I am not sure why you would need a dummy cell. You can not add salt or turn on the SWG for 30 days, so I would think the risk of scaling is low. Maybe the concern is if you are running an acid start-up with a low pH?
You could always just not plumb the cell in at all and then after start-up cut out the pipe and install the unions and cell.
The cell has already been installed.
I think the reasoning is to keep it from possible debris caused from fresh plaster start up.
It won't actually get turned on for 30 days after water goes in.
From pentair- After new pool construction has been completed, in order to prevent debris from entering the IntelliChlor cell assembly, it is recommended that the IntelliChlor pass-through cell (P/N 520588) be installed before installing the IntelliChlor cell. After the pool system has flushed the debris from the pipes, remove the pass-through cell and install the IntelliChlor cell.
We used to plumb in fake fittings for SWG, in case the cell needed to be cleaned, the owner could still run their pump. Now I think its a non issue. Cleaning doesn't take the length of time that a pool store quotes lol.
As PRS said, if its plumbed after the cartridge/filter, I cant see anything being an issue. I can only assume SWG Manufacturers recommend this as a safety net in case someone inadvertently turns on the SWG before the 30 days.
My experience says that cells have issues with Ch.