Finnleo CB18-1 Contactor Box add-on (dual 1-phase)

Finnleo CB18-1 Contactor Box Add-On (Dual 1-Phase Systems)

What the CB18-1 Does

The Finnleo CB18-1 is a required add-on contactor box used exclusively in dual-heater, single-phase sauna installations. When a sauna room is large enough to require two heaters working together — such as a dual Laava Pro or dual Magma Pro setup — one SaunaLogic2 (SL2 or SL2-C) control cannot safely switch high-voltage line current to both heaters through a single relay box alone. The CB18-1 pairs with a CB17-1 contactor box to split and manage the electrical load, with the CB17-1 handling the primary heater circuit and the CB18-1 serving as the secondary relay for the second heater. Together, the two boxes allow a single control panel to command both heaters in unison — synchronized temperature, timing, and shutdown — while keeping each heater's power circuit properly isolated and protected.

Heater and Electrical System Compatibility

The CB18-1 is engineered specifically for dual 1-phase (240V single-phase) heater configurations and is required — not optional — anytime two single-phase heaters are installed in the same sauna room under one SaunaLogic2 control. It is most commonly specified alongside dual Laava Pro Series and dual Magma Pro Series heater installations, where combined heater wattage exceeds what a single relay box can safely switch. The CB18-1 must always be installed as a companion to a CB17-1 contactor box; it does not function as a standalone unit. For 208V or three-phase dual-heater installations, the equivalent pairing is CB17-3 and CB18-3, so it's essential to confirm your heater's voltage, phase, and total combined kW draw before ordering to ensure the correct box pairing. If you're unsure which combination your dual-heater setup requires, share your heater models and electrical service details and a sauna specialist will confirm the exact configuration.

Construction & Installation

Like its CB17-1 counterpart, the CB18-1 is a heavy-duty relay enclosure rated for continuous sauna-environment operation, housing an internal contactor relay that switches full line-voltage current to its assigned heater on command from the low-voltage signal sent by the SaunaLogic2 control. It is installed remotely from the sauna room proper — typically in a dry utility space, closet, or mechanical area near the heater's electrical supply — and wired in tandem with its paired CB17-1 box so both boxes receive control signals from the same SL2 or SL2-C panel simultaneously. Installation must be performed by a licensed electrician in accordance with local electrical code, matching the box's amperage rating to the specific heater's electrical draw and the branch circuit protection feeding it.

Why Choose Finnleo

Finnleo, built by Sauna360 in Cokato, Minnesota, is one of the most trusted names in authentic Finnish sauna, and every component in the SaunaLogic2 ecosystem — from the touchscreen control down to the contactor boxes that power it — is engineered and safety-tested to work together as a complete, reliable system. Getting a dual-heater installation right means pairing the correct contactor boxes to your heaters' exact voltage, phase, and wattage the first time. As an authorized Finnleo dealer, we offer full factory warranty support, expert sizing help for multi-heater installations, and guidance before and after your purchase. Have questions about your dual-heater configuration or which contactor box pairing your project needs? Reach out and a sauna specialist will help you spec it correctly.