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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Technical Advice => Topic started by: abdi on October 05, 2005, 06:32:54 PM

Title: Relays and normally closed contact
Post by: abdi on October 05, 2005, 06:32:54 PM: as part of our contract with our client we do service some inergen system, some of those systems have relays with closed contact.

i.e The realy could be used to shut down the companie's server if the alrm is actived.

My question is how go you make sure that you don't shut down the company server whilst at tyhe same time carrying out service maintenance.

Thankfully I haven't come across one yet, so I haven't had the pleasure of shutting down one yet..

Now, I know you have to put a link some where, but I need detailed description and step and step of what actions to take...so I am confident next time I come up against it

I look forward to hearing from you fellas.

Kimd Regards
Title: Relays and normally closed contact
Post by: Allen Higginson on October 05, 2005, 07:15:01 PM: You would be better going through this site and getting on board as a trade member - www.thesecurityinstaller.co.uk
Title: Relays and normally closed contact
Post by: Allen Higginson on October 05, 2005, 07:27:19 PM: If it is only a closed contact on the relay and the relay operates by the panel switching the positive (normallly) to the coil via it's fire contacts then all you have to do is remove the feed to the relay.If it is permanently energized (not so normal!!) then you will have to advise the customer that they will have to isolate the signal at their end.This shouldn't be an issue as most use an input on their control gear which can be "forced" not to close down.
Title: Relays and normally closed contact
Post by: Graeme on October 05, 2005, 10:07:25 PM: or use the keyswitch to short across the common and normally closed.
Title: Relays and normally closed contact
Post by: Allen Higginson on October 06, 2005, 07:26:25 AM: Where did the keyswitch come from???Oh,you mean install one!!
Using a keyswitch is good practice but what I normally do is use a double pole switch with the relay coil feed on the normally closed and install a buzzaer/lamp arrangment using the normally open contact of te other pole so that when you isolate the relay feed you have a visual/audible warning to remind you (it's easy to forget !).
Title: Relays and normally closed contact
Post by: David Rooney on October 17, 2005, 06:25:58 PM: Abdi

If you are going into a computer room to carry out a service for the first time your company should ask for a statement from the system administrator that details all the shutdowns including if the Air Con shuts down on first stage, PDUs on second stage etc.

If they can't tell you then arrange for a complete shutdown of the EDP equipment so you can test and install any isolate switches as necessary (as mentioned above).

You do not want to risk shutting down peoples' computers as they tend to get upset and start talking telephone number compensation !

Good luck.....
Title: Relays and normally closed contact
Post by: Sean on December 04, 2005, 08:01:19 PM: I just use a mini 'gator-clip', and connect the two sides of the contacts.Let the relay do it's thing. As long as the aligator clip is there, the server will see no interuption of power.
Never used it on a server's power loop, but have used it on an n/c main disconnect relay (to keep the pilot lights from going out on gas ovens durring test)...samey-same electrically tho.
Title: Relays and normally closed contact
Post by: Graeme on December 05, 2005, 06:02:49 PM: no shortage of Gator's in Florida.
Title: Relays and normally closed contact
Post by: Allen Higginson on December 05, 2005, 09:51:03 PM: Quote from: Graeme Millar
no shortage of Gator's in Florida.
Owww,stop - my sides are splittin'!!
Title: Relays and normally closed contact
Post by: colin todd on December 06, 2005, 12:58:55 AM: Probably, the split, Buzzy, is the result of an overpressure caused by excessive intake of fizzy alcohol as you sent old geroge off to his final resting place.
Title: Relays and normally closed contact
Post by: Graeme on December 06, 2005, 06:58:32 AM: no Colin,the split is in his trousers due to too much Guiness.
Title: Relays and normally closed contact
Post by: Allen Higginson on December 06, 2005, 02:04:01 PM: Hmmmm - probably a bit of both there!
Title: Relays and normally closed contact
Post by: Graeme on December 06, 2005, 07:30:48 PM: glad i'm not an Engineer in Florida.
12 footers uniform is outrageous!!!

Buzzer lets not forget middle aged spread.