Accounting equation problems

It affects capital Indirectly because, depreciation is a charge to P&L a/c , as a result profit is affected because of this expense. hence depriciation affects both asset and liability side.

another way of looking at it is - depreciation (accumulated) is shown as a contra-asset, which means it reduces asset. Depreciation is also an expense, hence reduces profits, therefore capital. 

First of all depriciation is not a liability. Its a charge on the assets. Thus if you show assets on gross block basis, Depreciation A/C is debited and Accumulated Depreciation is credited. For the purpose of presentation, it is reduced from the gross block...

The idea of depreciation accumulated is in a sense a 'liability' of the future outflow of resources due to complete wear and tear of the asset and the need to replace it in the future. It's not a legal liability but a future outflow of resources due to the need to acquire new assets and replace existing ones. Some companies create an investment equal to the accumulated depreciation which can be earmarked for asset acquisition. It is suprising why accountants merely look at it as a charge against assets but don't question why a accumulated depreciation is carried and shown as a deduction from assets.