Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Water-Source Heat Pumps
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## The DOE federal floor at 10 CFR 431 is 12.2 EER for units below 17,000 Btuh and 13.0 EER for units from 17,000 to 135,000 Btuh, both with a 4.3 COP minimum for heating. ASHRAE 90.1-2022 sets the same floor for code compliance. ENERGY STAR and owner high-efficiency tiers run well above this; select the tier from the schedule, not from the floor. {note}
+## The cooling efficiency tier shall be specified as code minimum, ENERGY STAR, or owner high-efficiency, selecting the tier from the project schedule rather than the code floor.
+
```datasheet
label: Cooling efficiency tier (EER)
…6 unchanged lines
```
+## The minimum cooling EER at 86 °F entering water temperature shall be specified, consistent with the cooling efficiency tier selected for the unit.
+
```datasheet
label: Minimum cooling EER at 86 °F EWT
…6 unchanged lines
```
+## The minimum heating COP at 68 °F entering water temperature shall be specified, consistent with the cooling efficiency tier selected for the unit.
+
```datasheet
label: Minimum heating COP at 68 °F EWT
…30 unchanged lines
# Unit Configuration and Capacity {toc}
−## The unit mounting orientation shall be selected to suit the architectural layout and the available service access. {note}
+## The unit mounting orientation shall be selected to suit the architectural layout and the available service access.
−## Vertical (closet or chase) units stack supply and return in a single cabinet and suit perimeter closets in hotels and apartments. Horizontal units mount above the ceiling and suit office and corridor plenums. Console units are low-profile floor-standing perimeter units for under-window placement. Through-the-wall units serve a single room from an exterior wall. The choice is driven by the architecture, not by the mechanical system, so it must be coordinated against the architectural drawings. {note}
−
```datasheet
label: Unit mounting orientation
…8 unchanged lines
```
−## The unit type shall match the load-side distribution medium for the zone served. {note}
+## Vertical (closet or chase) units stack supply and return in a single cabinet and suit perimeter closets in hotels and apartments. Horizontal units mount above the ceiling and suit office and corridor plenums. Console units are low-profile floor-standing perimeter units for under-window placement. Through-the-wall units serve a single room from an exterior wall. The choice is driven by the architecture, not by the mechanical system, so it must be coordinated against the architectural drawings. {note}
−## Water-to-air units deliver conditioned air and serve the great majority of zone applications. Water-to-water units deliver hydronic heating or cooling water and serve radiant panels, chilled beams, or secondary hydronic loops. Selecting the wrong type strands the distribution system, so confirm it against the zone's terminal devices. {note}
+## The unit type shall match the load-side distribution medium for the zone served.
```datasheet
…6 unchanged lines
```
−## Each unit's cooling and heating capacity shall be established by a block or zone load calculation, not by floor area rule of thumb. {note}
+## Water-to-air units deliver conditioned air and serve the great majority of zone applications. Water-to-water units deliver hydronic heating or cooling water and serve radiant panels, chilled beams, or secondary hydronic loops. Selecting the wrong type strands the distribution system, so confirm it against the zone's terminal devices. {note}
−## Capacity is set by an ACCA Manual J or equivalent block load for the zone. Typical hotel and apartment units fall in the 0.75 to 2 ton range; the equipment class spans 0.5 ton (6,000 Btuh) to 11.25 ton (135,000 Btuh) per unit. {note}
+## Each unit's cooling and heating capacity shall be established by a block or zone load calculation, not by floor area rule of thumb.
```datasheet
…7 unchanged lines
```
+## Capacity is set by an ACCA Manual J or equivalent block load for the zone. Typical hotel and apartment units fall in the 0.75 to 2 ton range; the equipment class spans 0.5 ton (6,000 Btuh) to 11.25 ton (135,000 Btuh) per unit. {note}
+
+## The airside configuration shall be specified to suit the load-side distribution medium and the space layout serving the zone.
+
```datasheet
label: Airside configuration
…16 unchanged lines
## WSHP units ship as sealed hermetic packages. Keeping field refrigerant work out of the standard installation preserves the certified charge and avoids the leak risk and skilled-labor cost of field brazing the refrigerant side. {note}
−## The refrigerant type shall be confirmed against the HFC phase-down schedule applicable at the project location before equipment is ordered. {note}
+## The refrigerant type shall be confirmed against the HFC phase-down schedule applicable at the project location before equipment is ordered.
−## R-410A remains common across the installed base, but lower-GWP refrigerants such as R-32 and R-454B are replacing it in newer product lines. Several jurisdictions, including California under the AIM Act phase-down, restrict sales of higher-GWP equipment on a published timeline. Ordering R-410A equipment without checking the local schedule risks a unit that cannot legally be sold or installed when it arrives. {note}
−
```datasheet
label: Refrigerant type
…6 unchanged lines
```
+## R-410A remains common across the installed base, but lower-GWP refrigerants such as R-32 and R-454B are replacing it in newer product lines. Several jurisdictions, including California under the AIM Act phase-down, restrict sales of higher-GWP equipment on a published timeline. Ordering R-410A equipment without checking the local schedule risks a unit that cannot legally be sold or installed when it arrives. {note}
+
## Where multiple units share an enclosed space, the total refrigerant charge shall be evaluated against ASHRAE 15 and the building code for machinery-room classification and leak-detection requirements. {note}
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# Loop System and Conditioning {toc}
−## The system shall be a two-pipe water-loop arrangement with the boiler and heat-rejection equipment connected to a common loop. {note}
+## The system shall be a two-pipe water-loop arrangement with the boiler and heat-rejection equipment connected to a common loop.
## A reverse-return two-pipe loop is the most common arrangement because it self-balances and is forgiving of field variation. A direct-return two-pipe loop costs less to install but requires careful balancing valve selection at each unit. The choice trades first cost against balancing effort. {note}
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```
−## The loop shall be maintained within its design temperature band by automatic control of the boiler and the heat-rejection equipment. {note}
+## The loop shall be maintained within its design temperature band by automatic control of the boiler and the heat-rejection equipment.
−## The standard water-loop band is 60 °F to 90 °F. Common design setpoints are a 65 °F low limit that energizes the boiler and an 85 °F high limit that energizes the cooling tower or fluid cooler. A dead band between the two prevents simultaneous heating and rejection. {note}
−
```datasheet
label: Loop low-temperature limit (boiler on)
…16 unchanged lines
```
−## A loop temperature reset or setpoint schedule shall be included in the contract documents so the controls contractor has a defined basis of control. {note}
+## The standard water-loop band is 60 °F to 90 °F. Common design setpoints are a 65 °F low limit that energizes the boiler and an 85 °F high limit that energizes the cooling tower or fluid cooler. A dead band between the two prevents simultaneous heating and rejection. {note}
+## A loop temperature reset or setpoint schedule shall be included in the contract documents so the controls contractor has a defined basis of control.
+
## Omitting the boiler and cooling-tower setpoint basis from the documents is a chronic source of RFIs, because the controls contractor finds no setpoint to program. Stating the low limit, high limit, and any reset strategy in the specification closes that gap before it becomes a field question. {note}
−## The loop fluid shall be plain water for loops maintained above the freezing range; a propylene glycol solution shall be provided only where loop or ambient conditions can approach freezing. {note}
+## The loop fluid shall be plain water for loops maintained above the freezing range; a propylene glycol solution shall be provided only where loop or ambient conditions can approach freezing.
−## A building recirculating loop held at 60 °F or above needs no freeze protection and runs on plain water, which preserves capacity and pumping efficiency. Propylene glycol is reserved for hybrid arrangements where some portion of the loop can approach or fall below 32 °F; glycol reduces capacity and increases pumping head, so it is not added without cause. {note}
−
```datasheet
label: Loop fluid
…5 unchanged lines
```
−## The boiler and heat-rejection equipment shall be sized against the simultaneous loop load using a diversity factor, not the sum of every unit's peak. {note}
+## A building recirculating loop held at 60 °F or above needs no freeze protection and runs on plain water, which preserves capacity and pumping efficiency. Propylene glycol is reserved for hybrid arrangements where some portion of the loop can approach or fall below 32 °F; glycol reduces capacity and increases pumping head, so it is not added without cause. {note}
+## The boiler and heat-rejection equipment shall be sized against the simultaneous loop load using a diversity factor, not the sum of every unit's peak.
+
## In a mixed-use building, heating and cooling zones rarely peak together, and the loop recovers heat internally. Sizing the boiler and tower for 100 % simultaneous load grossly oversizes both. A diversity factor of 60 % to 75 % is typical for mixed-use buildings. {note}
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```
−## Each unit shall be provided with a balancing valve so that it receives its design loop flow. {note}
+## Each unit shall be provided with a balancing valve so that it receives its design loop flow.
## Without a balancing provision at each unit, the loop short-circuits to the path of least resistance and starves units at the hydraulic extremes. {note}
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## The submittal shall identify whether the two-position valve is factory-mounted by the unit manufacturer or field-mounted, and that responsibility shall be assigned in the contract documents. {note}
−## The valve can ship factory-mounted on the unit or be field-installed in the loop drop. Either is acceptable, but the documents must state which, or the valve falls between scopes and is omitted. Confirming factory-versus-field mounting on the submittal prevents that gap. {note}
+## The valve can ship factory-mounted on the unit or be field-installed in the loop drop. Either is acceptable, but the documents must state which, or the valve falls between scopes and is omitted. Confirming factory-versus-field mounting on the submittal prevents that gap.
```datasheet
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# Controls and Integration {toc}
−## Each unit shall be furnished with controls compatible with the project's control architecture. {note}
+## Each unit shall be furnished with controls compatible with the project's control architecture.
## A standalone thermostat suits a simple installation. A unit-mounted BACnet or Modbus controller allows point-level monitoring and is the norm for managed commercial and hospitality buildings. Full BAS integration adds demand-controlled loop temperature reset and central scheduling. {note}
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```
−## A desuperheater for domestic hot water heat recovery shall be provided only where the connection to the plumbing system is coordinated and shown. {note}
+## A desuperheater for domestic hot water heat recovery shall be provided only where the connection to the plumbing system is coordinated and shown.
−## Many units offer a desuperheater that recovers compressor heat to preheat domestic hot water. The option is wasted if the connection port is left capped because the plumbing tie-in was never coordinated. Resolve the connection in design, or do not specify the option. {note}
−
```datasheet
label: Domestic hot water desuperheater
…5 unchanged lines
```
+## Many units offer a desuperheater that recovers compressor heat to preheat domestic hot water. The option is wasted if the connection port is left capped because the plumbing tie-in was never coordinated. Resolve the connection in design, or do not specify the option. {note}
+
# Sound {toc}
−## Each unit shall meet a scheduled maximum NC level in the occupied space, stated at the scheduled airflow and external static pressure. {note}
+## Each unit shall meet a scheduled maximum NC level in the occupied space, stated at the scheduled airflow and external static pressure.
## Sound is critical in hotels and residences, where guestroom and bedroom NC targets of 25 to 35 are typical, while commercial office space tolerates NC 35 to 45. A bare NC number without the airflow and static-pressure test conditions is ambiguous and generates RFIs. {note}
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## Electrical characteristics and branch-circuit protection shall comply with NFPA 70 (NEC) Article 440 for hermetic refrigerant motor-compressors. {note}
−## NEC Article 440 governs minimum circuit ampacity and maximum overcurrent protection for the hermetic compressor in each unit. Branch circuits and disconnects shall be sized from the unit nameplate minimum circuit ampacity and maximum overcurrent protection, not from running amps. {note}
+## NEC Article 440 governs minimum circuit ampacity and maximum overcurrent protection for the hermetic compressor in each unit. Branch circuits and disconnects shall be sized from the unit nameplate minimum circuit ampacity and maximum overcurrent protection, not from running amps.
```datasheet
…12 unchanged lines
# Installation {toc}
−## Units shall be installed in accordance with the manufacturer's published instructions and with the service clearances shown on the approved submittal. {note}
+## Units shall be installed in accordance with the manufacturer's published instructions and with the service clearances shown on the approved submittal.
## Closet and chase installations are the most clearance-constrained. Units squeezed in without the filter-pull and compressor-access clearance the manufacturer requires become expensive to service for the life of the building. {note}
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# Testing and Commissioning {toc}
−## After installation, the entering and leaving water temperature and water flow at each unit shall be measured and shall fall within 5 % of the design conditions. {note}
+## After installation, the entering and leaving water temperature and water flow at each unit shall be measured and shall fall within 5 % of the design conditions.
## Field verification confirms that the loop actually delivers the design flow and temperature to each unit, which is what makes the certified capacity real on the project. A 5 % tolerance band on water temperature and flow is the practical acceptance criterion; units outside it indicate a balancing or sizing problem to resolve before acceptance. {note}
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# Warranty {toc}
−## The manufacturer shall warrant each unit against defects in materials and workmanship for the period stated below from the date of Substantial Completion. {note}
+## The manufacturer shall warrant each unit against defects in materials and workmanship for the period stated below from the date of Substantial Completion.
−## A one-year whole-unit warranty is the industry baseline. Extended compressor coverage of five years is widely available and commonly specified for equipment that is difficult to access after occupancy, such as ceiling-mounted units above finished spaces. {note}
−
```datasheet
label: Whole-unit warranty period
…14 unchanged lines
```
+## A one-year whole-unit warranty is the industry baseline. Extended compressor coverage of five years is widely available and commonly specified for equipment that is difficult to access after occupancy, such as ceiling-mounted units above finished spaces. {note}
+
# Spare Parts {toc}
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- Manufacturer's recommended spare-parts list
```