Commercial Electric Thermostat 200-550F, 36" Capillary, 3/16" x 14-3/4" Nickel Bulb. The 5000 Series (Model D1/D18) thermostat is DPST, for A.C. operation. Direct acting (contacts open on temperature rise). All 5000 Series have a positive off feature. U.L. file number E12103.