Manchester & Winchester Direct Vent Systems Model MDV500 - Manchester MDV600 - Manchester MLDV500 - Winchester BTU / HR 21,000 - 30,000 NG / 23,500 - 30,000 LP 22,000 - 32,000 NG / 26,000 - 32,000 LP 22,000 - 34,000 NG / 27,000 - 34,000 LP FE Ratings (Cdn. Fireplace Efficiency) 71.7% NG / 77.0% LP 71.0% NG / 77.7% LP 70.5% NG / 76.