Troubleshooting │ Vmax I&O Manual
Current target temp (User Menu reading 1-01) by 10ºF. Current target temp for a DHW Tank demand
is equal to DHW setpoint + 50ºF; if necessary increase DHW setpoint (Installer Menu setting 2-07) –
130 to 140ºF recommended.
o If the radiator symbol is flashing on the display, the DHW priority time may have expired. Cycle power
and consider increasing the DHW priority time (Installer Menu setting 2-09) and/or DHW setpoint
(Installer Menu setting 2-07).
o If the faucet symbol is flashing on the display, verify the DHW circulator is operating – DHW circulator
should be wired to DHW PUMP and L2 NEUTRAL (boiler terminals 11 and 14/15); see Figure 12-2.
o Verify plumbing is in accordance with instructions in Section 10.0.
Indirect Tank with Tank Thermostat (Not Applicable for VM110P):
o Verify DHW Mode is set to 2 (Installer Menu setting 2-08).
o Verify there is a Tank thermostat wired to COMMON and DHW (boiler terminals 3 and 6), see Figure
12-2.
o Verify there is a demand from the thermostat; when the demand is on, DHW temp (User Menu reading
1-03) will indicate “CLOS”; when demand is off, DHW temp will indicate “OPEn”. If uncertain about
thermostat operation, place a jumper between terminals 3 and 6; the faucet symbol will flash on display
when there is a DHW demand.
o Compare DHW setpoint (User Menu reading 1-04) with the boiler outlet temperature (displayed on
Main Screen); burner demand starts with the boiler outlet temperature drops below the DHW setpoint by
10ºF. If necessary increase DHW setpoint (Installer Menu setting 2-07) – 160 to 190ºF recommended.
o If the radiator symbol is flashing on the display, the DHW priority time may have expired. Cycle power
and consider increasing the DHW priority time (Installer Menu setting 2-09) and/or DHW setpoint
(Installer Menu setting 2-07).
o If the faucet symbol is flashing on the display, verify the DHW circulator is operating – DHW circulator
should be wired to DHW PUMP and L2 NEUTRAL (boiler terminals 11 and 14/15); see Figure 12-2.
o Verify plumbing is in accordance with Section 10.0.
4) Display Normal but DHW is not hot enough – perform the following steps:
Increase DHW setpoint (Installer menu setting 2-07):
o Indirect Tank with Tank Sensor (DHW Mode = 1) – recommended setting = 130 to 140ºF.
o Indirect Tank with Tank Thermostat (DHW Mode = 2) – recommended setting = 160 to190ºF.
Vmax VM110P – DHW flow rate is too great; NTI does not recommend exceeding 4 GPM. If necessary,
restrict overall DHW flow rate.
Indirect Tank – verify plumbing is in accordance with Section 10.0.
5) Display indicates an error (Err), lockout (Loc) or warning (Att); reference Table 17-3 in Section 17.0.
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