Step 01
Gather the physical coil dimensions
More info will be needed at the coil verification measure.
- Tube size (typical: 3/8″, 1/2″, 5/8″, or 1-1/8″)
- Number of rows (1 or 2 rows typical for heating, 3–8 rows typical for cooling)
- Fins per inch (typical: 6–14)
- Fin height (typical max is 60″. Coils taller than 60″ are typically stacked.)
- Fin length (typical max length is 240″)
- Coil depth (not critical for estimating, but typical is 3″–12″)
- Circuiting and connections (single or dual circuit, intertwined or face split, left- or right-hand, same- or opposite-end connections — not critical for estimating price)
- Flange sizes (typical 0″–2″ — not critical for estimating)
- Header and connection sizes (not critical for estimating)
- Pitched casing if a steam coil (not critical for estimating)
— Field measuring templates —
Download the right template
Print the measuring template that matches your coil type and bring it to the jobsite. Pick the variant that matches the connection arrangement on the coil you're replacing.
DX Evaporator
1 template
Water Coils
3 templates
Steam Distributing
3 templates
Standard Steam
2 templates
Booster Coil
1 template
Step 02
Gather all the design information
Different coil types need different data. Use the card that matches your coil.
Type 01
Chilled Water Coil
- CFM
- Capacity required
- Entering water temperature
- Leaving water temperature
- GPM
- Entering air temperature
- Leaving air temperature
- Glycol type and percentage (none, propylene, ethylene · 0–50%)
- Application
- How is the system controlled?
Type 02
Hot Water Coil
- CFM
- Capacity required
- Entering water temperature
- Leaving water temperature
- GPM
- Entering air temperature
- Leaving air temperature
- Glycol type and percentage (none, propylene, ethylene · 0–50%)
- Application
- How is the system controlled?
Type 03
DX Coil
- CFM
- Refrigerant (R-410A, R-22, R-454B, etc.)
- Capacity required
- Entering air temperature
- Leaving air temperature
- Condensing unit information (capacity, model number, staging, circuiting)
- Application
- How is the system controlled?
- Accessories required? Hot-gas bypass, TXVs, accumulators, filter driers, sight glasses, solenoid valves.
Type 04
Steam Coil
- CFM
- Capacity required
- Entering air temperature
- Leaving air temperature
- Steam pressure
- Coil type
- Steam distributing — no U-bends, designed for better freeze protection.
- Standard steam — looks like a hot-water coil. Not for makeup air or applications with EAT below 40°F.
- Application
- How is the system controlled?
Step 03
Verify performance
Chilled water, hot water, and steam are straightforward. DX is trickier.
Chilled water / Hot water / Steam: simply run a selection in the coil software program.
Direct Expansion (DX)
DX is a little trickier because the system performance depends on the paired condensing unit's performance. Use this four-step process:
- Run DX evaporator coil performance at 3 different saturated suction temperatures (SST) — example: 40, 45, 50.
- Run condensing unit performance at the same 3 SSTs (40, 45, 50).
- Plot the two lines on a graph. The point where they intersect is the System Design Capacity and SST.
- Run the evaporator coil selection with the SST you found in Step 3. Verify the new selection actually works (check capacity, LAT, etc.). If it doesn't, go back to Step 3 and add coil surface area and/or change the condensing unit size, then repeat.
Standard comfort cooling target: 45–50° SST.
Need help replacing a custom coil? The Applied Systems desk can run the selection for you.
Email the ASG desk →