After assessing the impact of climate change on the durability and energy performance of one retrofitting strategy for the building envelope, the design heating load was assessed based on the heat balance approach (McQuiston et al.
i] = Overall heat transfer coefficient of ith enclosure [DELTA]T = Temperature difference between indoor setpoint and design heating load temperature
These systems were designed to meet the design heating load using 140[degrees]F (60[degrees]C) supply water at 1.
For modulating, condensing boilers, design the system to meet the design heating load such that the return temperature does not exceed 13.
ELECTRICITY USED BY ALL ATTACHED HEAT PUMPS 836 MWh ELECTRICITY USED BY ALL CIRCULATING PUMPS 220 MWh BACKUP ELECTRIC HEAT 605 MWh BACKUP NATURAL GAS HEAT 213 MWh NATURAL GAS USED BY CENTRAL BOILERS 759 MWh TOTAL 2,633 MWh DESIGN HEATING LOAD
The ACCA Manual J design heating load
for the downstairs unit is about 21.
Surge is not an issue for positive-displacement compressors; therefore, single-compressor screw heat pumps are able to unload to a minimum capacity of 25% to 35% of the design heating load
The fluid temperature drop across the heat pump at the design heating load
is 5[degrees]C (9[degrees]F).
The total annual design heating loads
are larger than the cooling loads by about 10%.
First, buildings in colder climates often have appreciably smaller design cooling loads than design heating loads