64
PHTM II
Combi Installation, Operating & Service Instructions
110331-07 - 8/23
1. Boiler Control
Control simultaneously modulates blower speed
and gas valve position to control firing rate and
sequences up to three pumps and a 3 way valve
to respond to DHW and CH demands.
2. Flame Supervision/Air-Fuel Ratio Control
Control is a "Gas-Adaptive system" that regulates
air and gas flow mixture by measuring flame
signal and adjusting gas valve to achieve target
air fuel ratio. This eliminates need to make throttle
screw or offset adjustments. This system is self-
calibrating and continuously maintains air fuel
ratio at desired value.
3. Domestic Hot Water
DHW demand is detected by a DHW flow sensor.
When a DHW draw greater than 0.5 gpm is
detected, control diverts all boiler water flow
through plate heat exchanger, starts boiler pump
and modulates firing rate based on measured
DHW temperature and DHW set-point. When there
is a DHW demand, system pump will be turned
off, boiler services only DHW. Priority protection
is provided to ensure heating system is also
serviced.
4. DHW Recirculation
When "Recirculation (Comfort) Mode" is selected
(from Quick Menu
A
) a recirculation sensor and
auxiliary thermostat input are monitored and a
recirculation pump is controlled via aux pump
terminals in order to maintain a warm DHW loop.
Recirculation can reduce time needed for hot
water to appear at a fixture. Refer to internal
wiring diagrams Figures 20-1 and 20-2 for
recirculation pump and sensor connections and
piping diagram Figure 11-3 for recommended
piping layout.
5. Central Heat
CH demand is detected by a heating thermostat
call for heat. When CH demand is detected,
control diverts all boiler water to CH zones, starts
boiler pump and modulates firing rate based on
measured supply sensor and CH setpoint. When
DHW recirculation is not used control can accept
a second heating thermostat wired to the Aux
T'stat input. CH demands have separate setpoint
and maximum modulation rates.
6. Sensorless Reset
Control system monitors recent firing rate and
burner cycle data to infer current building heat
loss. Target supply water temperature is then
adjusted to match this heat load. No outdoor
sensor mounting or wiring is required. Boost
feature increases operating temperature setpoint
by 10°F (5.6°C) every 20 minutes CH demand
is not satisfied. This process will continue until
heat demand is satisfied (indoor air is at desired
temperature), or CH setpoint is reached. Once
heat demand is satisfied, operating setpoint
reverts to value determined by the Outdoor Reset
settings.
7. Pump Exercise
Connected pumps are automatically run for a 20
second exercise period after not being used for
longer than 7 days. This helps prevent pump rotor
seizing.
8. Pump Air Elimination (Pump Purge)
Pump purge is entered when power is cycled or
when there has been an over temperature hold.
During this state boiler pump and three way
valve cycle in sequence for two minutes to help
remove air from boiler water piping. This may be
interrupted by pressing the
!
reset
button
.
9. Built-in Safety Control
Control includes functions designed to ensure
safe and reliable operation. In addition to flame
supervision, control monitors supply water
temperature, differential water temperature, and
flue temperature safety limits. Boiler modulation
is adjusted when required to help avoid loss
of boiler operation due to exceeding limits.
Additionally, control accepts field installation of
external limits.
10. Fuel Conversion
The conversion from Natural Gas to LP Gas (or
vice versa) is made by changing gas valve setting
and a control parameter change on display.
11. Compatible with Multiple Boiler Sequencer
The control is compatible with multiple boiler
sequencer peer-to-peer networks. Control can
be connected to up to eight (8) boilers using
RJ45 Ethernet cable. Combi goes "on leave" from
network when DHW demand is present.
Control System Overview
The control manages all of the following boiler
functions:
16
Operation
(continued)
This section covers control features available via local display. For additional control features available via our App,
see Extended Features Manual available on our website or in our App.