Best with alarm in transfer switches and surge protection
Leviton's replacement for its 51120-1: a Type 1 surge panel with a 200 kA short-circuit rating, LEDs, an audible alarm and remote-monitoring contacts.
Our score: 7.8/10 out of 10Researched, not lab-tested
- Device
- Surge protector, Type 1
- Surge current
- 50 kA
- Short-circuit rating (SCCR)
- 200 kA
- Safety listing
- UL 1449 (per Leviton)
Is it right for you?
Pros
- UL 1449 listed Type 1 device
- 200 kA short-circuit current rating
- Status LEDs plus an audible alarm
- Form C contacts for a remote monitor
Cons
- Electrician install at the panel
- Reduced modes of protection (L-N, N-G only)
- 1,200 V protection rating line to ground, double the Square D's
- No GTIN or Canadian mark we could confirm
- Best for
- US homes where the panel sits out of sight and an audible alarm or a wired alert matters when the surge device has worn out.
- Not for
- DIY installation, three-phase services, or Canadian buyers who need a confirmed Canadian mark.
Our verdict
The P2120-B is the surge protector to choose if you want to know when it has stopped working. Besides status LEDs it has an audible alarm, and Form C dry contacts let an electrician wire it to a remote monitor, so a worn-out device doesn’t sit unnoticed in a basement panel. Leviton lists it as its replacement for the discontinued 51120-1.
It is a UL 1449 listed Type 1 device for 120/240 V split-phase homes, rated at 50 kA per mode with a 200 kA short-circuit current rating, the highest of the two surge devices we list. Its MOVs are thermally protected, and the polycarbonate housing is NEMA 4X. Leviton also offers a connected-equipment warranty, with the amount and terms on its warranty page.
The trade-offs: it uses reduced modes of protection (line to neutral and neutral to ground), its voltage protection rating line to ground is 1,200 V against the Square D’s 600 V, and Leviton’s page gave us no GTIN or Canadian certification we could confirm.
Setup and safety
This is electrician work. The P2120-B mounts on the side of the panel through a 3/4 in NPT nipple and is wired with 12 AWG leads, on a 20 A breaker as Leviton recommends. That means working in a live panel: have a licensed electrician fit it, and don’t open the panel yourself.
Why it helps. Lightning and grid switching send short voltage spikes into the house wiring. Owners on home-improvement forums generally think a panel-mounted surge device is worth having when it is installed with short leads, and still use plug-in protectors for sensitive electronics. Leviton notes that the 2020 US National Electrical Code (230.67) requires a Type 1 or Type 2 surge device on services supplying homes.
Checking it. Glance at the LEDs when you test your smoke alarms, and if the alarm sounds, call your electrician to check the device. If you want an alert where you’ll notice it, ask for the Form C contacts (rated 240 V, 2 A) to be wired to a monitor. For Canadian homes, the Square D HEPD80 has a Canadian mark stated by its maker.
Specs
Leviton P2120-B Type 1 Whole Home Surge Panel (120/240V)
Installation
| Device | Surge protector, Type 1 |
|---|---|
| Needs a licensed electrician | Yes |
| Enclosure | NEMA 4X |
Surge protection
| Surge current | 50 kA |
|---|---|
| Short-circuit rating (SCCR) | 200 kA |
| Voltage protection rating, L-N | 700 V |
Other details
| Safety listing | UL 1449 (per Leviton) |
|---|
Maker’s figures, checked 3 Nov 2026.
P2120-B questions
P2120-B or Square D HEPD80?
Choose the Leviton if you want to hear or be told when protection fails: it has an audible alarm and remote contacts, plus a 200 kA short-circuit rating. Choose the Square D HEPD80 for lower voltage protection ratings line to ground and a Canadian mark stated by its maker.
What does the alarm mean?
Leviton uses the status LEDs and the audible alarm to signal the device’s condition, so an alarm is the cue to have it checked by an electrician. Leviton’s instruction sheet sits on a part of its site we don’t read, so follow the sheet in the box for what each signal means.
Can it be used in Canada?
Leviton’s product page lists its UL 1449 listing and states no Canadian certification. If you are in Canada, have your electrician check the label, or choose a device whose Canadian mark is stated.