The Phase III Delta Classic HMG heater from Triangle Tube is a gas-fired sealed combustion combination heater used for both heat and domestic hot water. It features heat and hot water in a small footprint (28 in. x 21 in.), a corrugated stainless steel heat exchanger that prevents lime build-up, an immersed combustion chamber, a combustion efficiency of 80%+, and abundant hot water: 60 gallons in 10 minutes.