Manufacturer vs NEC

ModbusMan said:
A teenager? Wifey and I considered getting a nat-gas fired on-demand heater for exactly that reason, but the 3x cost versus a traditional 50gal put the kibosh on that.
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I don't know any teenager that stays in the shower after the hot water runs out.😀
I alsomdon't know of many places that take more than 3 hours to heat 40-50 gals, and our water supply is around 50° during the winter.
 
ModbusMan said:
A teenager? Wifey and I considered getting a nat-gas fired on-demand heater for exactly that reason, but the 3x cost versus a traditional 50gal put the kibosh on that.
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Was that many years ago? Because these days the cost of a tankless gas and a 50gal gas water heater are basically the same.
 
jaggedben said:
Was that many years ago? Because these days the cost of a tankless gas and a 50gal gas water heater are basically the same.
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Only three years ago last month... could be because I was able to purchase one of the last "traditional" tanks in the warehouse, rather than one of the newer models with condensers, recirc pumps, and all the other energy-efficiency bells and whistles now being required.
 
Butta Dawg said:
I have a contractor installing a water heater. The link provided here shows the specific one.

QR Code

www.wh1.co www.wh1.co

I took a look at the nameplate rating. It states 208v/240v, and at 240v, it requires 25A. (Really 25.4 or some decimal) regardless, I said at 125% of that would be 31.25A, were looking at #8's and a 40A breaker. But the manufacturer states on the name plate, max breaker to be used, 30A. For me, follow the NEC. But the contractor states they've done 100s of these on 30A breakers and #10s. I'm concerned, and they already installed it
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The manufacturer's stated maximum breaker size of 30A must be followed as per NEC 110.3(B). This means the circuit should be protected by a 30A breaker, and the conductors should be sized for 30A (e.g., #10 AWG copper wire).

Your contractor's installation of a 30A breaker and #10 AWG wire for the water heater is compliant with the National Electrical Code (NEC) due to the manufacturer's specific instructions. While water heaters are considered continuous loads, generally requiring conductors and overcurrent protection to be sized at 125% of the load, NEC 110.3(B) mandates that listed or labeled equipment be installed and used in accordance with any instructions included in its listing or labeling.

In this case, the manufacturer's explicit instruction for a "max breaker to be used, 30A" overrides the general 125% calculation for the overcurrent protection device. The manufacturer has tested and listed the water heater for safe operation with a 30A breaker. Therefore, the circuit must be protected by a 30A breaker. For a 30A overcurrent device, #10 AWG copper conductors (rated for 30A at 75°C per Table 310.16) are appropriate and compliant.

NEC References
  • 110.3(B)
    This code requires that listed or labeled equipment be installed and used in accordance with any instructions included in the listing or labeling, which is paramount when a manufacturer specifies a maximum breaker size.
  • 422.13
    This section defines storage-type water heaters with a capacity of 120 gallons or less as continuous loads for the purpose of sizing branch circuits.
  • 210.19(A)(1)
    This section generally requires branch-circuit conductors supplying continuous loads to have an ampacity not less than 125% of the continuous load.
  • 210.20(A)
    This section generally requires overcurrent devices for branch circuits supplying continuous loads to have an ampere rating not less than 125% of the continuous load.
  • 240.4(D)
    This section provides limitations on the overcurrent protection for small conductors, ensuring that conductors are adequately protected.
  • 240.6(A)
    This section lists the standard ampere ratings for fuses and inverse time circuit breakers, which are used when selecting the appropriate overcurrent device.
 
Electrical code Man said:
The manufacturer's stated maximum breaker size of 30A must be followed as per NEC 110.3(B). This means the circuit should be protected by a 30A breaker, and the conductors should be sized for 30A (e.g., #10 AWG copper wire).

Your contractor's installation of a 30A breaker and #10 AWG wire for the water heater is compliant with the National Electrical Code (NEC) due to the manufacturer's specific instructions. While water heaters are considered continuous loads, generally requiring conductors and overcurrent protection to be sized at 125% of the load, NEC 110.3(B) mandates that listed or labeled equipment be installed and used in accordance with any instructions included in its listing or labeling.

In this case, the manufacturer's explicit instruction for a "max breaker to be used, 30A" overrides the general 125% calculation for the overcurrent protection device. The manufacturer has tested and listed the water heater for safe operation with a 30A breaker. Therefore, the circuit must be protected by a 30A breaker. For a 30A overcurrent device, #10 AWG copper conductors (rated for 30A at 75°C per Table 310.16) are appropriate and compliant.

NEC References
  • 110.3(B)
    This code requires that listed or labeled equipment be installed and used in accordance with any instructions included in the listing or labeling, which is paramount when a manufacturer specifies a maximum breaker size.
  • 422.13
    This section defines storage-type water heaters with a capacity of 120 gallons or less as continuous loads for the purpose of sizing branch circuits.
  • 210.19(A)(1)
    This section generally requires branch-circuit conductors supplying continuous loads to have an ampacity not less than 125% of the continuous load.
  • 210.20(A)
    This section generally requires overcurrent devices for branch circuits supplying continuous loads to have an ampere rating not less than 125% of the continuous load.
  • 240.4(D)
    This section provides limitations on the overcurrent protection for small conductors, ensuring that conductors are adequately protected.
  • 240.6(A)
    This section lists the standard ampere ratings for fuses and inverse time circuit breakers, which are used when selecting the appropriate overcurrent device.
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I've got a EFM DF520 stoker boiler with a domestic hot water coil in it, and that feeds into an 80 gallon electric. During the winter you could take a hot shower for a week and never run out. Thank God I'm not even close to being a teenager
 
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