Warm air through the doors is often a large part of a room's load. Kelvin can work it out two ways, and always says which one it is using.
- 1
Under Doors and traffic, choose Add door. It starts from page defaults, so set each figure to the job's door.
- 2
Set its Wall and Along wall position, or drag it along a wall on the room plan. Then set its Width, Height, Type and Protection.
- 3
Choose its Traffic. The light, medium and heavy presets fill Passages per hour from page defaults with no cited source. Choose Custom to type your own.
- 4
Check Per passage, the seconds each passage holds the door open, and enter Stands open, the minutes per hour it simply stands open.
- 5
Under Sizing basis, choose the Infiltration method.
The two methods
- Doorway infiltration (detailed) works each door from its size, the time it is open each hour, a flow factor, and how well its protection keeps the air out, following ASHRAE Refrigeration Handbook Ch. 24. Each door has its own line in the load build-up.
- Air change rate (simplified) works from the room's volume. It is Kelvin's approximation of a legacy ASHRAE air-change table that the current chapter no longer prints. Heavy door usage doubles its rate. The doorway method ignores that switch and reads each door's own traffic instead.
- Auto — doorway when door data is complete uses the doorway method when every door has a width, height, type and protection, and air changes otherwise. The hint under the method says which one is in use, and why.
The Infiltration line in the load build-up gives the other method's figure beside the one in use, so you can read the two against each other.
When the doorway method reads high
The doorway method assumes the air through each opening reaches a fully established flow, which short personnel-door openings rarely do. When it reads more than twice the air-change figure, the load build-up warns you. Check each door's passages per hour and time per passage against the site, or choose the air-change method.
Door figures and their sources
- Per passage starts at the door type's figure. For conventional and high-speed doors that is the handbook's typical time, marked “Ch. 24 typical”. A personnel door's figure is Kelvin's assumption, marked “assumed”. Type the time you see on site and it is marked “entered”.
- Protection shows each option's effectiveness E, the in-service figure the handbook gives. E is lower on a freezer doorway, so the options follow the room's set point.
- Leaf U is the door leaf's own U-value. Leave it blank and the leaf conducts at its wall's panel U.
Note
With no doors, infiltration falls back to the air-change method. If you choose the doorway method for a room with no doors, it gives no infiltration load at all.