FTV I&O Manual
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Boiler and Heating System Piping
41
Boiler System Plumbing
FTV boilers use 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 10-6 through 10-9.
Table 10-2 Minimum Flow Rate Requirements
Model
Flow
(US gpm)
The flow rate through the FTV-Combi is determined by
the available head of the internal pump (see Figure 10-4).
When piped “Direct to Zones” the boiler flow rate will be influenced by the
piping losses of the distribution system; to avoid no/low occurances, set the
manual bypass valve to “MAX” (see Figure 10-3).
When piped Primary/Secondary the FTV-Combi boiler flow rate will be fixed
at approximately 8 GPM for space heating demands.
FTV110
4.4
FTV150
6
FTV190
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.
Circulating Pump Outputs
– FTV boilers are equipped with three 120VAC pump outputs:
1.
DHW PUMP – operates during a Domestic Hot Water (DHW) demand. The DHW PUMP output is not
used on Combi models.
2.
CH PUMP – operates during a Central Heat (CH) demand.
3.
BOILER PUMP – operates during any demand. The internal pump for Combi models is factory wired to
the BOILER PUMP output.
Use of these circulator outputs will depend on the system configuration selected; see Figures 10-6 through 10-9.
For further pump output details and wiring instructions see Section 12.0.
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 10-5.
Internal Circulating Pump (FTV-Combi Only)
– the FTV-Combi encorporates the ciculating pump
responsible for forcing water flow through the boiler, an can be utilized in one of two configurations:
1.
Primary/Secondary – the internal circulator drives flow through the boiler only; see Figures 10-8 and 10-9.
2.
Direct to Zones – the internal circulator drives flow through the boiler and the distribution system; see
Figure 10-10. This configuration is limited to zone valve (or non-zone circulator) distribution systems
with small flow requirements, i.e., systems requiring no more than 6 GPM at 9 ft. of head pressure. Plot
the expected head-loss of the distribution system against the “FTV-Combi Available Pump Head” curve
(Figure 10-4) to verify sufficient performance;
NOTICE:
if the available head from the internal pump
cannot support the needs of the distribution system, then a Primary/Secondary configuration must be
utilized.
Pressure Bypass Valve
– to avoid no/low water flow occurances in applications of the
FTV-Combi in “Direct to Zone” configurations must fully utilize the FTV-Combi’s
internal pressure bypass valve. The internal pressure bypass valve is utilized by
adjusting the manual bypass valve to “MAX”; see Figure 10-3.
