120-240 delta service question

[eman]

I work for a commercial electrical contractor and we have several
property management companies as regular customers.

We are required to replace main circuit breakers or test blocks in
services on a fairly regular basis. Most of the time, it appears that
the main circuit breaker or test block was burned up due to alum.
wiring installed from the test blocks to main c/b then from load side
of main c/b to panel.

We of course replace all wiring with copper and replace test bllock or
main c/b as required.

The question I have is it appears that most of the problems appear to
occur on 120-120 delta services. The high leg is usually the burned
(or most burned in some cases) leg.

On a high leg system, there is usaully a smaller load on the high leg
(Atleast in the case of these smaller tenant spaces where there is
limited 3-phase or 1-phase 240V equipment). This would lead me to
reason that one of the other legs would burn up due to load imbalance
more frequently that the high leg.

Is it just coincidence, or is there a reason why the high leg would
cause such a problem?

Thank you,

Eric

 

[SQLit]

I work for a commercial electrical contractor and we have several
property management companies as regular customers.

We are required to replace main circuit breakers or test blocks in
services on a fairly regular basis. Most of the time, it appears that
the main circuit breaker or test block was burned up due to alum.
wiring installed

snipped

The only problem with AL is the person installing it. I have installed AL
for 35 years with never a failure. All the US utilities use AL they can not
be all wrong.

I will bet your failures are workmanship, not material.

Are the breakers really rated for delta, not 3 phase but delta 3 phase?

Test blocks that I have seen and installed are not full current load
devices. They allow access to the CT's and PT's on the secondary side. All
the ones I have seen are wired with #10 solid. I sure would like a picture
of your test block (s) so I could further my education.
Looking forward to the pictures.