Viessmann Vitocell 300-V Technical Data Manual page 13

Technical Data
Vitocell 300-V, EVI Series Technical Data
Water Flow
(continued)
Example: Vitocell 300-V, 119 USG (450 L) capacity
Assume boiler output to tank is 238 MBH. Enter chart at left and draw horizontal line across to recovery rate of 284
GPH / 4.7 GPM for 140°F (60°C) domestic hot water under column A. Where the horizontal line intersects the 194°F
(90°C) curve is the point of intersection for the diagonal line used to size the pump. The diagonal line begins at the
origin and goes through the point of intersection extending up to the top of the chart. Read between the reference
diagonal lines to get a pump specification of 20 GPM at 8.4 ft. To summarize: For a Vitocell-V 300 with 119 USG
(450 L) capacity and 238 MBH input, the boiler water temperature is 194°F (90°C), difference between boiler return
and supply water temperature is 29°F (16°C), recovery rate is 4.7 GPM of 140°F (60°C) DHW, and the pump required
is 20 GPM, 8.4 ft. plus pressure drop in piping and boiler. If a multiple-tank application is required, i.e. 4 tanks at 238
MBH input each, then the pump selection would be (4 x 20 GPM) 80 GPM at 8.4 ft. plus piping pressure drop.
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