Article 285 of the National Electrical Code (NEC) covers Surge Protective Devices (SPDs), not surge arrestors. Surge arrestors are covered in Article 280. However, the principle you're asking about is similar for both. Let's address it focusing on SPDs under Article 285, as those are more common in residential applications.You're right that 285.23 allows SPDs to be connected anywhere on the load side of the service equipment. However, the question of whether you can "tap it directly to the load side conductors" and be compliant with tap rules requires careful consideration. The short answer is: it depends.

Here's a breakdown of why: SPD Connection Methods

285.25 outlines acceptable connection methods for SPDs. These methods include:

Dedicated Overcurrent Protection

Connecting the SPD to a dedicated circuit breaker or fuse. This is the most common and straightforward method.

Taps

Tapping the SPD conductors to the branch circuit conductors. This is where the tap rules come into play.

Tap Rules

NEC 240.21 specifically outlines the tap rules for conductors. These rules specify length limitations and ampacity requirements for tap conductors. If you're tapping the SPD conductors to the branch circuit conductors, you must follow the tap rules.

Considerations for SPDs



SPD Current Rating

SPDs, during surge events, can handle significant current. However, under normal operation, they draw very little current. The tap conductor ampacity must be sufficient to handle the normal current of the SPD, and be protected by an overcurrent device rated at its rating.

Length of Tap

The length of the tap conductors is critical. The tap rules place strict limits on the length of the tap conductor based on the ampacity of the feeder or branch circuit it is tapped from.

Physical Protection

The tap conductors must be physically protected from damage.

In a residential breaker enclosure, to tap the SPD directly to the load side conductors while being compliant with the tap rules, you must ensure the following


Tap Conductor Ampacity

The SPD tap conductors must have an ampacity suitable for the SPD rating.2.

Tap Length Compliance

The length of the tap conductors must comply with the length requirements of NEC 240.21. This often limits you to the 10-foot or 25-foot tap rules, and you need to make sure you meet the termination requirements.
3.

Physical Protection

The tap conductors must be adequately protected.4.

Local Amendments

Check with your local jurisdiction for any amendments or modifications to the NEC.

Common Scenarios and Explanations



Scenario 1: Dedicated Breaker

The simplest and most common method is to install a dedicated circuit breaker for the SPD. This avoids the tap rule complications.

Scenario 2: Very Short Tap

If you can make a very short tap (a few inches) directly from the branch circuit breaker to the SPD terminals, it's possible to comply with the tap rules. This is more likely to be feasible with a small SPD and a large breaker.

Scenario 3: Violating Tap Rules

Running a longer wire (e.g., several feet) from a breaker to the SPD without considering the ampacity and length requirements is almost certainly a violation of the tap rules.

Example

Let's say you want to tap an SPD to a 20-amp breaker in your panel. To comply with the 10-foot tap rule (240.21(B)(2)), the tap conductors must have an ampacity of at least 1/3 of the 20 amp breaker, or 6.67 amps. Also, the tap conductors must be protected from physical damage.

Practical Considerations and Recommendations



Best Practice

While tapping is permitted under specific conditions,

installing a dedicated breaker for the SPD is generally the best and safest approach. It eliminates the complexity of the tap rules and provides dedicated overcurrent protection. Consult a Qualified Electrician

Given the complexities of the NEC and the importance of proper SPD installation for safety, it is highly recommended* to consult with a qualified electrician to ensure code compliance and safe operation. They can assess your specific situation and determine the best method for connecting the SPD.

In summary, while Article 285 (or 280 for surge arrestors) allows connecting SPDs/arrestors on the load side, you must still comply with all other applicable NEC requirements, particularly the tap rules in 240.21, if you choose to tap to a branch circuit. A dedicated breaker is generally the preferred and safest method. Flag for review