Steam 2-Pipe Horizontal Riser & Up Feed Size

Steve_118

I have secured the mechanical installation for a university project specified in house by facilities management less design drawings, need some advice.

First- the existing mains are two pipe 5lbs steam system with pumped condensate return, there are a number of 3/4" and 1" capped taps available in the steam piping tunnel.

To be installed new on the first floor above the steam tunnel are 6 fin tubes. We are using Rittling 20" high sloped units with double row 2.5 foot 1" copper rated at 10.7 EDR per foot for a total of 53.5 edr per fin tube. The new office layout would most easily accomodate a 4 set fin tube grouping and a 2 set on an ell in the tunnel.

Can I group 4 fin tubes with a common supply and return installed on the tunnel walls such that the supply feeds 212 edr, then 159 edr, then 106 edr, then the final 53 edr and then the return gathers 53 edr, then 106 edr, then 159 edr, then 212 edr back into the sloped condensate return?

I have been studying "The lost art of steam heating" chapter nine- pages 132-133 with tables specifying pipe sizes for edr values. Am I correct in sizing 1 1/4" for the common 212 edr, dropping to 1" for the next 3 units at 106 edr, and 3/4" to the last unit, reverse for condensate return? Seem to big to me, but the tunnel is cramped and I want to do it right the first time.

Dan preface the section "Looking at pipe sizes" with "average tow-pipe steam job used the column for a "two ounce" pressure drop...... But seeing as this is an institutional 5lb system, should I be using a different set of tables?

I goes without saying that the remaining two in the "L" section leg would be piped separately, but in the same method.

I am attaching a floorplan of the job.

Thanks for assistance. By the way, in our town of 11,000 I know of only one 1-pipe steam system on a home, we probably have 40 at most hydronic systems of varying age and designs. All forced air other than these.