Wheelock EHS-EL1 Cuts Out?

Hey everyone,
So today I did the first initial test of my fire alarm system. Everything worked, all initiation devices were wired and operated correctly and the A/V’s did…for the most part at least.

I have my EHS-EL1 on the same NAC as my Wheelock 7002T for obvious reasons. The EHS-EL1 is NAC 1’s EOL while the 7002T is normal in out in out.

Signal coding is set to steady.

However, I couldn’t help but observe that while the 7002T operated correctly (horn skipped and everything), the EHS-EL1’s horn seemed to spaz out at times. It was hard to tell actually because of how loud it was and my ear is still ringing (I took off my hear I got protection to see what was wrong).

It will sound, but on random intervals will cut out (the horn that is). It will be like a long beep and then sort of a stutter and it starts up again.

I thought this may be because it’s on the EOL, maybe dropping voltage, but that simply doesn’t make sense. It worked perfectly when I tested it with batteries, so I don’t know what’s wrong with it. Is it because I twisted the EOL so it would fit into the terminals? Nothing went into trouble while in operation, so it is not the NAC, and it is not even close to overpowered. I find it very hard to believe two two wire horn strobes would be enough to cause this issue.

It does operate, but sporadically. It does operate most of the time though, and I want to test it to see if either it was me imagining things or something, but I don’t think so, although my ears were being shredded for the half a second I took off my hearing protection, so maybe.

Can anyone please advise? Is this alarm not compatible (I find this hard to believe since it requires filtered DC anyways.

Try removing the 7002T and see how it sounds. 7002T’s introduce a LOT of noise on their circuit, so that may be affecting the performance of the EHS-EL1.

Since we know the 7002 works properly, remove it from the NAC and test the EHS-EL1 as the sole device connected to the NAC.
If that fixes your problem then it’s possible that a slight voltage fluctuation could occur when the 7002’s strobe fires, and the EHS-EL1 signal is interpreting this slight fluctuation as a code or pulse. The solution would be to either put them on separate NACs or use a longer wire between the 7002 and the EHS signal.
If the EHS-EL1 performs the same way without the 7002 connected, let us know.
Also, I don’t recall off the top of my head, is the EHS a 4-wire signal?

Well I noticed the resistor fell out, but that wouldn’t be the issue, right?

It’s possible the resistor somehow got positioned in such a way that the vibrating of a horn allowed the leads of it to touch and short somehow (like if it was twisted around itself or pressed inward on itself or something), however that would be extraordinarily unlikely, and if it did happen the entire NAC would fail.

Try the EHS-EL1 by itself on the NAC (without the 7002t) and see if that fixes the problem.

The resistor actually wasn’t the issue. I got it to stay, and the resistor is on the EHS-EL1, not the 7002t.
Unfortunately, I cannot test it as when I went to take down the 7002t, one of the screws holding it to the box did not budge. Long story short, it was heavily stripped somehow and would not budge, so in order to free the 7002t, my dad had to break the screw. While this permanently damaged the backbox, it was our only option. I have since taken this back box down since I now need a new one, and since lots of wires passed through the box, I had to run around to multiple devices and remove the wires from the terminals to take down the backbox. I carefully removed these wires so that I can put them back in place once I get a new box and install it, which will hopefully happen tomorrow. I labeled the wires accordingly as to where and what they went to so that I won’t be confused and it will also expedite this.
Due to the holes in the board from the previous screw arrangement, I will have to reverse the screw arrangement, meaning I will not be able to mount any 2903 units without mounting the Simplex boxes up there (which I will be doing in the not so near future is replacing the current A/V boxes and pull station boxes with Simplex boxes; as this was how I originally intended to set the system up as, but I changed my mind because I wanted to use different devices as well). So that will be happening long from now, but at this time the current arrangement with standard 4" square boxes will remain.

I’m very sorry I cannot say I have a solution to the issue, and now after all this, I may just leave it alone. But, would another option be to make the 7002T the EOL? Would that solve the issue perhaps?

Try putting the EHS-EL1 on another NAC just to make sure it is in fact working properly and playing nice with the control panel.

What seems to be the cause of the issue is the 7002t causing voltage transients on the circuit. As the strobe capacitors discharge and the strobe flashes, it causes voltage fluctuation within the device. (Since the strobe is in series with the horn, this is what causes the 7002t’s horn to flicker when the strobe flashes) The 7002t does not use any onboard protection to keep this transient voltage off the rest of the NAC circuit, so the voltage fluctuation occurs throughout the circuit. The EHS-EL1 is likely interpreting this fluctuation as an attempt to code the horn, or the fluctuation is preventing the internal horn circuit from working properly.
It doesn’t matter whether the 7002t is before or after the EHS-EL1. In extreme cases, voltage fluctuation caused by motor bells/vibrating horns has actually caused CPU resets on unprotected panels.

One solution is to increase the wire length between devices. Wires add a small amount of resistance to any circuit, but if the wire is long enough it can keep voltage fluctuations to a minimum, or at least low enough so that the next device on the loop (if it’s far enough away) doesn’t get enough fluctuation to cause problems. This is why a Simplex 4002 can drive a large motor bell when it’s installed 100 feet away from the panel in a building, but if you put the same signal 3 feet away from the panel on your wall, as soon as it rings the voltage spike makes the CPU restart.

Here’s the TL;DR: The 7002t needs to be separated from the EHS-EL1 by a formidable length of wire to prevent voltage transients from messing up the EHS-EL1. If you really want to get fancy, it’s possible to solder some MOVs or maybe a flyback diode or something across the terminals of the 7002t to suppress the voltage spikes and keep them off the NAC circuit. I don’t have enough electrical engineering knowledge to tell you which of those options would work better, or what the MOV/diode would need to be rated for to supress transients but allow operating voltages to pass through.

Well, that’s interesting. I was hoping to use both devices in the system as this was how my Elementary School was set up. Due to the locations of the mounting boxes, I can’t increase the wire run between the two unless I were to make it longer and then tuck it in the back box. The EHS works properly on its own to my knowledge.

I really wanted to use both in my upcoming system test, and if it doesn’t damage the panel, can I do so? Or would it be more advisable to just use one notification appliance instead of two on NAC 1? It would be disappointing to say the least as I bought this panel with the intent to run multiple devices on the same NAC at the same time, like mechanical horns and other devices. I’d rather not remove any of those as it would make it boring, because after all it’s what I made the investment into this panel for.

I’m rather disappointed at this point. I was even going to use two mechanical horns in one test.

I only have two NACs and one of which is strictly intended for strobes only as it is non silenceable (set for audible silence and cannot be coded per the manual). If I wanted more I’d have to use a 4009 NAC Extender, which is out of my budget and there’s way too many types (conventional, IDNet addressable, one for ES series TrueAlerts, etc.).

I’m not too familiar with the 7002/7002t line of devices, since I’ve never owned one. (shocking isn’t it? I really need to start collecting some classic alarms!) However, I have seen pictures of some online where there are MOVs soldered across the terminals for voltage suppression. If you search eBay you may be able to find a 7002t with the appropriate protections.

Again, the problem you’re most likely having is the 7002t is making too much “noise” on the NAC circuit which is messing up the EHS-EL1. Since your panel has been fine so far I would not really worry about it. A 7002t really isn’t capable of generating enough transient spikes to interfere with a decently-protected CPU, typically it takes the much larger spikes caused by a more power-hungry continuous bell to cause panel problems. You can use a longer length of wire and just tuck it behind the back box if you like.
I read through the 4004 manual quickly and discovered that NAC 2 can indeed be set to silenceable via a jumper setting. Refer to section 3.9.
So you can put both signals on separate NACs and since these are 2 wire signals, for now that will solve your problem.
If in the future you want to add 4 wire signals for audible silence we will have to discuss another solution (although at this point you may have a panel equipped with more than 2 NACs or a larger system with enough wire runs to prevent the 7002t from being an issue).

Thanks, I appreciate the help!
For now, I think I’m going to just have the EHS-EL1 on NAC 1, or put them on separate NACs, like you suggested. In the future I plan on using 2 4-wire Simplex electronic horn strobes, so this doesn’t happen. I may still use both devices as well, and just put them on separate NACs like you suggested. I want to make a good while interesting new system test video and am afraid not using a 7002T would be boring for some viewers, but oh well. My elementary school system was primarily EHS units anyways, so it’s not like it wouldn’t be as interesting as it would with 7002Ts too (they had 7002 series devices in the speacial needs room, the gym, and the auditorium).

Plus, not to mention my pets freak won’t when both the 7002T and EHS are going, not to mention it’s extremely loud. So using just one might be a better alternative, but we’ll see.

Alright so here’s what I’ve decided to do. I’ll make my first new system test with the EHS, and then I’ll make a new system test 1.5 or something with just the 7002T. That should solve the problem.

All right sounds good. Once again, seems like the manual indicates that there are jumper settings which will allow you to set both NACs to silenceable, so that is definitely an option.

Ok, so it seems to work fine now with the exception that the tone almost sounds deeper and fluctuated a tad. I’ll post an unlisted YouTube video soon so you guys can hear it doing its thing. What’s weird is when I tested this with batteries it sounded good. Should I untighten the screws a bit perhaps?

Here’s the video:

Any suggestions? Tell me what you think.

I can’t hear anything audibly wrong with it from your video.

If you think there’s a sound problem it could be one of two things:

  1. The screws are slightly over tightened to the backbox and it’s causing something (either the plastic grille or piezo mount) to vibrate slightly unnaturally. Loosen the mounting screws just a tad. Look at the signal from the sides and the bottom to see if it’s slightly skewed/warped and watch it straighten as you back the screws off a little.
  2. The signal is just getting old and things aren’t as perfect as they used to be. No need for concern just don’t let it run for an extended period of time so that you prolong its life.

I’m gonna guess that when you tested it with batteries, you just had the device on its own, not mounted on a backbox.

It’s completely normal for a device to sound different when it is mounted on a box, versus when you are just bench testing it with batteries. When not mounted, the sound waves are allowed to exit from both sides of the device. On a box, the sound that escapes towards the rear of the horn encounters the mounting box and is allowed to reverberate in the box space before exiting towards the front of the device where you hear it. When combined with the small vibrations that are transferred to the box itself and the area surrounding where the box is mounted, a slightly lower pitch is to be expected.

Ok. That makes sense! Thanks for the clarification!