Modine PTP Greenhouse Heater Fuel Type:Natural Gas Single layer or stacked pad Single layer or stacked pad systems available to cover a small area or an entire sidewall FEATURES:Distribution & Return System Features:High efficiency systemLargest self contained PVC return gutter on the market todaySubmersible pumps Pad Features:Water is spread evenly over the pad surface as a film rather than droplets for uniform wettingPad surface dries quickly in absence of water to inhibit micro organism growthCoated pads are tough and durable for repeated cleaning 10 year heat exchanger warranty BTU Primer Most manufacturers advertise a heaters input BTU which is the amount of fuel a heater consumes per hour