Choosing a dormakaba BTS80 Floor Closer: Spring Size, Spindle Length, Offset Arm and the BTS80 F for Fire Doors

Before you order a dormakaba BTS80 floor closer, settle three things about the opening: the door width, the clearance you need under the door, and whether the door is center hung, offset hung or independently hung. dormakaba's BTS80 Series brochure and its BTS Series Applications and Accessories brochure turn those answers into a spring size, a spindle and a short list of packages.

How a BTS80 order string is built

The brochure's How to order page uses the example BTS80 D 74010 RH AMS 626. In order, that is the series, the package letter (D, a 3/4 inch offset door), the spindle, the hand, the fastener pack (AMS, all metal screws) and the finish. The spring size box after the package letter is empty in the example, and the chart notes that size 4 needs no entry. Handed units take LH or RH, explained in our door handing chart, and finish numbers such as 626 or 689 are listed in our finish codes chart. The chart also warns: "All combinations of features and options are not available for all models."

Spring size by door width

The size selection chart works from door width, with exterior and interior ranges.

The size chart has no weight column. The specification gives one limit for the series: doors up to 660 lb, up to 48 inches wide on the exterior and 54 inches on the interior. The chart is meant for average conditions, and for high or exceptionally heavy doors or wind pressure the brochure says "the next stronger spring size should be selected." The order chart labels size 3 as light opening force with no backcheck, size 5 as the size for the fire packages, with no delay and no hold open, and size 6 as strong.

BTS80 or BTS80 F: backcheck, delayed action, hold open

Where it is fitted, the backcheck sits at approximately 70 degrees. The technical details describe delayed action as extending the closing cycle to allow unobstructed passage; on the BTS80 it is selectable from 175 to 75 degrees. Hold open is selectable at points between approximately 75 and 175 degrees. You get one or the other: the brochure notes that turning the valve completely clockwise creates hold open and eliminates delayed action.

The BTS80 F for fire doors

The brochure states: "The dormakaba BTS80 F Series is listed by U.L. and C.U.L. under their continuing reinspection programs." Its technical details add "U.L. listed for use with fire doors." and "Non-hold open only." In the accessories brochure, the rated BTS 80 packages (E, F, C-E, C-F, L-E, L-F, IF and PF) list their closer as BTS 80F NHO.

dormakaba recommends the BTS80 F where a wall magnet holds the door open at 180 degrees, and its product page lists a separate BTS80 EMB Series, floor closers "specifically designed for fire/life safety applications with electromagnetic hydraulic hold open". Our guide to door stops and holders covers electromagnetic holders.

Spindle length and the clearance under the door

The spindle sets the door clearance, which dormakaba's spindle table lists as dimension x. The accessories brochure lists these spindles:

According to dormakaba, closers with extended spindle inserts are used with thresholds, carpeted floors and terrazzo pans, or where more clearance between door and floor is required. The clearances hold only if the closer and arm are installed per template. Pre-load spindles add a 3 degree pre-load to help hold the door closed; dormakaba says this is normally only necessary for center-pivoted single acting applications, and the hand must be specified. For a terrazzo pan, the accessories brochure says to add 1 inch to the desired clearance between the door and the finished floor when calculating the spindle size.

Concealed floor closer packages: center hung or offset arm

The package tables in the accessories brochure name the bottom arm for each package:

A and B are double acting, G and H single acting. In each offset group the accessories brochure labels the first package "standard" and the next two "20-min rated" and "up to 3-hr rated".

Each offset group in the package tables has its own bottom arm. The brochure describes the 75323 as a 3/4 inch offset standard-duty steel bottom arm, ordered with the hand specified, and adds: "Can also be used on fire doors rated up to three hours." The 15323 is the steel bottom arm for 1-1/2 inch offset doors. Offset packages also take top and intermediate pivots, and the intermediate pivot is marked optional in the standard packages and required in the rated ones. Our guide to door closer types explains center hung and offset hung, and our guides to Rixson pivots and floor closer parts and Calibre offset pivot sets show how other makers number theirs.

Cover plate, cement case and documents

dormakaba lists the universal cover plate 7410 as suitable for left and right hand, 3/4 inch offset, 1-1/2 inch offset and center pivoted doors. The closer body and cement case are 2-3/8 inches deep, which dormakaba calls suited for thin slab concrete construction. Installation instructions and technical drawings are in the Downloads section of dormakaba's BTS80 Series page; the BTS80 and BTS80F instructions also cover replacing a closer in an existing installation. For dormakaba products in our store, start from our dormakaba page.

Need help matching a BTS80 package to your opening? Our customer support team is available Monday - Friday, 8 AM - 4 PM Central Time, at 1-888-800-7789 or [email protected].