Viessmann Vitocell 300-B 79 Gal Dual-Coil Indirect Water Heater

A 79-gallon stainless steel indirect water heater with two internal coils, so a boiler and a solar thermal system or heat pump can share one tank. With the coils piped in parallel at 180°F supply, it carries an AHRI first hour rating of 496 GPH for multi-bath homes.

The upper coil is intended for the boiler and the lower coil for solar or heat pump input, and each works independently, so one heat source can be connected now and a second added later. In parallel the AHRI continuous rating is 429 GPH with a 67-gallon first draw; piped in series the figures drop to 460 GPH first hour and 393 GPH continuous. Combined coil surface is about 16 sq. ft and coil volume about 2.9 gal.

Because the tank and both coils are stainless steel, there is no sacrificial anode to service. Rigid PUR foam insulation keeps standby loss to roughly 0.6°F per hour. All coil, domestic hot and cold, and recirculation connections are 1 in. male NPT. Maximum working pressure is 150 psig on the domestic side and 220 psig on the coils, and the insulated tank weighs about 249 lb.

Highlights

• 79-gallon (300 L) stainless steel tank with two stainless coils

• Upper coil for a boiler, lower coil for solar thermal or a heat pump

• AHRI 496 GPH first hour and 429 GPH continuous with coils in parallel

• No sacrificial anode to replace

• Standby loss of about 0.6°F per hour with rigid PUR foam insulation

• 1 in. male NPT connections for coils, domestic water and recirculation

Specifications