Door closers: ubiquitous, yet unloved and often maladjusted
I’ve been struggling with a video script for a while that's suffering from a massive case of scope creep and it’s bothering me so much that I decided to shelve it for now. But, when one door closes… this thing might be why! This is a door closer. You see these everywhere in commercial buildings and they’re pretty simple devices. But there’s one thing about them not enough people seem to know: these are adjustable! You can change their closing speed and speed them up to help a door which isn’t latching properly or, get this, slow it wayy down so the door stays open longer and it doesn't slam. Especially if you work in a hotel which is full of these and also people sleeping, that's a really good thing to know! All you need is an Allen wrench or screwdriver and someone to tell you how to do that.
And I’ll happily play the role of that someone. I’ll also talk about why these are there in the first place, how they work, and probably some other stuff. First, let me show you how to adjust these. Luckily, I have one installed on the door to the warehouse. Wait, you have a warehouse? Yep! wwwhy? For storing two of them, but that’s not important right now.
We’re talking about door closers. So, this door, if I open it to 90 degrees then let it go, does this. It’s a nice and smooth swing all the way to the end and then, because there’s no latch hardware in the door right now, the door closer is the only thing holding the door shut. Which I’m pretty sure is a problem since this is a fire door but I didn’t do that so don’t look at me.
Now, if we look at the door closer body we’re going to find that there are two little holes on the side with an Allen screw in each one. Sometimes there's a cover over the door closer body so if you don't see it right away, you might have to take that cover off. The holes are labeled L and S. And of I tighten the one labeled S, watch what happens.
Now, the door is closing very slowly. That is, until it’s almost shut. Once it’s at about 15 degrees, suddenly it speeds up.
Why’d it do that? Well, that’s kind of the whole point of those adjustments. Most door closers like this have two separate speeds: a swing speed (sometimes called sweep speed) and a latch speed. That’s what the L and S stand for (though they’re not always marked the same on every door closer). The swing speed, which is what I just adjusted, is the speed at which it will close the door over the majority of its travel. You usually want this to be fairly slow to help people with mobility issues or just to make getting through the door easier when you’re holding stuff.
And in many jurisdictions the swing speed is actually codified. The Americans with Disabilities Act requires that the door take at least 5 seconds to close from 90 degrees. But when the door is about to shut, you might need it to speed up a bit to ensure it has enough momentum to successfully engage the latch. And that’s what the latch speed adjustment is for.
Right now the latch speed on this closer is pretty moderate. But if I loosen that adjustment screw, the door shuts with a pretty significant thud regardless of how slow the swing speed was. [THUD] And if I tighten that screw, well the door no longer slams at all.
Instead it shuts very gently. You can even adjust these so that the swing speed is faster than the latch speed. I don’t think there’s much reason to do that but if you did, the door would swing closed quickly but then slow down right near the end of its travel for a gentle close. And here’s what I’d really like to you to know: So long as the door will successfully latch under all conditions, you can have these be as gentle as you like. They do not have to slam the door, and in fact the whole reason this style of door closer exists is to keep that from happening! So if you install one of these and don’t actually adjust it to the door it's on, you’re making it very sad. But let’s back up a bit.
Why do we want the door to close on its own anyway? Well, I already mentioned that this is a fire door and that’s one of the main reasons. Fire, it turns out, is bad. There are some places where fire can be ok. Like for instance a fire… place.
It’s really just called fire place, huh? Er, but where we don’t want it, and especially when we don’t expect it, fire is really dangerous. And if a fire breaks out in a building, fire doors are incredibly important for life safety. They compartmentalize a building and keep fire from spreading to other areas, both by being a physical barrier and by restricting the supply of oxygen to the fire in progress.
True fire doors can withstand the intense heat of a fire happening on the other side of them for more than an hour. But fire doors only work if the door is actually shut, so rather than let us forgetful humans forget to close them, we put door closers on them so they always close by themselves. Fun fact, in situations where we want there to be a self-closing fire door but we also want it to stay open during not-fires, electromagnetic door holder-openers can be installed alongside a door closer.
When powered on, these door holders attract a small metal plate attached to the door to… hold it open. This is useful in situations such as a building with a long hallway that you ordinarily want unbroken for an unimpeded flow of people but which should be compartmentalized in the event of a fire to reduce spreading. The electromagnets are tied to the building’s fire alarm system, so they can be released if it detects a fire in progress or someone activates it manually.
When the system cuts power to those electromagnets throughout the building, they all let go of whatever doors they’re holding open and the door closers close the doors. And of course this system is fail-safe - the door closers are always trying to close the doors and the door needs to be actively held open, so if the holding system fails for any reason, the doors close. There are, of course, other reasons to keep doors shut.
One of which is security. When there’s any kind of restricted access to a space, even something as relatively low-security as an apartment building’s lobby, you generally want doors to lock automatically and require a specific action to unlock them from the outside. But any automatic lock, even something as simple as a keyed door knob which is always locked from the outside, is pretty useless if the door can be left open. So you slap on a door closer to make sure that door always closes behind you and always locks.
Of course you can defeat a door closer with a doorstop or... like, a brick but that takes a conscious effort and for people casually coming in and out throughout the day, the door closer ensures the building is secured. Actually, quick note about doorstops. They are the enemy of a secure building and also fire safety. The temptation to use them is the reason those electromagnetic door holder opener thingies get installed. When the need to keep the door open is obvious but the need for it to close in a fire is safety critical, they’re a great choice.
But there are always going to be random situations where you need a self-closing door to be held open, so certain people would like me to tell facilities managers about delayed-action door closers. They exist! They act like any other door closer except when you open the door completely. When opened all the way, an internal mechanism is tripped which holds the door open for a minute or two. And then it will close. This is a great compromise for situations like helping workers who need to move bulky tables into an event space which has critical fire doors that cannot be left open.
Alright and then the last major reason to keep a door shut besides safety and security is energy. It costs money to keep buildings heated and cooled, and we’re not paying to heat the outside! So exterior doors often have door closers to make sure nobody leaves them open and makes Dad angry. However, there’s a dual-role there in that case.
Exterior doors, when left open, can be a lovely supply of oxygen for fires so self-closing exterior doors are not strictly for energy saving purposes. But they sure help. Fun fact, the reason revolving doors exist is because they are functional airlocks. High-traffic buildings in areas where it gets real cold have them almost as a rule because the four panels of rotating glass mean the door is never actually open so there’s never a blast of cold air coming in as people enter and exit the building. Just little sections of air get exchanged. Of course there are accessibility concerns there so generally there are also standard doors with powered openers for those who need them, but you often find signage thanking you for using the revolving door if you can.
Vestibules with a door on each end are another way to achieve air locking - though in order to be truly effective both sets of doors should never be open at the same time. And when the doors are automated, uh that happens a lot. I’d kind of like there to be a mode you can turn on in extreme cold which forces people to wait in the vestibule until the first door has closed but that would be confusing and potentially unsafe so I can understand why I’ve never seen that. OK, so with all those particulars out of the way, how is this thing actually closing the door? Well, the answer's simple: With a spring. In fact a simple spring is all you need to keep a door shut. If you put one somewhere such that it gets compressed as the door opens, then the spring is gonna push the door shut once it's let go.
And this here is a spring hinge! This is technically a door closer. Look, it even says UL listed door closer bod. Body. These are fairly common in household environments thanks to building codes.
I have a couple on the door between my garage and the rest of my home because that wall is a firewall and you really don’t want that door left open in case there’s a car fire. Which can happen. These simple hinges contain a spring which is compressed as the hinge opens, meaning the hinge will always close unless someone is actively pushing the door open. These work mostly fine but… they slam doors.
Real bad. When the door is fully open and then let go, it consistently picks up speed as it travels and by the end of its travel it’s moving quite fast. So when it meets the frame [SLAM] there’s quite a bang.
That’s of course annoying but also can cause injuries if people get their fingers in the wrong place at the wrong time. That has even caused lawsuits when they were used in public places and public fingers got publicly pinched in public. And besides that little issue, these don’t always latch the door. The spring in these isn’t very strong. I mean it seems quite strong when this isn't attached to a door but with the massive amount of leverage a door provides the spring hinges don’t push back with all that much force, so if you let a door go when it’s already close to its closed position, these will hold it mostly shut but they may not have enough oomph to actually engage the latch. So… eventually we got these things! These also have springs, but there’s a twist.
A second mechanism is fighting the spring to regulate the speed at which this closes the door. There were several different ways that was accomplished over the years, and some of the alternatives to this one still survive. But this hydraulic mechanism is by far the most common we see today. The actual closing force is provided by a spring pushing on a sliding rack. That rack engages with a pinion gear which this arm is attached to. When I force the arm in this direction, the rotating pinion slides the rack such that the spring is compressed.
And when I let go, the spring pushes the rack back in the other direction and the arm returns to its original position. But the rack the spring pushes on is also attached to a piston inside a hydraulic cylinder filled with oil. And that’s where the speed control comes from. When you push the door open, a check valve opens which allows the fluid to pass from one end of the cylinder to the other, thus the piston can travel through the hydraulic fluid mostly unimpeded. But when it starts moving backwards via the force of the spring, that valve closes and now the piston is stuck.
The hydraulic fluid has locked it in place. But there are two additional paths oil can take to move between the two halves of the cylinder. And those paths each have a valve inside which can restrict the flow of the fluid. And guess where those valves are? Here and here.
The latch and swing speed adjustments are in fact valves which, when turned, increase or decrease the speed at which fluid can flow through them. And that in turn restricts the speed of the closing mechanism. When you tighten these valves, you restrict that flow more which slows the mechanism down. In fact you can completely close them and, well, the door closer then becomes truly stuck. Or you can completely open them and then the spring is basically free to close the door as fast as it can.
Careful, though, because you can remove these plugs and that’ll let the hydraulic fluid out which is A) unpleasant and 2) will break the door closer. Actually, on that note, if you ever see one of these on a door with streaks of grossness coming down from it, the seals inside have probably failed and the hydraulic fluid leaked out. That door closer needs to be replaced if you don’t want it to slam because, well, its damping mechanism is effectively gone. But anyway, the two different closing speeds are achieved by the differing paths of the oil bypasses.
During the bulk of the door’s travel, the latch speed bypass doesn’t actually do anything because both of its ports are on the pressurized side of the cylinder. But once the piston gets past this point, those ports are now on either side of it so they become a second bypass with its own dedicated speed setting. Pretty simple and pretty clever. But it’s not actually that simple.
I want to make you aware of some particulars which are important to keep in mind both when making adjustments and when installing a door closer. For a start, these come in different sizes which really just means different spring strength. The spring inside here is the only thing that actually produces closing force so you need to make sure it provides the appropriate amount. Wider and bigger doors need stronger springs than smaller, narrower doors.
And when you encounter a door that’s “heavy” - it’s likely got a door closer on there that’s just too big for it and you can’t exert enough leverage to easily overcome the spring. Then again, some models - including this one - allow you to adjust the spring tension so this is sold as sizes 1 through 4, appropriate for any interior door up to 3 feet six inches wide. Now, while the spring is the only thing directly providing closing force, thanks to our old pal momentum the door’s speed as it closes will affect its latching force and that’s why the latch speed adjustment exists. If there’s a door which needs a bit of a shove to positively latch, this will give it that shove. If the latch operates smoothly and the door fits well within its frame, that shouldn’t be necessary, though. The spring force alone will shut the door, but there’s a weird extra thing to consider which is easy to miss: in modern buildings, HVAC systems can produce air pressure imbalances between rooms or between the inside and outside.
If those pressure imbalances are significant enough, they can overcome the spring force and keep the door from completely closing. This means that a door closer which gently and successfully latches a door in some conditions might not latch it when the HVAC system is running, and in that case you have to adjust it for the worst case scenario and there will be times it closes with a bit of a slam. And by the way, I have not touched the adjustments on this door closer and watch how it behaves out of the box.
Yeah, this would absolutely slam a door without adjusting the latch speed. But when you consider that the manufacturer of this is most concerned with its products doing their basic job in as many situations as possible, it makes sense that they’d sell them with the latch valve pretty wide open. They’re counting on the installers to make that adjustment when it’s possible, but lots and lots and lots and lots and lots and lots of people just never touch it.
Ask anyone who has ever stayed in a hotel. Fun fact, I used to work in the hotel industry and one of the first things I did at a new property when I had some time on a slow day was go around the building and adjust all the door closers so they didn’t slam anymore. Almost none of them had been touched at all since the hotels were built, so almost every guestroom door slammed shut with quite the bang. Same with the stairwell doors. And that’s pretty annoying in the middle of the night, so I simply took the time (which wasn’t that much time at all) to go around, open every door, and adjust the closers. I slowed them down as much as I could while making sure that they latched properly, and then I sped them up just a tad to account for varying conditions.
Some doors had trouble latching and I had to leave them slamming somewhat, but I was able to silence the vast majority of the doors. It wasn’t much of a task, but nobody had thought to do that, and this is why you need a weird obsessive nerd somewhere on your staff! Now, to be honest, this bugbear of mine is the main reason I made this entire video and mostly I’m concerned with people knowing how to adjust door closers which already exist. But I would like to briefly talk about mounting these to a door because that’s way more complicated than it seems at first glance.
You’ll notice that the pinion gear which actually turns the door closer arm has attachments coming out on both the top and the bottom of the body. That’s because some doors are hinged on the right, while others are hinged on the left, so which way you need the arm to swing will change. But also, you may need this installed on the push side of a door or the pull side of the door. And sometimes you need to mount the closer body to the frame of the door and other times you need to attach it to the door itself. And you’ll also need to decide if you want the door to only open to 90 degrees or if you want a full 180 degree swing. All of those factors change how you need to mount this, which linkages you need, and how long those linkages need to be, and how they behave, and it’s confusing.
These are the instructions for mounting this door closer, and while it’s not rocket surgery it’s more involved than you’d think. And as with any rabbit hole you go down, it just keeps going. This is by far the most common type of door closer but there are many, many more. Some are installed in the floor so they can operate frameless doors, others are concealed within the door jamb which provides a sleeker look.
I’m sure many of those are adjustable in the same way as this but I’m gonna leave that to you to figure out. Oh right, and also many door closers have a back-check adjustment. Often labeled BC, that provides some speed restriction as you open the door. It generally only kicks in at the very end of the door’s sweep to slow it down before it opens completely.
This can be a necessary thing, especially on exterior doors which might fling open if the wind catches them, but it also prevents door flinging humans from damaging your doors by stomping out particularly angrily. Then of course there are powered door closers which also open doors, often activated with a button near them. They use an electric motor to open the door and hold it open for a short while before letting it close again, which makes entering and exiting a building easier for wheelchair users or anyone who might need help with a door. You don’t often see those as much as you used to, at least in my area, since most businesses have chosen to have fully automatic doors which respond to motion sensors, but they stick around in lots of places where traffic volume doesn’t justify going that far yet which require disability access.
I’ve mostly been focusing on commercial door closers but there are some common types you find at home. I already mentioned these spring hinges but if you’ve got a screen door it’s probably got one of these door closers on there so it doesn’t flap about in a storm. This is just a spring in a tube pulling on this stick, and when you pull the stick out the spring fights you and pulls the stick back inside. It uses air pressure to dampen the spring’s return, and even these are adjustable! At least, many of them are. This one has a screw at the back which you can tighten to restrict the flow of air leaving the cylinder which slows it down.
But then at the end you get a little toot. [toot] Turns out this has a latching speed, too! Though that’s not adjustable. But at this point, I’m just rattling on so why don’t we give this video a proper ending where it comes to a close? I had to, okay? I want to give a shout-out to Deviant Ollam who I reached out to after watching this amazing talk of his on fire codes. I figured he’d probably have a good list of door closer trivia and he delivered most excellently so thank you for your script consultancy.
There are a lot of things in our everyday lives that are just… there and you’re not gonna think of unless somebody brings them to your attention. And it is my sincere hope that at least a few facilities managers out there (or just bored people who work in buildings) give their door closers a little love so they can stop annoying people as they do their very important jobs. ♫ adjustably smooth jazz ♫ This might be why! This is… not gonna work. I screwed that uuuuuuup. ...speed them up to help a door which isn’t lassing prop… [painful sigh] brrrr ...and speed them up to help a door which isn’t lapping prop… crfff brrrp! So don’t look at me. Now, if we look at the door closer body.
I don’t like that deliver AT all. And in fact the whole reason this style of [bleep] These do not have to slam the door! And in fact the whole reason they exist… I need to back up because I skipped a very important caveat. …installing a door closer. For a start [thud] these… well that was… ...wonderful. Good time was had by all, I'm pooped! Yes, I should be - good lord what is happening in there? See, now that's why you need door closers.
To localize the aurora borealis entirely within the kitchen. It just makes sense!
2024-08-26 17:26
