Fluid Circulation Pump
©Aqua-Hot®
250-D03 Diesel Series Service Manual
REV 220302
p. 32
Circulation and Stir Pump
Introduction:
The fluid circulation pump operates to provide fluid
circulation to either the interior heating zone or the antifreeze
boiler tank depending on the heating and hot water needs at the
time. It is used when interior heat is demanded by circulating
propylene-glycol and water through the heating loop. It is used
to stir the fluid mixture in the tank to ensure optimal hot water
performance. The pump will also circulate the tank fluid while
the burner cycles on to ensure that the tank is completely and
evenly heated during a normal operating cycle.
Troubleshooting Condition:
Troubleshoot the circulation pump if the following conditions
have occurred:
• A lack of interior heat.
• Lack of hot water or supply is uneven.
Troubleshooting Procedure:
Follow the procedure to diagnose the fluid circulation pump.
1. Verify the following before troubleshooting the circulation
and stir pump:
• The ETS module is calling for heat
• The interlock switch is depressed
•
The overflow bottle is adequately filled
• The high-limit thermostats are not tripped
• There are no faults on the LCD screen.
2. Locate the LCD screen. Navigate to the TESTING page
(Figure 52a). Activate the internal circulation pump and if
necessary, the boost pump.
3. If the pump activates, navigate to the FAULTS page (Figure
52b).
• If there are any pump over-current faults displayed,
replace the circulation pump.
• If no faults, the pump is operating as intended.
Figure 51
Figure 53
Zone and Stir Pump
4. If the circulation pump does not activate, navigate to the
TEST screen and activate the internal circulation pump.
5. Using a multimeter, test for voltage between pins J6-7 and
J6-8.
• If there is voltage at these pins, the pump will need to
be replaced.
• If there is no voltage at these pins, replace the Aqua-
Hot controller.
Figure 52b
Figure 52a
