Chiller Pressure Rating 1

[MEngineer1924]

thread403-406098

Hi Engr.'s. Kindly help me to this. I have a 145 psi water column, do i need to add the Total dynamic head of the pump for me to specify the final chiller holding pressure/pressure rating. Or i can specify directly a 150 psi chiller since it can tolerate the given 145 psi. i look forward to hearing from you. thank you in advance.

Regards,

MEngineer

 

[LittleInch]

What you need to do is draw a diagram of your system noting relevant elevations and location of equipment, what the maximum pressure of your pressurizing system is, and the output head of your pump.

~The relative position of all these things is very important otherwise you can easily over specify or under specify your chiller.

If the pump is immediately d/s of the pump then yes, you need to add the head of the pump to the static pressure going into the pump to get the true operating pressure seen by the chiller,

however without details it's very difficult to be sure.

Often chillers are mounted on the top of a building to avoid / reduce this issue and give access to cooling air.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MEngineer1924]

Hi Sir LittleInch, I have attached the schematic of the system. i hope it would be a big help. Thanks

 

[LittleInch]

OK, that's better.

The bad news is your water column is not 145 psi, but actually much higher.

As drawn the head at the evaporator is 102m plus 50m differential head of your pump plus the extra height of where the FAHU above the roof deck is PLUS the missing item here which is your pressurization / expansion tank.

All systems like this need to have a tank/vessel to allow for water volume changes and usually have a maximum pressure. The more sophisticated one maintain a constant pressure, but your diagram doesn't show any. Usually there are set so that the pressure at the highest point is at least 10m

SO by my reckoning the head at the base of the system is 102+50+5?+10? = 167m = ~250 psi MIN
Find out what the pressuisation tank is set at.

There's a reason why a lot of HVAC plant rooms are on the roof....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MEngineer1924]

Thank you Sir. I am more enlightened now. By the way, the expansion tank is located before the suction of the pump and where the chillers located.