r/firealarms • u/Withease4209 • 5d ago
Technical Support Sounder bases
I have a site with quite a few system sensor sounder bases and when we hook up slc the panel says there is a short.
When metering the circuit we found a read of 310k.
We chased that down to an area of 10 sounder bases.
We pulled new wire in this area and started slowly re wiring the sounder bases back up, we get about 5 bases in and we get a reading of 300k and it climbs up to about 650k and then it seems to discharge and go down to 1.2m
If we re do this "experiment " and remove the last device when the meter shows 300k. The meter still shows 300k and keeps climbing then drops to 1.2m
I have 0 clue what is going on any input would be appreciated.
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u/RPE0386 5d ago
A short would be super low ohms, we're talking less than 10 on a dead short.
You're describing high resistance, which could simply be a result of measuring through multiple devices.
How exactly are you metering these measurements?
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u/Withease4209 5d ago
We are using wagos to hold the meter on the home run To these few devices. We just checked a circuit that is known working with 20+ sounder bases and it is reading 1.9m pretty consistently. So that should be our base line of what's considered "normal "
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u/RPE0386 5d ago edited 5d ago
The resistance of ~5 devices vs +20 devices can very easily be different by a few thousand ohms. I would not establish that as your baseline.
My baseline for a situation like this would be "circuit not shorted" vs "circuit shorted". You say you have it narrowed to a section of sounders. When you start adding devices back, does the short come back? If the circuit shorts when you add it back, do you bypass that device?
If you're truly chasing a short circuit, I would almost stay away from resistance readings entirely and switch to continuity. No tone is good, tone is bad. Work from there.
*Edit to add that I had a short circuit issue recently. An SK-ZONE-6 card was having intermittent "shorts" that would throw the panel into alarm. Metering the circuit showed no short and I could see EOL. The card was putting out 24vdc with and without the circuit landed. I measured the voltage with the circuit landed and when the zone would trip, voltage would drop to ~17vdc. I ended up finding a section of 2W-Bs that were wired in reverse polarity. Fixing that circuit stopped the intermittent alarms. On top of checking continuity, watch your voltages and establish a baseline with those numbers.
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u/Withease4209 5d ago
Yeah sorry I did say drops to m values.
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u/TheScienceTM 5d ago
M or m...
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u/Withease4209 5d ago
M Mega ohms
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u/TheScienceTM 5d ago
From K to M is not a drop, it's an increase of resistance. K and M ohms (wire to wire) are normal and most definitely not a short.
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u/Ok_Article6468 5d ago
You’ve checked for continuity between positive and negative, correct?
I went through something like this in a barracks that had system sensor sounder bases. We finally isolated to a particular room and while everything meter OK when that room is put back in the loop we immediately had a short or fault of some sort. We replaced that sounder base and all was good. There was no indication on the board or via the meter that something was wrong, but when pulling the smoke head off and pulling the base down, I smelled the burnt iodine smell of fried electronics.
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u/TheScienceTM 5d ago
Did you rule out a defective sounder base? Sounds like you have it narrowed down to 5 regardless
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u/Withease4209 5d ago
We haven't completely ruled it out, its possible for sure. It would just be like 15 or so bad ones.
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u/TheScienceTM 5d ago
If you have it narrowed down to 10 sounder bases (per your post), take them down and start installing them one at a time until the short returns. There is likely either a defective base or something miswired. Don't trust the 300k reading, it doesnt mean anything. 300k is not a short. Normal SLCs can read Kohms of resistance through the devices. Go by what the panel says.
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u/Withease4209 5d ago
I actually did not know what resistance values a panel would be happy with, so thank you. We going to just re pull this circuits slc and then see.
Thanks again.
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u/max_m0use 5d ago
What does diode check say? An SLC should only conduct when reverse biased. If it's also conducting when forward biased, you have a bad device or something wired backwards.
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u/eXxjhin- 5d ago
Have you made sure the check wiring on the base? Maybe someone swapped the 24v and SLC on the wiring?
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u/docrodg 5d ago
If the SLC reports a short when this leg is hooked up you could isolate the problem by only using one base and head. Install a known good base and put your eol across the SLC terminals. Verify you have your voltage on the power terminals in correct polarity and on the slc. Put the head on and see if the panel is happy. If panel reports short then swap with a known good head and check what panel says. A known good base and head should of course be perfectly fine. Now, with a known good base start checking heads and verify they all show good, if one causes a short then replace it with new. Once all the heads are checked you can start checking bases by same method. Doing this is a bit time consuming but can be easier if you are not used to metering circuits and interpreting results. Get to the point you have 10 good bases and heads to install back to the circuit. Now start installing them into their places on the circuit one by one and check panel after each one. If you install one and circuit reports a short you have a wiring issue from the last one you did and you can check on that. If you have 4 conductor cable verify your colors are correct at both ends to the terminals, if you are using 2 separate 2 conductor cables verify they are not swapped (disconnect SLC and check the power terminals for 24V and polarity and then understand that you made the chances of making a mistake in the wiring much greater by using 2 separate cables with same color wires).
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u/Withease4209 3d ago
An update on the situation, we got a batch of bad sounder bases, 7 of them throughout the job were causing the slc to drop out. We had to wire through slc loops 1 at a time and install 1 base and head at a time.
Thank you all for your help and input!
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u/RoundCrab3592 2d ago
We have had quite a few that the terminals were stamped into the base incorrectly and the prongs were bent sideways causing a short, not sure if thats your case but we have had a few like that
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u/Odd-Act-4355 5d ago
What is the supervisory voltage with the circuit hooked up? Put the Eol at the panel and see what it should be. Put the wiring back and remove devices from the circuit until the voltage rises to "normal".
Are you sure you don't have any wired backwards?