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
Tel. [phone] Fax. [phone] Page 4 of 44
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
Tel. [phone] Fax. [phone] Page 5 of 44
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.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
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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.
Visit armstronginternational.com for up-to-date information.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone] Page 7 of 44
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
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
Tel. [phone] Fax. [phone] Page 8 of 44
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.