MAKE UP WATER

[antony09]

I HAVE PROBLEM WITH THE MAKE UP FOR THE CHILLED WATER PIPE. WE INSTALLED AIR CONDITIONING FOR A 15 FLOOR BUILDING, THE CHILLED PLANT IS LOCATED IN THE GROUND FLOOR ALSO THE MAKE UP. THE RELIEF VALVE ARE ACTUATED ALL TIME. THIS VALVE IS SETTING TO 20 PSI, ALSO THE REGULATING VALVE IS SETTING TO 30 PSIG. THE PROBLEM IS THAT THE PRESSURE TO SUPPLY WATER TO THE SYSTEM IS TOO LOW AND WE NEED TO SUPPLY THROUGH THE BYPASS, ALSO THE REFIEF VALVE IS ALWAYS ACTUATED. QUESTIONS, THE MAKE UP IS WRONG INSTALLED (WE WILL NEED TO RELOCATE THE MAKE UP SYSTEM TO 12 FLOOR TO DECREASE THE PRESSURE NECESARY TO FILL THE SYSTEM), OR WE NEED TO CHANGE THE REGULATING VALVE AND THE RELIEF VALVE TO HANDLED MORE PRESSUR MAINTAINING THE MAKE UP IN THE SAME POSITION.

 

[friartuck]

15 Stories x 4m per storey=60m head or 6 bar (x14.5=psi=90PSI) so your relief valve will blow off and your fill pressure is not enough anyway.

Use a pressurisation unit consisting of a mini high pressure pump, with integral hi-lo pressure control stats. Any decent pump manufacturer will make one any they are not too expensive. (I would think $1500 would buy you one)

Try Grundfos



Friar Tuck of Sherwood

 

[antony09]

thanks friartuck, but we have booster system to increase the pressure installed in the building, to elevate the pressure to 150 psig, our question is, the following:
we only need to change the setting of the safety device, per example: pressure regulation to 90 psi and relief to 100 psi,it is correct, or we need to change the position of this devices.

 

[friartuck]

Are you using a specific pressurisation unit to serve the chilled water or are you using the mains site water (boosted to feed toilets etc).

A dedicated feed to the chilled water can be set to give you the design pressure. Do you have an expansion vessel or a feed tank.

If the safty valve is at the basement level, the static system pressure will be 90PSI as calculated but the working pressure will be greater if you have an expansion vessel. You need to know what the system design pressure is.
If you are using an expansion vessel, the size has to be calculated to accomodate the system water expansion. The larger the vessel, the lower will be the operating pressure. If you are simply using a feed tank open to atmosphere, the system operating pressure will be 90psi plus any affect of the circulating pump (depending on where you fit it)

The safty valve should be set to protect any part of the system that requires a specific protection pressure (Hopefully your components will be designed to operate at a pressure of at least 90psi plus an allowance)

A typical SV setting would be Static plus 25-50% i.e. 112 to 130PSI (If fitted in the basement) If fitted on the top floor it would be a lot less (Equivalent to the static head difference)

Dont overpressurise your system if you are filling off the mains as this affects the operation of the expansion vessel (If you have one)

The expansion vessel should also have a pneumatic cushion pressure equal to the static head above it i.e. if fitted in the basement, the cushion pressure should be 90PSI.



Friar Tuck of Sherwood

 

[antony09]

Are you using a specific pressurisation unit to serve the chilled water or are you using the mains site water (boosted to feed toilets etc). We are using the mains site water.

A dedicated feed to the chilled water can be set to give you the design pressure. Do you have an expansion vessel or a feed tank. We have an expansion vessel

 

[lilliput1]

You need an expansion tank and you need to replace the makeup PRV and the relief valve. The engineer should have designed them for the required duty.
The makeup & expansion tank should be connected to the pump suction. They can be at the top of the building or at the bottom. The PRV discharge pressure must equal the static head (up to the highest point of the piping)at the PRV location plus about 10 ft to make sure air will not get in the piping.
The RV must be set to the maximim pressure at its location so no point of the piping will be above say 120 to 150 psig max. when the effects of pump head & static head + expansion tank max pressure rise are taken into account.
See AMTROL engineering guides on sizing expansion tanks.

 

[imok2]

Antony: Some considerations are in order related to the expansion tank connections.

1.A tank with an air/water interface is generally used wih an air control system that contiually reverts air into the tank and should be located in a place where air can best be released such as the installation of an air seperator tied into the same line as the tank and the suction side of the pump

2.Within reason the lower the pressure in the tank, the smaller the tank so in a vertial system, the higher the tank is placed the smaller it can be.

3. The tank should be connected at the "point of no pressure change" (suction side of pump) The connection point of the tank is very important and should be based on the pressure requirements of the system, remembering that the pressure at the tank connection will not change as the pump is turned on or off.

4. I would relocate the expansion tank on the 12th floor if its convenint for you with the prv tied in as previously explained and if you assume ten ft/floor then you have 30ft of static pressure...devide this by 2.3 ft/psi= 13psi add 10ft for insurance so say ~15psi