Setting com_lim to 'N' produces an unexpected result

[pauldodds]

I have an emissions counter for LULUCF emissions (GHGmLULUCF).  It is negative in 2010.  The normal COMBAL equation, for com_lim = 'UP', is:

 _EQE_COMBAL(UK.2010.GHGmLULUCF.ANNUAL)#8172:
                                 - VAR_COMNET(UK.2010.GHGmLULUCF.ANNUAL)#3205
                                 - 439.288824543984 VAR_FLO(UK.2010.2010.ALU00.ALAND.ANNUAL)#4728
                                  = 0

I tried to disable the COMBAL equation by setting com_lim to 'N', but this then changed the COMBAL equation to:

 _EQE_COMBAL(UK.2010.GHGmLULUCF.ANNUAL)#8172:
                                 - VAR_COMNET(UK.2010.GHGmLULUCF.ANNUAL)#3205
                                 + VAR_COMPRD(UK.2010.GHGmLULUCF.ANNUAL)#3493
                                  = 0

This latter equation caused an infeasibility.  Yet I was not expecting an equation to be created when using 'N'.  Can you explain this to me?


(Further notes: the first COMBAL equation does not produce an infeasibility as long as COM_BNDNET is set to a large negative value, so the model is working.  But I'm interested to know what the 'N' option is doing.  Both equations are from the CPLEX writelp option.)