Short answer: the FD-4 Trinity is a 2-person indoor cabin with two heat sources, a 1,750W infrared array and a 1.9kW Harvia stove, that runs on a 120V plug. It is the only hybrid here that avoids a 240V circuit. At $7,795 you pay for that convenience.
Can a 120V outlet run both heaters?
Run the numbers. At 120V, the 1,750W infrared array draws about 14.6A. The 1.9kW stove draws about 15.8A. Either one nearly fills a 20A circuit by itself, and together they would exceed it.
The listing calls for 120V at 15-20A with a NEMA 5-15P plug. I’d plan on a dedicated 20A circuit with nothing else on it, and I’d ask the dealer one direct question: can both heaters run at the same time, or does the controller switch between them? The answer changes how you’ll use the sauna.
How hot does each side get?
The infrared side tops out at 170°F and the stove side at 190°F. The stove is small for a traditional heater, so expect a longer warm-up than a 240V sauna. The stove also needs 29 lbs or more of sauna stones, which some dealers sell separately. Ask whether they are in the box.
Will it fit?
The exterior is 48” x 48” x 83” tall, which is 16 sq ft of floor. Check your ceiling: 83” is 6 ft 11 in, so a 7 ft basement ceiling leaves 1 inch. The interior is about 14 sq ft, snug for two adults. Weight is 437 lbs.
What the listing leaves out
Finnmark’s own page doesn’t state a warranty term for this model. Select Saunas lists 2 years on the traditional heater. The larger FD-5 is listed elsewhere with 10 years on the cabin, so ask whether the FD-4 gets the same and get it in writing.
How it compares
The FD-5 Trinity XL seats 4 for $8,995 but needs a 240V circuit. Bottom line: choose the FD-4 when a 240V run is impractical. Infrared Saunas With Two Heater Types: Worth It? covers the hybrid question.
