How to Field Measure a Coil

How to field measure a coil

1.) Determine the type of coil: hot water, chill water, steam, DX, condenser 2 Stand in the air stream & determine the location of the supply & return headers. Meaning is it a same end connected (supply & return header) on the same end; or opposite end connected with the supply on one end and the return on the other.

2.) If you can find the original coil model number note in on the drawing that you plan to complete.

3.) Once you have determined the type of coil complete an appropriate drawing for that coil with the following information.

4.) Count the number of rows deep in the direction of the airflow from front to back. This can be anywhere from 1 thru 10 rows.

5.) Count the number of fins per inch. Place a ruler on the fins & count the number in one inch.

6.) Measure the finned area. This dimension is A and B on the drawing. The “open” area that air passes across.

7.) Most coils are cased around the fin area. This is the metal frame that surrounds the finned area or dimensions CT, CB, D, & E.

8.) Then measure the depth of the coil. This should be the depth of the coil frame not just the fin pack. Dimension H on your drawing.

9.) The I dimension is the overall length of the coil to include the header and return bends. The return bends can stick outside the frame of the coil. Do not include the connection stubs as they will be measured later.

10.) Dimension J is the length of the supply & return stubs. These can be from 1 to 8 inches in length. This is not the diameter.

11.) Measure the diameter of the supply & return connections and note on the drawing. Also define the type of connection that is needed. MPT, FPT, or SWT.

Additional Helpful Points

Count the number of tubes in the face of the coil and the number of tubes that feed each header. This is used the determine the pass or circuiting of the coil.

Note the tube size (OD). Water, DX, and condenser coils are usually ½ or 5/8. Steam coils are usually 5/8 to 1 1/8.

The hand of a coil is determined by the following. Stand in the air stream with the air at your back. It’s a RH coil if the headers are on you right and a LH if the headers are on your left.

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