Correct me if I’m wrong but with the above said, it would mean that when a 60 gal. electric water heater requiring a 10/2 and 30 amps. breakers is replaced with a 40 gal. water heater the conductor would have to be replaced with 12/2 and 20 amps. breakers.
I don’t see the need to replace the conductor in the above example, only the breakers which leads me to believe that breakers also protect the load.
Mike
I dont have time to fully break this down, but I will tonight.
Cord and plug connected loads differ a great deal in ampacity, and as such, represent a unique circumstance. Dont confuse them with dedicated loads and dont apply the code provisions for them to all circuits.
More to follow when I have time.
Marcel, in my experience the element sizes are the same. It is just the tank capacity that differs.
Wattage is also different. For example a GSW 40 gal is 3,000W while a 60 gal is 4500W thus the 12/2 20 amp versus the 10/2 30 amp.
I have seen 40s as wall as 80s all have 4500w elements.
Agree, and 3800w or 5500w elements but around here what I see is the 3000w for the 40s and 4500w elements for the 60s.
Man…you guys lost me now.
One 220 appliance, one 220 breaker only. No double-taps allowed. Check manufacturer’s instructions. Get the model number off of the appliance, and check on the internet.
I had one two months ago on a re-hab, which was wired by an electrical contractor. One 220 wire went to a junction box, then both the seperate wall oven and seperate range top where all wired together in one under-counter junction box. Shame that the re-habber left both instruction books, which explained the right way to wire up the appliances, which I showed to the prospective home buyer.
I have done many home inspections for buyers that are electrical engineers. They hire me because they have no idea on how homes are wired. They all were involved with other areas of the electrical industry; IE design of the wire and conduit, over-head pole placement, large wire/light pole wiring/connections, even commerical writing of regulations.
Caution should be had by all who recommend electricians.
4500 divided by 240 equals 18.75
18.75 times 125% equals 23.4 total amps for this water heater.
Table 310.15(B)(16) for a 60 degree conductor and we have #10 conductor
240.4(D) and we see that the maximum overcurrent device that can be used on a #10 is 30 amps.
What we don’t see in 240.4(D) is anything about water heaters but only about conductors.
We size the conductor for the load being served and the overcurrent device for the conductor not the load. If we was sizing the overcurrent device for the load being served then we would be installing a 25 amp breaker instead of a 30.
If this doesn’t work take a look at 210.3
**210.3 Rating. **
Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device. The rating for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes. Where conductors of higher ampacity are used for any reason, the ampere rating or setting of the specified overcurrent device shall determine the circuit rating.
If one choose to do so they could install a larger conductor than is required and use a smaller overcurrent device such as #10 on a 20 amp breaker and the circuit would still be a 20 amp circuit no matter what the load on the circuit is.
What is not allowed is to install a #12 conductor and a 30 amp breaker as the breaker is larger than the conductor no matter the size of the load.
Joseph, I am impressed. There are more numbers there than in General Petreaus’s emails to his mistress.
Not true. There are times when ovens and cooktop can share the circuit. This is just one example. Also two loads not used at the same time could share the circuit.
BTW it has been 240 and 120 for many years.
Correct.
210.19(A)
(3) Household Ranges and Cooking Appliances. Branch-circuit conductors supplying household ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances shall have an ampacity not less than the rating of the branch circuit and not less than the maximum load to be served. For ranges of 8¾ kW or more rating, the minimum branch-circuit rating shall be 40 amperes.
.
**Exception No. 1: Conductors tapped from a 50-ampere branch circuit supplying electric ranges, wall-mounted electric ovens, and counter-mounted electric cooking units shall have an ampacity of not less than 20 amperes and shall be sufficient for the load to be served. These tap conductors include any conductors that are a part of the leads supplied with the appliance that are smaller than the branch-circuit conductors. The taps shall not be longer than necessary for servicing the appliance. **
I would say that anyone calling an electrician that knows the code would be well advised. Might even save some money not making two circuit installs
Thanks for posting that Mike.
In the case that I mentioned, both the double-wall oven and the range top were double-tapped into a juction box under the cabinet/range top. The wire leading from the junction box to the breaker panel was way under-sized, and the breaker at the panel was only a 30 amp. Both the double-wall oven and the range top were brand new.
The breaker tripped when the oven elements and the range top elements were set on “High”. Junction box was so hot, that I could not touch it. New 220 appliances need to be on seperate circuits/breakers.
Anytime I see double-tapped wall ovens and range tops, it gets written up; and I see it often. Read new appliance manuals. Seperate circuits are required for warranties on 220 appliances.
Worth repeating!
Not with regard to separate built-in cooking units (wall oven and cooktop) as they are considered as one appliance around here anyway…
Which was my point all along in where you stated that overcurrent should be rated to conductor…
Cheers,
Well it appears I got a good discussion going and then I ran off to make some more money. Guys I was looking at the breaker through the eyes of a thermographer and saw a un-even temp on a double pole breaker with the same amps on each leg indicating a loose connection. Be it right or wrong I never see the cooktop and a seperate oven on the same breaker in my area. The breaker it’s self was only 30 amps as I stated above and it tripped before the test was completed. It actually only tripped on one side. At that point I am done with it that is where the sparky takes over how he rewires is strictly on him
Charley,
One did not need an IR camera to find that defect, but a picture is worth a thousand words/posts as the saying goes…
Cheers,
Comon Marcel its called marketing and I do it well;-)
