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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Technical Advice => Topic started by: bibbage on February 05, 2010, 02:54:58 PM
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Hi, We have a site with a 2 loop panel with 54 devices on one loop and 64 on the other, they are a mixture of Hochiki MCP, Heat, Smoke, Sounders and Beacons all on the Loop, there are 61 Beacons.
Previously there was a Kentec panel fitted which was very difficult to control, i.e. One man test would not work and it was difficult to cancel the sounders. The Kentec was replaced by a C-Tec XFP and exactly the same thing is happening. To get the sounders to stop the panel has to be reset about 3 times and omt does not work, there is a situation when the sounders stop and the beacons carry on flashing.
The panel seems to work fine with the sounders disabled and it always goes into fire when tested.
The installation is not ideal because the loops have been taken to a nearby box and back to the panel with 5 radials on one loop and 4 on the other, obviously a conventional system converted to addressable (not very well)! The wiring is micc.
I spoke to C-Tec and Kentec and they seem to think the radials would make no difference to operation, I'm not so sure, any ideas?
Thanks in advance
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I don't think the radials would be a problem. I'm guessing there are adequate short circuit isolators for each leg?
Personally I would never have gone from Kentec to C-Tec but ...
I've never had problems with Kentec/ESP one man testing and the like... we've got a few sites with networked panels and it works fine.
Is it a single stage system - are the sounders set to default ring or are they being controlled through cause and effects - are there any delays set up?
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I would try and singular address the alarm devices , as they sit 127 behind any device they are attached to . Try this on one loop and dump the other loop out of the panel .
When you address them keep them in rotation ie 1-30 etc.
I know this is a pain to do , but to have 2 panels do the same thing is very weird.
The only thing about the wiring I can think of is maybe on the mineral , you are getting capacitance , so try loading the loop with a resistor 4k7 and see if that calms it down, check you have no earth faults, it will take a period of time for all the loop to silence as the command from the panel has to get to each device , refer to what I said above about the addresses .
Kentec should be bullet proof with Hochiki .
Best of British.
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There are no delays set and no special cause and effect.
Galeon, do you mean address the sounders and the beacons separately, not sure what you mean.
Cheers
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As far as I remember OMT works for conventional bits; it disables the conventional outputs of a radial output circuits, but has no effect on loop powered outputs, which have to be isolated by program... etc. or am I wrong?
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Could be the possibility of too much current draw in alarm??? Kentec and C-TEC panels don't have a particularly high loop current output, causing the issue of not many alarm devices being able to oeprate on a single loop.
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Hi Big Fella, I checked loop voltage in alarm and it was not much lower than in normal state.
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There are no delays set and no special cause and effect.
Galeon, do you mean address the sounders and the beacons separately, not sure what you mean.
Cheers
Yep
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Hi, We have a site with a 2 loop panel with 54 devices on one loop and 64 on the other, they are a mixture of Hochiki MCP, Heat, Smoke, Sounders and Beacons all on the Loop, there are 61 Beacons.
Previously there was a Kentec panel fitted which was very difficult to control, i.e. One man test would not work and it was difficult to cancel the sounders. The Kentec was replaced by a C-Tec XFP and exactly the same thing is happening. To get the sounders to stop the panel has to be reset about 3 times and omt does not work, there is a situation when the sounders stop and the beacons carry on flashing.
The panel seems to work fine with the sounders disabled and it always goes into fire when tested.
The installation is not ideal because the loops have been taken to a nearby box and back to the panel with 5 radials on one loop and 4 on the other, obviously a conventional system converted to addressable (not very well)! The wiring is micc.
I spoke to C-Tec and Kentec and they seem to think the radials would make no difference to operation, I'm not so sure, any ideas?
have experienced a delay in pressing the silence button to the last sounder stopping.
i know with other panels that beacons that are programmed as other outputs they will not stop when sounders silence is pressed-only reset.
you will have more capacitance on the loop in micc and it also reduces your loop lengths. check for earth faults etc
Thanks in advance
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There is the usual delay when silencing, but I can hear sounders faintly from furthest area away from panel and then they gradually get closer until they are all sounding again, as I said I have to reset about 3 times to get them to stop.
I will try loading the loops with a resistor to counter act any capacitance, easiest option!
As for earth faults, because the radials are terminated in a plastic box adjacent to the panel the earths are not connected, there are no earth faults at the connection box. Perhaps another thing to try connecting them up to the panel!
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It might be worth hanging another panel off the loops , maybe a cel , they work well with Hochiki , just a thought.
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I had an Aritech panel that the sounders took ages to silence and eventually would not silence and the reset button would have to be pressed.
We replaced for an Advanced Panel and this cured the problem . the sounders stop almost instantly now.
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I agree that the most likely cause of the problem is the capacitance caused by using MICC cables. This can seriously affect the data signals on an addressable system. In this case, the data signal being sent to switch off devices, is being corrupted by the effect of the capacitance and some/all are not responding to it
The situation with the radials is not the problem, and as long as one radial doesn't cover any area greater than 2000m2 then it also complies with BS.
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Do you have the same problem if you stick 0 volts on the "continuous" input ?
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If capacitance is the most likely cause and I tend to agree, will loading the loop with resistance reduce it's effect? Will the capacitance be greater because of the radial circuits, in other words would there still be a problem if was a true loop?
Thanks for all the replies so far.
Do you have the same problem if you stick 0 volts on the "continuous" input ? not sure what you mean by this David.
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The only way to see if capacitance is affecting the data is to use an oscilloscope to see how it is affecting the waveform of the data pulses. There may be ways of compensating for the effects of capacitance, but I would suggest that you talk with Techincial at Apollo for advice because modifying capcitance values is fraught with potential problems.
Putting a resistor across a pair of wires carrying data is generally used to increase the current flow in the circuit. When more current is flowing in a circuit, the affect of low-current but high-voltage external interference is reduced. I'm not sure that this will help in this case because the problem seems to happen when higher currents are flowing anyway (i.e. the sounders are operating)
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Do you have the same problem if you stick 0 volts on the "continuous" input ? not sure what you mean by this David.
If you put 0 volts on the CNT terminal - remote input - it forces the panel to send a global "turn on" command to all sounders pretty much instantaneously - used for class change.
It would prove that there is definately no cause and effect issues that could be affecting the sounders... which I guess are all set to default ring ?
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I know this sounds silly, but when you press the silence alarms button, do you press it ONCE it and wait for all sounders to stop, or do you press it more than once as the sounders have not stopped instantly?
Reason I ask is the silence button is also a resound button, if you press it once it will send a “silence” signal around the loop, (which on some panels like Kentec and Ctec can take a while to fully circle the loop) if you press it again you will send the “resound” signal around the loop. Which sounds like your problem.
I use to get this as a common call out with some panels as the customer would press silence and expect the system to silence instantly, and because it does not, they get impatient, press it again which re sounds the system. (if you press silence/resound too many times on a cretin closed protocol panel they have a tendency to go into CPU fault and lock up with the sounders active and no way to silence) :o)
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Hi Spanner.
I realised this could be the problem so I tried it again and made sure I only pressed silence once, but I had to press reset at least 3 times before the sounders stopped completely. Of course there is also the problem that OMT doesn't work either, it all works fine with the sounders disabled though!
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Putting a resistor across a pair of wires carrying data is generally used to increase the current flow in the circuit. When more current is flowing in a circuit, the affect of low-current but high-voltage external interference is reduced. I'm not sure that this will help in this case because the problem seems to happen when higher currents are flowing anyway (i.e. the sounders are operating)
Surely if the voltage is fixed ie. 24volts then increasing the resistance across the circuit must decrease the current ?
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David, if you add any resistor in parallel with an existing circuit the overall resistance of the circuit is always reduced and, Ohms law shows us that, therefore the current drawn by the circuit increases.
In systems carrying data using voltage pulses, the liklihood of it being interfered with by RF and EMI created by nearby electrical systems is reduced by more current being drawn in the circuit. Increasing the current decreases the liklihood of interference.
This is why you will find that many systems using data being transmitted over a pair of wires require a resistor to be connected and the end of the circuit as standard. I have noted that this is often a 120R resistor. Such a circuit running at 12V DC therefore has 100mA flowing through it due to the resistor plus whatever current is drawn by the actual equipment on the circuit.
There are a lot of other parameters to take into account when loading a data signalling circuit with a resistor, but it is generally something well worth trying when that circuit is being affected by corruption.
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Top man... never knew that.
Thanks Wiz.
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A bit late- I know- appologies had a very similar problem on kentec solo (10 years ago) with a mixture of loop imterfaces and conventional sounders. When testing silently all worked perfectly with the bell circuit connected loads of weird stuff happened lights not coming on detectors, interfaces firing willy nilly etc etc. the bell circuit wire was causing the problem only one wire had to be connected for problem to happen. Never found out properly what it was but assumed it was the proximity of the wires in conduit( Fp100 in galv conduit) (And the sudden change to +V when sounders operate) stuck a relay on sounders with thru monitoring but powered from separate psu sorted problem. Have not heard of anything like it recently assumed been fixed by manuf