Enviro VDD User Manual

ENVIRO-TEC
25
FORM ET115.24-NOM12 (718)
ELECTRIC HEATER TROUBLESHOOTING GUIDELINES
Problem Possible cause Corrective action
Electric Heat
will not operate
CAUTION:
UNIT MAY BE
EXTREMELY
HOT. TAKE
GREAT CARE
WHILE
TROUBLE-
SHOOTING
Insufcient airow
Verify that airow is sufcient to provide a minimum of
70 CFM per kW of electric heat. Heater is not designed
to operate below 70 CFM/kW.
Loss of demand
Verify that heat command signal is not dropping out.
Re-view schematic. For standard heaters, verify 24VAC
at heater control ‘W’ terminal. For multi-stage units,
verify demand at W and S2 terminals. For units with
proportional heater control, verify analog signal at COM
and SIG terminals of Heat controller.
Loss of 24VAC Verify 24V at transformer and at ‘R’ terminal.
No airow
Electric heat will not operate unless fan motor is enabled.
Possible loose wiring. Verify integrity of wiring to TS1
terminal. Possible loss of fan command. Verify fan relay
is enabled - 24VAC at coil of fan relay. Possible bad fan
relay. If fan relay is enabled but doesn't actuate, replace
relay. Possible Hand-Off-Auto switch fault (if present).
If Hand-Off-Auto switch is in Hand position and 24VAC
doesn't pass to fan relay, replace HOA switch.
Primary limit switch tripped
Verify no loss of demand to unit. Verify that voltage
exists on magnetic heater contactor during demand for
heat. If demand reaches unit but not contactor, primary
limit is tripped. It is an automatic reset limit switch that
guards against overheating as a resulting of insufcient
air passing over the limit switch. The primary limit
switch(es) will auto-reset once the unit cools down. This
may take up to an hour. NOTE: dual blower units have
two heater racks and two primary limits.
Primary limit faulted or damaged
wire/wire harness
Remove power from unit. Wait for unit to cool down.
Disconnect primary limit wire or wire harness (refer to
wire diagram for unit.) Verify continuity across primary
limit. If primary limit is veried good, verify continuity
across wire or harness and to each side of primary limit. If
no continuity, replace wires or wire harness.
Secondary (high) limit switch
tripped
The secondary limit may be manually reset. If unit is hot,
wait for the heater to cool down. This may take up to an
hour. Reset switch(es). Verify if heater will start.
Improper wiring connections Verify wiring per wire diagram.
Open or damaged heater elements
With power removed, inspect the heating elements,
disconnect heater wire harnesses. (The harnesses with the
black plug.) Use a volto-ohm meter to measure resistance
across the electric heat power harness coming out of the
heater section. If the meter measures an open or shorted
circuit, replace with new elements.

Enviro VDD Specifications

General

Brand	Enviro
Model	VDD
Category	Fan
Language	English