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LCN SEM7840-825 SEM Series Door Armature
SEM Series Fire/Life Safety Closers/Holders
All SEM series magnets are UL listed for smoke barrier or labeled fire doors.
Tested and certified under ANSI Standard A156.15. heavy duty, electrically controlled door holding magnets. Magnets are fail safe and hold until the current is interrupted. A manual door closer is used to control and close the door.
Manufacturer Resources
LCN Full Line Catalog
Product Specs
- Series:
- SEM 7800 Series
- ADA Compliant:
- Yes
- Mounting Detail:
- Surface - Magnet
- Subcategory:
- Fire and Life Safety Closers
- Product Group:
- Door Controls
- Product Subgroup:
- Parts and Accessories
- Product Type:
- Door Magnets
- Commercial/Residential:
- Commercial
- Electronic:
- Yes
- Mounting Method:
- Wall Mount
- Product Category:
- Door Controls
- Department:
- Door Hardware
LCN SEM7840-825 689 – Frequently Asked Questions
1) What does the LCN SEM7840-825 door armature actually do, and do I still need a door closer?
The SEM7840-825 is the armature half of an SEM Series electromagnetic door holder. The magnet holds the door open and releases it when current is interrupted, so it is fail safe on alarm or power loss. It does not close the door. A manual door closer controls and closes the opening once the magnet drops, so the armature and magnet are specified alongside a closer, not instead of one.
2) Does the SEM7840 magnet mount on the wall or on the door?
The magnet body is a surface-mounted wall mount unit, and the armature is the mating plate that goes on the door leaf. So you need clear wall surface behind the open door position to land the magnet, with the armature aligned to it on the door face.
3) What happens to a door held by an SEM magnet when the power drops or the fire alarm trips?
The door releases. SEM magnets are fail safe and hold only while current is present, so any interruption, an alarm signal, a power failure, or a pulled circuit, drops the hold and lets the closer swing the door shut. That is the behavior a fire marshal is looking for on a smoke barrier opening.
4) Is the SEM7840-825 armature a standalone part or a replacement piece?
It is the armature only, the plate that mates to the magnet face. Buy it when the magnet body is in service and the armature on the door is damaged, missing, or being relocated after a door swap. If you are outfitting a new opening you need the magnet and the closer as well.
5) Is an SEM magnetic hold-open acceptable on an ADA accessible opening in a commercial building?
Yes, the SEM Series hold-open is ADA compliant and specified for commercial use. Because the magnet holds the leaf fully open under normal conditions, the opening force question during hold-open does not arise, and the door closer you pair with it governs the closing side of the accessibility requirement.
6) Do I need to run power to the door for an SEM magnetic holder?
Power goes to the magnet, not the armature. SEM units are electrically controlled and hold only while energized, so the wall-mounted magnet needs a supervised circuit tied into the fire alarm or smoke detection system. The armature on the door is a passive steel plate with no wiring, which is why nothing has to be run through the hinge side.
7) Magnetic hold-open versus a closer with a built-in hold-open arm on a fire door, which should I use?
On a labeled fire door or smoke barrier you want the magnet. A mechanical hold-open arm keeps the door open regardless of the alarm; the SEM magnet is fail safe and releases the moment current stops, which is what a rated opening requires. The tradeoff is wiring: the magnet needs a wall location and a circuit off the alarm system, plus a separate manual closer to do the closing.
How fast can I get the LCN SEM7840-825 689 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the
continental
U.S.
Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit,
reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the LCN SEM7840-825 689 come with a warranty?
Absolutely. The LCN SEM7840-825 689 is backed by a manufacturer’s warranty.
For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the LCN SEM7840-825 689?
You can call, text, or email our expert support team for fast answers. We’re here to help with
product
selection,
installation tips, and troubleshooting. Contact Us
Why buy the LCN SEM7840-825 689 from ZenSupply?
ZenSupply makes it easy to get the commercial door hardware you need—fast shipping, expert support,
and
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every order.
Our team is always ready to help you choose the right product for your project.