Data cable problem, dropping speed

[Jobos]

I have a PC that keeps dropping its network speed from 1Gbps to 100Mbps and sometimes 10Mbps but the PC next to it is fine with a solid 1Gbps connection. I've done some fault finding by swapping the network cable with the cable on the next PC and pinpointed the fault to the connection. On the switch the connection takes much longer to establish with the LEDs going on and off a good while before settling down and then as said to a slower speed than the others.

 

Last summer the room was refurbished and things were moved around so taking off the trunking cover and tracing the cables I find the cables have been extended by way of junction boxes. The junction boxes look ok with neat punch down connections and I can't see anything amiss apart from the divider is missing from part of the trunking run with the data and power cables crossing over each other.

 

I've checked the cabling with a basic tester and all the connections are there but would this cable crossover be enough to cause noise in the data cables thereby reducing the speed?

[steveg]

How long is the run? it could be a combination of all the factors, especially if it is a fairy long run. It shouldn't be jointed and it shouldn't be run with power cables like that, but you can normally get away with 1 or the order. If you can't borrow a proper cable tester, maybe remove the cable from the junction box and stick a socket on there temporarily, see if that fixes the problem, would also let you re-route the cable away from the power when you put it back.

[Jobos]

How long is the run? it could be a combination of all the factors, especially if it is a fairy long run. It shouldn't be jointed and it shouldn't be run with power cables like that, but you can normally get away with 1 or the order. If you can't borrow a proper cable tester, maybe remove the cable from the junction box and stick a socket on there temporarily, see if that fixes the problem, would also let you re-route the cable away from the power when you put it back.

 

Some good points there, thanks. I've never seen a junction box like this before, I've got a connector that you crimp a plug on each end and join with a double ended socket but when time is money... I've a good mind to hand this to the site manager who dealt with the contractor that installed it. If they had checked the cabling with the proper tester in the first place the issue would have been spotted.

 

Edit: The run is 5m more from where the photo was taken but to get back to the cab it runs through the roof space so a lot of work to pull a new cable through.

Edited May 11, 2021 by Jobos

[steveg]

I'm guessing they didn't issue test certificates for the cable runs? Looks a lot like a job done by an electrician or general builder who does a bit of data cabling!

[3s-gtech]

I've never had any success with inline joiners. Wherever I've found them, they've subsequently been ripped out. Getting more than 100Mbps over them seems to be pure chance (yes, I know that a patch panel is also a joint).

[Chris_Cook]

What's the total length of cable? Are there any high current/noise devices near it (lift motors/fluorescent lights etc)?

 

Whilst not ideal, you should be able to get a 1Gb connection with a junction box and crossing mains wires. If the mains cables are single insulated, then keeping them separate is more critical, as the trunking/divider is part of the insulation. But that looks like twin and earth.

 

You could try better joiners if re-running the cable is not an option. I'd avoid putting plugs on solid core cable, unless you have plugs for solid core. You can probably tape a new cat5 cable on the end of the old one, and pull it through. It just won't pull round corners, so you would have to do a bit at a time.

 

I'd also double check the patch cables at each end, and try a different PC. Its possible one of those is bad.

 

If its recent work, then like you say its best to hand it back and say try again.

[chazzy2501]

if you have the tool open the coupler and re-punch the connectors.

[msi_school]

I have used joiners and couplers at home and for temporary installations at work, as @3s-gtech says they can be variable. I had one at a site that worked flawlessly for five years in a temporary installation that was going to be in use for 6 months at the maximum but I have also replaced them within weeks because they were flaky.

 

My advice would be to try and replace then, you might be able to use the old cable as a pull cord for the replacement.

 

But if this is going to be a bear you could start by repunching as @chazzy2501 suggested or putting RJ45 ends on and use a coupler this will also allow you to test the separate sections of the cable because the problem may not be the joiner but somewhere in the roof void.

 

I assume you have also tried swapping the PCs to confirm it is a wiring issue?

Edited May 12, 2021 by msi_school
Spelling

[Jobos]

I have used joiners and couplers at home and for temporary installations at work, as @3s-gtech says they can be variable. I had one at a site that worked flawlessly for five years in a temporary installation that was going to be in use for 6 months at the maximum but I have also replaced them within weeks because they were flaky.

 

My advice would be to try and replace then, you might be able to use the old cable as a pull cord for the replacement.

 

But if this is going to be a bear you could start by repunching as @chazzy2501 suggested or putting RJ45 ends on and use a coupler this will also allow you to test the separate sections of the cable because the problem may not be the joiner but somewhere in the roof void.

 

I assume you have also tried swapping the PCs to confirm it is a wiring issue?

 

Yes I swapped the PC and patch cables as the first test to rule them out but @steveg was spot on with his guess that the work was done by an electrician. I've got the electricians coming back this afternoon to take a look but I'm not holding my breath that they will being the correct tester.

[Davit2005]

This reminds me of an issue I had with Internet at a previous school. The internet would absolutely trickle depending on usage. Turned out that the cable was hanging on a few strands.

 

I'd suggest making sure cable is punched down properly into patch panels on either end. Testing wise a proper cable tester like a fluke that can test the actual connection and make sure it is up to spec.

 

Have you tried swapping switch ports at all as a further test.

[Jobos]

This reminds me of an issue I had with Internet at a previous school. The internet would absolutely trickle depending on usage. Turned out that the cable was hanging on a few strands.

 

I'd suggest making sure cable is punched down properly into patch panels on either end. Testing wise a proper cable tester like a fluke that can test the actual connection and make sure it is up to spec.

 

Have you tried swapping switch ports at all as a further test.

 

Yes and into different switches.

[speakercon]

I hate using joiners if at all avoidable and would always prefer to replace the cable but working in older buildings which often have celling voids that are inaccessible due to asbestos they've been my only realistic option on numerous occasions, and to be honest I've not had any issues with them.

 

I always use these - https://cpc.farnell.com/pro-signal/bt-855/coupler-wired-cat5e/dp/CS13869

 

I've also seen power and data in the same dado with no separator many times, not ideal (or compliant!) but I've not seen it cause any problems in the real world. Maybe I've been lucky!

 

If it’s dropping to 100mb its likely that one or more of the blue/brown cores has a poor connection. As others have said I’d reterminate all the connections starting at the socket module, then the coupler and then finally the patch panel if no joy. If none of that works the cable is probably damaged somewhere or the socket/coupler/patch panel itself.