Pressure for piping risers

[Takket2]

This question came up when trying to size a compression tank for a heating hot water system. The boilers have a maximum operating pressure of 60 psi. The person sizing the compression tank asked me what the fill and maximum pressures were. So, i was going to tell him 60psi was the maximum pressure, but when I asked a senior engineer what the initial fill pressure should be he said we would need a boiler that can handle more preesure because based on the height of the risers we needed over 100psi in the piping system.

Isn't this really high??? The maximum pressure on our piping in the standard spec is only 150psi. I calculated the required head pressure on the pumps based on equivalent lengths in the system as 60 ft of head which is only 26PSI (using psi = 0.434*head). Shouldn't this be the system pressure for sizing a compression tank?

The compression tank will be in the basement and the top of the heating hot water riser is about 130 feet up on the 8th floor.

Our "senior engineer" has a tendancy to make a mistake or 2 so it has my worried.

 

[Krausen]

The senior engineer appears to be correct on factoring the height of your risers (130 ft head or approx 56 psi). You'll need to provide this to buck these heights, along with the 26 psi for the system's head losses, if I'm interpreting your post accurately. This brings your max pressure up to approx 82 psi total. Rounding up to an even 100 psi seems reasonable.