Armstrong Digital-Flo DF41540, Installation, Operation & Maintenance Manual

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Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstrong international.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. (269) 279-3602 Fax. (269) 279-3130
Page 26 of 44
Problem Probable Cause Corrective Action
Unable to bring
Digital-Flo
®
up
to temperature.
System fault.
a. Open steam isolation valve.
b. Increase steam pressure. Do not exceed 15 psi.
c. Reduce domestic water flow rate.
d. Correct condition causing high temperature shutoff valve to close.
e. Open steam trap isolation valve, if equipped.
f. Steam trap is blocked. Disassemble trap and clear blockage(s).
g. Back pressure in the condensate line may be too high. Temporarily
disconnect the pipework downstream of the steam trap. While running the
condensate to drain, determine if the hot water comes up to temperature. If
so, investigate potential problems on the condensate return system or install
a pump trap to overcome the higher back pressure.
h. A check valve may be defective and requires replacement. If the re-circulation
line is not hot, a failed check valve may cause cold water to bypass the heat
exchanger.
DRV fault.*
DRV Troubleshoot
Guides.
See DRV Troubleshooting Guide in the following section.
Heat exchanger fault.
a. Vent trapped air (gases) from heat exchanger shell.
b. Clean scaled or fouled heat exchanger tubes.
Water from
Digital-Flo
®
is
too hot.
System fault.
a. Reduce steam pressure
b. Steam is superheated – reduce superheating.
DRV fault.*
DRV Troubleshoot
Guides.
See DRV Troubleshooting Guide in the following section.
System
temperature
rises during
periods of
no system
demand.
System fault.
a. Confirm continuous recirculation of at least 5 gpm to each DRV40, and at
least 10 gpm to each DRV50 or DRV80.
b. Check for air locks and closed valves.
c. Blowdown strainers, then remove and thoroughly clean all strainer screens.
d. Confirm return temperature is at least 2°F below DRV set point
e. Confirm installation and location of check valves is correct. Refer to
schematics. Ensure that check valves are fully functional.
f. Verify hot water and cold water supply pressures are balanced and constant.
Ensure that there is adequate mixed return flow to the cold water inlet of the
water heater.
g. Rule out that a higher temperature cross-connection (from kitchen or laundry
loop) is feeding water into the return line. Eliminate cross-connections.
DRV fault.*
DRV Troubleshoot
Guides.
See DRV Troubleshooting Guide in the following section.
Digital-Flo
®
Troubleshooting Table:
*Add DRV T-Shoot Guides