Measured Savings from Integral Flue Dampers and Thermal Vent Dampers on Domestic Hot Water Heaters i

Research suggests that standby losses (jacket and stack) for commercial tank-type water can account for as much as 13% of the total energy used to heat domestic hot water in apartment buildings. Potentially, losses up the stack could be reduced by retrofitting existing heaters with automatic vent dampers, or by replacing them with water heaters equipped with integral flue dampers. Previous tests of these strategies have been either limited or inconclusive. As a result, this research was undertaken to further investigate the benefits of using an integral flue damper versus a thermal vent damper on commercial tank-type water heaters. These measures were examined in two multifamily buildings. All tests were conducted using an alternating mode design monitored by a computerized data acquisition system.

Tank-type DHW heaters installed with integral flue dampers are significantly more efficient (about 3% to 4%) than the identical tank heater without any damper. Savings for this measure were 6% and 4% for the two cases investigated, corresponding to annual energy reductions of about 13 MBtu and 11 MBtu. Paybacks based on the marginal cost of an IFD heater over a conventional heater were about 10 years, but paybacks based on the total cost of this equipment were well over 30 years. Since this is longer than most multifamily building owners are willing to accept, other financial incentives or appliance efficiency standards may be required to encourage this measure. By comparison, tests of thermal dampers installed on the same heaters showed no efficiency improvement and no savings potential. Both of these results are consistent with the findings of previous research.

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Measured Savings from Integral Flue Dampers and Thermal Vent Dampers on Domestic Hot Water Heaters in Multifamily Buildings