Hardware For Door Pairs

Some challenging questions relating to pairs of doors (commercial/institutional)

  1. Is a pair of doors without a center mullion more efficient than two 3’ doors? Can a building evacuation REALLY be more facilitated by a door pair? Can lines be shorter and better managed though a single leaf vs a door pair?
  2. Is anyone aware of any studies done by safety testing agencies that would or would not support two single doors over one door pair? Can anyone cite such a reference?
  3. Not withstanding the new cable devices, are rim exit devices better than vertical rods? Why or why not?

1. The omission of a mullion may have as much to do with what is transported through the door than just people flow.

Think a load of cargo on a cart that is 60" wide. If this opening is attached to a group meeting area, it might be an important access point for equipment.

This is an example of a mullion for those who may not be familiar:

An alternative to fixed mullions are 'removable mullions':

Mullions impact door usability, but they also tend to increase/simplify door security. Having a fixed positive latching point in a mullion beats vertical rods any day.

In general flow calculations are linear, and I'm not sure a mullion has a negative impact on egress volumes. However, I'll confirm that with some contacts and report back here.

2. Cost is the biggest factor. One double leaf door is less expensive to fabricate/install/maintain than two single doors immediately adjacent to each other. Getting two butted frames to align properly sounds really maddening to me.

3. Vertical rods are a very maintenance-intensive component. Show me a double door with rods, and I will show you a door that likely does not latch properly. There are 'security minded' hardware consultants that refuse to spec vertical rods on perimeter doors because of this.

The need to have a clear opening 6' wide for moving things in and out is one i have heard many times from architects. The real truth is that they really don't want an ugly mullion. While it may look better to have a pair w/o a mullion, its one of those "forever" choices that will (as you pointed out in item 3) be problematic for the life of the building. As to the cost, I'm not so sure it costs less to do a pair of doors. At $12-1700 a leaf uninstalled, vertical rod devices (VonDuprin Grade 1) top the charts as the most expensive hardware on the market, particularly if one or more of the devices is electrified (add another $1200 or so per leaf).

Still, i wonder if any studies have been done on the issue...both from the life safety and traffic control perspective.

  1. I will have to see if I can dig it up again, but I read a study a few years ago that showed that egress times are faster with a pair with a center mullion -- it effectively creates two "lanes" of egress that people move through in a more orderly fashion -- than with an open pair.
  2. It was said above, but I avoid vertical rods like the plague. In the absolute best-case scenario, they are a pain in the neck. In a heavy-use or abuse scenario, they are a total nightmare. And, that's not an indictment of any specific brand -- they are all difficult to work with.
  3. There are some scenarios where I would adamantly refuse to install vertical rods and require the installation of a mullion or tell them to go somewhere else -- schools are the main ones, but any sort of institutional or as mentioned above heavy use and abuse, I would require it. The only doors that are remotely acceptable to me to use vertical rods on are doors that are rarely used or are primarily for emergency egress purposes only.

I will have to see if I can dig it up again, but I read a study a few years ago that showed that egress times are faster with a pair with a center mullion -- it effectively creates two "lanes" of egress that people move through in a more orderly fashion -- than with an open pair.

After reading your response, I remember reading the same thing. I'll try to find the citation.

I could not have said it better. But i do wish you could find that study. Some time ago, i was watching a show on Science Channel and the guy being interviewed did a demo. He filled a big room with people and told everyone they had to leave as fast as possible when the alarm went off. In one case, he used a single door pair (no mullion). In another, he placed a simple "velvet rope" on the inside (not a mullion, but it seemed to suggest that a mullion would perform similarly). The building emptied much quicker. I think the series was called "Brain Games" but I could not seem to find it again.

By the way, you probably know that this hardware could cost you as the integrator a bundle in service calls that are not your problem.

No question about it. And, bigger than the cost of the service calls is the cost of a really ticked-off customer that their door that they just spent a boatload of money on doesn't work a year later. Nor does it cover their frustration when they see the tiny pebble that gets pulled out of the latch is going to cost them $200 for an after-hours service call.

With that said, one thing I said above that I'm going to walk back a little bit -- if you *HAVE* to install verts (concealed or surface), for goodness sakes buy a good product. I won't recommend a product here unless someone asks, but there may be no better real-life illustration of "you get what you pay for" than vertical rod panics.

if you *HAVE* to install verts (concealed or surface), for goodness sakes buy a good product. I won't recommend a product here unless someone asks, but there may be no better real-life illustration of "you get what you pay for" than vertical rod panics.

Is this code talk for 'von duprin'? :)

Mentioning good products based on experience is helpful for discussion purposes. Disclose you are a dealer if true, but otherwise recommendations are helpful and encouraged!

Is this code talk for 'von duprin'? :)

Ha! No. At least, not specifically.

Full disclosure -- I work for Stanley Convergent Security, which is a sister company of Stanley Mechanical Solutions, which owns Precision Hardware. It should be noted that despite working for a "sister" company, I'm in no way incented to sell Precision over anything else. Generally, I sell what the customer asks for, assuming it's a quality product, and only provide recommendations one way or the other when asked.

Von Duprin makes fine products. They wouldn't be the name they are without being a good product. And, to be abundantly clear, they would fit within my recommendation above for "a good product".


In my opinion, Precision is a better, more robust product. The caps of the bars are made from investment cast steel instead of stamped metal, and is a more substantial product than Von Duprin. The electrified devices are rock-solid. The devices come standard with a 5-year warranty compared to the Von Duprin's 3. The finishes are actual architectural finishes -- vastly different than Von Duprin in that regard as well.

Again -- while I think Precision is better, Von Duprin is a good product. Sargent is an OK product. And....that's basically where my list stops. :)

Hope you are right. I just approved a submittal with about 300 Precision exit devices, most of which are electrified. I have used all the above, but to my knowledge VonDuprin is the only one that can use a cable instead of a solid rod. First reports from users say that it has worked well with few problems. Anyone else with this experience?

What type of devices? Rim, mortise, SVR, CVR? ELR or MLR? Assuming it's probably a mix, but hopefully they're mostly rims with mullions. :)

Either way, I can't imagine you'll be disappointed, as long as whoever is installing knows what they're doing. For goodness sake, make sure whoever is wiring the devices from power supply to device knows it needs 4-wires for power for ELR devices (plus 2 more for REX if TS option is included), and to not skimp on wire gauge (follow mfg guidelines).

I've had no experience with the cable devices, but I personally don't see much difference -- i think it's mostly marketing hype. While the rods themselves can cause issues, the vast majority of the issues I've ever seen are related to the latch, not the rods themselves. If there is care taken to protect and install the rods correctly, and if they're maintained regularly, the issues would be minimized either way.

Just my $.02. Not saying it may not have some value, but I'd need to see a lot more before I made a wholesale switch to them.

Actually, they are all rim devices, with SDC LPS and REX switches. About 100 are also equipped with SDC motorized latch retraction. Another 200 or so rim devices are existing, and SDC worked nicely in a retrofit application.

By the way, just this last May, SDC changed the design of their LPS, believe it or not, using a magnet and a small reed switch. No more reliance on microswitches. WAY TO GO SDC! Can't wait to see them actually installed.

If you're just now specifying, can I ask why you're going with the SDC retrofit kit instead of the MLR option from Precision? I have to admit I don't know the difference in price, but the MLR option was officially released by Precision early this year. I think it may actually be a reworked SDC option so it's probably not a big deal, but I would at least ask about that if it's not already too far down the line -- it's also probably going to be less expensive.

UND1- Just my opinion; I would not argue at all with most of the comments here about Verticals. They are expensive, harder to install and when they start to fail, they are a nightmare. I will add to that by saying the power supply for Von Duprin is 12 AMPS!! That is a ton of power required in facilities that may or may not have that much power available. When we are talking about standard office complexes, that is an entire circuit dedicated to one power supply for one door.

Here is what else I will say. We have installed hundreds of them in a number of states. I have not had one AHJ reject them, ever. The clear advantage is that you have to use your credentials to get in, and they offer mechanical egress. Just push on the bars from the inside and exit. They meet the fire code everywhere we go. We get push-back from some AHJ's on other means of egress from time to time, but never a word about vertical rods.

Yes we do use Von Duprin and no others, but that is more about inventory than anything else. They are very expensive. We don't have to keep a variety of every expensive parts on trucks. Just one.

All good points. A few quick notes -

  1. The 12A draw is a low-voltage draw, not a high-voltage one. The actual draw of a single power supply at 120vac is closer to 2A, although I don't have the chance to do the math. We frequently power multiple power supplies from a single circuit. Regardless, the inrush is indeed enormous, but it's not quite 12A @120vac. :)
  2. Agreed on AHJ's, but that's true for panics in general. You can install a mullion and rim devices for less money than verts, and they will cost WAY less over the lifetime of the devices to service and maintain as well. The ONLY reason I have for ever doing verts is when it's a shipping/receiving door or something like that where large items are FREQUENTLY moving through. If it only happens occasionally, install a keyed-removable mullion instead of a fixed, and have them take it out for the once-a-month where they have deliveries or something like that.

Inrush drops to about 250MA for holding purposes. Used to be that the EL devices were warrantied only if you use the PS900 series power supplies, but i understand that is no longer the case. I dont think Precision cares about who's power supply you use. Am i Correct on that Undisclosed 2 Integrator??

  1. The continual draw is higher than 250ma for Von Duprin -- it's not published, but it's likely closer to 750mA-1A.
  2. There are two "flavors" of Precision, similar to Von Duprin . ELR ("Electric Latch Retraction")is similar to the Von Duprin "EL" option, which is a solenoid-driven, high-inrush device that requires a dedicated power supply. For Precision, it's an ELR15x (where X = 1 through 4 for the number of devices to power), similar to the Von Duprin PS914-xR. So, yes, Precision ELR also requires a dedicated power supply. For what it's worth, the Precision ELR devices have 2 solenoids inside -- one is for retraction at 15A, the other for holding at 1A.

The other option for Precision is "MLR" or "Motorized Latch Retraction", similar to Von Duprin QEL, is a motor-driven and quieter retraction option than ELR. This device actually does not require any dedicated power supply at all, and can be powered from any filtered and regulated power supply (Altronix, LifeSafetyPower, etc), but it's still very important to check your power requirements as they do still draw 1A apiece. Also very important to check your wiring distance and gauge, as the voltage drop can be substantial over long distances. It's not a manufacturer requirement, but anything over about 150 feet, I always just pull 16-gauge wire, and anything over 250 feet I pull 14-gauge wire. It's a little bit more expensive, but I refuse to allow a $1500 bar to be rendered inoperable or cause me problems over an extra $25 in wire costs.

Good info. The reason why I specified SDC is that it was bid about 6 months ago and cost was less, by a good margin. May not go with the same decision next time. But i like the SDC stuff. Also impressed with the new design of the LPS switch... Wish the same thing would happen to the REX. One thing i did note, was that the new LPS switch does not seem adjustable; while the old one was (albeit by actually bending the lever on the microswitch which i don't like)