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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Technical Advice => Topic started by: Galeon on August 20, 2008, 10:09:07 AM
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I may have took up one of my suppliers wrong , but I will ask him to clarify the point is there any requirement incoming or existing that conventional call points now need to have a led indication once they have been activated.
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BS 5839 -method of operation of MCP's in a system should be that of type A as specified in BS EN 54-11, where the change to alarm condition is automatic when the frangible element is broken or displaced.
BS EN 54-11, states that “if” an additional visual indicator is provided it shall be positioned within the operating face or within the front face of the MCP which released an alarm, be red in colour and visible from a distance of 2m directly in front of the MCP in an ambient light intensity up to 500 lx.
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No.
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What they said
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Thank you boys , whether you are in the banter squad or not.
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I may have took up one of my suppliers wrong , but I will ask him to clarify the point is there any requirement incoming or existing that conventional call points now need to have a led indication once they have been activated.
All conventional manual call points I have seen up till now are just simple switches and have no electronics circuitry incorporated, particularly the pre1988 manual call points.
As for post1988 manual call point it may incorporate a simple internal resistor, some people call it the ‘fire resistor’, some call it the ‘trigger resistor’, once the call point is triggered it shorts out the ‘fire resistor’ to make it in parallel with the EOL, and as a result, the equivalent resistor value would be quite similar to the fire resistor itself, because the fire resistor is usually 10 times smaller then the EOL...etc
Sorry all of that is not the main answer to the original post but just to say, apart form that internal resistor, there is no electronics circuitry to make an LED to light up in simple conventional manual call point.
As for what is required by BS5839 in this issue, I prefer to leave it to the relevant expert as unfortunately, I am not :)
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Further to Benzerari's answer the operation of a manaul call point in a non-addressable system ibasically just ncreases the current flowing through the zone wiring circuit to a level recognised by the control panel as a fire condition.
If this amount of current is fully or partly provided by the operation of a LED indicator or not, has no bearing to how the concept works.
There is no recommendation in BS for MCPs to have LED indication of operation.
There is no recommendationt in BS for MCPs to not have LED indication of operation.
In my opinion, the small extra cost of having MCPs with integral LED indication of operation is far outweighed by the benefit of being able to quickly identify which MCP has been operated in a zone of a non-addressable system.
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I assume you mean it would be of use for fault finding as surely you would know which call point was used by the fact it's glass has been broken/resettable element in used position.
How often do MCPs cause false alarms without having their element broken/used? I've once had one not reset after using a test key and needing replacing before the fire alarm could be reset, but that's about it.
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I assume you mean it would be of use for fault finding as surely you would know which call point was used by the fact it's glass has been broken/resettable element in used position.....
Sorry Anthony B, I thought my post was clearer than it obviously was.
My opinion was based on the assumption that it is sometimes difficult to see an operated element on a MCP from a few feet away (sometimes a few inches!) but an illuminated LED may be seen from probably up to 10 metres or more.
The LED on a MCP for use in non-addressable systems wouldn't illuminate to what I would call system faults, but it would obviously illuminate to a 'fault' on a call point affecting the operating element that in turns affects the operating switch which in turn allows the 'alarm' current to flow.
MCPs with LEDs cost less than £1 more than those without. It seems a small price to pay for the time that could be saved searching a zone and being able to look for LEDs on detectors from a distance but having to get very close to each MCPs if they don't have LEDs.
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....How often do MCPs cause false alarms without having their element broken/used? I've once had one not reset after using a test key and needing replacing before the fire alarm could be reset, but that's about it.
Anthony B, I've found that most test key functions on MCPs use quite a fiddly arrangement (mainly to try and ensure a some other 'simple' tool can't be used to operate the test facility) and it is easy to 'jam' that arrangement in use, leaving the glass/element no longer pressing against the operating switch. This means the MCP still in an operated condition. Normally, in these cases, you can see that the element/glass hasn't repositioned itself into it's normal/standby position and can often be repaired. If not, as you say, the MCP has to be replaced.
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With Wiz
i installed resetable mcp's with led's in an HMO stairwell mainly due to the forsight of them being hit by people who don't stay in the block.
The resetable element is not always easy to see when it has been pushed in,so the led helped greatly for the confused customer in the middle of the night.
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So if BS gets updated and recommended that conventional call points had leds , it could effectively cut down the search distance within a zone .
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So if BS gets updated and recommended that conventional call points had leds , it could effectively cut down the search distance within a zone .
No because the search distance relates only to the distance required to locate a fire,not to actually inspect the device that has ativated.
Under 13.2.3 of 5839:part 1 the avtual search distance of 60m relates to the entrance to a zone proptected by non-addessable AFD.
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So if BS gets updated and recommended that conventional call points had leds , it could effectively cut down the search distance within a zone .
Also, if incorporating a simple electronics circuit into a conventional manual call point, the major impact I think is not the cost of a simple LED in serial with its protecting resistor and a small relay to switch the feed to light up an LED in fire condition...
It is rather the manufacturing process of this additional (as it looks) simple electronics circuit, just to do a simple function, this might not make conventional MCP cost effective in this emerging competition, probably some manufacturers might cope with, but not every manufacturer would support that additional cost… etc
This remind me, about two years ago when proposed to Apollo company, a ‘seven segment display’ to be incorporated in any addressable head to display the right programmed address so (what you see is what is really set), their answer as a marketing specialist of the product was as I stated above.
But we never know, the BS may trigger on day that competition, with just a simple decision.
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Benzerari,
MCPs with integral LEDs for non-addressable exist now. Most MCP manufacturers offer them as an option. They are nothing special. They just cost a bit extra.
No relay is required. Just the LED and the appropriate current limiting resistor.
I can understand Apollo showing no interest in having a visual display of the set address on an addressable device. This would be costly for the benefits achieved especially as it would need three digits. If such a display was only to be used during addressing then why provide something so costly for use for just a few seconds. If this is dispaly was to be illuminated at all times, it would add to the current consumption (it's important to keep this down in addressable systems) and so any benefit for it could equally be achieved by a simple label.
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Benzerari,
MCPs with integral LEDs for non-addressable exist now. Most MCP manufacturers offer them as an option. They are nothing special. They just cost a bit extra .
Indeed, nothing special a part from the additional cost...
No relay is required. Just the LED and the appropriate current limiting resistor. .
This depends of which design is better for which make and current consumption requirement in both quiescent and fire conditions. whether monitoring that additional electronics circuit with a small current in quiescent condition then an increase of current in fire condition. Or totally keeping that additional electronics circuit off the zone circuit in quiescent condition, probably to save power consumption...etc, and in this case a relay or transition would be a must...
I can understand Apollo showing no interest in having a visual display of the set address on an addressable device. This would be costly for the benefits achieved especially as it would need three digits. If such a display was only to be used during addressing then why provide something so costly for use for just a few seconds. If this is dispaly was to be illuminated at all times, it would add to the current consumption (it's important to keep this down in addressable systems) and so any benefit for it could equally be achieved by a simple label.
I have seen in several occasions smoke and heat detectors wrongly labeled, probably because the system has been modified several times, and the tasks had never been completed, but if a '7 segment display' was fitted the address would never ever shows wrong and that's the point.
Apollo Company liked the idea when explained to them, but they rejected it just because of the cost effective issue. It’s the manufacturing process cost that matter rather than the component cost...
Above that they said thank you and we welcome all ideas from field engineers.
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Hi Benz - if the LED is only illuminated when the MCP has been activated then you are talking an increase of around 20mA on the zone.
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i found in a site with mcp's with led's,some plonker run down the stairs and operated all the call points. It activated the FA but the current consumption prevented the led's to operate.
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Hi Benz - if the LED is only illuminated when the MCP has been activated then you are talking an increase of around 20mA on the zone.
But what is the question in this issue?
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Hi Benz - if the LED is only illuminated when the MCP has been activated then you are talking an increase of around 20mA on the zone.
But what is the question in this issue?
Im not sure what you are asking Benz but what I was saying (!) is that one LED will only add 20mA to the zone and (as Wiz has pointed out) it is not necessary to use anything other than a current limiting resistor to drive the LED.
However,munltiple activations could case the ~LED's not to activate as Graeme has said.
The original post was were they required under the current 5839 and the answer si no,they are an option that manufacturers offer or provide.
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i found in a site with mcp's with led's,some plonker run down the stairs and operated all the call points. It activated the FA but the current consumption prevented the led's to operate.
Are you talking about addressable MCP or conventional one?
I agree very few conventional MCPs in the market have got LEDs incorporated, and the LED normally should Light up as soon as the MCP is activated, and fire condition has taken place, this would not be the case in analogue addressable MCP, the LED in my understanding would not light up straight forward, because when activating an analogue addressable MCP, in fact all it does it sends fire signal to the fire alarm panel, the panel takes a bit of time to process the signal, and then decide if its fire condition, if it is the case the fire alarm panel then, send an output signal authorising the MCP's LED to light up and alarms goes off...
Conventional MCP with LED incorporated doesn't have any data communication with its panel it sits passively in the zone circuit, and its the external action (human, leak of water.. ) which trigger straight forward the LED to light up...
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Hi Benz - if the LED is only illuminated when the MCP has been activated then you are talking an increase of around 20mA on the zone.
But what is the question in this issue?
Im not sure what you are asking Benz but what I was saying (!) is that one LED will only add 20mA to the zone and (as Wiz has pointed out) it is not necessary to use anything other than a current limiting resistor to drive the LED.
However,munltiple activations could case the ~LED's not to activate as Graeme has said.
The original post was were they required under the current 5839 and the answer si no,they are an option that manufacturers offer or provide.
Sorry; now I got your point, yes indeed multiple activations would drop the equivalent resistor value below the limit value required to set alarm condition, also it may cause insufficiency of current to light up LEDs of the activated MCPs.
That's true
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i found in a site with mcp's with led's,some plonker run down the stairs and operated all the call points. It activated the FA but the current consumption prevented the led's to operate.
Grame, got your point, this can even happen to the majority of conventional system's, if you trigger say 5 call points in the same zone circuit, the next ones in the same zone circuit wouldn't activate till you reset the system... due too the drop in equivalent resistor below the limit required to set fire condition in some systems triggering multi call points in the zone can reach to the point where triggering the next ones would set fault condition of (short circuit)... and that's where conventional technology sophistication is limited...
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Guys, Am I misunderstanding what you are saying?
A number of non-adderessable MCPs with intergal LEDs all operating at once won't alter the overall resistance of the circuit and thus prevent an alarm condition as such. If one MCP operating draws enough current to put the zone in fire condition, additional ones operating won't reduce that current, only increase it.
Obviously, if you had a large number all operating at exactly the same time you might draw so much current that a zone short-circuit fault is given. By the liklihood of this is virtually impossible.
The reason that a zone with a large number of MCP's operated one after the other may not illuminate LEDs correctlty can only be down to current limiting circuitry in the zone circuitry of the non-addressable fire panel. In fact, what would normally happen is that as additional MCPs were operated each already illuminated LED would get a fraction dimmer until eventually no LEDs would appear to be illuminated because the current limiting would cause a volt drop on the zone wiring sufficiently high enough to prevent it.
But on addressable systems where current being taken on a loop is even more critical, some control equipment types will purposely not send the data to tell an LED on an operated MCP to illuminate, if it senses the current being drawn on the loop is getting too high. The control panel still reacts to further pieces of equipment being operated but just does not send the information back to the device to illuminate the LED
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Guys, Am I misunderstanding what you are saying?
A number of non-adderessable MCPs with intergal LEDs all operating at once won't alter the overall resistance of the circuit and thus prevent an alarm condition as such. If one MCP operating draws enough current to put the zone in fire condition, additional ones operating won't reduce that current, only increase it.
Obviously, if you had a large number all operating at exactly the same time you might draw so much current that a zone short-circuit fault is given. By the liklihood of this is virtually impossible.
The reason that a zone with a large number of MCP's operated one after the other may not illuminate LEDs correctlty can only be down to current limiting circuitry in the zone circuitry of the non-addressable fire panel. In fact, what would normally happen is that as additional MCPs were operated each already illuminated LED would get a fraction dimmer until eventually no LEDs would appear to be illuminated because the current limiting would cause a volt drop on the zone wiring sufficiently high enough to prevent it.
But on addressable systems where current being taken on a loop is even more critical, some control equipment types will purposely not send the data to tell an LED on an operated MCP to illuminate, if it senses the current being drawn on the loop is getting too high. The control panel still reacts to further pieces of equipment being operated but just does not send the information back to the device to illuminate the LED
Confused??Tune in next week.....The real or hypothetical situation of all MCP's active with internal LED's on a conventional system could stop the internal LED's activating but would not stop the activation of the fire alarm.
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The best way to prove any claim is through drawings, unfortunately in here I couldn't find a way to dispaly it.
We are still talking about the same thing, but seen from different angles... :)
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Guys, Am I misunderstanding what you are saying?
A number of non-addressable MCPs with intergal LEDs all operating at once won't alter the overall resistance of the circuit and thus prevent an alarm condition as such. If one MCP operating draws enough current to put the zone in fire condition, additional ones operating won't reduce that current, only increase it.
Obviously, if you had a large number all operating at exactly the same time you might draw so much current that a zone short-circuit fault is given. By the liklihood of this is virtually impossible.
The reason that a zone with a large number of MCP's operated one after the other may not illuminate LEDs correctlty can only be down to current limiting circuitry in the zone circuitry of the non-addressable fire panel. In fact, what would normally happen is that as additional MCPs were operated each already illuminated LED would get a fraction dimmer until eventually no LEDs would appear to be illuminated because the current limiting would cause a volt drop on the zone wiring sufficiently high enough to prevent it.
But on addressable systems where current being taken on a loop is even more critical, some control equipment types will purposely not send the data to tell an LED on an operated MCP to illuminate, if it senses the current being drawn on the loop is getting too high. The control panel still reacts to further pieces of equipment being operated but just does not send the information back to the device to illuminate the LED
Wiz;
Let's brainstorm things from the beginning,
You have claimed that to add an LED to a conventional MCP to be light up in fire condition, you said this necessitates a simple LED with its current limiting resistor... and that's fine that will work, but...!
I assumed the LED with its current limiting resistor call it 'Rd' will be fitted in serial with the MCP own internal resistor call it 'Ri', therefore only when that MCP is triggered both resistors will be seen in serial 'Rd+Ri' their sum will be in turn seen by the panel, in parallel with EOL called 'Re', the total equivalent resistor in that triggered circuit will be as follows:
1/(Rd+Ri) + 1/Re = 1/Req ----------------> Req = Re(Rd+Ri) / (Re+Rd+Ri)
Req: will be the EOL seen by the panel in the activated zone circuit, it should be within the tolerance of resistors that meant to set fire condition. i.e. in case of EOL =4K7 Ohm, and Ri= 470 Ohm then:
'Req' should remain within (Ri - 200 Ohm ) < Req < (Ri + 200 Ohm)
(Just as an example this depends to the make)
If many MCPs are triggered in the same zone this will drop 'Req' below say (Ri - 200 Ohm ) in which the panel is meant to generate a short circuit fault. ( post 1988 system)
Also if many MCPs are triggered the panel will see the internal resistors of the MCPs (Ri+Rd) all in parallel with the EOl resistor 'Re' this will split the current (even it's higher in fire condition)... to be drawn through all Nodes and what will reach the LEDs to light them up may not be enough to some extend, that's why an accurate calculation is needed to suit each make...
There are many ways to save enough current to light up the LEDs even if all MCPs are activated, this will necessitate the right electronics circuit to do the job, not just an (LED and its limited current resistor)
Therefore, there is no guaranty that any make of conventional system will accept an upgraded conventional MCPs with LEDs... :)
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Benz,
I enjoyed your Ohms law calculations. It was like being back at school!
I did make the point that if in the unlikely event of a large number of MCPs operating at exactly the same time then the total current drawn could equate to the value required to initiate a zone short-circuit fault condition and not a fire condition. And I would point out that this would be true whether they had LEDs or not!
However, this event is so unlikley that it is almost impossible!
What you seem to be forgetting is that a fire condition overides any fault condition on the control panel. Therefore the first call point to operate will initiate the fire condition. Further call points subsequently operating do not cause a short-circuit fault to operate and somehow reset the original fire condition!
Obviously, if a number of manual call points on one zone are operated during a fire condition, each will draw current from the control panel but the panel is already in fire condition and so won't then change to a short-circuit fault indication. However because the zone monitoring circuitry is current limited (if it wasn't it would have to be fused and this could cause all sorts of problems) too many MCP LEDs could exceed the current limit and cause a volt drop sufficient to cause the LEDs not to illuminate properly.
Fire detectors have LEDs to indicate operation and they are across the same pair of zone wires as the MCPs. the concept works equally well with a call point!
The only reason that MCPs don't have them as standard is because 'in the old days' of non-control panels systems you couldn't really have them without introducing a third wire at the call points and everybody got used to not having them because you could tell if the MCP had been operated by the broken glass anyway (have we gone around in circles here?). Many people have still not realised the advantages that they bring to modern systems at very little cost.
All of the above relates to most modern non-addressable fire alarm systems.
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The original post was were they required under the current 5839 and the answer si no,they are an option that manufacturers offer or provide.
Agreed. See my post of 16.45 on 20th August.
Benzerari has taken the post in a slightly different direction and the points raised need discussion/clarification
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Benz,
I enjoyed your Ohms law calculations. It was like being back at school!
Thank you for that, good to remember isn't?
I did make the point that if in the unlikely event of a large number of MCPs operating at exactly the same time then the total current drawn could equate to the value required to initiate a zone short-circuit fault condition and not a fire condition. And I would point out that this would be true whether they had LEDs or not!
Yes indeed, but not only operation at the the same time but in the same zone circuit too...
However, this event is so unlikley that it is almost impossible!
Do you mean is possible then?
What you seem to be forgetting is that a fire condition overides any fault condition on the control panel. Therefore the first call point to operate will initiate the fire condition. Further call points subsequently operating do not cause a short-circuit fault to operate and somehow reset the original fire condition!
This is true in general speaking, if the system is not overloaded at all. But if upgrading the system with the MCP of LEDs while it was designed to support the none LEDs ones, this may cause (system overload) and so cause the system to underperform, I myself seen a conventional system with say 5 MCPs triggered the next ones in the same zone didn't trigger, till reseting the system properly, then carrying on with testing, even if you carry on without reset some of the makes sets fault of short circuit and the cause as I stated previously.
Obviously, if a number of manual call points on one zone are operated during a fire condition, each will draw current from the control panel but the panel is already in fire condition and so won't then change to a short-circuit fault indication. However because the zone monitoring circuitry is current limited (if it wasn't it would have to be fused and this could cause all sorts of problems) too many MCP LEDs could exceed the current limit and cause a volt drop sufficient to cause the LEDs not to illuminate properly.
The zone circuit in fire condition will be current limited because of the EOL new value that monitor the current in the zone circuit and not the other way around. the more call points triggered the less value of EOL will take, and so the more current drawn to the zone circuit to its max fixed by the fuse.
Fire detectors have LEDs to indicate operation and they are across the same pair of zone wires as the MCPs. the concept works equally well with a call point!
The only reason that MCPs don't have them as standard is because 'in the old days' of non-control panels systems you couldn't really have them without introducing a third wire at the call points and everybody got used to not having them because you could tell if the MCP had been operated by the broken glass anyway (have we gone around in circles here?). Many people have still not realised the advantages that they bring to modern systems at very little cost.
All of the above relates to most modern non-addressable fire alarm systems.
Yes indeed and No comments in this :)
Finally, sorry guys of deviating the discution in a different way
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been away for a few days but shoot me now....please :)
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been away for a few days but shoot me now....please :)
Never,in the field of fire alarms,has so much been said,by so many,about so little (sorry Winnie!)!
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Is there any thing new, under the sun, guys?
All what have been said, is usual to the majority, no thing special :)
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A great man once said 'Everyone is entitled to their own opinions - no matter how f*****g stupid they may be'
But there is a big difference between opinion and fact. When someone doesn't understand facts, then it is time to move on ;)