What was the fire alarm designer thinking?
Do you install the fire alarm system just like the designer shows? Is the fire alarm designer out of touch?
Do you just do what works and then move on?
Do you install however you want and ignore the plan?
What's Code got to do with it?
The designer has to follow code. The drawings will get looked at in deep detail.
The fire alarm system design has to have extensive explaination, deep description of exactly what will be installed.
The designer draws what code specifies must be, then shows the plans to the plan reviewer/AHJ with a promisary note that the system is intended to function safely and be installed in the manor it was designed
The plan reviewer looks the fire alarm plans over and approves or disaproves the layout of the fire alarm system as depicted in the drawings.
Those plans are required to be on site at the time of installation. So the installers see all of what is on record as the aproved method of installation.
It is now up to the installer to install as he feels. A wise person would install only as the plans show. If anything fails, then the fault lands on the person who made the decision. If an installer decides that they should install differently, (either due to an obstruction, lack of supplies, doesnt want to move his ladder)Then he best hope that his decision saves lives. If anything fails to save lives, then the fault is on the installer for making a decision.
Code says "Install device here, and do it just like this". If what you have done does not match code, then you did it wrong.
What to do if you see a problem in the drawings.
Contact the designer directly. Describe the issue. Discuss a solution. The solution may be a redesign and resubmittal to the AHJ for review. The solution could be As-built drawings, or even a non-issue. Any and every time you see something wrong, contact the designer. Contact your project manager. Get verification that there is a problem that needs to be resolved. Get approval to make your changes, or don't make changes.
So, what was the designer thinking?
Of course the fire alarm designer wasn't thinking of the easiest way to do the job. The designer was thinking of the only way the job should be done.
The fire alarm designer was thinking of ways to make it clear and easy to read precisely, without a doubt, what has to be installed and where. The cable was laid to show you the complete path that is either the least amount of voltage drop, least effort on the installer, or company policy for service at later dates.
The fire alarm designer was making sure this fire alarm system saves lives, passes review, meets budget, is clean and presentable, and completes the project as contracted.
Do your best.
Install to the best of your ability, the way the system was designed.
Read all code and notes in the drawings and the cover page.
Workmanship matters with fire alarm. If you lack high quality workmanship, you risk failure in the life safety system that someone counted on you to install.
All variations in the install from what the plan reviewers accepted, now falls on the person who made changes.