HTP 399M - Manual (Page 21)

21
G. HYDRONIC PIPING WITH CIRCULATORS, ZONE VALVES, AND MULTIPLE BOILERS
This boiler may function in a closed loop 15 psi system. A factory installed water pressure switch ensures adequate pressure in the
system. The boiler will not operate without a minimum of 10 psi water pressure. This assures you that if the system does have a leak,
the boiler will lock out (PRO on the display) before it damages the heat exchanger.
The included temperature and pressure gauge allows the user to monitor the system pressure and outlet temperature from the boiler. It
is important to note that the boiler has a minimal amount of pressure drop that must be calculated when sizing the circulators. Each
installation must also have an air elimination device that will remove air from the system.
Install the boiler so the gas ignition components are protected from water (dripping, spraying, etc.), and allow clearance for basic
service of the circulator, valves, and other components.
Observe minimum 1” clearance around all un-insulated hot water pipes when
openings around pipes are not protected by noncombustible materials. On a boiler installed above radiation level, some states and local
codes require a low water cut off device (See Part C this section). If the boiler supplies hot water to heating coils in air handler units,
flow control valves or other devices must be installed to prevent gravity circulation of boiler water in the coils during the cooling cycle.
Chilled water medium must be piped in parallel with the boiler.
Freeze protection for new or existing systems must use glycol specifically formulated for hydronic systems that includes inhibitors to
prevent the glycol from attacking the metallic system components. The system should be check annually, and as recommended by the
glycol producer, to ensure that the system is operating with the correct glycol concentration and inhibitor level. Allowances should be
made for the expansion of glycol solution in the system, as 50% by volume glycol solution expands 4.8% in volume when increasing in
temperature from 32oF to 180oF, while water expands 3% over the same temperature rise.
The boiler should not be operated as a potable hot water boiler. Operating this boiler as a potable water boiler will VOID warranty.
The basic steps listed below provide a basic installation guide for the boiler.
1. Connect the sy
stem return marked “Boiler In”.
2.
Connect the system supply marked “Boiler Out”.
3. Install purge and balance valve or shut off valve and drain on system return to purge air out of each zone.
4. Install a back flow preventer on the cold feed make-up water line.
5. Install a pressure reducing valve on the cold feed make-up water line, (15 psi nominal on the system return). Check temperature and
pressure gauge, which should read minimum pressure of 12 psi.
6. Install a circulator as shown in piping details (this section). Make sure the circulator is properly sized for the system and friction loss.
7. Install an expansion t
ank on the system supply. Consult the tank manufacturer’s instruction for specific information relating to
expansion tank installation. Size the expansion tank for the required system volume and capacity.
8. Install an air elimination device on the system supply.
9. Install a drain valve at the lowest point of the system. NOTE: The boiler cannot be drained completely of water without purging the
unit with an air pressure 15 psi.
10. The safety relief valve is installed at the factory. Pipe the discharge of the safety relief valve to prevent injury in the event of
pressure relief. Pipe the discharge 6” above the drain to a drain. Provide piping that is the same size as the safety relief valve outlet.
Never block the outlet of safety relief valve.
H. CIRCULATOR SIZING
The heat exchanger has pressure drop which must be considered in your system design. Refer to the graph in Figure 6 for pressure
drop through the heat exchanger for rec
ommended pump selection at a 20∆t design.
The chart below represents various system temperatures and their respective flows and friction loss through the boiler, which will aid
circulator selection.