How to Identify the Type of HVAC Coil in Your System Without Original Drawings

air handling

How to Identify the Type of HVAC Coil in Your System Without Original Drawings

by Kyle Couch Apr 4, 2025

Even without original specs, you can identify coil type by looking at airflow direction, tube layout, fin density, and connection orientation.
Key indicators — such as refrigerant lines, air handler placement, and number of tube rows — help differentiate between evaporator, condenser, and hot/chilled water coils.
Tube size, casing dimensions, and connection type (threaded, flanged, sweat) provide critical clues for rebuilding or replacing the coil accurately.
Taking correct measurements and photos allows KCL to reverse-engineer a replacement coil even if documentation is missing.
KCL offers on-site coil identification and measurement services across Ontario, helping avoid guesswork, downtime, and incorrect orders.

It’s one of the most common scenarios we run into: a coil has failed, and no one has the original drawings, model number, or spec sheet. The unit may be decades old, installed during a renovation, or built into a custom air handler.

Now you’re left wondering — what kind of coil is this, and how do I replace it?

Don’t worry. With a few strategic steps (or a quick call to KCL), you can get the information you need to identify the coil type and get a perfect replacement — no guesswork, no downtime.

Step 1: Determine the Coil’s Function

Start by identifying the purpose of the coil within the system. You can often tell this based on location and refrigerant piping.

🔄 Evaporator Coil

Typically located inside an air handler or refrigeration unit
Cold to the touch when operating
Absorbs heat → refrigerant evaporates inside
Signs: suction line (larger pipe), cold airflow, condensation pan

🔁 Condenser Coil

Found in outdoor units (rooftop or pad-mounted)
Hot during operation
Releases heat → refrigerant condenses inside
Signs: hot air discharge, high-pressure lines, external fan

🌡️ Hot or Chilled Water Coil

Connected to a boiler or chiller
Contains water or glycol, not refrigerant
No compressor or expansion valve nearby
Signs: 2–4 pipe hydronic connections, mechanical room location

Step 2: Look at Airflow Orientation

This tells you how the air moves across the coil and helps define its casing and support configuration.

Horizontal Airflow: Side-to-side orientation
Vertical Airflow: Top-to-bottom (common in AHUs and fan coils)
Slant or “A” Coils: Typically in residential or compact units, set at an angle

Note the direction of airflow relative to the tubes and fins — this will impact replacement coil design.

Step 3: Measure the Coil

Even without drawings, physical measurements give you everything a manufacturer needs to recreate the coil.

Critical Measurements:

Finned Height & Finned Length
Casing Height, Length & Depth
Tube Diameter (3/8″, 1/2″, 5/8″)
Number of Rows (front to back)
Fin Spacing (FPI — Fins Per Inch)

Pro tip: Count FPI by measuring 1 inch along the fin line and counting visible ridges.

Bonus Tip:

Take high-resolution photos from multiple angles — including close-ups of:

Connection points
Casing flanges
Tube bends and headers

Step 4: Identify Connection Types and Locations

Improper connection matching is one of the most common failure points in replacement coils.

Record:

Pipe size (OD) and thread/sweat/flange style
Connection orientation (left/right/top/bottom)
Distance from reference points (e.g., coil corner to centerline of inlet)

This helps manufacturers design a drop-in replacement that doesn’t require pipe work.

Step 5: Gather Operational Clues

If the coil is still operating, or if you have access to system design info:

Refrigerant type or water/glycol mixture
System pressures or temperatures (if known)
Load conditions or square footage it serves

All of this supports correct capacity matching — even without an original datasheet.

KCL’s Coil Identification Service

You don’t have to go it alone. If any of the above seems risky, time-consuming, or outside your scope — just call KCL.

We’ll:

Visit your site
Measure the coil in place
Identify type, size, and materials
Produce a custom-engineered drawing for replacement
Deliver a drop-in-ready coil built to match

This service is especially helpful for:

Legacy systems
Multi-zone air handlers
Industrial refrigeration units
Transit, school, or commercial infrastructure

Frequently Asked Questions

What if I’m not sure what type of HVAC coil I have?

Send us photos, dimensions, and connection details. In most cases, we can identify the type from that alone — and confirm it with a site visit if needed.

Do I need original specs to order a coil?

Not at all. We specialize in reverse-engineering coils using physical measurements and system function.

What’s the risk of guessing wrong?

Big. A mismatched coil can damage the system, reduce efficiency, and cause safety issues. That’s why we recommend precise measurements and KCL’s support.