I have an issue in Connect, where an undersized sub-main cable is being allowed to pass and not show up as an error.
16mm2 XLPE/SWA cables to table 4E4A (3 phase 4-c) under ground in a duct max load is 75A.
The sub-main is protected by a 100A MCCB, therefore the minimum size in accordance with 4E4A is 35mm2 (rated to 115A for underground)
If I un-tick the fix it button on the cable size, Connect will calculate the cable size to be 16mm2 with no errors. If however I fix it at 16mm2 it comes up as a red warning that the cable cannot carry the required current.
I have had this issue before where Connect undersized an underground sub-main with out an error warning, and I picked it up when I did my checks on the data. At the time I put it down to a glitch with the model, as I had re saved a previous project .
Can you please advise why this would occur.
Stuart - This may need to go to a service ticket, ultimately, as we may need to see the project. However, in the first instance, can you examine the default data for the project (17th Edition Menu, Defaults) and check what the Ground Thermal Resistivity is set to? if this is set incorrectly it could have a large impact on underground cables.
Duncan Brown
Duncan,
What should the default value be?
Stuart - You should be looking at around 2.5 Km/W - Is this the figure that you have?
For some unknown reason it's set to 0.5.
Table 4B3 has the thermal resistivity at 2.5, and when I create a new project the default value is 2.5.
I've never changed this figure in the defaults, and no one else has access to change it.
This does solve the issue, but why is the default value changed?
Stuart - Could it be possible that the project was created on an earlier version of the software? That may account for the discrepancy. Glad to hear it resolved the issue.