pressure issue with a newly installed boiler

[Guy in DC]

Doesn't matter if pump is before or after boiler because the pump is a circulator just moves water around rather than like a well pump that takes a few pounds of pressure and raises it 50 to 100's of lbs. There is no problem if the pressure is a few lbs high. Boiler relief valve with blow off at 30lbs.
Heres a chart for working and bursting pressure for black pipe.

Wrought Steel Pipes - Bursting Pressures vs. Size

Theoretical bursting and working pressure of wrought steel standard, extra strong and double extra strong pipes.

www.engineeringtoolbox.com

Thank you! I wouldn't worry much about the pipe bursting then.

 

[John Gayewski]

John, if you refer to the pressure relief valve opening I described in the old post, it was a different issue: the autofill valve was broken.

Would you advise to change the extension tank for a larger then?

Also, someone told me that the entire system was not properly vented so I might have some air inside, which induces pressure variation? Would it be a problem and if so how to fix it?

If you had air the pressure would drop, not increase. There would be other issues related to flow and heating. I would get a bigger expansion tank yes.

 

[Sponsor]

 

[Guy in DC]

Thank you very much John!

 

[Fitter30]

This problem is the contractor problem their fix bt.lowering the water pressure isn't a fix. The only fix is a larger extank. See the ceiling is plaster normally the original extank was either above the original boiler or close by. It would have at least two straps holding it tight to the ceiling spanning two floor joists three to five feet apart. There should be either holes where the straps were fastened or patches in the plaster. See if can find them and measure the distance between them.

 

[Guy in DC]

This problem is the contractor problem their fix bt.lowering the water pressure isn't a fix. The only fix is a larger extank. See the ceiling is plaster normally the original extank was either above the original boiler or close by. It would have at least two straps holding it tight to the ceiling spanning two floor joists three to five feet apart. There should be either holes where the straps were fastened or patches in the plaster. See if can find them and measure the distance between them.

I looked at the ceiling and there is no marks and I doubt it was patched since the ceiling looks intact. Maybe it was located on the floor?

 

[Fitter30]

Have you run across any cast bronze valves or any thing that might have been left from the original boiler system. Could even be a glass tube 5/8" diameter x 12" long. Could be stuffed under the basement steps. Take a pic of it.

 

[Guy in DC]

Hi Fitter, There is no old parts that I can find. However, the system was alternated: the cast iron pipe are around 3.5 inch diameters, which were cut and connected to 1 inch copper connected from/to a boiler.
Anyway, I ordered much larger tank https://www.supplyhouse.com/Amtrol-112-1-90-Extrol-EX-90-Expansion-Tank-14-Gallon-Volume and the installer will come to change it - they need to cut the pipes and relocate the scoop to accommodate larger diameter tank. I will charge accordingly and will out an tank isolator https://www.supplyhouse.com/Bluefin-ETI050-1-2-Expansion-Tank-Isolator-w-Waste-Male-x-Female
Hopefully it will solve the issue.

Thanks you and John for help

 

[Guy in DC]

Thanks again John and Fitter30. I replaced the expansion tank for EX90 and no pressure issue anymore. When the system is cold, the pressure is 14psi, when reaches 180F, the pressure increases 20-22 psi.