On Wednesday, May 7, 2014 5:55:40 PM UTC-4, Ray DELETETHIS wrote:
We live in a six-unit apartment building which is heated by radiators.



The boiler is a commercial, as opposed to residential unit. I understand

these don't last as long as residential systems.



First time I've heard that.




Could anyone share any experience with such boilers?



Ours is nine years old, and already the large copper conduits are showing

signs of corrosion in the joints, suggesting leaks.



I assume by "large copper conduits", you mean copper pipes.
Pipes aren't part of the boiler. It's very likely that what you
think is serious corrosion is just superficial, possibly left over from
the flux when they were soldered, etc.



Can this be repaired rather than replaced?

Without knowing more about what exactly the real problem is,
can't say. Some pics would sure help. It's quite possible that
nothing is wrong at all. But if it's an apartment
and you're renting, why do you care? If the heat works, and there
are no actual leaks, what's the real issue?