Zooz 700 Series Z-Wave Long Range Smart Relay ZEN51 - Behind-Switch

In this review of the Zooz 700 Series Z-Wave Long Range Smart Relay ZEN51, the bottom line is simple: it is a compact, reliable way to add Z-Wave on/off control to an existing wall switch or light fixture while preserving your switch style. It is best for DIYers and integrators who need a small relay that fits in crowded boxes, supports 3-way setups, and offers Z-Wave Long Range and SmartStart for easier pairing. The most compelling reason to buy is the combination of compact size and versatile dry contact output that lets this relay handle a variety of 120 V signal monitoring tasks safely when installed per instructions.

Key Features

• Smart relay for on/off control: Adds Z-Wave control to your existing mechanical switch without changing the switch appearance, ideal for traditional homes.
• Dry contact output: Provides a dry contact output useful for non-lighting applications while the input expects 120 V for accurate signal monitoring.
• 3-way compatible: Works in multi-switch 3-way circuits and can be installed at the fixture where neutral is available if switch boxes lack neutral.
• Smart bulb mode: Lets you keep power to smart bulbs while still controlling them via Z-Wave so switches retain normal function without cutting power.
• Compact form factor: Measures 1.5 in x 1.4 in x 0.7 in so it fits in most crowded single-gang boxes and simplifies retrofit installs.
• Z-Wave Long Range and security: Supports the 700 series features including extended range, SmartStart, and S2 authenticated security when the hub also supports them.

Who It's For

This relay is aimed at homeowners, electricians, and smart home tinkerers who want to convert a conventional mechanical switch to a Z-Wave controlled circuit without replacing the visible switch. It is especially useful for installations where a neutral is available at the fixture or in boxes and for projects that benefit from a small relay that fits behind existing switches.

Users who rely solely on smart speakers without a Z-Wave hub should look elsewhere since a compatible Z-Wave hub is required for control. Also avoid using this relay with dimmers, electronic or smart switches, tube lights, or high-demand motor loads above the specified limits.

Pros & Cons

Pros

• Compact size and tidy pigtail wiring make installation in crowded boxes straightforward.
• Reliable pairing and operation reported with SmartThings, Hubitat, and Home Assistant when using an updated Z-Wave hub.
• Versatile dry contact output and smart bulb mode expand use cases beyond simple lighting control.

Cons

• Neutral wire is required, so it is not suitable where no neutral is present and you cannot access the fixture for installation.
• Power limits apply (do not exceed 150 W LED or 960 W incandescent) which restricts some heavy-duty loads.

Specifications

Our Verdict

The ZEN51 is a practical, good-value relay for anyone who needs discreet Z-Wave on/off control behind an existing switch or at a light fixture. Its compact size, reliable pairing with major hubs, and smart bulb mode make it a smart retrofit choice, provided a neutral is available and loads stay within the stated limits.

Frequently Asked Questions

Does this need a hub?
Yes. A compatible Z-Wave hub is required to include and control the relay; smart speakers alone will not work.

Can I use it with dimmer switches?
No. This relay must be used with mechanical on/off or momentary switches only and not with dimmers or electronic switches.

What are the load limits?
Do not exceed 150 W of LED or 960 W incandescent and use small fans under 1/2 HP only.