Surge suppressor installation

Specific Inspection Topics Electrical Inspections
1

Good afternoon.

Here’s the situation and then my question about the installation of a surge suppressor (Type 2) at an electrical sub-panel:

Leviton Surge Suppressor # 511250-1 (instructions: https://a89b8e4143ca50438f09-7c1706ba3fabeeda794725d88e4f5e57.ssl.cf2.rackcdn.com/spec_sheets/files/000/022/733/original/leviton-51120-1-installation-instructions.pdf?1442945250 )

Cutler-Hammer sub-panel

Inside the Cutler-Hammer panel, there is a 70-amp double-pole circuit breaker with a pair of 4 AWG wires feeding another sub-panel adjacent to the Cutler-Hammer panel. A pair of 12 AWG wires run from the Leviton Surge Suppressor to the 70-amp double-pole circuit breaker. So, the 70-amp circuit breaker is double tapped (each terminal has a 4AWG wire and a 12 AWG wire). The breaker is not designed to be double tapped (and the wires are two different sizes too) This deficiency is not my concern here.

The Leviton installation instructions essentially says this: Select circuit breakers as close as possible to each service entrance lug. Twenty-Amp (20A) circuit breakers are recommended and may share surge protective device (SPD) and branch circuit leads. The breakers provide additional failure protection as well as an SPD connection and servicing disconnect.

Here’s my question: Is the 70-amp circuit breaker too big for the surge suppressor? Leviton states 20-amp “circuit breakers are recommended” but beyond this recommendation I do not see where Leviton requires or even mentions a minimum or maximum amperage rating for the circuit breaker. Does it matter?

Thanks.

2

From the link you provided it sounds like it needs a 20 amp OCPD:

CAT. NOS. 51120-1 AND 51120-3 SPD DEVICES MUST BE INSTALLED ON A LINE THAT IS SERVED BY DISCONNECT MEANS, SUCH AS 20-AMP CIRCUIT BREAKERS OR 20-AMP
FUSED DISCONNECT SWITCHES.

3

Thanks. Maybe I’m splitting hairs but I read that to mean an OCPD was required but because of the wording (“such as”), I didn’t take it to mean that specifically a 20-amp breaker was mandatory.

4

I agree that it’s poorly worded but both of the examples in their literature contain overcurrent protection.

5

Should also really be in the service panel if it’s meant to protect the entire house.

What would happen if there is short across those 12 AWG conductors (protected by 70amp breaker) feeding the SPD?

6

The 70 amp circuit breaker would open.

7

Hmmm… looking at the trip curve of Eaton breakers the max trip time (~15milliseconds) is achieved at about 5000% the rating of the breaker or 3500amps for 70amp breaker. The #12 copper will reach 2000F or its melting point @ 3500amps in 70milliseconds. Pretty close. I would not try it at home :slight_smile:

Here is a better question… can SPD cause an extended overload condition in excess of 20amps?

8

How much current would flow if the CB were 20 amps instead of 70 amps?

9

assuming the resistance of 20 & 70 breakers is the same then the current would also be the same. However, I still wouldn’t trust 70amp breaker as much as I would a 20amp with #12 conductors.

10

The IEEE manual on SPD’s says to follow the manufacturer’s recommendations regarding OCP closely and if there’s any doubt, give them a call.

11

Double Pole 20A

Emanuel J. Ramondino
Applications Engineer, Technical Services
T: 1-631-812-6705 | F: 1-800-832-9538
Leviton Manufacturing Co., Inc.
www.leviton.com | eramondino@leviton.com

From: Corporatetechsupport <corporatetechsupport@leviton.com>
Sent: Monday, August 26, 2019 2:50 PM
To: Ramondino, Emanuel <ERamondino@leviton.com>
Subject: FW: Home Solutions

|Question|What is the max circuit breaker size fo the Surge Suppressor model # 511250-1|

I was curious so i asked. Leviton, His reply is at top. I think the “such as” is referring to Breakers or Fuses

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12

You went above and beyond, Dennis. Thanks. It’s much appreciated.

1 Like