Armstrong Digital-Flo Series Instruction manual

785-E-EN
Digital-Flo®
Steam-to-Water,
Shell and Tube, Water Heater
Installation, Operation & Maintenance
Manual
Please read and save
these instructions

Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone]
Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Contents
Safety ........................................................... 1
General Description ........................................... 2
Specifications ................................................3-4
Specification Matrix ......................................3-4
Materials of Construction.................................. 4
Connection Detail.............................................. 5
Dimensions ...................................................6-7
Precautions ...................................................8-9
Installation Requirements................................ 9-16
Commissioning............................................17-18
Safety Shutoff Valve..........................................19
Preventative Maintenance............................... 20-24
Troubleshooting ...........................................25-33
Spare Parts ................................................34-39
Steam Trap Assemblies.................................. 40-41
Limited Warranty and Remedy .............................42

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Page 1 of 44
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone]
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.
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.
If the instructions following a safety icon are not followed, adverse
consequences may occur – including property damage, personal injury, or,
in extreme cases, death.

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Page 2 of 44
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone]
General Description
Digital-Flo®is an instantaneous water heater that heats on demand and stores very little hot water. Digital-Flo®transfers heat
from steam to cold water and then precisely blends hot water, cold water, and recirc return water to a programmable mixed
water outlet setpoint.
Digital-Flo®water heaters utilize digital technology to monitor the hot water inlet, the cold water/recirc return inlet, and the
mixed water outlet. Digital-Flo®is supplied pre-piped and pressure tested with a Digital Recirculating Valve (The Brain®–
Models DRV40, DRV50, and DRV80).
Two (2) inlet and one (1) outlet thermistors integral to the DRV provide time-proven water temperature control accuracy. The
precise control of the DRV eliminates 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 Digital-Flo®water heaters may be integrated directly 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.
Digital-Flo®is engineered to precision 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 (see Typical Layout diagram that follows for specific locations):
• The Brain DRV40, DRV50, or DRV80 Digital Recirculating Valve
• Heat exchanger module (shell 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 causes excessive heat exchanger scaling.
Please note:
1. Because the Digital-Flo®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.

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone] Page 3 of 44
Specification Matrix
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 EACH DRV80 or DRV50, and 5 GPM (19 LPM) for EACH 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)
Control Circuit Fuse 3 A (5A w/ SAGE™)
Enclosure Protection Rating (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.
Digital-Flo®: Single Heater & Single DRV
Optional Standard Optional
Model Heat
Exchanger
Double-Wall
Tube Bundle DRV SAGE™
For Building
System (BS)
Integration
DF 415 DW 40 BS
DF 535 DW 40 BS
DF 665 DW 50 BS
DF 8120 DW 80 BS
Example of Single-Wall Tube Bundle, with SAGE™: DF41540BS
Example of Double-Wall Tube Bundle, without SAGE™: DF415DW40
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)

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
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Digital-Flo®Parallel: Two Heaters & Single DRV
Configured for Two Heaters Flowing Through One DRV
Optional Optional Standard Optional
Model Heat
Exchanger
Double-Wall
Tube Bundle
Redundant
Heaters DRV SAGE™
For Building
System (BS)
Integration
DF 415 DW P 40 BS
DF 535 DW P 50 BS
DF 665 DW P 80 BS
DF 8120 DW P 80 BS
Example of Single-Wall Tube Bundle, with SAGE™: DF415P40BS
Example of Double-Wall Tube Bundle, without SAGE™: DF415DWP40
Digital-Flo®Redundant: Two Heaters & Two DRV's
Second Heater & DRV Configured for Redundant Backup Service Only
Optional Optional Standard Optional
Model Heat
Exchanger
Double-Wall
Tube Bundle
Redundant
Heaters DRV's SAGE™
For Building
System (BS)
Integration
DF 415 DW P 40-40 BS
DF 535 DW P 40-40 BS
DF 665 DW P 50-50 BS
DF 8120 DW P 80-80 BS
Example of Single-Wall Tube Bundle, with SAGE™: DF415P40-40BS
Example of Double-Wall Tube Bundle, without SAGE™: DF415DWP40-40
Specifications – continued
Single-wall, heat exchanger
Double-wall, heat exchanger
Component Material
Heat Exchanger Shell Carbon steel, ASTM SA-106, Gr. B, ASME
“U” stamped with 316 SS two-pass head
Heat Exchanger Tube Bundle 5/8-in OD x 16 BWG wall, admiralty brass
Heat Exchanger Tube Sheets “Lead-free” brass
Heat Exchanger Tube Bundle End Cap “Lead-free” brass
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
Component Material
Heat Exchanger Shell Carbon steel, ASTM SA-106, Gr. B, ASME
“U” stamped with 316 SS two-pass head
Heat Exchanger Tube Bundle Copper tubes - 5/8” OD inner w/ 3/4” OD
grooved outer
Heat Exchanger Tube Sheets Steam-side – Carbon steel
Water-side - “Lead-free” brass
Integral Supply Pipe Work “Lead-free” brass / Type L copper
Integral Valve and Fittings “Lead-free” brass or bronze
Condensate Piping Cast iron & carbon steel
DRV Body AISI 316L stainless steel

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
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Digital Shell & Tube
Model
Water Side Steam Side
Connections @ 7.5 ft/sec
(2.3 m/s)
Flow @ 7.5 ft/sec
(2.3 m/s) Connections Capacity @ 15 psi (1
bar)
Hot/Cold Recirc. Capacity @ 90°F (50°C) Delta T
Typical @120°F (49°C) Setpoint
Steam
Inlet
Conden-
sate Outlet
DF41540 1” 1” 18 GPM 2 NPT 3/4 NPT 858 lb/hr (389 kg/hr)
DF415DW40 1” 1” 18 GPM 2 NPT 3/4 NPT 858 lb/hr (389 kg/hr)
DF415P40 1-1/2” 1” 36 GPM 2 NPT 3/4 NPT 1,716 lb/hr (778 kg/hr)
DF415DWP40 1-1/2” 1” 36 GPM 2 NPT 3/4 NPT 1,716 lb/hr (778 kg/hr)
DF53540 1-1/2” 1” 41 GPM 2-1/2 NPT 1 NPT 1,954 lb/hr (886 kg/hr)
DF535DW40 1-1/2” 1” 41 GPM 2-1/2 NPT 1 NPT 1,954 lb/hr (886 kg/hr)
DF535P50 2” 1-1/2” 73 GPM 2-1/2 NPT 1 NPT 3,479 lb/hr (1,578 kg/hr)
DF535DWP50 2” 1-1/2” 73 GPM 2-1/2 NPT 1 NPT 3,479 lb/hr (1,578 kg/hr)
DF66550 2” 1-1/2” 73 GPM 3 NPT 1-1/4 NPT 3,479 lb/hr (1,578 kg/hr)
DF665DW50 2” 1-1/2” 73 GPM 3 NPT 1-1/4 NPT 3,479 lb/hr (1,578 kg/hr)
DF665P80 3” 2” 165 GPM 3 NPT 1-1/4 NPT 7,720 lb/hr (3,502 kg/hr)
DF665DWP80 3” 2” 165 GPM 3 NPT 1-1/4 NPT 7,720 lb/hr (3,502 kg/hr)
DF812080 3” 2” 165 GPM 4 FLG 2 NPT 7,863 lb/hr (3,567 kg/hr)
DF8120DW80 3” 2” 165 GPM 4 FLG 2 NPT 7,863 lb/hr (3,567 kg/hr)
DF8120P80 3” 2” 165 GPM 4 FLG 2 NPT 7,863 lb/hr (3,567 kg/hr)
DF8120DWP80 3” 2” 165 GPM 4 FLG 2 NPT 7,863 lb/hr (3,567 kg/hr)
* 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.
Connections Detail

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 F
DF41540 20.0 (508) 43.2 (1,097) 25.4 (645) 54.7 (1,389) 72.3 (1,837) 36.0 (915) 385
DF41540BS 20.0 (508) 52.0 (1,321) 25.4 (645) 54.7 (1,389) 72.3 (1,837) 36.0 (915) 410
DF415P40 20.0 (508) 75.5 (1,918) 26.4 (670) 54.7 (1,389) 79.8 (2,027) 36.0 (915) 580
DF415P40BS 20.0 (508) 75.5 (1,918) 26.4 (670) 54.7 (1,389) 79.8 (2,027) 36.0 (915) 605
DF53540 20.0 (508) 44.5 (1,129) 26.4 (670) 66.9 (1,698) 66.9 (1,698) 45.0 (1,143) 804
DF53540BS 20.0 (508) 52.0 (1,321) 26.4 (670) 66.9 (1,698) 66.9 (1,698) 45.0 (1,143) 829
DF535P50 20.0 (508) 76.7 (1,948) 27.1 (687) 66.9 (1,698) 66.9 (1,698) 45.0 (1,143) 1,234
DF535P50BS 20.0 (508) 76.7 (1,948) 27.1 (687) 66.9 (1,698) 66.9 (1,698) 45.0 (1,143) 1,259
DF66550 30.0 (915) 50.0 (1,270) 36.0 (915) 79.9 (2,029) 116.2 (2,950) 57.0 (1,448) 1,094
DF66550BS 30.0 (915) 52.0 (1,321) 36.0 (915) 79.9 (2,029) 116.2 (2,950) 57.0 (1,448) 1,119
DF665P80 30.0 (915) 74.1 (1,883) 40.3 (1,024) 79.9 (2,029) 111.0 (2,818) 57.0 (1,448) 1,835
DF665P80BS 30.0 (915) 74.1 (1,883) 40.3 (1,024) 79.9 (2,029) 111.0 (2,818) 57.0 (1,448) 1,860
DF812080 34.0 (864) 53.0 (1,345) 43.5 (1,105) 83.0 (2,107) 128.1 (3,253) 57.0 (1,448) 1,507
DF812080BS 34.0 (864) 53.0 (1,345) 43.5 (1,105) 83.0 (2,107) 128.1 (3,253) 57.0 (1,448) 1,532
DF8120P80 34.0 (864) 75.9 (1,929) 42.9 (1,090) 83.0 (2,107) 129.1 (3,279) 57.0 (1,448) 3,011
DF8120P80BS 34.0 (864) 75.9 (1,929) 42.9 (1,090) 83.0 (2,107) 129.1 (3,279) 57.0 (1,448) 3,036
Refer to column D for minimum tube bundle replacement distance.

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
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Armstrong International
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Dimensions and Weight
Model
Dimensions
in (mm) Weight
A B C D E F
DF415DW40 20.0 (508) 43.2 (1,097) 25.4 (645) 76.4 (1,941) 71.6 (1,819) 36.0 (915) 465
DF415DW40BS 20.0 (508) 52.0 (1,321) 25.4 (645) 76.4 (1,941) 71.6 (1,819) 36.0 (915) 490
DF415DWP40 20.0 (508) 75.5 (1,918) 26.4 (670) 76.4 (1,941) 87.9 (2,232) 36.0 (915) 740
DF415DWP40BS 20.0 (508) 75.5 (1,918) 26.4 (670) 76.4 (1,941) 87.9 (2,232) 36.0 (915) 765
DF535DW40 20.0 (508) 44.5 (1,129) 26.4 (670) 76.5 (1,944) 89.6 (2,277) 45.0 (1,143) 1,080
DF535DW40BS 20.0 (508) 52.0 (1,321) 26.4 (670) 76.5 (1,944) 89.6 (2,277) 45.0 (1,143) 1,105
DF535DWP50 20.0 (508) 76.7 (1,948) 27.1 (687) 76.5 (1,944) 98.1 (2,492) 45.0 (1,143) 1,317
DF535DWP50BS 20.0 (508) 76.7 (1,948) 27.1 (687) 76.5 (1,944) 98.1 (2,492) 45.0 (1,143) 1,342
DF665DW50 30.0 (915) 50.0 (1,270) 36.0 (915) 88.7 (2,253) 115.1 (2,923) 57.0 (1,448) 1,373
DF665DW50BS 30.0 (915) 52.0 (1,321) 36.0 (915) 88.7 (2,253) 115.1 (2,923) 57.0 (1,448) 1,398
DF665DWP80 30.0 (915) 74.1 (1,883) 40.3 (1,024) 79.9 (2,029) 110.7 (2,811) 57.0 (1,448) 1,892
DF665DWP80BS 30.0 (915) 74.1 (1,883) 40.3 (1,024) 79.9 (2,029) 110.7 (2,811) 57.0 (1,448) 1,917
DF8120DW80 34.0 (864) 53.0 (1,345) 43.5 (1,105) 77.3 (1,963) 126.6 (3,216) 57.0 (1,448) 1,550
DF8120DW80BS 34.0 (864) 53.0 (1,345) 43.5 (1,105) 77.3 (1,963) 126.6 (3,216) 57.0 (1,448) 1,575
DF8120DWP80 34.0 (864) 75.9 (1,929) 42.9 (1,090) 77.3 (1,963) 127.6 (3,242) 57.0 (1,448) 3,050
DF8120DWP80BS 34.0 (864) 75.9 (1,929) 42.9 (1,090) 77.3 (1,963) 127.6 (3,242) 57.0 (1,448) 3,075
Refer to column D for minimum tube bundle replacement distance.
Dimensions – continued

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
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Precautions
WARNING! The design of the Digital-Flo®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 the application. The
heater design does not incorporate a water quality control system.
Since the Digital-Flo®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 Digital-Flo®. 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.
Only designated, qualified and competent personnel shall conduct product installation in
accordance with these instructions.

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Page 9 of 44
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221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
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Precautions – continued
Installation Requirements
Plumbing:
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 4mg / l (ppm) for continual usage.
The Digital-Flo®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
(NEMA 12-rated) 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.
A licensed plumber or pipe fitter familiar with local code requirements should install the Digital-Flo®water heater and
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 Digital-Flo®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. (See Steam Piping
Installation Detail on following pages.)
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.

Page 10 of 44
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Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Installation – continued
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.
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.
See Steam Piping Installation Detail on following pages.
Note: The water supply pressure must be controlled such that the maximum operating conditions (refer to
page 4) 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.
Single-wall and Double-wall connections and sizes
Building
Recirculation
Connection
Steam
Condensate
Return
Connection
Electric Connection
Mixed Water Outlet
Connection
Steam Inlet Connection
Cold Water Supply
Connection
Stand Removed for Clarity

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
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Installation – continued
Steam Piping Installation:
1. Install the Digital-Flo®with adequate room to allow for tube bundle removal when cleaning is required. See Table 12-1
for specific dimensions.
2. If 2-15 psig of steam is available a pressure reducing valve is NOT required. If a pressure reducing valve is required, an
Armstrong Inverted Bucket Steam Trap is recommended to drain condensate at the inlet of the pressure reducing valve.
3. An Armstrong Y-strainer should be installed before the pressure reducing valve to reduce the chance of dirt fouling.
4. If an externally piloted pressure reducing valve is used, the control pipe should be pitched away from the PRV and
installed at the pressure gauge on the shell of the heat exchanger.
5. A steam safety relief valve should be used prior to the heat exchanger if either or both of the following conditions exist.
(1) If the maximum steam pressure could exceed the minimum water pressure in the tubes, or (2) The maximum steam
pressure could exceed 150 psig (the maximum steam pressure rating of the shell).
IMPORTANT -Steam supply pipe size coming to the heat exchanger should NOT be smaller than the steam connection
supplied on the heater, otherwise steam flow could be restricted. If a pressure reducing valve is used, installation
should be as close as possible to the Digital-Flo®. Downstream piping from the Pressure Reducing Valve should be
expanded immediately after the PRV to accommodate the expanded volume of steam.
6. To vent start-up air, an Armstrong Thermostatic Air Vent is included and installed on the top connection, opposite the
trap drain connection of the heat exchanger. This discharge can be piped to drain or the floor if preferred.
7. Install a suitable steam pressure gauge in the 1/4” coupler located in the top mid section of the heat exchanger shell.
This gauge will help diagnose pressure problems should they occur. This port may also be used for a PRV external
control pipe if a PRV is required.
Typical installation shown. Always consult local codes and standards for detailed installation requirements.
NOTE: Digital-Flo®assembly is provided with (1) Armstrong Steam Trap, (1) Vacuum Breaker (1) Safety Relief Valve, and
(1) Thermostatic Air Vent. All other items shown in gray not included.

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone] Page 12 of 44
Installation – continued
Electrical:
The Digital-Flo®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 Digital-Flo®control cabinet. An electrical schematic for a Digital-Flo®control system with a single DRV mixing
valve and a single HW shutoff valve appears in Figure 1 below.
Figure 1: Electrical Schematic for a Standard Digital-Flo®with a Single DRV

Page 13 of 44
Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone]
An electrical schematic for a Digital-Flo®control system when equipped with a single DRV mixing valve, a single HW shutoff
valve, and the optional SAGE™feature appears in Figure 2 below.
Installation – continued
Figure 2: Electrical Schematic for a Standard Digital-Flo®with a Single DRV and SAGE™

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone] Page 14 of 44
Installation – continued
An electrical schematic for a Digital-Flo®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 Digital-Flo®with Two DRV’s

Page 15 of 44
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone]
Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Installation – continued
An electrical schematic for a Digital-Flo®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 Digital-Flo®with Two DRV’s and SAGE™

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone] Page 16 of 44
Installation – 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.

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone] Page 17 of 44
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 Digital-Flo®BEFORE introducing steam into the heat exchanger.
Only designated, qualified and competent personnel shall conduct commissioning in
accordance with these instructions.
Commissioning
1. Perform a visual overview and confirmation that the Digital-Flo®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 Digital-Flo®
b. Confirm all steam/condensate lines are connected correctly, and that all isolation valves are closed.
2. Energize the Digital-Flo®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.

Designs, materials, weights and performance ratings
are approximate and subject to change without notice.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone] Page 18 of 44
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 Digital-Flo®
7. Supply steam to the Digital-Flo®, 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 Digital-Flo®, 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