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COMMON TERMS
For insulating purposes “R” value is a measure of the resistance of a
substance to heat flow.
Recovery rate is the amount of water that is heated to a specific temperature
rise, per hour. An example might be that a water heater has a recovery rate
of 30 gallons of water per hour at 80° F temperature rise.
Thermal efficiency is approximately the percentage of generated BTU
that enters the stored water. A percentage of the total BTU input passes
out through the vent piping.
Temperature rise is the increase in the temperature from its
coldest “inlet” water temperature to the desired hot (outlet) setting.
Typically this is assumed to be 40° entering water; 120° desired
stored water or 80° “temperature rise.”
Standby efficiency is the water heater’s ability to contain heat in the tank.
A minimum of tank water heat loss per hour is desired.
Sample: temperature change per hour = BTU/H loss/square foot of tank surface
“R” value
Water hammer is a concussion of moving water against the sides of a
containing pipe or vessel on a sudden stoppage of flow.
Ex: 1/2˝ copper pipe, 5GPM flow (7.2ft/sec.) – stop.
Pressure rise of approximately 412 psi
3/4˝ copper pipe, 5GPM flow (3.3ft/sec) – stop.
Pressure rise of approximately 188 psi
Polarity – Verify that an electrical socket has
correct “polarity.” Verify that the “Neutral”
(typically white on a 120V circuit) wire has
no power to ground and that the “Hot”
(typically black wire on a 120V circuit)
has 115 – 125V to ground.
Watts divided by Volts
= Amps (single phase)
(
Watts x .557) divided by
(Volts) = Amps (3 phase)
TC-093
COMMON TERMS
Volts x amps = watts.
Volts divided by amps
= ohms (resistance)