Are you reading the spec right for your unit? There's a huge difference between mA and micro amps? I haven't seen a unit that draws 130 mils before, in alarm.
Smoke / fire / heat detector recomendations
- Thread starter relay
- Start date
Are you reading the spec right for your unit? There's a huge difference between mA and micro amps? I haven't seen a unit that draws 130 mils before, in alarm.
The spec for the 2WTA-B has 130 ma as the max alarm current, however, you have to read the footnote that says that is the max current the FACP can be capable of supplying in normal polarity. In reverse polarity the 2WTA-B draws 30 ma for the detector in alarm and 12 ma each additional 2WTA-B in the loop.
I am curious why you stated in a previous post in this thread that you have to have a seperate isolated power supply. You never want an isolated power supply in a system like this. You ALWAYS want to common the negatives so that the devices have the same reference point. You can just use the SMKAUX on an ELK for resettable fire power up to its rating.
The power supply issue was a mistype, getting interupted while typing with 2 small girls in the house and not completely proofreading after the train of thought.
A system power supply used for protective devices should have a common negative with the main panel. In some cases, it's not completely necessary, or even at all, but it's generally accepted as a "best practice"
The biggest issue is the poster nov0798 was thinking of using an AC transformer to power the smokes, also didin't specify the unit/manufacturer to my knowledge.
A system power supply used for protective devices should have a common negative with the main panel. In some cases, it's not completely necessary, or even at all, but it's generally accepted as a "best practice"
The biggest issue is the poster nov0798 was thinking of using an AC transformer to power the smokes, also didin't specify the unit/manufacturer to my knowledge.
Yea I was thinking the 2WTAB's as suggested. The specs on the website say milliamps or mA. So 130 mA = .13A. So the 16 units at max of .13A would = 2.08 + the 25 mA for the MOD, so .025A more, so 2.1 ish amps.
I chose that power supply for its tons of extra capacity over what I really need, plus their cheap. Why couldnt I use an AC to DC transformer to power the smokes if I wanted to ?
Please go back reread the spec. The 130 ma is not the max alarm current that will be drawn in alarm. That is te max alarm current for the zone in normal not reversed polarity (technically an irrelevant rating for an installer who is using te detector with a UL Listed compatible panel as its already been verified). What that rating really is saying is that the alarm panel zone shall be incapable of providing more than 130 ma under any condition so that the detector is not damaged in normal polarity. Something that UL has already verified for you when they tested detector compatability with your ELK.
In alarm the first detector is 35 ma and additional detectors are about 12 to 15 ma. Youwill not need anywhere's near as much power as you stated. So 11 detectors in alarm will draw about 210 ma with the reversing relay. 20 detectors will draw about 375 ma in alarm with the reversing relay. You may not need an aux power supply on your system. Crunch your numbers and verify your particular setup. I rounded my numbers a little based on personal experience but you will get very close results.
The spec is very confusing but look at the note in the spec sheet and you should be to piece it together if you reread it a few times. If you have difficulty dont be surprised as i know a lot of Engineers that have problems with this particular spec sheet.
Please excuse the typos i am doing this on my ipad. Good luck.
Mfg Spec
In alarm the first detector is 35 ma and additional detectors are about 12 to 15 ma. Youwill not need anywhere's near as much power as you stated. So 11 detectors in alarm will draw about 210 ma with the reversing relay. 20 detectors will draw about 375 ma in alarm with the reversing relay. You may not need an aux power supply on your system. Crunch your numbers and verify your particular setup. I rounded my numbers a little based on personal experience but you will get very close results.
The spec is very confusing but look at the note in the spec sheet and you should be to piece it together if you reread it a few times. If you have difficulty dont be surprised as i know a lot of Engineers that have problems with this particular spec sheet.
Please excuse the typos i am doing this on my ipad. Good luck.
Mfg Spec
mustangcoupe
Senior Member
Digger
Just clarification as I read this differently
30 mA for the unit in alarm and 12 ma all other in the loop. Does this mean if a second and third go into alarm then it would be 30 * 3 and the rest at 12 mA (standby current)
if so, I would consider the 30 mA * total number of sensors = total current so it Never can over current the PS and cause shutdown issues...
The 12 ma is for the current for eac detector in the loop that is sounding. The standby current is micro not mili amps.
So 6 detectors would be 1 x 30 plus 5 x 12 plus 25 = 115 ma total in alarm if one trips The 25 ma is the relay.
If more detectors go in alarm there current goes up (lLED etc).. So yes 30 x each in alarm not 12.
So 6 detectors would be 1 x 30 plus 5 x 12 plus 25 = 115 ma total in alarm if one trips The 25 ma is the relay.
If more detectors go in alarm there current goes up (lLED etc).. So yes 30 x each in alarm not 12.
The part of the spec that is copied is just the alarm current. The standby current is 50 ua which is microamps.
A 2wire smoke zone trips on current. Each panel is different but it is usually a few ma to trip the zone. So about 20 smoke detectors on a zone would draw about 1 ma in standby which is not enough to trip the zone until a detector actually goes into alarm.
A 2wire smoke zone trips on current. Each panel is different but it is usually a few ma to trip the zone. So about 20 smoke detectors on a zone would draw about 1 ma in standby which is not enough to trip the zone until a detector actually goes into alarm.
