Instruction manual
6
Servicing should only be performed by a Qualied Service Agent
VENTING
This section of the Service Manual is not a complete venting installation instruction. Refer to the Instruction Manual that came with
the boiler/water heater; ensure the venting has been installed per all Instruction Manual requirements. Failing to install the factory
provided vent and/or intake air terminations, exceeding the maximum equivalent vent and/or intake air piping lengths, adding too
many elbows to the intake air and/or vent pipes, installing the wrong vent intake air pipe size, will cause operational problems,
improper combustion, rough starting/operation and Control System lock out costs to correct installation errors are not covered under
the limited warranty.
GENERAL VENTING INFORMATION
The boilers/water heaters covered in this manual are operationally equivalent to Category IV appliances and may be installed in
either a Power Vent or Direct Vent conguration.
Category IV Appliance
Category IV appliances operate with a positive vent (exhaust) static pressure and with vent gas temperatures low enough to produce
condensate in the vent piping.
Power Vent Conguration
Power Vent congurations derive all combustion air from the room where they are installed and discharge all ue gases to the outdoor
atmosphere through a sealed vent (exhaust) pipe. Power vent congurations have one vent pipe connected to the boiler/water heater
which can be terminated in a vertical or horizontal arrangement.
Direct Vent Conguration
Direct Vent congurations derive all combustion air directly from the outdoor atmosphere through a sealed intake air pipe and
discharge all ue gases to the outdoor atmosphere through a sealed vent (exhaust) pipe. Direct Vent congurations have two pipes
connected to the boiler/water heater, one vent pipe and one intake air pipe. Direct Vent congurations can also be terminated in a
vertical or horizontal arrangement.
WATER PIPING
Ensure all water piping requirements, diagrams and piping installation instructions contained in the Instruction Manual that came with
the boiler/water heater have been observed and followed. Factory installed pumps on XB boilers/XWH water heaters are sized for
up to a maximum of 25 equivalent feet (7.6 m)of outlet (supply) and inlet (return) piping; 50 equivalent feet (15.2 m) total. Exceeding
these limitations will lead to Control System lock outs and can permanently damage the boiler/water heater's heat exchangers. A
bypass line must be installed between the outlet and inlet piping of the boiler/water heater on the "system side" of the boiler/water
heater's circulation pump to prevent condensation on the copper heat exchanger.
TEMPERATURE RISE & FLOW RATE
Water ow rates through the boiler/water heater are critical. Flow rates that are too low may cause excessive lime/calcium accumulation
inside the heat exchanger; while ow rates that are too high can lead to velocity erosion that can eventually cause water leaks. Boiler/
water heater efciency is also affected by ow rates. Measuring the actual water ow rate (gallons per minute) through the boiler/
water heater is often impractical in the eld. Because the temperature rise through the boiler/water heater is directly linked to the ow
rate and is simple to measure, temperature rise is commonly used to conrm proper ow rates.
Temperature rise is calculated by subtracting the inlet water temperature from the outlet water temperature. Temperature rise is
commonly referred to as the "Delta T" and expressed as ΔT. The temperature rise through the boiler/water heater should be set
between 20° F and 30° F. Temperature rise (ow rate) is set by throttling a ow control valve installed in the boiler/water heater's outlet
(supply) water line with the boiler/water heater ring at 100%. Never attempt to throttle the outlet valve unless the boiler/water heater
is ring at 100%. Valves on the boiler/water heater's inlet (return) water line must never be throttled and left fully open at all times
except when servicing the boiler/water heater. The outlet temperature, inlet temperature are shwon on the display system. Delta T
(ΔT) must be below 75° F. If this is exceeded, the display will show an alert and the individual burner will lock out.