TRICOIL traces the cooling-coil air process on a psychrometric chart and calculates
the room sensible load, latent load, and coil performance. It is designed for single-zone systems
with any mix of outside and return air — from 0 % to 100 % OA.
STEP 1 — Set Outdoor Design Conditions
Type a city name in the Design Location picker and select a design frequency
(0.4 % / 1 % / 2 %). Click Apply to load outdoor dry bulb and wet bulb.
Use Cooling (DB/MWB) for most projects. Switch to
Dehumidification (DP/MCDB) when outside air fraction exceeds roughly
30 % or when latent load governs — labs, hospitals, school gyms, 100 % makeup-air units.
The dew point and mean coincident dry bulb fill automatically from ASHRAE 2017 Table 1;
verify against your project-specific tables before finalizing.
STEP 2 — Enter Airflows and Room Conditions
Enter Outside Air CFM and Return Air CFM
(supply = OA + RA). Set the Room DB and RH % —
75 °F / 50 % is a common starting point. The mixed-air state
(Point A) updates instantly as you type.
STEP 3 — Set Coil Leaving and Supply Air Conditions
Point C is the air leaving the cooling coil — enter DB and WB to match
your coil selection or target ADP. Point D is the supply air delivered
to the room — equal to C for a DX system; slightly warmer for systems with reheat or
fan heat downstream of the coil. Adjust the Coil Efficiency slider to position D
automatically, or drag it on the chart.
Reading the Psychrometric Chart
A — Mixed air entering the coil
B — Apparatus dew point (coil process direction)
C — Air leaving the coil
D — Supply air into the room
Room — Design room condition
The D→Room line is the Room Sensible Heat Factor line.
If D lies on the RSHF line through the room point, the coil is
correctly sized for both sensible and latent load simultaneously.
Drag to Explore
Each labeled point on the chart has a dashed-circle drag handle. Grab and drag:
C — slides along its constant-RH curve (coil physics); adjusts latent capacity
D — moves horizontally (constant humidity ratio); simulates reheat or fan heat
Room — repositions the design room condition freely
The Live Load Box (lower-right of the chart) updates in real-time —
Total Cooling (tons), Sensible (MBH), Latent (MBH), and RSHF. Use this to confirm
the coil selection satisfies your load calculation.
Typical Design Workflow
- Select location → Apply outdoor conditions
- Enter OA CFM, RA CFM, room DB & RH
- Set Point C to match coil leaving conditions
- Scroll below the chart → press ▶ Calculate Performance
- Confirm D→Room RSHF line aligns with room load
- Check Live Load Box — Total & Latent satisfy load calcs
- If latent governs, switch to Dehumidification design and repeat
All psychrometric calculations use ASHRAE IP equations at standard atmospheric pressure (14.696 psia / sea level).
Results are for design verification — always cross-check against coil manufacturer's certified data.
