Creating WSHP Systems

A water-source heat pump (WSHP) is a self-contained refrigeration unit that serves one zone. It rejects heat to, or pulls heat from, a building-wide water loop. Each unit has its own compressor and can switch between heating and cooling. Because every unit shares the same loop, a unit cooling a sunny south office adds heat that a unit heating a north office can then use.

Here’s what’s inside a single unit and how it connects.

Each unit runs a standard vapor-compression cycle between two heat exchangers:

• Water-to-refrigerant coil: a coaxial tube-in-tube or brazed-plate exchanger connected to the building loop.
• Air-to-refrigerant coil: a fin-tube coil with a blower that conditions the zone air.

A reversing valve sets which coil is the condenser and which is the evaporator, so the same unit can cool or heat. An expansion device sits between the two coils. It is usually a bidirectional TXV, or an EEV in newer units.

The water loop is held within a moderate band, typically around 60–90°F for a boiler/tower loop. Within that band, every unit has a good heat source or sink in either mode. Central plant equipment only intervenes when the loop drifts outside the band.

The type of loop the heat pumps share is the main design choice for this system.

Hybrid loops also exist. They pair a smaller ground field with a fluid cooler or boiler to cut drilling cost.

Click the left or right arrows at the bottom of the mindmap to step thru the slideshow.

I'll start by connecting to Revit on your computer and inspecting the open model so I can locate the rooms, the mechanical room, and the available MEP families.

Doors are hosted without a location point; I'll use bounding-box centres instead.

Step 1 – Model review done. Model "261103 WSHP System" is open and healthy (0 warnings). Findings:

• Layout (L1, deck/L2 at 12'-0"): South side has a conference room (x −63 to −31) and three offices; north side has a conference room and two offices, with the Mechanical Room (Room 100) in the NE corner (x 1.8–17.8, y 39–54). Open office runs between them (y −1.3 to 39.1). Only the Mechanical Room is a placed Room; the others are defined by walls only.
• No ceilings are modeled, so there's no ceiling height to work from. I'll assume a 9'-0" ceiling with plenum equipment at ~10'-0", and the open-office unit at 11'-0" as you specified.
• No water-source heat pump family is loaded. The closest loaded terminal units are VAV Unit – Parallel Fan Powered (sizes 2–6). Since your routing step refers to the units as "VAV units," I'm checking that family's connectors now to see whether it can stand in for the WSHPs.
• Also loaded: Air Handling Unit – Split System – Vertical, Boiler: Standard, Scroll Chiller – Water Cooled, supply grilles/diffusers, return diffusers, and CHW/HHW supply & return piping systems.

Imperial WSHP families exist in the local library. Let me list the imperial horizontal ones.

Step 2 – Equipment families. The VAV fan-powered family has no water connections, so it can't take the hot/cold water piping you want. I found Autodesk's stock WSHP – Horizontal – High Efficiency – 2-5 Tons – Left Return – Right Discharge family in your local Revit 2027 library and loaded it into the model. It has a supply-air outlet, a return-air inlet, and two water connection pairs (a main pair and a smaller auxiliary pair), which I'll use for chilled water and heating hot water respectively.

Planned unit sizes (layout only, not a load calc): 2 Tons for each of the four plenum units, 5 Tons for the open office. Heads-up: ~3,500 sf of open office would normally need roughly 8–10 tons; 5 Tons is the largest size in this family. Placing the units next.

Step 3 – WSHP units placed (all on L1, marked WSHP-1 to WSHP-5):

Each plenum unit's return-air inlet faces the corridor side (toward the AHU duct trunks) and its supply outlet faces the room interior. One issue: at 11'-0" WSHP-5's top is at 12'-9", which is above the L2 level (12'-0"). L2 has no floor modeled so there's no hard clash, but if 12'-0" is the actual deck you'd want to drop it to about 10'-2". Next: registers and supply ducts.

Revit 2027 needs 64-bit element IDs; fixing that.

Moving the symbol activation inside the transaction.

Step 4 – Supply registers and WSHP supply ductwork done. All connections succeeded:

• WSHP-1: 16x12 main runs east at the south-office centerline, with 24x24 ceiling diffusers (9'-0" ceiling assumed) tapped into each of the three south offices.
• WSHP-2: same arrangement serving the two north offices.
• WSHP-3 / WSHP-4: 16x12 mains, each with two ceiling diffusers at the quarter points of the south and north conference rooms.
• WSHP-5: 18x19 exposed main runs west across the open office at 11'-11" centerline. Four 12x4 double-deflection registers are duct-mounted on its underside at about 22'-3" spacing.

Register marks are WSHP-n-S1, S2, etc. The far ends of the mains are open (no end caps placed yet). Next: AHU, boiler and chiller in the mechanical room.

Step 5 – Central equipment placed in the Mechanical Room (NE corner):

• AHU-1 (Air Handling Unit – Split System – Vertical, size 10): south side of the room. Its supply outlet is on top and its return inlet faces north.
• B-1 (Boiler – Standard): SE corner of the room.
• CH-1 (Scroll Chiller – Water Cooled, 20 Tons): along the north wall, with chilled-water connections facing south.

What I found: the only AHU loaded is a split-system unit. Its pipe connections are refrigerant lines, not hydronic, so the AHU itself won't get CHW/HHW piping. The chiller's condenser-water connections will also stay unconnected, since no cooling tower was requested. Next: supply ducts from AHU-1 to each WSHP.

Step 6 – AHU-1 supply ducts to the WSHPs done; every fitting connected:

• A 19x16 riser rises from the AHU outlet.
• Near the top of the riser, a 12x8 trunk takes off west at 10'-7" and runs above the north rooms.
• A second 12x8 trunk takes off east, drops south through the east strip, and runs west along the south edge of the open office.
• Each plenum WSHP gets a 10x6 branch off its trunk, with a transition up to the unit's inlet collar.
• The riser turns at 11'-11" into a 19x16 branch that runs south to WSHP-5's inlet, with a transition.

One consequence of your layout: the AHU supply connects to each WSHP's return-air inlet. That makes AHU-1 act like a ventilation/primary-air unit feeding the heat pumps. Sizes are placeholders, not calculated. Next: return air ducts.

Step 7 – Return air ductwork done; all fittings connected:

• South rooms: one 24x24 return grille in each office and the conference room (south side of each room). They tap into a 14x10 return main at 11'-5" that runs east, then north up the east strip.
• Open office: two duct-mounted return grilles on a 14x10 main along the south part of the open office, which tees into the east-strip return.
• North rooms: one return grille per room on a 14x10 main along the north wall, which turns south into the mech room.
• At the AHU: the north and east returns tee together above the AHU. The return then drops down and transitions to the AHU's 52x22 return collar.

Return mains sit above the supply ducts and AHU trunks to avoid crossing them. Next: chilled water and heating hot water piping.

Step 8 – Hydronic piping done; every branch, tee and corner connected.

Four 2" mains (CHWS, CHWR, HHWS, HHWR) run as a stacked rack just above the 9'-0" ceiling, between 9'-2" and 9'-11". The rack follows a loop: along the north rooms, through the mech room, down the east strip, and west along the south rooms. The west ends are capped.

Connections:

• Each WSHP: its main water pair is on chilled water and its smaller auxiliary pair is on heating hot water. The branches are staggered so the four pipes don't cross each other.
• CH-1: CHW supply and return connect to its evaporator connections.
• B-1: HHW supply and return connect through 3"→2" reducers.

Caveat: the family flags the WSHP's auxiliary pair with the opposite flow direction from a heating coil. Revit may report flow-direction warnings on the HHW system, so I'm checking now.

The WSHP system is fully modeled and connected in 261103 WSHP System, with 0 warnings. I haven't saved the file; tell me if you want me to save it.

All 5 heat pumps, 22 supply/return grilles, about 51 duct runs and about 109 pipe runs are in place on L1. Each of the four water systems (CHWS-1, CHWR-1, HHWS-1, HHWR-1) traces all the way from the chiller or boiler to every WSHP.

Assumptions:

• Units: No heat pump family was loaded, so I loaded Autodesk's stock WSHP – Horizontal (2–5 Ton) family from your Revit 2027 library. Your routing step said "VAV units"; I treated those as the WSHPs.
• Ceiling: No ceilings are modeled, so I assumed a 9'-0" ceiling and set the plenum units at 9'-9".
• Sizes: Duct and pipe sizes are placeholders, not engineered.
• Water connections: Each WSHP's main water pair is on chilled water and its smaller auxiliary pair is on heating hot water. The family flags the auxiliary pair's flow direction backwards for a heating coil.

Things you should review:

• WSHP-5 height: at 11'-0" its top is at 12'-9", above L2 (12'-0"). If 12'-0" is the real deck, drop it to about 10'-2".
• WSHP-5 capacity: 5 Tons is the largest size in this family; ~3,500 sf of open office would normally need around 8–10 tons.
• AHU supply into the WSHPs: the ducts are physically connected to each WSHP's return-air inlet. Revit keeps that segment as its own small system per unit because the system classifications don't match, so AHU-1 reads as a ventilation/primary-air unit feeding the heat pumps.
• Unconnected equipment: the chiller's condenser-water connections, the AHU's refrigerant lines, and all condensate drains are left open (not requested).
• Open duct ends: the 10 dead-end duct mains have no end caps yet; the four pipe mains are capped.
• No clash check: I stacked systems at separate elevations to avoid crossings, but haven't run a clash detection.

I'll turn the summary into a spreadsheet; first checking which spreadsheet format is available here.

I've made an Excel file, WSHP_System_Summary.xlsx, from the last answer. There's no editable spreadsheet format in this session, so it's a regular Excel file instead.

It has six tabs:

• Summary: counts that recalculate from the other tabs (5 WSHPs, 3 central units, 22 air terminals, 7 open review items), plus the duct/pipe run counts and warning count from Revit.
• Equipment: each unit's mark, family, size, location, what it serves and its elevation.
• Air Terminals: all 22 supply and return terminals, with room and what each connects to.
• Systems: the air and water systems, with sizes and connection status.
• Assumptions: the four assumptions from the summary.
• Review Items: the seven items to check, each with an "Open" status. One of them is that the Revit model still isn't saved.