Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessories

[baldsparkies]

Have been concerned about an install thats running on the warm side.

MCCB is rated at 200 250A supply cable is supposed to be 95mm swa (4 Core) which surprises me looks more like 70mm at best 50mm worst. Nothing on the side wall (Darn those manufacturers)

Now the MCCB has a design operating temp of 65 degrees and the tech dept as confirmed that table 4D4A not 4E4A should be used for cable sizing and current ratings.
The logic being that whilst 90 degree thermoplastic offers a higher design current Table 4D4A should be used to keep the temps within the design limits of the connected devices. Also with the MCCBs the max currents do drop off considerably as temps increase.
All this makes perfect sense, but my main concern is a supposed 95mm cable running hot to the touch when only pulling 170 amps per phase. If 95mm we should be looking at 304A with xlpe or 251A with the 70 degree.
Connections are all good so would you guys be of the same thoughts as me ie 95mm + 170 amps = cable running at close to ambient temp, not blimey thats getting warm WTFs going on here.
Thanks for your thoughts on this one my learned friends, always nice to have second opinions.
I deffo am going to try and get the cable sizing verified asap. Will be armed with a set of calipers and checking the outer diameter which i think should be around 41.7mm. if its a 95mm cable might check lug sizing as well

 

[Deleted member 26818]

Re: Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessorie

Sounds dodgey, what's it feeding?

 

[baldsparkies]

Re: Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessorie

Sounds dodgey, what's it feeding?

UPS and IT data racks, don't think it should be running warm to hot though, not if its a 95mm no way.
trouble is swa sizing is a pain, when your just looking at it. I still get it wrong sometimes and ive been doing it long enough.
trouble is the overaul diameters vary by only a few mm from one size lower to one size higher. especially if by different cable manufacturers

 

[Deleted member 26818]

Re: Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessorie

Could there be harmonics causing the heating?
Is it possible to measure the resistance, and then work out the CSA from that?

 

[baldsparkies]

Re: Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessorie

Could there be harmonics causing the heating?
Is it possible to measure the resistance, and then work out the CSA from that?

Can't power down spin, Only an 8 metre run as well.
I honestly think the cable is a 50mm it just looks to small to me. if so everything would start to make sense, as said, 170 amps just aint going to run hot through a 95mm cable, Connections are tight and on such a small run almost free airspace on a cable tray somethings not adding up. Harmonics are present yes but negligable ups has inverters and they always like to make themselves known lol.

 

[Deleted member 26818]

Re: Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessorie

Sounds like you are going to have to run a larger cable.
How long will the UPS last?

 

[baldsparkies]

Re: Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessorie

Not long enough Spin but its genny backed so no probs there.
They have been told the installed cable is rated at 300 amps.
To be honest if they start adding loads to anywhere near that I reckon I will be making cups of tea on the blooming thing.
I dont like the way all the quoted figures being supplied to them are at max ratings.
Thats what they are intending loading to, so no margin for error or unknown variables.
These things are running 24-7 so you cant allow for any diversity.
Will get back when I have sussed it, but thanks for your input Spin much appreciated.

 

[Mark_Burgess]

Re: Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessorie

Is there any chance of opening the DB and measuring the OD of one of the conductors without powering down?
Maybe its time they run the back up genny as it should once in a while and that will give you the opportunity to check.

 

[benji]

Re: Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessorie

can you get a look at the lugs to see whats stamped on them

 

[Knobhead]

Re: Safe operating temperatures XLPE 90 degree vs table 4D4A for connected accessorie

If the UPS will allow time, disconnect and have a look at one of the lugs. Hopefully some markings will be clear enough to read. Have you taken a temperature measurement of the cores near the breaker? If they’re in tolerance I’d leave well alone.

I’ll admit trying to identify modern cables with compressed cores and XLPE insulation is a pain in the a*se.