Loop powered door retainer

[Mr. P]

TW, the door might spin through 180 degs or the building spin and the door stay put (may be good for waking people up- or could be used as an auto exit eject system -- patent pending!!)

But seriously, Wiz capped it, as the door closers should be set to overcome this possibility, but, also I have never encountered that problem. Having in place a system for securing the use of means of escape at all material times means any closer-device problems will be high-lighted and dealt with before getting out of hand, or the RP may find themselves in the crud.
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[GregC]

Having tried wirefree and doorguards I would need asbestos gloves to touch either again.

[Tom W]

Having tried wirefree and doorguards I would need asbestos gloves to touch either again.

Why?!

[Tom W]

There are problems with all systems. The magnets "should" have something to overcome the chance of risidual magnetism. The problem with magnets is that any sparky can install them. If they have not correctly installed them, there is a chance when you have complete power failure that the magnets could still retain the door. There have been cases of this. It makes me worry that a system that is retaining power in its magnet station is not going to keep/use this power in the event of a mains failure and or standby power. 

[Wiz]

This discussion is way out my league but I would still like to ask a question.

On the subject of residual magnetism previously you spoke of reversing the polarity of the magnet now if a permanent magnet was fixed to the door and an electro magnet in the device. When you reversed the polarity wouldn’t the magnets repel each other and in this situation would residual magnetism be a problem?

TW, to answer your question, in typical fashion, this thread is talking about two things at once!

The traditional method of door holding was by a simple electromagnet.

The new method is to have a permanent magnet on the wall and a permanent magnet on the door. These permanent magnets have opposing poles so they attract/hold together. To get the door to release, you physically twist one of the permanent magnets so that you get oppossing poles and the magnets repel and the door hold releases.

In this new method no continuous electrical power is needed to keep the door held closed. The only power is required when you need to power whatever physically twists one magnet. This low power consumption method is ideal for battery-operated or other low current consumption necessary systems.

In his promotion of the new method over the traditional electromagnetic method, Piglet highlighted the problem of residual magnetism in electromagnets. I suggested that this problem was well known and methods were available to deal with it.

[Wiz]

There are problems with all systems. The magnets "should" have something to overcome the chance of risidual magnetism. The problem with magnets is that any sparky can install them. If they have not correctly installed them, there is a chance when you have complete power failure that the magnets could still retain the door. There have been cases of this. It makes me worry that a system that is retaining power in its magnet station is not going to keep/use this power in the event of a mains failure and or standby power. 

An electromagnet doorholder is the most simple fail-safe door-holding method available - when you lose power the magnet simply releases! It is the other versions that have the most potential to fail!

If it is suggested that a 'sparky' is not up to installing and testing an electromagnetic door holder for correct operation then there is no hope for the world!

As a fire alarm engineer there are many things that I feel that 'sparky' should leave for to me to do, but installing and wiring up an electromagnetic door-holder circuit is not one of them!

With his training and experience 'Sparky' can do many things very well, in fact, including many things that a fire alarm engineer can't do!

[Tom Sutton]

To Mr P Ho! Ho! Ho! 

Thanks Wiz My interest was not about residual magnetism, I had never heard of the concept of reversing the polarity of the magnet as opposed to switching off the supply and this seems an interesting development and as you explained it, residual magnetism would be even be less of a problem.

[Mr. P]

Sorry TW, I need to get out more...

[GregC]

Having tried wirefree and doorguards I would need asbestos gloves to touch either again.

Why?!

Because I got my fingers burnt.

Doorguards haven't worked for any of the customers that I have suggested them to and even though I told them of the potential issues I was still blamed and the wirefree ones were a pain for signal strength, with hindsight the hard-wired ones would have been easier and cheaper to fit.

They might be good in some applications but I am yet to be convinced after my experiences.

[kurnal]

GregC
I would be very interested to hear of the type of problems you had with the dorgards - was it related to issues such as insufficient alarm audibility, or uneven floors or too much ambient noise? I use quite a lot of them and provided you carry out a test in situ befdore fitting,  and use the door plate if necessary I have had few problems. 

[GregC]

Centre for young adults with learning difficulties, the doors would close when the trolleys were pushed through with the glasses and cutlery for dinner times, on some floors the gap between the bottom of the door and the floor was uneven or flexed as people walked in and out of the office causing the doors to move, we inherited these and have swapped them to hard wired.

Nursing home, the units are quite bulky and the residents were forever banging their heels or kicking the units in the corridors, these were also changed.

[Tom W]

Centre for young adults with learning difficulties, the doors would close when the trolleys were pushed through with the glasses and cutlery for dinner times, on some floors the gap between the bottom of the door and the floor was uneven or flexed as people walked in and out of the office causing the doors to move, we inherited these and have swapped them to hard wired.

Nursing home, the units are quite bulky and the residents were forever banging their heels or kicking the units in the corridors, these were also changed.

Just FYI I will say it mostly sounds like incorrect installing.

Trollys - The units are sound adjustable, turn them up should be end of problem or use the radio one.

Uneven floors - They supply raised floor plates now.

Kicking the units - Not much you can do about that!

[Galeon]

You will always have a problem with the communications part of the loop , trying to meet that bit of the standards , however if you build in redundancy to the panel with a second processor that will take over automatically , this can get you around that .

As with any device that uses standard batteries to release 'the permanent magnet', there is always a danger that the cell could fail or short circuit , and actual not be picked up as a fault on the monitoring side of door retainer unit.

I have looked at system X and it looks to be fairly good to me , however it says it complies with Category B doors , you still have the problem looking for a system for Category A .

I will update you guys as soon as practicable , when I have some more defined solid constructive news , thanks for the comments so far.

[Tom W]

I have looked at system X and it looks to be fairly good to me , however it says it complies with Category B doors , you still have the problem looking for a system for Category A .

FYI They have a hardwired version of the system x coming out to meet Cat A

See page 11  http://www.fia.uk.com/objects_store/focus_issue10_may09.pdf

[Galeon]

Good news then , however unless you wire the main controller to the 240v of the fire alarm supply ,and have fail safe fire and fault contacts along with Wizz's other beloved sections of BS document , it still aint no good to use unless the deviations are recorded and agreed and accepted .