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Hot Water Generation – Steam/Water Double Wall
Digital-Flo® Steam/Water Shell and Tube Heat Exchanger
Model DF535DWP50
DF535DWP50 is a complete pre-piped parallel (redundant)
instantaneous steam/water shell and tube heater. The assembly
includes a properly sized shell and tube heat exchanger with a
Digital Recirculating Valve (DRV50).
Digital technology provides enhanced water temperature control
accuracy and enhanced user safety in a single control component.
Operational Specifications
• +/-2°F water temperature control at points of use 25’
downstream during demand
• +/-2°F water temperature control during zero system demand
“idling” periods
• 2°F minimum valve inlet to outlet temperature requirement
(system recirculation temperature loss)
• Automatic shutoff of hot water flow upon cold water inlet supply
• Automatic shutoff of hot water flow in the event of a power
• Programmable set point range of 81-158°F (27-70°C)
• Programmable 1st level hi/lo temp alarm display
• Programmable temperature error level for double safety
2-1/2” NPT
Steam Inlet
Technical Specifications
Maximum steam pressure: 15 PSIG
Maximum domestic pressure: 150 PSI
Minimum recirculation flow: 10 GPM
Design conditions: Domestic-41 GPM (Redundant)/73 GPM
(Parallel) at 100°F delta T using 15 PSIG steam
Complete assembly Lead Free Compliant
All domestic side valve fittings and isolation valves, strainers,
inlet/return check valves, inlet system blend and return
thermometers pre-piped.
DRV – all wetted parts 316 stainless steel
DRV to be UL Listed
Heat Exchanger shall be double wall with 5/8” copper inner,
¾” ID copper outer tube expanded into steel (steam side) and
brass (water side) tube sheets.
Water pipe of type L copper
Fabricated carbon steel frame with machine grade enamel
120 volt power supply required
Secondary (double) safety shut-off valve included
2” NPT
Mixed Water
2-1/2” NPT
Steam Inlet
1” NPT
813 IB
(1143 mm)
2” NPT
Cold Water
SPCO Relay Outputs – Relay which is energized during
LCD Display – Provides information on set point, delivered
temperature, error messages and alert conditions.
RS485 Serial Port – Connects the DRV to either Modbus RTU or
BrainScan®. (See DF535DWP50BS for package with BrainScan®.)
Modbus RTU – DRV can be configured to communicate directly
with Building Automation Systems (BAS) using Modbus RTU
(1948 mm)
1-1/2” NPT
Recirc Water
(2493±25 mm)
For a submittal drawing, refer to D589725.
Designs, materials, weights and performance ratings are approximate and subject to change without notice. Visit for up-to-date information.
Armstrong Hot Water Group, 221 Armstrong Blvd., Three Rivers, MI 49093 – USA Phone: 269-279-3602, Fax: 269-279-3130
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