Installation and Operation Manual
TFTN 085-199
44
10.3 Boiler System Plumbing
The TFTN boiler uses a low mass heat exchanger that requires a minimum rate of forced water circulation any time the
burner is operating (See Table 10-2 for minimum flow rate requirements). To ensure the minimum flow rate is attained,
NTI strongly recommends installing the boiler
in a “Primary/Secondary” plumbing configuration utilizing “Closely Spaced
Tees”
or a “Low Loss Header”
to de-couple the Boiler-Primary loop from the System-Secondary loop(s). See the examples
of Primary/Secondary Loop configurations in Figures 10-3 through 10-8.
Table 10-2 Minimum Flow Rate Requirements (at Max Power)
Model
Flow (US gpm)
Model
Flow (US gpm)
TFTN085
3.5
TFTN285
11
TFTN110
4.4
TFTN340
13
TFTN150
6
TFTN399
15
TFTN199
8
Failure to ensure the minimum water flow rate through the boiler when the burner is operating
will result in “short
-
cycling”, reduced performance and operating efficiency, and may also cause
overheating and premature failure which will void the warranty. Failure to follow instructions may
result in fire, property damage, serious injury or death.
Circulator Pump Outputs
–
TFTN boilers are equipped with four (4) dedicated 120VAC pump outputs:
1.
BLR PUMP
–
operates during CH, DHW or Buffer Tank demands.
2.
DHW PUMP
–
operates during DHW demand only.
3.
AUX1 PUMP
–
configurable as None, System Pump, DHW Recirc (pump) or Buffer Tank (pump) via parameter Auxiliary
Pump 1 Selection (24.7.0). Default setting = None
•
When configured as System Pump, the operation of the output is dependent on the setting of parameter System
Pump Activation Logic (24.4.6); when set to CH Only, the output only turns on during CH demands. When set to
Always Active, the output will also turn on during DHW demands if DHW Mode (24.5.2/24.5.3) is configured as
Downstream IWH (24.5.2 = Tank Sensor or Aquastat and 24.5.3 = CH Only).
•
When configured as DHW Recirc, the output turns on when the DHW Recirc temperature drops below the DHW
Recirc Setpoint (24.20.5/24.20.6).
•
When configured as Buffer Tank, the output turns on when the buffer tank temperature drops below the Buffer
Setpoint (20.0.3) if Buffer Tank Function (20.0.0/20.0.7) is set to Fixed or Variable Temperature.
4.
AUX2 PUMP
–
configurable as None, System Pump, DHW Recirc (pump) or Buffer Tank (pump) via parameter Auxiliary
Pump 2 Selection (24.7.1). See AUX1 PUMP for description of how output functions. Default setting = System Pump.
NOTE
: Buffer Tank and DHW Recirc temperature inputs connect to the boiler at sensor inputs
AUX1 NTC
and
AUX2 NTC
,
which are configured via parameters Auxiliary Sensor 1 (24.6.1) and Auxiliary Sensor 2 (24.6.2).
NOTE
: Use of these circulator outputs will depend on the system configuration selected; see Figures 10-3 through 10-8.
For further pump output details and wiring instructions see Section
Circulators responsible for forcing water flow through the boiler must be sized to account for the
head loss of the boiler and boiler piping at the required flow rate; see Table 10-3 and Figure 10-2.
Zone Outputs
–
in addition to the four (4) dedicated circulator outputs, the TFTN is also equipped with three (3) zone outputs
(
ZONE 1
, ZONE 2 &
ZONE 3
), each activating when the respective zone’s room thermostat calls for heat
(via inputs
T-
STAT #1
,
T-STAT #2
&
T-STAT #3
). The zone outputs deliver the power that is applied to terminal
ZONE INPUT
(see Figures
10-3 through 10-8). Each output is protected with a 5 Amp fuse.
NOTE
: when supplying terminal
ZONE INPUT
with 24VAC from the boiler’s 24V Supply (as depicted in
Figures 10-3, 10-4
and 10-5), the circuit is further protected by the 2 Amp fuse located on the Low Voltage Connection Board.
