Instruction Manual

THREE EASY
STEPS
STEP 2 - (continued)
Variable Air V
olume units (VAV)
The "Thermo-V" electric heater developed by Thermolec eliminates the common problems that are
encountered in the application of an electric heater to a
VAV box as described below:
A. When the V
AV Box is in the minimum opening position, the air flow is often below the minimum
required to operate a standard electr
ic heater, causing element o
v
erheating and possible tr
ipping of
the thermal cut-outs. The common solution is to increase the minimum ventilation air flow to
accommodate the minimum air flo
w required to operate the heater which translates into energy waste.
B. The static pressure in the duct downstream is so lo
w that even the most sensitive pressure
differential switch is unable to detect sufficient pressure to activate the electric heater.
The common solutions are:
1. To create an artificial pressure by adding restrictions at the outlet (perforated plate), which
creates a costly and unnecessary pressure loss when the box is in a fully open position.
2. To measure the pressure upstream of the
VAV box, which could be dangerous
, since, with a
restricted or totally closed bo
x, there is pressure without air flow.
The electric heater will ha
ve to
rely solely on it’
s safety thermal protections to shut off.
Common Pr
oblems Encountered