Armstrong Digital-Flo DFS1540 Owner's manual

Digital-Flo®Semi-Instantaneous
Steam-to-Water, Shell and Tube,
Water Heater Installation Operation
& Maintenance Manual
789-EN
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these instructions.

2Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Table of Contents
Safety........................................................................... 3
General Description .......................................................... 4
Typical Piping Layout ........................................................ 5
Specifications ................................................................. 6-8
Dimensions .................................................................... 9
Precautions .................................................................... 10
Installation Requirements................................................... 11-16
Commissioning................................................................ 17-18
Safety Shutoff Valve.......................................................... 19
Periodic Maintenance........................................................ 20-23
Preventative Maintenance and Fitting Spare Parts...................... 24
Troubleshooting ............................................................... 25-33
Spare Parts .................................................................... 34-37
Steam Trap Assemblies...................................................... 38-39
Limited Warranty and Remedy ............................................. 40

3
Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Safety
Icon Legend
— DANGER! … Injury or death and property damage are imminent
— WARNING! … Injury or death and property damage are possible
— CAUTION! … Potential property damage, expensive repairs, and/or
voiding the equipment warranty may result
BURN HAZARD! Contact with steam, hot water, or hot metal surfaces can
cause severe skin burns. Skin exposure to 140°F (60°C) water or metal for
only five (5) seconds may cause a second degree burn.
If the instructions following a safety icon are not followed, adverse
consequences may occur – including property damage, personal injury, or,
in extreme cases, death.
General Safety Guidelines:
1. This product is designed and constructed to withstand conditions expected during normal use.
2. Inappropriate use of this product could cause damage to the product and other property. It may also result
in personal injury or, in extreme cases, death.
3. Installation or maintenance must be carried out in accordance with the instructions provided in this
product manual by designated, qualified and competent personnel.
4. Installation shall comply with all applicable federal, state, and local sanitary, construction, plumbing and
regulatory codes.
5. Improper installation, start-up, operation, maintenance, or service may void the warranty.
6. When installing, commissioning or servicing this product:
a. ALWAYS ensure that all steam and water supply, recirculation, and return lines are isolated.
b. ALWAYS carefully relieve any residual internal pressure in the system or connecting pipe work before
breaking or loosening any plumbing joints.
c. ALWAYS allow hot parts to cool before commencing work, to avoid the risk of burns.
d. ALWAYS wear appropriate personal protective equipment (PPE) before carrying out any installation or
maintenance work

4Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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General Description
Note: In this manual “DFSI” stands for “Digital-Flo Semi-Instantaneous” and is the brand designation.
DFSI is a semi-instantaneous-type of water heater, i.e., it heats on-demand with minimal on-board hot water storage. DFSI
transfers heat from steam to cold water and it precisely controls the blended hot water and cold/return water, discharge
temperature.
DFSI water heaters employ digital technology to monitor the inlet hot water supply, the mixed inlet cold/system return water, and
the blended water temperatures. DFSI is supplied pre-piped and pressure tested with an integral, digital re-circulating valve (The
Brain®– Models DRV40 / 50 / 80).
Two (2) inlet and two (2) outlet thermistors integral to the digital re-circulating valve (DRV) in addition to the time-proven, water
temperature control accuracy of the DRV eliminate the requirement for separate components typically associated with steam-to-
water, heat exchangers:
• PID temperature controller
• High temperature limit thermostat
• High temperature limit controller
• Cold water injection valve
• Internal circulating pump
• Compressed air requirement
All DFSI water heaters may be integrated into building automation systems (BAS) that communicate via Modbus RTU. In the
presence of other protocols (Modbus, BACnet™, and LonWorks™) SAGE™ can provide seamless monitoring, measuring, and
reporting directly to office PC’s or mobile apps.
DFSI is precision engineered and crafted with pride to deliver years of superior performance and customer satisfaction provided:
1. Installation, commissioning, operation and maintenance are in accordance with the recommendations provided in this product
installation and operation manual (IOM) in addition to generally-accepted plumbing, pipe-fitting and maintenance guidelines.
2. Periodic attention is given, as necessary, to maintaining the product, the accessory fittings & components and the overall
plumbing/distribution system in sound functional order.
Standard components include (refer to the Typical Layout diagram that follows for specific locations):
• The Brain®DRV40, DRV50, or DRV80 Digital Recirculating Valve
• Heat exchanger module (fabricated in accordance with the ASME Section VIII Division 1 Boiler and Pressure Vessel
Code, aka, an ASME “U-stamped” pressure vessel)
• Thermometers & Pressure Gauges
• Check valves
• Inlet strainer(s)
• Isolation valves
• Safety shut-off valve
An application-related, low surface temperature option is available that requires a secondary, steam control valve for conditions
where high mineral content water indicate excessive heat exchanger scaling could occur.
Note:
1. Because the DFSI is customizable, there may be optional components that are not addressed in this installation and operation
manual (IOM).
2. Armstrong reserves the right to make design or specification changes without notification.
3. Refer to IOM-501 for The Brain®– Model DRV50/80 and IOM-775 for The Brain® – Model DRV40 for specific DRV content and
information.
4. Refer to IOM-690-B for specific SAGE content and information.

5
Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Typical Piping Layout

6Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Specifications
Operating Specifications
Steam Supply Pressure 2-15 PSIG (0.14-1 barg)
Water Supply Pressure 20-150 PSIG (1.4-10 barg)
Minimum Inlet Supply Water Temperature 34°F (1°C)
Set Point Range (DRV) 81-158°F (27-70°C)
Minimum System Recirculation Flow 10 GPM (38 LPM) for DRV80 or 50 / 5 GPM (19 LPM) for DRV40
Minimum System Draw Off 0 GPM / LPM
Minimum Distance to First Outlet 25 ft (7.62 m)
Minimum Recirculation Loop Temperature Loss 2°F (1°C)
General Specifications
Control Circuit Fuse 3 A (5A w/ SAGE®)
Enclosure Protection Rating Electrical Enclosure – Nema 12
DRV – Nema 3S
Signal Cable Fittings (DRV) 3/8” liquid-tight, conduit fitting
Battery (DRV) Qty. 2, type CR-P2, 6V rating
Power Supply Requirements 120/240 VAC / 50-60 Hz / 1 Ph.
Insulation Jacket Aspen Aerogel Pyrogel (R-Value = 12.5)
Component Material
Heat Exchanger Shell 316 Stainless Steel, ASME “U” Stamped
Heat Exchanger Tube Bundle 3/4” x 20 BWG Copper
Heat Exchanger Tube Sheets 304 Stainless Steel
Integral Supply Pipe Work “Lead-free” brass/Type L copper
Integral Valves and Fittings “Lead-free” brass or bronze
Condensate Piping Cast iron & carbon steel
DRV Body AISI 316L Stainless Steel
Technical Specifications
Single-Wall, Heat Exchanger

7
Designs, materials, weights and performance ratings
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Specifications - continued
Double-Wall, Heat Exchanger
Specification Matrix
Model Heat
Exchanger Tube Bundle DRV
DFS
Digital-Flo Semi-
Instantaneous
15
DW
Double-Wall
Optional
40
35 50
50 50
90 80
SAGE™
BS
Optional
Stand Height
HT6
HT6=6” Taller
Optional
HT12
HT12=12” Taller
Optional
HT18
HT18=18” Taller
Optional
HT24
HT24=24” Taller
Optional
Insulation
Jacket
RF
Removable
Fiberglass
Optional
SS
Stainless Steel
Casing
Optional
Component Material
Heat Exchanger Shell 316 Stainless Steel, ASME “U” Stamped
Heat Exchanger Tube Bundle 5/8” Double Wall Copper
Heat Exchanger Tube Sheets 304 Stainless Steel
Integral Supply Pipe Work “Lead-free” brass/Type L copper
Integral Valves and Fittings “Lead-free” brass or bronze
Condensate Piping Cast iron & carbon steel
DRV Body AISI 316L Stainless Steel

8Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Specifications - continued
Digital-Flo®Semi-Instantaneous Shell & Tube w/ Single-Wall, Tube Bundle
Model
Water Side
Connections @ 7.5ft/sec [2.3m/s]
Steam Side
Connections
Hot/Cold Recirc. HX Capacity @ 100ºF
[55ºC] Delta T*
Max Package
Capacity at 120ºF
[49ºC] Blend
Outlet*
Steam/
Condensate
Inlet/Outlet
Capacity @ 15psi
[1bar]
DFS1540 1” [25mm] 1” [25mm] 14gpm [53lpm] 18gpm [68.1lpm] 2” [50mm] 737lb/hr [334kg/hr]
DFS3540 1.5” [40mm] 1” [25mm] 27gpm [102lpm] 35gpm [132.5lpm] 3” [80mm] 1421lb/hr [645kg/hr]
DFS5050 2” [50mm] 1.5” [40mm] 46gpm [174lpm] 60gpm [227.1lpm] 3” [80mm] 2421lb/hr [1098kg/hr]
DFS9080 3” [80mm] 2” [50mm] 84gpm [318lpm] 106gpm [401.3lpm] 4” [101.6mm] 4422lb/hr [1714kg/hr]
*Assumes 40 to 140ºF [4.4 to 60ºC]; Using Blend Formula w/ a mixing valve setpoint of 120ºF [49ºC] to determine Max. Package
Capacity
Digital-Flo® Semi-Instantaneous Shell & Tube w/ Double-Wall, Tube Bundle
Model
Water Side
Connections @ 7.5ft/sec [2.3m/s]
Steam Side
Connections
Hot/Cold Recirc.
HX Capacity @
100ºF [55ºC] Delta
T*
Max Package
Capacity at 120ºF
[49ºC] Blend
Outlet*
Steam/
Condensate
Inlet/Outlet
Capacity @ 15psi
[1bar]
DFS15DW40 1.5” [40mm] 1” [25mm] 14gpm [53lpm] 18gpm [68.1lpm] 2” [50mm] 737lb/hr [334kg/hr]
DFS35DW40 1.5” [40mm] 1” [25mm] 27gpm [102lpm] 35gpm [132.5lpm] 3” [80mm] 1421lb/hr [645kg/hr]
DFS50DW50 2” [50mm] 1.5” [40mm] 46gpm [174lpm] 60gpm [227.1lpm] 3” [80mm] 2421lb/hr [1098kg/hr]
DFS90DW80 3” [80mm] 2” [50mm] 84gpm [318lpm] 106gpm [401.3lpm] 4” [101.6mm] 4422lb/hr [1714kg/hr]
*Assumes 40 to 140ºF [4.4 to 60ºC]; Using Blend Formula w/ a mixing valve setpoint of 120ºF [49ºC] to determine Max. Package
Capacity
Factory connections are US nominal pipe sizes (NPS) w/ ANS taper pipe threads (NPT) or ASME/ANSI B16.5, Class 150, bolted
flange connections, as noted. The nearest equivalent pipe sizes in SI (the metric system), known as “diametre nominel”, are
listed in parentheses. Consult factory for pressure drop information.
Operational Limitations (all models):
Steam pressure, maximum allowable = 150 PSIG (10 barg) and maximum operating = 15 PSIG (1 barg)
Water pressure, maximum allowable = 150 PSIG (10 barg)
Setpoint temperature, maximum allowable = 158°F (70°C)

9
Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Dimensions
Dimensions and Weight
Model
Dimensions
In (mm) Weight
A B C D E
DFS1540 23.5” (598mm) 86.0” (2185mm) 43.9” (1116mm) 44.4 (1129mm) 16.4”
(416mm)
SW = xxx lbs [xxx kgs]
DW = xxx lbs [xxx kgs]
DFS3540 25.0” (636mm) 86.9” (2207mm) 48.5” (1231mm) 48.8” (1240mm) 17.1”
(434mm)
SW = xxx lbs [xxx kgs]
DW = xxx lbs [xxx kgs]
DFS5050 26.1” (663mm) 88.4” (2245mm) 56.7” (1440mm) 54.6” (1387mm) 18.8”
(477mm)
SW = xxx lbs [xxx kgs]
DW = xxx lbs [xxx kgs]
DFS9080 29.6” (752mm) 91.5” (2324mm) 57.6” (1463mm) 65.4” (1662mm) 4.4”
(113mm)
SW = xxx lbs [xxx kgs]
DW = xxx lbs [xxx kgs]
F G H I J
DFS1540 21.3” (542mm) 80.8” (2052mm) 42.8” (1087mm) SW=21.1” (536mm)
DW=20.3” (515mm) 35” (899mm)
DFS3540 22.8” (578mm) 81.4” (2067mm) 45.3” (1150mm) SW=19.2” (488mm)
DW=18.4” (467mm) 35” (899mm)
DFS5050 25.5” (646mm) 82.6” (2098mm) 46.8” (1189mm) SW=17.3” (439mm)
DW=16.3” (413mm) 35” (899mm)
DFS9080 28.0” (712mm) 81.7” (2076mm) 49.6” (1259mm) SW=15.4” (390mm)
DW=14.4” (365mm) 35” (899mm)
All dimensions apply to both single wall and double wall units.
Refer to drawings on previous page for locations.

10 Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Precautions
WARNING! The design of the DFSI electrical system is NOT suitable for installation in
interior spaces classified as “hazardous locations”, i.e., spaces containing explosive and
combustible vapors or dusts, as defined in the National Electrical Code, NEC.
WARNING! Always use appropriate lockout-tagout procedures when turning off and
disconnecting power sources during installation, service, and repair. Failure to follow
safety precautions may result in property damage, shock causing personal injury, or even
electrocution and death.
WARNING! Always use appropriate personal protective equipment (PPE) when working with
high-voltage electricity.
WARNING! Water conducts electricity. DO NOT stand in water or touch wet surfaces while
working with “live” electrical equipment.
WARNING! The factory-supplied, pressure relief valve is a required safety device.
• DO NOT remove the relief valve from the heater
• DO NOT plug the open end of the relief valve
• DO NOT install any valve(s) or restrictions in the pressure relief valve, drain line
CAUTION! The requirements of all applicable local and regional equipment installation codes
supersede the installation instructions in this manual. Governing codes must be followed.
In the absence of these codes, installation shall conform to these instructions and the
guidelines contained in the latest edition of the National Electrical Code (NEC), NFPA 70.
CAUTION! For long & satisfactory service, Armstrong recommends the facility use, or install,
effective electrical surge and lightning protection to protect this equipment.
Water Treatment Requirements:
The end user shall be responsible for providing effective water treatment systems suitable to his application. The heater
design does not incorporate a water quality control system.
Since the DFSI design incorporates a steam-to-water, shell & tube type, heat exchanger, minimizing scaling and deposit
formation on heat exchange surfaces is critical to maintaining satisfactory operation. Therefore, consistent control of system
water quality could be a very important factor in maintaining the water heating performance of the DFSI Under certain
conditions (e.g., water with a high dissolved mineral content or high discharge water temperatures), scale build-up in the
heater and associated plumbing may be rapid & excessive causing heater performance to deteriorate to a noticeable level.
Periodic cleaning and descaling may be required under these conditions.
Where chloramine / chlorine disinfection is practiced, DO NOT exceed a chloramine / chlorine concentration of 50 mg/l (ppm)
in water, per one hour dwell time. Such procedures must be conducted strictly in accordance with the information supplied
with the disinfectant and with all relevant Guidelines/Approved Codes of Practice. Water must have levels of chloramine /
chlorine lower than or equal to 4 mg/l (ppm) for continual usage.
In any case, routine inspection & maintenance of the entire heater, especially the heat exchanger, the control valves, and other
wetted components, is highly encouraged to monitor normal wear and to detect and correct abnormal conditions that could
cause damage, system failure, and a subsequent hot water outage occur.
Only designated, qualified and competent personnel shall conduct product installation in
accordance with these instructions.

11
Installation Requirements
The DFSI water heater requires connections to adequate sources of low-pressure, saturated steam; electrical power (120VAC
/ 60 Hz /1 Ph., typ.); and clean (usually potable) cold water. Connections to a steam condensate return system, a recirculated
return water circuit, and to a system that will utilize, distribute, or store the mixed (heated), potable water are also required.
Although the physical construction of the heater incorporates highly corrosion-resistant materials and watertight control
enclosures, the device is intended to be located within a structure or protective enclosure furnished by the end user. The
enclosure should provide adequate free space around the heater for service and maintenance. In locations w/ severe climates,
means to protect the heater from low (freezing) and high ambient temperatures may also be required.
Proper installation usually requires mounting and securing the heater to a rigid base or foundation that can provide adequate
bearing support, prevent movement and tipping, and resist differential settling. The base or foundation material should be able
to withstand, without significant degradation, occasional exposure to moisture and wetting.
Support all steam and water piping connecting to the heater from a fixed structure capable of independently holding the
operational weight of the piping. Consider employing design features in the piping and supports to accommodate thermal
expansion and contraction of the piping during normal operation.
Plumbing:
A licensed plumber or pipe fitter familiar with local code requirements should install the DFSI water heater and they
should also oversee commissioning. Refer to the typical installation diagram that follows for a depiction of the location of
connection points.
1. Before beginning any installation or maintenance procedure, always ensure that all supply, return, and recirculation water
and steam lines are isolated, i.e. shutoff valves are closed.
2. Ensure any residual internal pressure in the system or connecting pipework is carefully relieved.
3. Allow hot parts to cool before commencing work, to avoid the risk of burns.
4. Always wear appropriate personal protective equipment (PPE) before carrying out any installation or maintenance work.
5. Place the DFSI water heater in the desired mounting location ensuring that there is adequate free space from adjacent
walls and other obstructions for service and maintenance access. If movement or tipping of the water heater could occur,
secure the heater stand or base to the floor.
6. Connect an appropriately-sized, boiler steam supply line to the heat exchanger steam connection.
Note: In the event the tube bundle must be extracted from the heat exchanger, allow sufficient clearance between
the removable head end of the heat exchanger and any obstructions to enable complete tube bundle removal from
the heater (refer to the “Dimensions” table for tube bundle lengths). Assure sufficient clearance distances on all
other sides of the heater assembly for service access.
Note: The water supply pressure must be controlled such that the maximum operating conditions (refer to page 8)
are not exceeded. Use a pressure reducing valve (PRV) to control pressure fluctuations or reduce line pressure where
necessary. Water pressure must exceed steam pressure at all times.
Note: The DRV is designed for continuous recirculation. A recirculation pump (not supplied) must be installed
on the recirculation line to the unit. The recirculation pump should operate continuously. Avoid switched power
sources, timer-controlled power sources, and power sources tied to energy conservation circuits.
7. Connect an appropriately-sized, condensate return line to the outlet of steam trap(s).
8. Connect inlet cold water supply to the inlet piping, isolation valve (tagged accordingly).
9. Connect outlet mixed water supply to the discharge piping, isolation valve (tagged accordingly).
10. Connect recirculation return line to the recirculation piping, isolation valve (tagged accordingly).
11. Pipe the outlet from the factory-supplied water, pressure relief valve to a sanitary drain to avoid contact with hot water
should a pressure release occur. The drain line should terminate over the drain with the open end exposed to atmospheric
pressure. The relief valve, drain line should slope downward toward the sanitary drain in a manner that allows all water to
completely flow from the line. Standard cracking pressure for the factory-supplied, pressure relief valve is 165 PSI.
Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Each DRV40 requires a minimum continuous recirculation of 5 gpm.
Each DRV50 or DRV80 requires a minimum continuous recirculation of 10 gpm.

12 Designs, materials, weights and performance ratings
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Installation Requirements - continued
Electrical:
The DFSI water heater requires external electrical power to operate the DRV and the hot water, safety shutoff valve.
A licensed electrician, or electrical contractor, should run electrical current from a 120-240 VAC / 50-60 Hz / 1 Ph. power source to
the DFSI control cabinet. An electrical schematic for a DFSI control system w/ a single DRV mixing valve and a single HW shutoff
valve appears in Figure 1 below.
Figure 1: Electrical Schematic for a Standard DFSI w/ a Single DRV

13
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Installation Requirements - continued
An electrical schematic for a DFSI control system when equipped w/ a single DRV mixing valve, a single HW shutoff valve,
and the optional SAGE™feature appears in Figure 2 below.
Figure 2: Electrical Schematic for a Standard DFSI w/ a Single DRV and the SAGE™Option

14 Designs, materials, weights and performance ratings
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Installation Requirements - continued
An electrical schematic for a DFSI control system when equipped with two DRV mixing valves, and two HW shutoff valves appears
in Figure 3 below.
Figure 3: Electrical Schematic for a DFSI with Two DRV’s

15
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Installation Requirements - continued
An electrical schematic for a DFSI control system when equipped with two DRV mixing valves, two HW shutoff valves, and
SAGE™appears in Figure 4 below.
Figure 4: Electrical Schematic for a DFSI with Two DRV’s and SAGE™

16 Designs, materials, weights and performance ratings
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Installation Requirements - continued
Electrical Connection Procedure:
1. Connect the line voltage wire to the side of the fused terminal block marked “LINE”.
2. Connect the neutral wire to a terminal block marked “ACC”.
3. Connect the ground wire to the ground terminal block marked
4. Energize the power source to the control panel and turn the manual selector switch to the “ON” position.
5. The display of the DRV should illuminate, and the safety shutoff valve should power open. Confirm that the safety shutoff
valve position indicator moves from “CLOSED” to the “OPEN” position.
6. Turn the manual selector switch to the “OFF” position.
7. The display of the DRV should deactivate and the safety shutoff valve should power closed. Confirm that the safety shutoff
valve position indicator returns to the “CLOSED” position.
WARNING! The manual selector switch DOES NOT completely de-energize the DRV, and it DOES NOT de-energize the
safety shutoff valve. The control panel must be de-energized (following standard lock-out tag-out procedures) from
the source before opening the control panel, and before servicing the DRV or the safety shut-off valve.
Notes:
The DRV is designed for continuous recirculation. A recirculation pump (not supplied) must be installed on the recirculation
line to the unit. The recirculation pump should operate continuously. Avoid switched power sources, timer-controlled power
sources, and power sources tied to energy conservation circuits.
Each DRV40 requires a minimum continuous recirculation of 5 gpm.
Each DRV50 or DRV80 requires a minimum continuous recirculation of 10 gpm.

17
Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Commissioning
WARNING! The following procedure should ONLY be performed by qualified persons.
DO NOT attempt any of the following actions if you are:
1. NOT experienced with handling high-voltage, electrical power
2. NOT using appropriate personal protective equipment (PPE)
DO contact a qualified HVAC or electrical contractor instead.
WARNING! Water conducts electricity. DO NOT stand in water or touch wet surfaces
while working with “live” electrical equipment.
WARNING! Failure to follow these instructions may result in a fire, explosion, or
electrocution causing property damage, personal injury, or even death.
CAUTION! If cold water pressure is lost while steam is present, overheating and
hydraulic pressure shock “water hammer” damage may occur in the heater and
the plumbing system. Verify that adequate water volume and pressure is
supplied to the DFSI BEFORE introducing steam into the heat exchanger.
Only designated, qualified and competent personnel shall conduct commissioning in
accordance with these instructions.
1. Perform a visual overview and confirmation that the DFSI is installed per our installation schematics located in our
IOM’s
a. Confirm all water supply lines are connected correctly, and that all isolation valves are closed.
i. Hot Water
ii. Cold Water
iii. Mixed Water
iv. Recirculation return from the system loop to the DFSI
b. Confirm all steam/condensate lines are connected correctly, and that all isolation valves are closed.
2. Energize the DFSI control panel, turn switch(es) on, and verify DRV display(s) is/are illuminated.
a. Confirm the safety shutoff valve(s) opens (blue actuator valve on hot supply line to DRV)
3. Flood the system slowly and in the following sequence:
a. Cold water supply
b. Mixed water outlet
c. Hot water supply
4. Create a demand in the system loop
a. Open 4-5 fixtures (slop sinks, showers, baths, etc…)
5. Turn on recirculation pump(s)
a. Confirm continous minimum flow of ≥ 5 gpm to each DRV40, ≥ 10 gpm to each DRV50, or≥ 10 gpm to each DRV80.

18 Designs, materials, weights and performance ratings
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Commissioning - continued
Note: During system start-up, the DRV display may read a “temp low” condition. This error condition should
clear during commissioning. If the error condition does not clear, refer to the DRV IOM Troubleshoot Guide.
6. Open the condensate discharge isolation valves on the DFSI
7. Supply steam to the DFSI, slowly
a. Purge any condensate/water in the system
b. DO NOT exceed 15 psi of steam pressure
8. Confirm all supply temperatures and pressures are sufficient
a. Hot water
b. Cold water
c. Recirculation return
9. Observe the DRV adjust to and maintain the setpoint pre-programmed at the factory (based information provided
on the IDF). Give open fixtures time to evacuate air from the system.
10. Shut off all open fixtures and confirm presence of continuous recirculation.
11. Monitor DRV outlet and confirm it is maintaining set point
a. New systems may take some time for the recirculation return temperature to rise to an appropriate level.
Note: The setpoint of the DRV is preset based on information provided to Armstrong. To adjust the DRV
setpoints, high limit error temp, or to enable/disable other integral valve features, refer to the DRV
installation and operation manual (IOM).
Note: When starting-up a DFSI, it is very important that the water supply is turned on to the unit BEFORE any
steam is turned on. Once the unit is operating, the inlet water valve should NEVER be closed unless the steam
is turned off first. When shutting down a unit, BEFORE closing off the supply water to the unit, always first shut
off the steam and then allow water to run through the unit until it has cooled and completely condensed all
remaining steam in the heat exchanger.
Display as seen during normal operating mode
Temp. 119˚F
Setpoint 120˚F
Temp. 119˚F
Setpoint 120˚F
Current Outlet Temperature
Current Setpoint

19
Designs, materials, weights and performance ratings
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The electrically actuated safety shutoff valve is a redundant safety feature linked to a relay in the DRV. The DRV is self-diagnostic
and configured to assure closure of the hot water inlet under the following conditions:
• Power failure
• DRV Temp Error
• DRV Motor Error
• DRV PCB Error
• DRV Thermistor Error
• DRV Battery Error
In the event of a power failure, the DRV and the safety shutoff valve are configured to close the hot water inlet via internal battery
power. The DRV battery (non-rechargeable/replaceable) does not provide back-up power to the DRV during a power outage; only
power to actuate closure of the hot water inlet. The safety shutoff valve battery (rechargeable/replaceable) will only actuate the
valve to the closed position; the valve will not actuate to the open position in the presence of battery power only. The system will
return to normal when power is restored.
In the event of a DRV error listed above, the DRV and the safety shutoff valve (via the closed DRV relay) are configured to close
the hot water inlet via the building power source.
In response to a DRV error, the DRV relay remains closed until personnel have had an opportunity to diagnose the error, correct
the cause of the error, and perform a manual restart of the DRV (power off for 10 seconds). This is an intentional, pro-active
safety measure.
Safety Shutoff Valve
Turning a DRV control panel power switch to the off position does not completely de-energize the DRV, or the safety
shutoff valve. Both are internally “live” unless the DFSI control panel is locked-out/tagged-out from the building power
source.
NOTE: The DRV relay
is programmed at the
factory to only close
in response to a DRV
ERROR. If the relay is
responding to ALERTS
and closing the safety
shutoff valve, connect
to the DRV and confirm
via the programming
software that the
Activate Relay on Alert
box is unchecked.

20 Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Periodic Maintenance
BURN HAZARD! Contact with hot water or metal surfaces can cause severe
skin burns. Skin exposure to 140°F (60°C) water or metal for only five (5)
seconds may cause a second degree burn.
• Prior to performing any invasive procedure, close the steam inlet following
lockout/tagout procedures and allow the heat exchanger to cool. (Always
close steam inlet before closing water inlet!)
• De-energize the DFSI electrical control panel following lockout/tagout
procedures.
• Stop recirculation pump(s), close cold water inlet, and relieve water pressure
before breaking any couplings and joints.
Interval** Task
Quarterly Check heat exchanger temperatures and flow rates against standard specifications.
Quarterly Check bolted joints for loose fasteners, and for signs of steam or water leakage. Tighten or replace excessively cor-
roded parts and fasteners as needed.
Quarterly Check condition of heat exchanger and two-pass head for signs of leakage and excessive corrosion. Tighten joints
or replace parts as required.
Quarterly Wipe down assembly. Check for damaged components. Touch-up paint as required.
As required Descale system (frequency depends on water quality).
As required If excessive leakage is found, replace worn or damaged plumbing, parts, and heat exchanger gaskets as required.
Critical Preventive Maintenance
Batteries: Replace DRV battery every 12 months**, or more frequently if frequent power interruptions compromise
battery life. See DRV IOM for comprehensive maintenance details.
O-Rings & Seals: Replace DRV O-Rings & Seals every 12 months**, or more frequently if exposed to harsh water
conditions. See DRV IOM for comprehensive maintenance details.
Safety Shutoff Valve: Exercise the safety shutoff valve every 6 months**, or more frequently if exposed to harsh water
conditions. Turn off the DF control panel power switch to the DRV, confirm closure of the safety shutoff valve, turn
power switch back on, and confirm the safety shutoff valve fully opens. (See page 19 for more on the safety shutoff
valve)
Strainers: Clean supply strainers every 6 months**, or more frequently if exposed to harsh water conditions.
Blowdown strainer, remove and thoroughly clean basket screens, flush strainer body.
** Intervals are recommended. Site conditions and maintenance trends may support extending or reducing preventive
maintenance intervals. (Exception: DRV battery replacement should not exceed one year interval)