Today I had a strange occurrence with a EOL. The system was not reporting the zone open even though I was holding the door open and looking at the keypad. After a period of troubleshooting found that the 3.74k resistor was now 5.86k. Replaced with new and all is well. This is the second time in 17 years that this has happened to me. Very Strange??? I wonder what would make it change in this way. Any thought???
Well, If your panel showed no open zone and the door was open.....the size of the resister is a small factor....if the door "switch" was open, the circuit should be open. So! it sounds like a ground past the resister and before the switch that probably got "fixed" when you changed the EOLR . and yes the EOLR value does matter...just one way to possibly explain it. Just draw out the simple circuit and you can see that an open switch MUST open the panel, no current flow...but a suitable ground in the right spot ....it can bypass the switch. and a ground on the other side of the resistor will open the circuit. This is the reason for a lot of intermitten problems... that "go away" after you check things....look for nicked wires etc.
And how does this account for the fact that the resistOr changed it's value?
17 | > years that this has happened to me. Very Strange??? | > I wonder what would make it change in this way. Any thought??? | >
| > Responsible comments requested. | | | Well, If your panel showed no open zone and the door was open.....the | size of the resister is a small factor....if the door "switch" was | open, the circuit should be open. So! it sounds like a ground past the | resister and before the switch that probably got "fixed" when you | changed the EOLR . and yes the EOLR value does matter...just one way | to possibly explain it. Just draw out the simple circuit and you can | see that an open switch MUST open the panel, no current flow...but a | suitable ground in the right spot ....it can bypass the switch. and a | ground on the other side of the resistor will open the circuit. This | is the reason for a lot of intermitten problems... that "go away" after | you check things....look for nicked wires etc. |
3.74K sounds like a zone doubled NX panel to me? If there in fact was a short to ground after the resistor but before the switch it should also affect the corresponding upper zone, especially if the resistors are installed in the can.
Thanks for all the thought even if they were slightly off tangent.
Yes the resistOr did change value (up) and I would think that a high voltage surge would have degraded the value down not up if not open altogether. Weird things do happen and sometimes in ways you would not expect.
this one drove me nuts today...kept stripping it back putting it in the termination block on a new smoke (old house, old wire) and the freeking thing would break after we put it back up...i about had a fit...happend 3 times on different terminations...up down up down up down. Maybe I should just become a salesman and keep my fat ass on a cushioned chair.
If you begin with a resistor with a 20% tolerance (no tolerance band), and with some age and heat, the carbon in it can change it's resistive/conductive properties. If you really want to control this better, try either 10% tolerant resistors (silver tolerance band) or better yet 5% (gold tolerance band) resistors.
No Al. That is not correct. Tolerance is a measure of the precision of the resistor in manufacturing. It does not mean that the resistor will change over time.
Resistors are never made to the exact value indicated by the color codes. Manufacturers use the tolerance color band to tell you just how accurately the resistor was made. It is a measurement of the imperfections. Gold = within 5% of dead-on. Silver = within 10%. In other words, the tolerance band indicates the range of possible values that a given resistor may have. For example, a resistor with three red bands and one gold band is rated at 2200 Ohms but it can actually read anywhere from
2090 to 2310 Ohms. Whatever its value was when made, it will remain at that same value permanently.
To determine the exact range that the resistor may be, take the value of the resistor and multiply it by 5%, 10%, or 20% for gold, silver or no tolerance band, respectively.
The above statement is based upon a misunderstanding of resistor tolerance.
If you really want to be picky, use 5-band resistors but have fun finding an alarm manufacturer that supplies them. 3-Band and
5-band resistors do exist, though they're not appropriate for use in alarm circuits.
It is highly unlikely that the gentleman has a 20% tolerance resistor but even if he did that would not mean that the carbon is more likely to change value.
Correct Robert, I don't remember the tolerance band on this particular resistor but I believe it to have been a 10% Silver. That would mean it would have had a high range of 4.114k but it was at 5.86k that would be
56.7% increase in value. We will never know what happened to have changed it so drastically.
Is not true that if copper is heated and quickly cooled it will lose it ductile strength and become brittle?? Maybe when it was processed it was not tempered properly. Just be happy in the fact that is was not stranded wire and all but one strand had broken. A good reason to use solid wire in Fire Alarms.
It's too bad you didn't keep the resistor. It might have been interesting to examine it. My best guess is it was poorly made to start with (stuff happens) and it chose your installation in which to make its home. :^)