REVISED SPECIFICATIONS 657-27-107.pdf

SECTION 22 34 00 – Domestic Water Heaters (DHW Generator Systems)

VA St. Louis HCS – John Cochran Division | Project 657-27-107JC

SECTION 22 34 00

DOMESTIC WATER HEATERS (DHW GENERATOR SYSTEMS)

PART 1 – GENERAL

1.1 SUMMARY

A. Provide complete Domestic Hot Water (DHW) Generator Systems including semi‑instantaneous or instantaneous steam‑to‑water double‑wall heat exchangers; DHW storage tanks; DHW recirculation pumps; thermostatic mixing valves; expansion tanks; steam PRV stations, traps and condensate accessories; instruments/sensors; BAS/ECC integration; commissioning;

flushing/disinfection; and all incidental work to deliver a fully functional, code‑compliant DHW system.

B. Design, products, and installation shall comply with VA PG‑18‑10 requirements for DHW systems, including temperature control, Legionella mitigation, recirculation, commissioning and

BAS monitoring.

1.2 RELATED REQUIREMENTS

A. Section 22 11 00 – Facility Water Distribution (piping, valves, insulation, identification).

B. Section 01 35 26 – Safety Requirements (shutdowns, escorts, ICRA).

C. Section 13 05 31 – Seismic Restraint Requirements (equipment and piping).

1.3 REFERENCES

A. VA Plumbing Design Manual PG‑18‑10 (September 1, 2026).

B. VA Design Submission Requirements PG‑18‑15.

C. VA Seismic Design Handbook H‑18‑8.

D. ASSE 1017 (Master Thermostatic Water Mixing Valves), ASSE 1016 (Combination

Pressure‑Balancing/Thermostatic Shower Valves), ASSE 1070 (POU tempering valves).

E. AWWA C651 (disinfection).

1.4 ADMINISTRATIVE REQUIREMENTS

A. Coordination: Coordinate shutdowns, phasing, escorts, and infection control with COR/CO per

Section 01 35 26.

B. Pre‑installation meeting: Review rigging routes, access/maintenance clearances, BAS points, commissioning sequence, and eradication test procedures; record minutes.

1.5 SUBMITTALS

A. Product Data: Heat exchangers (double‑wall), DHW tanks, recirculation pumps, thermostatic mixing valves, expansion tanks, steam PRVs/traps/condensate units, instruments and BAS devices.

B. Shop Drawings: System layout; piping schematics with valves/bypasses; equipment rigging and maintenance clearances; control diagrams; BAS/ECC point lists and alarm matrix.

C. Calculations: expansion tank sizing; recirculation balance (heat‑loss method); eradication flow verification (≥30 gpm at 170–180°F).

D. Commissioning Plan: Functional tests, BAS trending, temperature verification, eradication run, and disinfection plan.

E. O&M Manuals: Include procedures for routine thermal eradication and supplemental disinfection

(if applicable).

1.6 QUALITY ASSURANCE

A. Professional Engineer (PE) of record shall stamp design drawings, equipment schedules, risers, and calculations per PG‑18‑10.

B. Non‑proprietary specification approach; provide VA‑approved equals based on salient characteristics.

C. Codes and Standards: Comply with IPC, NFPA, ASHRAE, ASSE referenced in PG‑18‑10.

1.7 DELIVERY, STORAGE, AND HANDLING

A. Protect HX(s), tanks, pumps, valves, and instruments from damage; store per manufacturer instructions; maintain cleanliness to prevent contamination before installation.

1.8 WARRANTY

A. Provide manufacturer’s standard warranty; include HX plates/tubes, valves, pumps, instruments, and controls.

1.9 SYSTEM DESCRIPTION AND PERFORMANCE REQUIREMENTS

A. DHW Supply Temperature: Deliver 140°F (60°C) at source; maintain 124°F (51.1°C) minimum at end of recirculation loop.

B. Thermal Eradication: System shall provide 170–180°F water at ~30 gpm and include bypass provisions to circulate elevated temperature per eradication procedures.

D. Recirculation: Provide continuous DHW recirculation sized by heat‑loss method; redundant pumps in patient‑care buildings; limit temperature drop to ≤6°F and maintain velocities within

PG‑18‑10 limits.

E. BAS/ECC Monitoring: Provide analog and digital sensing on emergency power; trend and alarm

DHW discharge deviation (+5°F), recirculation return temperature at loop end, pump run/fail/lead‑lag.

F. Non‑Proprietary Equipment: Provide basis of design and VA‑approved equal options with salient characteristics listed in submittals.

1.10 SEQUENCING AND OUTAGES

A. Maintain DHW service during replacement; propose phasing to limit outages; coordinate tie‑ins after hours as required.

PART 2 – PRODUCTS

2.1 GENERAL

A. Provide products suitable for potable water use and compatible with eradication temperatures;

materials shall withstand 180°F circulation and disinfection chemicals where applicable.

2.2 DOMESTIC WATER HEATERS (STEAM‑TO‑WATER HX)

A. Type: Semi‑instantaneous or instantaneous, DOUBLE‑WALL construction for potable DHW.

B. Capacity: Sized to meet design DHW flow at 140°F discharge and eradication mode; include inlet/outlet thermowells and pressure/temperature test plugs.

C. Steam Supply: Provide PRV(s), control valves, and safeties sized/selected to meet HX duty;

field‑verify plant steam pressure.

2.3 DHW STORAGE TANKS (WHEN REQUIRED BY DESIGN)

A. ASME rated; internal finish per manufacturer for potable use; accessories for drain, temp/pressure relief, and sampling ports. Size using gallon‑per‑hour method with diversity.

2.4 DHW RECIRCULATION PUMPS

A. Provide redundant lead/lag pumps for patient‑care buildings; size by heat‑loss method to limit loop drop to ≤6°F; ensure velocities remain within PG‑18‑10 guidance.

2.5 THERMOSTATIC MIXING VALVES

Not applicable

2.6 THERMAL EXPANSION TANKS

A. Provide DHW expansion tanks sized to the system; list in equipment schedules.

2.7 STEAM ACCESSORIES

A. PRV Station: Sized for duty with gauges, strainers, and isolation valves.

B. Steam Traps: Float and thermostatic or manufacturer‑recommended; sized to HX condensate rates.

C. Condensate Unit: Pumps/tanks sized to HX load; include check valves and isolation.

2.8 BAS/ECC INTEGRATION

A. Provide analog and digital devices on emergency power; minimum points: DHW supply temperature; end‑of‑loop return temperature; pump run/fail and lead/lag status; alarm setpoints;

trend logs.

2.9 ACCESSORIES

A. Provide pressure/temperature test plugs at key branch connections and equipment nozzles;

provide sampling ports per Legionella mitigation design.

B. Insulation: Meet ASHRAE 90.1 and VA requirements; size return to limit losses.

2.10 SEISMIC RESTRAINTS

A. Provide engineered seismic restraints and PE‑stamped calculations for equipment and piping per

H‑18‑8 and Section 13 05 31.

PART 3 – EXECUTION

3.1 EXAMINATION

A. Verify existing conditions, plant steam pressure, and points of connection; notify COR of discrepancies prior to work.

3.2 INSTALLATION

A. Provide concrete housekeeping pads; install vibration isolation as required.

B. Install piping per PG‑18‑10; minimize dead‑ends; keep fixture run‑outs to volumes and lengths specified to ensure turnover and reduce stagnation.

C. Identify piping and equipment; maintain access/maintenance clearances; show rigging routes.

3.3 FIELD QUALITY CONTROL

A. Perform system tests; verify DHW supply at 140°F and return ≥124°F at loop end; document readings.

B. Flush and disinfect new/modified DHW piping per AWWA/IPC methods; record procedures and results.

3.4 COMMISSIONING

A. Execute the Commissioning Plan: functional test of HX, mixing valves, pumps, BAS points; trend temperatures and flows; conduct eradication run and verify alarms. Provide final commissioning report.

3.5 BAS/ECC POINT‑TO‑POINT

A. Verify each BAS input/output; confirm alarm thresholds; demonstrate trend logs for temperature profiles and pump operation.

3.6 TRAINING

A. Provide training for facility staff on operation, eradication procedures, alarms, and routine maintenance.

3.7 CLOSEOUT

A. Submit as‑built drawings, O&M manuals, commissioning results, BAS point list, alarm matrix, and test logs.