Page 18 ZC-KI6_VSS1709
is driven from the control through the 8-
gang relay.
Insufficient or no heat
• Plugged air filter or coil. Refer to
Maintenance section for filter care
and coil cleaning.
• Air in heating loop; purge system.
• Inlet and outlet connections to air
handler backwards; reverse
connections.
• Water heater supply tube (dip
tube) is restricted or damaged;
check and/or replace.
• Supply water temperature set too
low or not calibrated properly;
check water temperature. In the
case of water heater; If the
temperature has been set low
because of homeowner
preference, it may be necessary
to install an anti-scald valve to
control the faucet temperature and
raise the operating temperature of
the water heater.
• Restrictions in heating loop;
remove restrictions, check valve
stuck, isolation valves too
restrictive, left partially closed after
purging or closed valve.
Cold water at hot faucet
When heat source is a water heater, the
most probable cause is reverse flow
through the heating loop from a stuck
check valve or a faulty single-lever faucet
somewhere in the home; repair or
replace valve.
Fan runs for cooling but not heating
Room thermostat may be connected
improperly. Refer to Electrical section or
wiring schematic on air handler for
proper installation.
Heating during Standby Mode
Probable cause is thermal siphoning.
See check valve description for details;
repair or replace check valve. Check
elevation of air handler above water
heater to see if motorized valve required
for positive shut-off.
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