 | NEC and instant hot water heater |
|
|
Question: I have a friend who in installing a instant hot water heater in his mountain cabin. The spec sheet says it draws 54 amps @ 240V. Now here's my questions: 1- 1999 NEC article 422-13 says that a storage type water heater shall have a circuit rating not less than 125% of the nameplate rating. That would mean the circuit for this heater would be 67.5 amps Is that an accurate interpretation of this section, even though it's an instant type heater and not a storage type? 2- Article 422-11(f)(1) says at the end of the first paragraph that the load shall not exceed 48 amps and shall be protected at not more than 60 amps. How does this apply to an instant hot water heater that draws 54 amps? I may just tell him to call the state inspector and get an interpretation and guidance on this. Any thoughts? I sure wish he'd have just gone with a standard storage type heater. Oh, I need to rough-in for a wall mounted oven. What's the easiest way? For the cook top I just left the cable hanging and will mount a box when the cabinets are in. But I don't know what to do for the oven.
Answer: -The 125% rating applies to loads which may be on continuously, such as storage water heaters. The instant type may not fit this definition since it's unlikely to be on for long periods. The intent of this section was to require that large (resistor bank) loads be sub-divided into branch circuits *within* the appliance, each branch not to exceed 48 Amps. There is no way you can meet this. Is the heater UL listed? -The 125% rating applies to loads which may be on continuously, such as storage water heaters. The instant type may not fit this definition since it's unlikely to be on for long periods. > 2- Article 422-11(f)(1) says at the end of the first paragraph that the load > shall not exceed 48 amps and shall be protected at not more than 60 amps. > How does this apply to an instant hot water heater that draws 54 amps? The intent of this section was to require that large (resistor bank) loads be sub-divided into branch circuits *within* the appliance, each branch not to exceed 48 Amps. There is no way you can meet this. Is the heater UL listed?
|
 |
|
| |
Submit Your Question
Home