General & Safety Information; Description Of Heater; For Whom Is This Manual Intended - andrews MAXXflo EVO CWH 90/302 Installation And Maintenance Manual

1.0 GENERAL & SAFETy INFORMATION

1.1 DESCRIPTION OF HEATER

This Andrews Water Heaters MAXXflo EVO is a gas fired, low NOx, twin heat engine, cascading, direct fired
water heater, with an integrated stainless steel tank.
Fully automatic electronic controls are integrated into the heater, with a wide range of control and sensor
options available. The controls also provides voltage free outputs for Enable, Burner On and fault indication.
Full BMS integration is available through the use of Modbus and optional protocol devices.
Access to the controls of the heater via the internet and/or mobile phone app, is possible through an optional
web server device available from Andrews Water Heaters.
Each heat engine module consists of a stainless steel combustion chamber, premix burner, modulating fan,
gas valve, ignition and flame detection electrodes, water pressure sensor and a NTC flue sensor for safety
supervision.
Each heat engine module is equipped with NTC sensors for precise temperature control on flow and return
manifolds. Fully premixed, radiating, modulating burner, integrated with gas valve to deliver precise gas/air
mixture throughout the full modulation range.
Common combustion air intake manifold, takes air from boiler room (type B23 flue) or directly from outside
via a combined flue system (C13, C33, C53 & C63).
The safety and operation functions of each heat engine are managed by micro processor controlled circuit
boards, one for each heat engine. The upper controller also acts as the cascade master controller, modu-
lating the heat engines according to the demand, based on data from the systems sensors. Control is per-
formed using comparison parameters between the requested temperature and the global flow temperature.
Control Logic:
When a demand is started (the sensor of the DHW tank is less than the set point of the DHW tank - Hyster-
esis), the heat engine is ignited quickly (in the case of the MAXXflo EVO 90 & 120 the second heat engine
starts approximately 60 seconds after the first heat engine ignition). The controls calculate the charge set-
point (factory standard is the setpoint of the DHW tank + 3 C) and the heat engine (s) modulate the pump (s)
O
and burner (s) so that the charge temperature in the tank does not exceed the charge set point.
When the temperature at B3 sensor equals the set point of the DHW tank, the burner (s) are switched off
during operation and the control elements remain in stand-by until the heat demand is restored.
If the temperature of the DHW tank (B3 sensor) is less than the DHW setpoint - DHW hysteresis, the de-
mand will be restarted and the operation as described above will start again.

1.2 FOR wHOM IS THIS MANuAL INTENDED?

This manual is intended for the heating specialist who installs commercial/industrial heating plant and equip-
ment.
General 4 MAXXflo EVO