What causes excessive pressure build up in a hot water boiler

Sateesh Cherukuri

We have a boiler in an 8 unit apartment building. As the boiler is heating the hot water, the pressure build up is over 10 psi, is this normal, what is normal? what is causing the pressure to build up so quickly (in less than a minute). Thank for your help.

[Deleted User]

Sateesh, it has been my experience

That the precharge in heating system expansion tanks often does not match the requirements of the installation. Check the precharge pressure of the tank, (and remember that better manufacturers use Nitrogen not air). If the expansion vessel has no diaphragm it becomes a rgular service item that can also become waterlogged. In both cases the pressure rises rapidly because the increased volume has no other place to expand to. The increased volume acting against the pressure gauge translates into higher pressure.