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Will This Boiler Have Slow Cond Return? Want to avoid a Pump.
1920's 3 story, 2000 sq ft per floor schoolhouse---
Presently this 1 pipe parallel flow system is zoned off of a 1M+ BTUH, 1955 Kewanee.
The other zone is for a 2 pipe system discussed in my other posting.
The 1 pipe system has only 414 EDR connected. There are 8 capped take offs on the steam main.
The steam main has 12' of 6", 100' of 4" and then 35' of 2 1/2" dry return before dropping in the boiler room.
(Presently thru F&T then to cond pump to existing Kewanee)
There are also 3- 2" rad risers about 14' high.
The boiler will be PB 63-04, 458 EDR. 10.8 gal of water for steaming. Evap rate of 0.23 GPM.
The plan is to pipe 2-2" risers 30" high into a 3" drop header.
It seems that with 147' of pipe, a considerable amount of water is needed to just "wet the pipe" before condensate water will return. The pitch on the piping has been checked and there is no water hammer on the system ever thru the entire cycle.
I will have the chance to time the return this winter as the old system will still be is use, but wanted an early heads up on if a condensate receiver/accumulator/tank might be advisable. Hoping not to need a feeder pump.
Plenty of "A" dimension. Water line will be approx 30" off floor and end of dry return is about 8' above floor.
The air vents will be at the end of the dry return. The 147' of pipe contain 12.45 cubic feet of air.
I planned to install 5 B&J Big Mouth vents. Hoping to run the system in ounces considering the now over sized piping. (2 1/2" steam main would carry the 414 EDR).
All of the NBP and 80% of the steam main will be insulated with 1" FG.
Garden level basement is now heated by boiler jacket losses and 4" piping.
Ceiling rads are long gone.
Need to put together a price for the entire project within a few more days.
If the simple gravity return might not work I would need to allow more in the budget.
Any and all comments welcome! TIA