The short answer is 'it depends'. There are at least 3 or so armor encumbrance rules options.
The basic one is that all armor counts, so yes. (SR4A p161) Penalties start when the total B and/or I exceeds Body*2. (Note that stacking doesn't mean add everything *for the purposes of damage resistance*; only the highest B or I counts, while everything counts to encumbrance.)
Arsenal (p44) provides the option of 'no encumbrance for any single armor item'; e.g., one armor suit. The player can lose this grace by doing more stacking/accessorizing; IMO, suit+helmet is fine, but suit+helmet+PPP+shield, etc. is not.
A second Arsenal option is for Milspec armor to use Body*3 as the limit. For me, this never comes up.