1. What is a B Vent Size Calculator?

Definition: This calculator determines the appropriate B vent size based on appliance BTU rating, vent height, and lateral run according to code tables.

Purpose: It helps HVAC professionals and installers select the correct vent size for gas appliances to ensure proper draft and safety.

2. How Does the Calculator Work?

The calculator uses code tables that relate:

Where:

• \( BTU/h \) — Appliance heat input rating
• \( Height \) — Vertical vent height (feet)
• \( Lateral \) — Horizontal run length (feet)

Explanation: The calculator references manufacturer tables or code requirements to determine the minimum vent diameter needed.

3. Importance of Proper Vent Sizing

Details: Correct vent sizing ensures proper draft, prevents spillage of combustion gases, and maintains appliance efficiency and safety.

4. Using the Calculator

Tips: Enter the appliance BTU rating, planned vent height, and lateral run length. All values must be > 0 (except lateral can be 0 for straight vertical vents).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between height and lateral?
A: Height is the vertical portion from appliance to termination, while lateral is the horizontal offset.

Q2: Where can I find the code tables?
A: Refer to NFPA 54/ANSI Z223.1 or the International Fuel Gas Code for complete tables.

Q3: Does this calculator work for all vent types?
A: No, this is specifically for Type B vents used with gas appliances.

Q4: What if my configuration isn't in the tables?
A: Consult the vent manufacturer or a mechanical engineer for non-standard installations.

Q5: How does altitude affect vent sizing?
A: Higher altitudes may require larger vent sizes - consult local codes for adjustments.