Replacement Steam Boiler Piping

Mark_35

I would appreciate comments from the steam experts out there on my piping plan for a replacement boiler. This is a two-pipe Trane vapor system with convectors for terminal units. About 350 sq ft EDR. It operated at about 8 oz pressure with the old boiler. Please see picture and sketch.

The old 4” steam header had two 4” feeds straight up from the old Ideal Model 12 boiler. These header was pretty close to the top of the old boiler – about 12”. Three, 2” steam lines take off at three different locations along the top of the header and pitch down nicely to drip traps at the ends of the mains. The 4” header pitches down to a 2” equalizer line at the right end in the photo. The easiest way to install the new boiler (Peerless 63-4L - 383 sq ft) is to put it right below the header and feed up with two 2-1/2” feeds into the original 4” tees, with offsets for expansion. This does not meet standard “near boiler” piping recommendations, since the three supplies take off at the ends and at the center of the header. It did work fine with the old boiler. The steam velocities will be very low (about 10 fps in the 2-1/2” risers) and even lower in the big header.
Re-piping to put all the system supplies between the boiler feeds and the equalizer would be a lot of work. I would probably have to take out the 4” header and have a very long horizontal run to the equalizer line.

Has anyone run into a situation like this? Am I going to get condensate hanging up in the heater (or in the steam riser offsets)?

Any advice or comments would be much appreciated.