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Inlet Box Position Dial

Run the Inlet Box Position Dial MicroSim Fullscreen

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About This MicroSim

An inlet box's position states where its opening faces. FanPedia measures it around the fan as seen from the drive side, in 45° steps from 45 to 360, with 360 at the top and the angle increasing clockwise (FanPedia p. 144). Unlike the discharge angle, it does not change direction with rotation.

Position Description Box location (drive side)
45 Angular Down Intake Upper right
90 Horizontal Right Intake Right
135 Angular Up Intake Lower right
180 Bottom Up Intake Bottom
225 Angular Up Intake Lower left
270 Horizontal Left Intake Left
315 Angular Down Intake Upper left
360 Top Down Intake Top

The sim opens in Explore mode with a CW fan and the box at 360. Move the box around the housing and read each number and description; switch the drawn rotation between CW and CCW and watch the box and its number stay where they are. Once you have visited both members of a pair, the panel points out that 45 and 315 (and 135 and 225) share a description.

Press Start challenge for eight duct descriptions in a fixed order. Move the box to meet the duct and press Check. The position numbers stay hidden until you check, so you place the box by where the duct arrives; the check then shows the number. An answer is correct when the position equals the answer; there is no partial credit. You get two attempts. A wrong first attempt gets a hint: the mirror position with the same description says "Same description, other side"; on duct 8, which is drawn on a CCW fan, the counterclockwise count says the angle does not follow rotation; anything else says to find where the duct arrives. A second wrong attempt marks the correct position with a dashed ✓ ring, shows the answer and the reason, and counts the duct as missed. Only first-attempt answers count; mastery is 7 of 8. Explore mode is never scored.

The housing is drawn with a top horizontal discharge so the drawing has an outlet; the inlet box is on the inlet face, so it may pass behind the outlet in this end view.

How to Use

  1. In Explore mode, press Clockwise ⟳ (or the Right arrow key) to walk the box around the housing, reading each number and description. Clicking near a position also moves the box.
  2. Switch the rotation to CCW: the box and its number do not move.
  3. Press Start challenge. Read the duct description, move the box to meet the duct and press Check (or Enter). A correct answer reads "✓ Correct: position 90, Horizontal Right Intake." in a solid green box; a wrong one reads "✗ Not quite." with a hint in a dashed red box.
  4. Press Next duct (or Enter). After duct 8 the summary lists the score, the mastery line and any missed ducts with their reasons. Explore mode returns to free exploration; Start over runs the eight ducts again.

Keyboard: Left and Right arrow keys move the box; Enter checks the duct, and Enter again goes to the next one. Tab reaches every button; Space presses a focused button.

Data label: "Source: FanPedia p. 144 · Positions as seen from the drive side", at the bottom left of the drawing.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

<iframe src="https://moroshek.github.io/FanTASTIC-textbook/sims/ch12-inlet-box-position-dial/main.html"
        height="602px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Learning Objective

The learner will use the drive-side inlet box angle convention to set the correct inlet box position for eight duct-approach descriptions, with at least 7 of 8 correct on the first attempt (Bloom: Apply, verb: use).

Audience

Adult professional development: new application engineers, sales staff, representatives and facilities staff who have read the "Inlet Box Position" section of Chapter 12.

Duration

10 minutes

Prerequisites

  • Inlet box and inlet box position
  • Viewed from the drive side
  • The eight inlet box position numbers and their descriptions
  • The difference between the inlet box angle and the discharge angle

Activities

  1. Explore (3 min): Walk the box all the way around. Name the two pairs of positions that share a description, then switch to CCW and confirm nothing moves.
  2. Challenge (5 min): Set the eight ducts. Say the number aloud before pressing Check.
  3. Review (2 min): For each missed duct, find the mirror position and explain why the number, not the description, pins down the side.

Common Misconceptions Addressed

  • The inlet box angle counts in the direction of rotation: duct 8 is drawn on a CCW fan, and the counterclockwise count gets "The inlet box angle does not follow rotation".
  • The description alone identifies one position: ducts 5 to 8 use the shared descriptions in pairs.
  • The inlet box angle is read from the inlet side: the drawing and every duct are described from the drive side, and a mirrored answer gets "Same description, other side".

Assessment

  • "Correct on first attempt: n of 8" is the running score; mastery is 7 of 8 on the first attempt.
  • Follow-up: an order reads CCW 90 discharge with the inlet box at 90. Which side is the box on, and why does the rotation not change it?

References

  1. Duct (flow) - Wikipedia overview of air ducts and how they connect to fans.
  2. Centrifugal fan - centrifugal fan construction, including inlets and housings.
  3. FanPedia: The Fan & Blower Encyclopedia - Twin City Fan's reference; p. 144 defines the inlet box positions determined from the drive side.