to parallel 2 sets of #8 for 4 #8s altogether, and each cable should be on a seperate 40 amp breaker.

At this point I begin to explain to both the customer and the guy on the phone that there's a major problem here with what they're asking me to do, parallel (2) 40 amp breakers to create 80 and that it doesn't make any sense and violates all kinds of codes, 310.4 for starters. So I told my client to upgrade to the 60 amp instead of this mess.

If you know any other codes this violates post em.
Click to expand...


Thats no different than some indoor hot tubs require 2 - 20 circuits ran to 2 gfci outlets under the tub , one for pump and one for heater. If you ran # 8 for 40 amp then you would have to have a sub panel with 2 - 20 amp breakers to feed the 2 GFCI outlets . In this case the plugs are the disconnect means .:grin:
 
I wired up one several years ago that had 3 elements of 8 kw each. Had to return a few days later and cap off 1 of them. They were kicking on and off too fast and causing lights to flicker. Was a total stupid idea. Between what it cost to wire it and cost of unit itself just plain stupid. Do customer a favor and sell them on gas or stick to a typical 40 gal 4500 watt tank. I am thinking of going to gas for my own place when my tank goes bad. Just 1 more step in being ready for huricane.
 
iwire said:
No I cannot. :)

There are a number of NEC sections that specify how equipment will be built.

For example.





I can't explain them but I know they are there.:)




Pretty sure yes.
Click to expand...

Thanks. I get the idea. I had seen those articles before but dismised them for whatever reason and never thought twice about them possibely because I did not understand. Now I now it just is...
 
bluesmoke...oops said:
The feeder was from 2 100A 240V 2 pole breakers. What would be the bare minimum code compliant way to do it? I'm just wondering for future knowledge.
Click to expand...

There are 200 amp 2 pole breakers that look like 2 100 amp breakers with a handle tie but in fact are one factory assembled unit. GE and Siemens are a couple of brands that come to mind that have this type. If your case actually had 2 separate 100 amp breakers it was likely done incorrectly.
 
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