Domestic Hot Water Heaters - Sizing
Domestic hot-water systems supplies taps in houses or buildings with hot water.
Output Heating Capacity
Output heating capacity of a domestic hot-water system:
hout = q ρ dt cp (1)
hout = heating capacity, output (Btu/h)
q = flow rate (gph)
ρ = 8.34 - density of water (lbs/gal)
dt = temperature rise (oF)
cp = 1.0 - specific heat of water (Btu/lboF)
Input Heating Capacity
Input heating capacity of a domestic hot-water system:
hin = q ρ dt cp / μ (2)
hin = heating capacity, input (Btu/h)
μ = efficiency
Recovery rate for an electrical heater in a domestic hot water system:
RR = hin μ / dt ρ
= P (3413 Btu/kW) / dt ρ (3)
RR = recovery rate (gal/h)
P = electrical power supplied by heater (kW)
Temperature rise in an electrical heater in a domestic hot-water system:
dt = hin μ / q ρ
= P (3413 Btu/kW) / q ρ (4)
Electrical Power Supply
Electrical power supply to a domestic hot-water systems:
P = q ρ dt cp / (3413 Btu/kW) (5)
• Water Systems
Hot and cold water service systems - design properties, capacities, sizing and more.
Hot Water Consumption per Occupant
Consumption of hot water per person or occupant.
Hot Water Content in Fixtures
Content of hot water in some common used fixtures - basins, sinks and baths.
Hot Water Supply - Flow Rates to Fixtures
Hot water consumption of some common equipment as basins, sinks, baths and showers.