header and main piping configuration

the piping up in the ceiling is the header from 3 boilers ago, it should have been removed when the coal boiler was replaced.

it has places for condensate to collect which will stop or slow the steam at that point so the mains won't heat evenly. it is very likely you will have balance problems and problems with water hammer if you don't remove the old header and pipe each main separately to the new header. each riser should slope toward the main so the riser can't collect water. the tees should come off the top or off the side at a 45 from the header and you should use 45s to offset to connect the mains to the header. If the mains aren't parallel flow they need to be dripped before the header and all drips need to go below the water line before they connect.

the header should be connected i the order of:

riser(s) from boiler

risers from header to mains

equalizer.

the equalizer should reduce in the vertical either with a vertical reducer or reducing ell so it doesn't trap water in the header

you may need to make the header a u shape to get enough space for the fittings for all the mains.

You need to check the load on those branches on each pipe and add them up to see if the pipe feeding them is large enough. This should be easy to do if you measured the radiation to size the boiler.

Sizing the pipe for the attached radiation is your justification.

You may be doing a lot of extra piping for no reason

or

Those branches need to be brought to the boiler separately.

You won't know until you check.

It is likely that the one 2" main is not large enough to feed everything.

Best explanation is "Hay Boss! Do you want it right the first time, or would you like to go back several times over the next year or two, to solve banging, and uneven heat issues for free, while still paying us our wages?"