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cwicks
Joined: 21 Apr 2006
Posts: 4
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| Posted: Fri Apr 21, 2006 7:18 pm Post subject: Replacing a Napco 850 control board |
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Hi,
I bought a home with a Napco 850 security system already installed. However, the system cannot be armed, since the previous owner did not get the codes from the prior owner when he bought the house. The company that installed the system is no longer in business, so the system is essentially dead.
I'd like to replace the control board with a newer unit like the Gemini P815, and simply hook it up to the existing sensors. My question concerns the end of line resistors. The 850 uses 1K resistors, while the P815 uses 2.2K resistors. I'm assuming this might be a problem unless I replace the resistors, but tracking down the end of line for each zone is going to be a major pain.
So, the question is: Is the difference in resistor values going to cause a problem? Is there a workaround if it does? Is there another system that uses 1K Resistors?
It would be nice to just replace the control board and the keypads, but if I have to do a bunch of wiring in addition, I might just reconsider the whole idea. Thanks.
Charlie |
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Ralph
Joined: 16 Dec 2005
Posts: 165
Location: Smithtown, NY
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| Posted: Mon Apr 24, 2006 2:18 pm Post subject: |
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| The EOLs are generally located in the panel itself. Perhaps you could snap a picture of the panel and post it here (you can use photobucket.com for free image hosting). |
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cwicks
Joined: 21 Apr 2006
Posts: 4
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| Posted: Mon Apr 24, 2006 3:11 pm Post subject: Here's a pic of the 850 board |
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Here's a pic of the 850 board. Not sure where the EOL resistors are...
http://home.earthlink.net/~c-and-s/850board.jpg
Charlie |
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Ralph
Joined: 16 Dec 2005
Posts: 165
Location: Smithtown, NY
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| Posted: Mon Apr 24, 2006 4:17 pm Post subject: |
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| Most installers will put the EOLs at the end of the line with the sensor. Hvae you check on the sensor end? |
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cwicks
Joined: 21 Apr 2006
Posts: 4
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| Posted: Mon Apr 24, 2006 5:28 pm Post subject: Checking the sensor end |
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Well there's the rub. While I was able to trace out the wiring with a tone and probe, the way the wires are run makes it impossible to find where the real end is. I don't really want to dig out sensors embedded in window frames or open up walls to to find which sensor is the end. I'm thinking that since all the zones are N/C circuits (no mixed N/C and N/O), I can just add the extra resistance at the board connection and have an easy fix. Or am I missing something?
Charlie |
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Ralph
Joined: 16 Dec 2005
Posts: 165
Location: Smithtown, NY
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| Posted: Tue Apr 25, 2006 4:40 pm Post subject: |
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| It wouldn't be something I would reccomend, if the resistance of the cable itself plus the two resistors is off, you will have huge headaches. |
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cwicks
Joined: 21 Apr 2006
Posts: 4
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| Posted: Tue Apr 25, 2006 5:26 pm Post subject: adding resistance to the line |
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I would think it would be a whole lot easier to just use an ohm meter and measure the line resistance and add what is needed to equal 2.2k ohms, rather than to open up walls and/or door and window frames. It should't be difficult to tailor each line resistance fairly accurately...
Charlie |
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Ralph
Joined: 16 Dec 2005
Posts: 165
Location: Smithtown, NY
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| Posted: Wed Apr 26, 2006 8:40 am Post subject: |
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| I gave a quick call to the folks at Elk Products (excellent security company) and they informed me that as long as the resistors are installed in series they will be fine. |
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