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 28 of 44
Problem Probable Cause Corrective Action
Unable to
adjust system
temperature.
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. Confirm hot water and cold water supply pressures are nominally equal.
Correct supply pressure differential greater than 15 psi.
c. Check for air locks and closed valves.
d. Confirm installation and location of check valves is correct. Refer to
schematics. Ensure that check valves are fully functional.
e. Blowdown strainers, then remove and thoroughly clean all strainer screens.
f. Confirm return temperature is at least 2°F below DRV set point.
g. Check the steam pressure at the heat exchanger shell. If the steam pressure
is decreasing under normal conditions, there may be insufficient steam
available to meet the hot water demands.
DRV fault. See DRV Troubleshooting Guide in the following section.
No display on
DRV
and/or
no control.
System fault.
a. Confirm uninterrupted power to Digital-Flo
®
control panel.
b. Check status of DRV power switches on the Digital-Flo
®
control panel.
DRV fault. See DRV Troubleshooting Guide in the following section.
Digital-Flo
®
“bangs” and
“hammers”
during
operation.
System fault.
a. Steam pressure has dropped and a vacuum has formed inside the heat
exchanger. Increase steam pressure or reduce water flow through the heater.
b. Water pressure has dropped below the steam pressure and steam is forming
inside the tubes. Increase water pressure or water flow through the heater.
Heat exchanger fault.
a. The shell of the heat exchanger is not properly drained. Confirm condensate
is draining freely (steam trap is not blocked & return line is not pressurized).
b. Remove and inspect tube bundle for tube or seal failures.
Water leaking
from DRV.
DRV fault.
a. Check all DRV seals for wear and/or damage. Clean, lubricate or replace.
b. Body casting failure – replace DRV.
Digital-Flo
®
Troubleshooting Table – continued