Trinity
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Installation and Operation Instructions
Ti Series
32
10.0 COMBI BOILER DHW PLUMBING AND OPERATION
The Trinity Ti boiler comes in two versions; Standard (non-Combi) and Combi. Both versions are designed to provide Space and
Domestic Hot Water (DHW) heating. To provide DHW heating, the Standard version must be installed in combination with an
Indirect Fired Hot Water Heater, see Figure 10-2 for installation details. The Combi version of the Trinity incorporates an indirect
fired DHW heat exchanger (Brazed Plate) and the controls necessary to heat DHW without requiring the addition of an Indirect
Fired Hot Water Heater. The Combi option is only available on models Ti150 and Ti200, as smaller units would not produce
adequate DHW.
The Trinity Combi is designed for installations where there is a limited DHW demand, such as smaller apartments and condos. In
applications where there is a greater DHW demand NTI recommends the Combi in conjunction with a DHW storage tank (Figure
10-2), or a Standard Trinity in conjunction with and Indirect Fired Hot Water Heater (Figure 10-2).
DHW Description of Operation
The Trinity Combi heats domestic hot water on demand, indirectly, using a brazed plate heat exchanger. Using the factory
supplied and field installed flow switch, the Trinity Combi recognizes a DHW demand when the flow switch provides a contact
closure to terminals A-C on the top of the boiler; the contacts of the flow switch close at a DHW flow rate of approximately 0.5
gpm or greater. Once the flow switch contact is made, the Combi immediately goes into DHW mode regardless of the status of the
Central Heating system (with the exception of an Er5 DHW lockout, see troubleshooting section). The burner fires and the Combi
attempts to achieve a boiler temperature equal to the programmed “LO” setting (See Section 12.0). The LO setting is accessed via
the menu in the Sentry 2100 controller, and should be set at a value sufficient to heat the potable water, i.e. 150-165ºF. NTI
provides a Thermostatic Mixing Valve adjustable from 100 to 145°F; the mixing valve shall be installed between the Combi DHW
outlet fitting and the hot water supply pipe to the fixtures (See Figures 10-1 and 10-2), thus providing user protection from
scalding hot water.
Code requirements may require the maximum setting of the Thermostatic Mixing Valve to be fixed at
120°F or lower, see “Thermostatic Mixing Valve” below and the instructions included with the valve.
Combi DHW Plumbing & Set-up
DHW Inlet & Outlet Connections –
The Trinity Ti Combi has two potable water connections, Inlet & Outlet, which exit the left
side of the Trinity Cabinet; on the inside of the cabinet the two lines are connected to the Brazed Plate Heat Exchanger; see
Figures 10-1(c) and (d) for identification of the DHW Inlet and Outlet fittings. See Figures 10-1 and 10-2 for installation details.
Thermostatic Mixing Valve –
A Sparcomix AM101-US-1 is provided with your package. This valve regulates the water
temperature leaving the plate heat exchanger, and must be used in every instance. The dial can be set to the desired temperature
required. Consult the Honeywell manual SD/IS150 for detailed instructions and settings. (Note: the valve must be set to a supply
temperature of not more than 120˚F. It is the responsibility of the installer to set the valve and remove the dial.)
Scald Hazard
- Hotter water increases the risk of scald injury. There is a hot water scald potential if the
thermostatic mixing valve is set too high. Be sure to follow the adjustment instructions provided with
the thermostatic mixing valve. Failure to follow these instructions may result in serious injury or death.
DHW Filter –
Install a 100 micron or lower filter prior to the entrance of the DHW flow switch. Failure to protect the flow switch
from dirt and debris will cause it to malfunction.
Check Valve –
A check valve must be field provided and installed on the outlet of the mixing valve to prevent expansion devises
down stream from back flowing when the water pressure drops during cold water draws. Failure to prevent the backflow will
cause water to flow forward through the flow switch, activating it, when the cold-water draw has ended and the water pressure
increases.
Throttling Valve –
Install a throttling valve, after the mixing valve, to regulate the maximum hot water flow rate. The Combi is
limited to a firing rate of 150MBH (200MBH for Ti200C); therefore excessive flow rates will result in cooler hot water
temperatures.
Drain and Isolation Valves –
Install drain and isolation valves on the inlet and outlet of the brazed plate heat exchanger, as shown
in Figures 10-1 and 10-2 so it can be flushed free of possible build-up caused by dirt or hard water.
Hard Water –
To prevent the formation of scale on the inside of the brazed plate heat exchanger and other components in the
domestic hot water system, water with hardness higher than 50 ppm Calcium Carbonate must be treated with a “Water Softener”
prior to entering the appliance. Plugging of the domestic system by scaling or accumulation of dirt is not the responsibility of NY
Thermal Inc., and suitable steps shall be taken to avoid it.
