1 Scope
NOTE This standard covers the performance, materials, construction, and installation of liquid-to-liquid heat exchangers that transfer heat between two circulating fluid circuits in building mechanical systems. (1.1)
NOTE A heat exchanger transfers heat between two fluids that are kept physically separated so the streams do not mix, allowing one circuit to heat or cool another while maintaining hydraulic separation. Heat exchangers are used to isolate circuits at different pressures, to break a tall building into independent pressure zones, to transfer heat from steam or a central plant to a hydronic loop, and to preheat domestic water from a recovered or central heat source. (1.1.1)
NOTE This standard addresses three construction families: (1.1.2)
- Gasketed plate-and-frame exchangers achieve a close temperature approach and high heat transfer per unit volume by stacking thin corrugated plates that create narrow, turbulent flow channels.
- Brazed-plate exchangers are a compact, sealed variant of the plate type with no gaskets and no field-serviceable interior, suited to high-pressure duty in a small envelope.
- Shell-and-tube exchangers pass one fluid through a bundle of tubes and the other across the tubes inside a cylindrical shell, and are preferred for steam-to-water service and high design pressures.
NOTE This standard does not cover the following, which are specified elsewhere: (1.1.3)
- The boiler, chiller, steam source, or water heater that supplies the exchanger, under Boilers, Chillers, and Water Heaters.
- Connecting piping, isolation valves, and accessories on each circuit, under Hydronic Piping.
- Circulating pumps, under Hvac Pumps.
2 Referenced Standards
NOTE The following standards are referenced in this document. (2.1)
NOTE The most recent edition of each referenced standard in effect on the date of the Contract shall govern unless a specific edition is identified. (2.1.1)
| Standard |
Title |
| ASME BPVC Section VIII, Division 1 |
Rules for Construction of Pressure Vessels |
| ASME BPVC Section VIII, Division 2 |
Alternative Rules for Construction of Pressure Vessels |
| TEMA |
Standards of the Tubular Exchanger Manufacturers Association |
| ANSI/AHRI 400 (I-P) |
Performance Rating of Liquid to Liquid Heat Exchangers (AHRI 401 is the companion SI standard) |
| ASME B16.5 |
Pipe Flanges and Flanged Fittings: NPS 1/2 Through NPS 24 |
| ASME B31.9 |
Building Services Piping |
| ASME B31.1 |
Power Piping |
| NSF/ANSI/CAN 61 |
Drinking Water System Components — Health Effects |
| NSF/ANSI/CAN 372 |
Drinking Water System Components — Lead Content |
| ASHRAE Handbook |
HVAC Systems and Equipment |
3 Submittals
3.1 Action Submittals
NOTE The Contractor shall submit the following action submittals for each heat exchanger before fabrication or ordering: (3.1.1)
- Product data for each exchanger, including type, construction class, and rated capacity.
- A certified thermal selection sheet stating duty, both flow rates, all four terminal temperatures, LMTD, and the fouling resistance applied to each side.
- Materials of construction for plates, tubes, shell, frame, gaskets, and brazing alloy.
- Design pressure and temperature for each fluid circuit and the corresponding nozzle flange class.
- Pressure-drop curves or calculated pressure drop for each circuit at design flow.
- Dimensioned drawings showing nozzle sizes, ratings, locations, orientation, and overall envelope.
- Required clear space for plate removal, bundle pull, or unit servicing.
- Net and operating weight, support locations, and seismic anchorage requirements where applicable.
☑ Product data for each exchanger
☑ Certified thermal selection sheet (duty, flows, temperatures, fouling)
☑ Materials of construction schedule
☑ Design pressure and temperature per circuit
☐ Pressure-drop curves or calculated pressure drop
☑ Dimensioned drawings with nozzle schedule
☑ Service clearance (plate removal / bundle pull) dimensions
☐ Weights, support points, and anchorage requirements
NOTE The Contractor shall submit the following informational submittals for each heat exchanger: (3.2.1)
- The ASME Manufacturer's Data Report (Form U-1 or U-1A) for stamped pressure vessels.
- AHRI 400 certification documentation where certified performance is required.
- NSF/ANSI/CAN 61 and NSF/ANSI/CAN 372 certification listings where potable water is present.
- Hydrostatic or pneumatic shop test reports for each pressure boundary.
- Welder and brazing procedure qualification records for shell-and-tube and welded-plate units.
☑ ASME Manufacturer's Data Report (Form U-1 / U-1A)
☐ AHRI 400 certification documentation
☐ NSF/ANSI/CAN 61 and 372 certification listings
☑ Shop hydrostatic / pneumatic test reports
☐ Welding / brazing procedure qualification records
3.3 Closeout Submittals
NOTE The Contractor shall submit the following closeout submittals before Substantial Completion: (3.3.1)
- Operation and maintenance manuals covering cleaning, gasket replacement, and plate or bundle removal.
- A record of the as-built plate count, plate arrangement, or tube bundle configuration for the unit.
- A spare-parts list with the manufacturer's part numbers for gaskets and plates.
- The warranty document executed in the Owner's name.
☑ Operation and maintenance manuals
☑ As-built plate count / bundle configuration record
☐ Spare-parts list with part numbers
☑ Executed warranty document
4 Quality Assurance
NOTE Each heat exchanger required to be a pressure vessel under ASME Section VIII shall be designed, fabricated, inspected, and stamped in accordance with that Code. (4.1)
NOTE A heat exchanger above the ASME size and pressure exemption thresholds shall bear the ASME U-stamp, or the UM-stamp where the unit qualifies as a small vessel under the Code. (4.1.1)
NOTE The ASME stamp shall not be specified for a unit that falls below the Code's exemption thresholds. (4.1.2)
NOTE Requiring an ASME stamp on an exempt unit narrows the field of compliant manufacturers and adds cost with no code benefit; confirm the design pressure and volume against the exemption limits before requiring a stamp. (4.1.3)
NOTE Each shell-and-tube heat exchanger shall be fabricated to the TEMA mechanical class specified for its service. (4.1.4)
NOTE TEMA Class C shall be the basis for shell-and-tube units in general commercial HVAC and hydronic service. (4.1.5)
NOTE TEMA Class R shall be specified only for severe industrial or petroleum service, and Class B only for chemical-process service. (4.1.6)
NOTE Specifying TEMA Class R for an ordinary building hydronic loop over-specifies wall thicknesses and tolerances and increases cost without benefit in HVAC service. (4.1.7)
NOTE Each heat exchanger wetted by potable domestic water on any circuit shall be certified to NSF/ANSI/CAN 61 for every wetted material. (4.1.8)
NOTE Each heat exchanger wetted by potable domestic water shall also comply with NSF/ANSI/CAN 372 for lead content. (4.1.9)
NOTE NSF certification covers the plates, tubes, gaskets, and brazing alloy individually; a unit assembled from non-certified components will fail inspection in jurisdictions that enforce NSF 61, which is required by regulation in most U.S. states. (4.1.10)
NOTE Where certified thermal performance is specified, the heat exchanger shall carry current AHRI 400 certification and its published ratings shall be drawn from the AHRI directory. (4.1.11)
NOTE Do not require AHRI 400 certification without first confirming that capable manufacturers carry certification for the selected product line; not every line participates in the program, and a mandatory certification requirement can narrow the field to a single source. (4.1.12)
● ASME U-stamp required
○ ASME UM-stamp acceptable (small vessel)
○ Below ASME exemption threshold (no stamp)
● Class C (general commercial HVAC)
○ Class B (chemical process)
○ Class R (severe industrial / petroleum)
☐ NSF/ANSI/CAN 61 (health effects)
☐ NSF/ANSI/CAN 372 (lead content)
○ Required (AHRI directory listing)
● Not required (manufacturer's rated performance)
5 Environmental and Service Conditions
NOTE The heat exchanger shall be selected for the design pressure, design temperature, fluid, and flow rate of each of the two circuits it serves. (5.1)
NOTE The design pressure of each circuit shall equal or exceed the maximum working pressure of that circuit, including pump shutoff head and static height, plus a margin. (5.1.1)
NOTE The design temperature of each circuit shall equal or exceed the maximum operating temperature of that circuit. (5.1.2)
NOTE Steam-to-water service imposes a high-temperature, higher-pressure condition on the steam side that drives both the material selection and the pressure-vessel and piping code jurisdiction. (5.1.3)
NOTE On steam-to-water exchangers the steam supply and condensate return connections may fall under ASME B31.1 piping jurisdiction; coordinate the nozzle-to-piping interface with the mechanical engineer of record. (5.1.4)
NOTE The fouling resistance applied to each fluid side shall be stated on the thermal selection sheet and shall be taken from TEMA or ASHRAE reference values for the service. (5.1.5)
NOTE Omitting the fouling allowance is the most common selection error; a unit selected for clean duty alone will be undersized once a fouling film develops in service. (5.1.6)
NOTE Where a glycol solution circulates on either side, the exchanger shall be selected using the actual glycol concentration and operating temperature range, not water properties. (5.1.7)
NOTE Glycol raises viscosity and lowers the heat transfer coefficient and specific heat relative to water; selecting on water properties for a glycol circuit undersizes the unit. (5.1.8)
NOTE The terminal temperature approach shall be specified for the duty and shall not be set tighter than the service requires. (5.1.9)
NOTE Each heat exchanger shall be selected to deliver the scheduled heat transfer rate at the scheduled flow rates and terminal temperatures of both circuits with the specified fouling allowance applied. (6.1)
NOTE The heat transfer rate, the entering and leaving temperature on each side, and the flow rate on each side together define the duty and are interdependent; fixing any four determines the fifth. (6.1.1)
NOTE The thermal selection shall be verified using the log mean temperature difference and the appropriate LMTD correction factor for the flow arrangement. (6.1.2)
NOTE The selection shall include a fouling allowance such that the clean unit has surface margin above the duty equal to the specified fouling resistance on each side. (6.1.3)
NOTE The pressure drop across each circuit at design flow shall not exceed the value scheduled for that circuit. (6.1.4)
NOTE Pressure drop and heat transfer trade against each other: narrower, more turbulent channels raise the heat transfer coefficient but also raise pressure drop and pumping energy, so each circuit carries a pressure-drop limit. (6.1.5)
NOTE The thermal duty and circuit conditions are project-specific and shall be taken from the equipment schedule.
heat exchanger schedule (6.1.6) 00.002
Default: 0.0005 hr·ft²·°F/BTU
00.002
Default: 0.0005 hr·ft²·°F/BTU
7 Heat Exchanger Type
NOTE The heat exchanger type shall be selected for the service pressure, temperature, fluids, and serviceability required by the application. (7.1)
NOTE A gasketed plate-and-frame exchanger shall be selected where a close approach, future capacity expansion, or full mechanical cleaning of the heat transfer surface is required. (7.1.1)
NOTE A gasketed plate-and-frame unit can be opened, its plates cleaned, and its plate count increased in the field, making it the serviceable, expandable choice for hydronic and domestic water duty. (7.1.2)
NOTE A brazed-plate exchanger may be selected where a compact envelope and high design pressure are required and field servicing of the interior is not. (7.1.3)
NOTE A brazed-plate unit is sealed and cannot be opened, cleaned internally, or expanded; it is replaced rather than serviced. (7.1.4)
NOTE A shell-and-tube exchanger shall be selected for steam-to-water service and for high design pressures beyond the range of plate units. (7.1.5)
NOTE A copper-brazed brazed-plate unit shall not be selected for steam service; specify a nickel-brazed unit or a gasketed plate-and-frame unit for steam-to-water duty, and verify the maximum steam pressure and temperature rating. (7.1.6)
NOTE A semi-welded plate exchanger may be selected where one circuit carries a mildly aggressive fluid, such as condensate or glycol, that is better contained on a laser-welded plate pair than against a gasket. (7.1.7)
NOTE A fully welded plate exchanger may be selected for high-pressure, high-temperature duty where no gasket is acceptable and field cleaning is not required. (7.1.8)
● Gasketed plate-and-frame
○ Brazed-plate
○ Shell-and-tube, U-tube
○ Shell-and-tube, straight-tube fixed tubesheet
○ Shell-and-tube, removable-bundle floating-head
○ Semi-welded plate
○ Fully welded plate
8 Plate-and-Frame Construction
NOTE Plate-and-frame requirements in this section apply to gasketed, semi-welded, and fully welded plate exchangers as indicated. (8.1)
8.2 Plates
NOTE Heat transfer plates shall be corrugated stainless steel of the alloy specified for the service. (8.2.1)
NOTE Plates shall be Type 316 stainless steel for standard hydronic, domestic water, and treated-water service. (8.2.2)
NOTE Plates shall be titanium where the fluid contains chlorides at a level that threatens stainless steel, such as seawater or heavily chlorinated water. (8.2.3)
NOTE Type 304 stainless steel plates shall not be used in treated-water systems where the chloride concentration exceeds 200 ppm. (8.2.4)
NOTE Type 304 stainless steel is susceptible to chloride stress-corrosion cracking; selecting it on cost alone risks plate failure in chlorinated systems, where Type 316 or titanium is required. (8.2.5)
NOTE The plate pack shall be arranged to deliver the specified thermal duty and pressure drop, and the gasketed frame shall allow the plate count to be increased for future capacity. (8.2.6)
● Type 316 stainless steel
○ Type 304 stainless steel
○ Titanium
8.3 Frame
NOTE The frame of a gasketed plate exchanger shall be carbon steel or Type 304 stainless steel with a fixed end plate and a movable pressure plate joined by tie bolts. (8.3.1)
NOTE Carbon steel frame surfaces shall be finished with a corrosion-resistant coating. (8.3.2)
NOTE The tie bolts shall compress the plate pack to the dimension that seats the gaskets, and a tightening dimension shall be marked on the frame. (8.3.3)
● Carbon steel, coated
○ Type 304 stainless steel
8.4 Gaskets
NOTE Gaskets on a gasketed plate exchanger shall be elastomeric and compatible with the fluids, temperatures, and pressures of both circuits. (8.4.1)
NOTE Nitrile (NBR) gaskets shall be used for standard water and glycol service within the temperature limit of the material. (8.4.2)
NOTE EPDM gaskets shall be used for steam condensate service and for slightly acidic systems. (8.4.3)
NOTE Nitrile gaskets shall not be used on steam or high-temperature condensate service. (8.4.4)
NOTE Nitrile loses elasticity and fails at the temperatures of steam-to-water duty; EPDM is the correct gasket for steam-to-water plate exchangers. (8.4.5)
NOTE Fluoroelastomer (FKM) gaskets shall be used where high temperature or chemical resistance beyond the range of EPDM is required. (8.4.6)
NOTE Gaskets shall be of a field-replaceable design, either clip-on or glued, and the type shall be recorded so replacements can be ordered. (8.4.7)
● Nitrile (NBR)
○ EPDM
○ Fluoroelastomer (FKM)
● Clip-on (glueless)
○ Glued
9 Brazed-Plate Construction
NOTE A brazed-plate exchanger shall consist of Type 316 stainless steel plates joined by a brazing alloy compatible with the service. (9.1)
NOTE The brazing alloy shall be copper for standard non-potable hydronic service. (9.1.1)
NOTE The brazing alloy shall be nickel for steam service, for aggressive fluids, and where copper leaching is not acceptable. (9.1.2)
NOTE A copper-brazed unit shall not be used for steam service or for potable water where copper leaching is restricted; a nickel-brazed unit is required for those applications. (9.1.3)
NOTE The brazed-plate unit shall be rated for the design pressure of both circuits, and the manufacturer's maximum pressure rating shall be verified against the higher-pressure circuit. (9.1.4)
10 Shell-and-Tube Construction
10.1 Bundle
NOTE The tube bundle type shall be selected for the cleaning, thermal-expansion, and cost requirements of the service. (10.1.1)
NOTE A U-tube bundle may be selected where lower cost is preferred and the tube interior does not require mechanical cleaning. (10.1.2)
NOTE A U-tube bundle accommodates differential thermal expansion between shell and tubes because each tube is free to grow, but its bent return ends cannot be mechanically brushed. (10.1.3)
NOTE A straight-tube fixed-tubesheet bundle may be selected for the lowest cost in small commercial domestic water and hydronic duty. (10.1.4)
NOTE A fixed-tubesheet bundle shall not be used on high-differential-temperature steam-to-water service. (10.1.5)
NOTE In a fixed-tubesheet design the shell and tubes are rigidly joined at both ends; on high-delta-T steam service the differential expansion between them overstresses the joint, so a U-tube or floating-head bundle is required. (10.1.6)
NOTE A removable-bundle floating-head exchanger shall be selected where both the tube side and the shell side must be mechanically cleaned and where differential expansion must be accommodated. (10.1.7)
NOTE A floating-head bundle is fixed at one tubesheet and free to slide at the other, accommodating expansion while allowing the entire bundle to be pulled for cleaning. (10.1.8)
● U-tube (removable)
○ Straight-tube, fixed tubesheet
○ Straight-tube, floating head (removable)
10.2 Materials
NOTE The shell shall be carbon steel unless the shell-side fluid requires a corrosion-resistant alloy. (10.2.1)
NOTE The tubes shall be selected for compatibility with the tube-side fluid and the heat transfer required. (10.2.2)
NOTE Tubes shall be admiralty brass or copper for standard hydronic and domestic water service. (10.2.3)
NOTE Tubes shall be 90/10 or 70/30 cupronickel where the fluid is more aggressive or where higher erosion resistance is required. (10.2.4)
NOTE Tubes shall be stainless steel where chlorides or water chemistry rule out copper alloys. (10.2.5)
● Carbon steel
○ Type 304 stainless steel
○ Type 316 stainless steel
● Admiralty brass
○ Copper
○ 90/10 cupronickel
○ 70/30 cupronickel
○ Type 316 stainless steel
10.3 Expansion Accommodation
NOTE A shell-and-tube exchanger on steam service shall accommodate the differential thermal growth between the shell and the tubes. (10.3.1)
NOTE Expansion shall be accommodated by a U-tube or floating-head bundle, or by a shell expansion joint on a fixed-tubesheet unit. (10.3.2)
NOTE Steam raises the tube-wall temperature well above the shell-side water temperature, so the tubes grow more than the shell; without an expansion provision this differential overstresses the tube-to-tubesheet joints. (10.3.3)
● U-tube bundle
○ Floating-head bundle
○ Shell expansion joint (fixed tubesheet)
11 Connections
NOTE Nozzle connections shall be sized, rated, and arranged for the circuit they serve. (11.1)
NOTE Flanged connections shall conform to ASME B16.5 at the pressure class required for the circuit. (11.1.1)
NOTE The flange class shall be verified against the circuit design pressure; Class 150 shall not be specified for a steam circuit whose pressure exceeds the Class 150 rating, where Class 300 is required. (11.1.2)
NOTE Connections smaller than the flanged range may be grooved or threaded where consistent with the circuit pressure and the connecting piping. (11.1.3)
NOTE The connection arrangement, same-end or opposite-end, shall be coordinated with the piping layout before the exchanger is ordered. (11.1.4)
NOTE A gasketed plate exchanger can be built with both circuits connected at one end or at opposite ends; fixing the arrangement without the piping layout causes field conflicts, so coordinate the locations on the drawings.
mechanical room piping plan (11.1.5) ● ASME B16.5 flanged, Class 150
○ ASME B16.5 flanged, Class 300
○ Grooved
○ Threaded (NPT)
● Same-end (both circuits connect at one end)
○ Opposite-end
12 Accessories
NOTE Each circuit of the heat exchanger shall be provided with full-port isolation valves so the unit can be removed from service without draining the system. (12.1)
NOTE Each circuit shall be provided with a drain valve at its low point and a vent at its high point so the unit can be drained and filled for servicing. (12.1.1)
NOTE A bypass shall be provided where the exchanger must be serviced without interrupting the circuit it serves, or where capacity must be modulated around the unit. (12.1.2)
NOTE Omitting isolation, drain, and vent provisions forces the system to be partially drained to service the exchanger; coordinate these accessories with the connecting piping. (12.1.3)
NOTE A temperature gauge and a pressure gauge shall be provided on the entering and leaving connection of each circuit to allow performance to be verified in service. (12.1.4)
☑ Full-port isolation valves, each circuit
☑ Drain valve, each circuit low point
☑ Air vent, each circuit high point
☐ Service bypass
☑ Temperature gauges, entering and leaving
☑ Pressure gauges, entering and leaving
13 Insulation and Casing
NOTE A heat exchanger on heating service shall be insulated to limit surface temperature and standby heat loss. (13.1)
NOTE Field insulation of the exchanger and its connecting piping shall be provided under
Mechanical Insulation.
(13.1.1) NOTE A removable insulating jacket should be provided over a gasketed plate exchanger so the plate pack can be reinsulated after servicing. (13.1.2)
NOTE A factory insulating jacket may be specified on a shell-and-tube unit where a finished appearance and consistent surface temperature are required. (13.1.3)
● Field insulation only
○ Removable insulating jacket
○ Factory insulating jacket
14 Testing
14.1 Shop Testing
NOTE Each pressure boundary shall be hydrostatically tested at the shop to the pressure required by ASME Section VIII for the unit. (14.1.1)
NOTE A pneumatic test shall be substituted for the hydrostatic test only where a hydrostatic test is impractical and the substitution is permitted by the Code. (14.1.2)
NOTE The shop test report shall be furnished as an informational submittal for each unit. (14.1.3)
14.2 Field Testing
NOTE After installation, each circuit shall be hydrostatically tested with the connecting piping in accordance with the applicable piping code, ASME B31.9 for building services piping and ASME B31.1 for steam supply and condensate piping. (14.2.1)
NOTE Each circuit shall be flushed clean of construction debris before the exchanger is placed in service. (14.2.2)
NOTE A strainer shall be installed and verified on the entering side of each circuit to protect the narrow plate channels or tube bundle from debris. (14.2.3)
NOTE The narrow flow channels of a plate exchanger foul and block quickly when debris from a dirty system reaches them, so upstream straining and flushing are required before startup. (14.2.4)
NOTE After startup, the entering and leaving temperatures of each circuit shall be measured and compared against the certified selection to verify the duty. (14.2.5)
☑ Hydrostatic test with connecting piping
☑ System flush before placing in service
☑ Upstream strainer verified on each circuit
☑ Performance verification (temperatures vs. selection)
15 Installation
NOTE The heat exchanger shall be installed level, plumb, and supported in accordance with the manufacturer's instructions. (15.1)
NOTE Clearance shall be maintained on the movable-plate side of a gasketed plate exchanger sufficient to open the frame and withdraw the plate pack. (15.1.1)
NOTE Clearance shall be maintained at the bundle end of a removable-bundle shell-and-tube exchanger sufficient to pull the full length of the bundle. (15.1.2)
NOTE Locking in the unit location without reserving plate-removal or bundle-pull clearance prevents the exchanger from ever being serviced in place; verify the clearance against the equipment layout.
equipment clearance plan (15.1.3) NOTE Connecting piping shall be independently supported so that no piping weight or thermal load is transferred to the exchanger nozzles. (15.1.4)
NOTE A unit on steam service shall be installed with the steam-side and condensate-side piping arranged to drain condensate freely and to admit no condensate slug to the unit. (15.1.5)
NOTE Where shown, the exchanger shall be anchored to resist seismic loads in accordance with the project structural requirements.
seismic anchorage detail (15.1.6) 16 Delivery, Storage, and Handling
NOTE Each heat exchanger shall be delivered with its nozzle openings capped or plugged to keep the interior clean and dry. (16.1)
NOTE Gasketed plate exchangers shall be stored with the plate pack compressed to the tightening dimension and protected from ultraviolet light, which degrades the gaskets. (16.1.1)
NOTE Units shall be lifted only at the manufacturer's designated lifting points and shall not be lifted by the nozzles or tie bolts. (16.1.2)
NOTE Units shall be stored indoors or under cover and protected from freezing until placed in service. (16.1.3)
17 Warranty
NOTE The manufacturer shall warrant each heat exchanger against defects in materials and workmanship for the warranty period, beginning at Substantial Completion. (17.1)
NOTE The warranty shall be issued in the Owner's name and shall be delivered as a closeout submittal. (17.1.1)
● 1 year
○ 2 years
○ 5 years
18 Spare Parts
NOTE The Contractor shall furnish the spare parts required to return each serviceable exchanger to operation after a gasket or plate failure. (18.1)
NOTE For each gasketed plate exchanger, a complete set of replacement gaskets shall be furnished. (18.1.1)
NOTE For each gasketed plate exchanger, replacement plates shall be furnished in the quantity specified to cover field damage during servicing. (18.1.2)
NOTE Spare parts shall be delivered in labeled containers identifying the unit they serve and shall be turned over to the Owner at Substantial Completion. (18.1.3)
☑ One complete set of replacement gaskets per gasketed unit
☐ Replacement plates per gasketed unit
☐ Replacement strainer screens per circuit