74
PHTM II
Combi Installation, Operating & Service Instructions
110331-07 - 8/23
19
Troubleshooting
(continued)
Table 19-1: Troubleshooting with No Active Fault Code (continued)
Indication
Possible Causes
Corrective Action
Water At Shower Or
Faucet Is Cold
Draw rate exceeds combi's rated
capacity.
Verify draw rate and temperature rise are both at
or below ratings shown in Table 3-1.
Draw rate below combi's rated
capacity.
Verify draw rate is above rating shown in Table
3-1.
DHW flow limiter is dirty or clogged.
Verify there is no debris or build up in flow limiter
and clean if present. Replace if necessary.
Defective 3-way valve.
Check 3-way valve can respond to CH and DHW
demands and has desired effect on water flow,
replace if necessary.
Defective 3-way valve wiring.
Check 3-way valve wiring. Correct if necessary.
Defective tempering valve.
Check tempering valve (field supplied) by
adjusting valve and observing output, replace if
necessary.
Tempering valve adjustment required.
Check setting on tempering valve (field supplied).
Control DHW setpoint too low.
Press + / - Display buttons to adjust DHW setpoint.
Defective DHW Flow Sensor
Check DHW Flow Sensor is functioning properly.
Plate heat exchanger dirty.
Check plate heat exchanger performance and
back flush if necessary. Replace if back flushing
does not improve performance.
Recirculation (Comfort) Mode is used
and Recirculation Pump is not On.
Recirculation pump is turned Off when calibration
is required. Pump operation will continue after a
calibration.
Boiling, Kettling, or
Water Hammer
Low Water flow through plate heat
exchanger.
Remove and inspect plate heat exchanger, flush
heat exchanger if required.
Air in system.
Cycle boiler power to initiate pump air elimination
function. Air is removed from boiler loop when
there are no "air noises" in the heat exchanger.
Low system water pressure.
Check boiler water pressure, adjust feedwater as
necessary.
Rough ignitions
Insufficient gas supply pressure.
Refer to Table 3-5 for required pressure range.
Dirty or defective burner.
Refer to Section 18 Service and maintenance for
proper procedure to check burner. Replace if
necessary.
Dirty or damaged ignitor/flame sensor
Check ignitor/flame sensor gap and distance
to burner. See Figure 18-2 and Table 18-3 for
distance specification Replace ignitor/flame
sensor if necessary.
Relief Valve
Opening
System pressure exceeds relief valve
setting.
Lower system water pressure below rating of
supplied safety relief valve.
Replace standard safety relief valve with higher
rated valve up to the maximum pressure of the
heat exchanger. 50 psig (345 kPa)
Improperly sized expansion tank.
