Square D® NF Merchandised Panelboards MH50, is a enclosure steel panelboard box has NEMA1 degree of protection, cULus certified. Warranty period is 18 month. Square D® NF Merchandised Panelboards MH50, is a enclosure steel panelboard box has NEMA1 degree of protection, cULus certified. Warranty period is 18 month.