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GLOSSARY OF TERMS AND SYMBOLS
This glossary of terms and symbols is provided to assist you in understanding some of the
language used throughout this manual.
dB(A) - sound pressure level in decibels, “A” range
DC - direct current
AC - alternating current
WFCD - water flow control device
FB - feedback information
Hz - hertz
IC - integrated circuit
BTU/H - British thermal units per hour
PSI - Pounds per square inch
LED - light emitting diode
GPM - gallons per minute
mA - milliamps
W.C. - inches of water column
mm - millimeters
NOx - oxides of nitrogen NO & NO
2
OHS - overheat switch
PCB - printed circuit board
CPU - central processing unit
POT - potentiometer
rpm - revolutions per minute
SV - solenoid valve
Ø - diameter
∆°F - delta T or temperature rise above ambient
POV - modulating valve
TE - thermal efficiency
TH - thermistor
T
IN
- temperature of incoming water
T
out
- temperature of outgoing water
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