Fire Alarm problem.

[pennychew]

Been meaning to post something up about this for a week or two but never had a chance, its a bit long winded but stick with it!

A company i do the maintenance for asked me to bring a spark in to look at a fire alarm panel they were having bother with, the company that maintains the alarms for the group had been called in a fortnight before for some issue with the panel.

Two engineers had already been to the job, the first guy replaced a fuse and all was well, the second guy (1 week later) replaced the panel and added a load of extra stuff as he reckoned something in the stores DB was pulling too much current and knacked the fire alarm panel. This guy put a seperate PSU and relay in but when he powered it up something was clicking in the DB so he left it and i got the phone call to bring a spark in.

Me and my spark went in and it turns out the guy who added all the extras in has left the alarm company, the new guy they sent up didnt seem to know much tbh and seemed to be relying on my spark to put his alarm panel back to how it should be for him.

We found a knackered relay in the DB which is energised by 24v from the fire alarm panel and in turn energises a 240v coil contactor that switches the air con on. Obviously this is so the air con is switched off in the event of a fire. Left at at that and went and bought a new relay the next day.

My spark has got a new job working away so i took a guy from the forum back with me so we could plug the relay in and try it out. Plugged the relay in and nothing, we manually operated the relay with the toggle on the top and sure enough the contactor pulled in and the A/C switched on. Checked the AUX output from the alarm panel and there was nothing.

We found a 24v output from inside the alarm panel that cut out when we triggered a call point and connected this up to the aux cable to the relay in the DB, This pulled the relay/contactor in and everything was working fine.

I got a phone call a couple of days later to say the alarm panel was beeping so i called in to have a look, it was in fault mode and was showing an earth fault and a sounder fault. Being confident the electrical side was ok i told them to get the Fire alarm company back out as it needs checking that all the terminations are in the right place as its been messed on with that much! the alarm guy came out again and says there is still something wrong with electrical side??

I called in today to get some pics and draw a wiring diagram up to post on here and see what the opinions are, while i was there i looked inside the fire alarm panel and the engineer has disconnected the 24v aux supply and it seems to be working fine as there was no air con in the store and it was mega hot i flipped the toggle on the relay to bring the air con on but obviously the fire alarm has no control over it at the minute which needs sorting.


Relay and contactors in an enclosure under the DB



Alarm Panel Connections

I though i had a picture of the extra bits that have been added but it doesnt look like i have

Also the alarm panel seems to be a Gent Xenex but there are no details on the unit...

Let me know if i havent explained anything correctly, i knew nothing at all about fire alarms before this job but i'm getting my head around the way operate a little now

Stu

 

[trev]

I should probably add that the 24v output from the panel that we "found" wasn't just a hit and miss, trial and error thing. (yes the bloke from the forum was me) there was a wiring diagram on site which identified the output to connect to.
Anyhow as Stu said, this output pulled the relay in which in turn pulled the contactor in. When the alarm was activated the contactor dropped out again as expected. When Stu got the follow up call the panel was showing an earth fault. Now, 3 or 4 earths were disconnected for belling out purposes and were reconnected in exactly the same terminals they were removed from and all passed the tug test. After reconnection we were there a good 15 to 20 minutes with absolutely nothing happening on the panel to alert us to something being wrong.
The alarm guy says there's something wrong, I think the panel is buggered.

 

[tazz]

Straight away the gent as many other panels, has a current limiter on the aux supply...with the gent, its output is only 100mA.
When testing, if the voltage from aux drops to 5v or less in fire condition , the the current limiter has kicked in.
Would suggest, the relay being driven, takes more than 100mA. Try installing and smaller 24v 50mA relay, to inturn, drive the larger relay.

 

[pennychew]

That sounds like the reason the first engineer put a separate psu and relay in, the thing that made me think twice though is that the shop has been open 2 years and the problem has just started now, the relay was definitely damaged, I should have measured the resistance in the coil of the new one to see what current it will be pulling

 

[pennychew]

Does it sound plausible that if the current draw is too high you would get the fault lights for earth fault and sounder fault flashing?

 

[trev]

If he'd taken the relay in the board out then we probably wouldn't have the problem Stu. That's probably what shafted the existing relay.

 

[tazz]

Cant see it effecting the earth/sounder circuit as this would indicate just that, sounder 1 or sounder 2 has a earth fault,
I thing this is throwing you of the sent, and they are 2 separate faults.
You are lucky as I am in Newcastle at the moment and could spare you an hour tomorrow afternoon, to do some checks and help out

 

[trev]

Why didn't you say you were coming up? Could have had a pint or 3 and put another face to a name.

 

[tazz]

Left a loverly sunny 31c London, to arrive at a windy 17c Newcastle, lol. Got a best Western and a small hotel to finish off tomorrow, I should have said, and could have met up in hotel for a few free beers.

 

[trev]

Windy and 17 degrees? This is our summer mate.

 

[pennychew]

I'm supposed to be finishing a job off in Manchester tomorrow morning but I could probably reschedule... What time would be best for you?

 

[trev]

Stu, go to Manchester mate if you need to. I'll meet Tazz there at whatever time he can make it.
I can ring you later on to tell you what the crack is.

 

[pennychew]

I'd love to be there mate, plus I'll need to sort a permit. I might do Manchester Sunday morning instead but wor lass will get the hump as we're supposed to be taking the kids out!!

 

[tazz]

Dont mind really, enjoy Newcastle we get a lot of work here for electronic hotel locks, and the guys are great to work with...plus we get free accom, food a beer.

 

[tazz]

will pm you Trev