I have a ventilation system in the loft, that came with a wired controller; a display and couple of buttons about the size of a light switch. It also had bundled with it approximately 10 metres of telephone cable terminated in a 4P4C connector at one end (intended to plug into the ventilation unit's BMS socket) and bare wire the other, for connecting to the controller thing
The cable was no way long enough to make it down stairs, and the house is more or less built now so routing it would make quite a mess. I did however have a spare cat 6 network cable within 10 metres, routing around the eaves, so I took the phone cable to the cat 6, crimped each of the 4 phone wires to a pair in the cat 6 (I figured why not use 2 cores in the cat6, lower the resistance..) and then connected the controller up at the other end. Powering it all up showed a fault code on the controller
I dug out a modem wire and shaped the 6P4C connector to fit the BMS socket, then wired that up - controller works fine on this 1 metre cable. I also noted that if I disconnect only wire #2 from the controller, leaving the other 3 connected, then I get the same fault code with the short wire
Thinking I had a broken wire, I tested the adapted (the joined telephone + cat6 ) cable for continuity by joining telephone pairs 1,2 and 3,4 together then multimetering the other end, noting a resistance of 2.5 ish ohms for each loop. I then joined 1 and 3 and 2 and 4 and checked them again; all connected as they should, and the multimeter went OL when I had an assistant disconnect the wires from each other.. so right now I don't think there's a break in the wire, or a short between cores. NOTE; I couldn't test right from the 4P4C plug because my multimeter probe cant reach the contacts. I've hence made the (perhaps unreasonable) assumption that because it was new out of a packet an hour ago, it can't have a problem. Continuity has been tested from the point where it splices into the cat 6, down 3 floors to the controller end.
So my question is, is the resistance likely to be a problem? The controller has 0-5v written on it, and I recall reading that the signalling on the wires is something low voltage and serial, maybe the 4 cores are -v, +ve, tx and rx; I know that the controller powers off if cores 1 or 4 are disconnected, and shows a fault code if 2 is disconnected, nothing happens if 3 is disconnected, but I didn't check if the controller will operate the vent unit with #3 disconnected. The controller, even though it shows a fault code, seems to be capable of operating the vent unit. Note that the vent unit has its own equivalent LCD display and it never mentions any fault codes
Should I still be looking at a break or fault in the wire (as noted I haven't been able to test the whole wire), or could some amount (and what would be a high amount?) of resistance cause a problem akin to a disconnected wire?
Thanks!
The cable was no way long enough to make it down stairs, and the house is more or less built now so routing it would make quite a mess. I did however have a spare cat 6 network cable within 10 metres, routing around the eaves, so I took the phone cable to the cat 6, crimped each of the 4 phone wires to a pair in the cat 6 (I figured why not use 2 cores in the cat6, lower the resistance..) and then connected the controller up at the other end. Powering it all up showed a fault code on the controller
I dug out a modem wire and shaped the 6P4C connector to fit the BMS socket, then wired that up - controller works fine on this 1 metre cable. I also noted that if I disconnect only wire #2 from the controller, leaving the other 3 connected, then I get the same fault code with the short wire
Thinking I had a broken wire, I tested the adapted (the joined telephone + cat6 ) cable for continuity by joining telephone pairs 1,2 and 3,4 together then multimetering the other end, noting a resistance of 2.5 ish ohms for each loop. I then joined 1 and 3 and 2 and 4 and checked them again; all connected as they should, and the multimeter went OL when I had an assistant disconnect the wires from each other.. so right now I don't think there's a break in the wire, or a short between cores. NOTE; I couldn't test right from the 4P4C plug because my multimeter probe cant reach the contacts. I've hence made the (perhaps unreasonable) assumption that because it was new out of a packet an hour ago, it can't have a problem. Continuity has been tested from the point where it splices into the cat 6, down 3 floors to the controller end.
So my question is, is the resistance likely to be a problem? The controller has 0-5v written on it, and I recall reading that the signalling on the wires is something low voltage and serial, maybe the 4 cores are -v, +ve, tx and rx; I know that the controller powers off if cores 1 or 4 are disconnected, and shows a fault code if 2 is disconnected, nothing happens if 3 is disconnected, but I didn't check if the controller will operate the vent unit with #3 disconnected. The controller, even though it shows a fault code, seems to be capable of operating the vent unit. Note that the vent unit has its own equivalent LCD display and it never mentions any fault codes
Should I still be looking at a break or fault in the wire (as noted I haven't been able to test the whole wire), or could some amount (and what would be a high amount?) of resistance cause a problem akin to a disconnected wire?
Thanks!
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