Rinnai 37AHB SERIES Installation, Operation And Maintenance Manual page 13

Installation
Piping Configuration
When employing a Tankless Water Heater in a
combination hydronic hot water heating system, the
system is considered an Open Loop System; i.e. the
system must be configured to simultaneously deliver
both domestic hot water and space heating. By
definition, if the circuit is sealed off from the
atmosphere at all locations (as is true for most modern
hydronic systems) it is called a closed loop system.
Conversely If the circuit is open to the atmosphere at
any point, it is called an open loop system. Current
Rinnai tankless products are not certified for closed
loop applications. Furnaces may be used in closed
loop application only with the new Rinnai Condensing
Boilers. Refer to Boiler Manuals for more details.
Open Loop System
If piping is done in accordance with the recommended
schematic diagram shown in Figure 11, the following
purge and priming procedure applies.
PURGING AND PRIMING THE SYSTEM:
The following procedure describes how the Rinnai®
system may be piped to eliminate the need for a
"purge cart" to fill the system and remove entrapped
(DV)
Field Supplied Ducting
- Typical Piping Arrangement For Direct Space Heating and Domestic Water Supply with Tankless
Figure 11
Water Heater. Open Loop
(BV)
All piping to be 3/4 inch.
Field Supplied
Evaporator Coil
Rinnai Corporation Hydronic Furnace (37AHB) Manual
air bubbles.
STEP 1: CLOSE the air separator venting valve.
STEP 2: CLOSE ball valve 3 (BV
STEP 3: OPEN drain valve 3 (DV
MUST be connected and draining to a sink, drain or
outdoors.
STEP 4: CLOSE drain valves 1 & 2 (DV
and OPEN ball valve 2 (BV
STEP 5: OPEN cold water supply main valve (ball
valve 1 - BV ). The system will begin the prime/purge
1
process using the street pressure. Entrapped air
bubbles being pushed out of the system will be evident
by a slight vibration of the discharge hose connected
to drain valve 3 (DV ). The hose will stop vibrating
3
when laminar flow is achieved.
STEP 6: CLOSE drain valve 3 (DV
STEP 7: OPEN ball valve 3 (BV
purged, primed and ready to go.
STEP 8: OPEN the air separator venting valve.
Note: For an open loop system, use expansion tank
approved for potable water use only.
);
3
) to which a hose
3
and DV
1
).
2
);
3
). The system is now
3
)
2
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