Control Valves for Ahu Chilled Water

CONTROL VALVES FOR AHU CHILLED WATER

Home

About Us

Membership

Gallery

Publication

Board of Directors

Forum

News

Career

Contact Us

Login Form Index Username Recent Topics Rules Help Search

Events Calendar

Welcome, Guest Username Password: Remember meLogin

April 2012

S M T W T

F

S

Password

Forgot your password? Forgot your username? Remember Me PSME-CRSA Main Forum What is Engineering? CONTROL VALVES FOR AHU CHILLED WATER (1 viewing) (1) GuestREPLY TOPIC NEW TOPICPage: 1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Latest Events

LoginForgot your password? Forgot your username? Newsflash

TOPIC: CONTROL VALVES FOR AHU CHILLED WATER1 year, 1 month ago

#17 CONTROL VALVES FOR AHU CHILLEDPosts:2

beriawel_arnold Fresh Boarder Calling to all aspiring under board Mechanical Engineers who wish to take the Special Professional Licensure Board Examination( SPLBE) review will start on April 27,2012, PSME-CRSA invites you to its MECHANICAL ENGINEERING BOARD EXAM REVIEW CLASSES.OFFLINE

No events Board of Directors 2012

Dear PSME-CRSAsians, Please see below history of interactions regarding the above mentioned topic (CONTROL VALVES FOR AHU CHILLED WATER) From: randy cerrado To: [email protected] Engr. Teody, Sorry for my delay response, been quite busy on my Facebook Account for awhile (joke only). With reference to control valve (2 or 3-way), control valve are primarily used not only to control the flow of chilled water in HVAC system, but also to hot water and condenser water and they have specific requirements for design including issues of safety and material compatibility. For design perspective, you must always locate your control valve per standard engineering practice or per manufacturer recommendation. This will place your design safe & correct because most of the design reviewer specially a consultant like American or British Engineer they are book dependent. They will argue with you in any subject if you are inventing another wheel. I. The following are some standard practice for choosing control valve location: 1. For 2-way Valve: Traditionally installed in return or supply line. References:

Click the image below...

PSME-CRSA

Share

5

PSME Special Awardee

Today Yesterday This week Last week This month Last month All days

105 98 203 1996 5932 4443 171862

We have: 1 guests, 2 bots online Your IP: 46.240.68.10 Internet Explorer 8.0, Windows Today: Apr 30, 2012 Visitors Counter

ASHRAE Application; Chapter 26 Design and Application of Controls ASHRAE System & Equipment; Chapter 12, Hydronic Heating & Cooling System Design Manufacturer IOM: (Ex. Carrier Catalog, Fan Coil Unit). New Members

http://psmecrsa.org/index.php?option=com_kunena&func=view&catid=4&id=17&Itemid=67[5/1/2012 12:04:31 AM]

CONTROL VALVES FOR AHU CHILLED WATER Who's Online 2. For 3-way Valve (Mixing): Traditionally installed in return line. References: We have 3 guests online ASHRAE Application; Chapter 26 Design and Application of Controls PSME Sponsor ASHRAE System & Equipment; Chapter 12, Hydronic Heating & Cooling System Design Manufacturer IOM: (Ex. Carrier Catalog, Fan Coil Unit). 3. For 3-way Valve (Diverting or By-pass): Traditionally installed in Supply line. References: ASHRAE Application; Chapter 26, Design and Application of Controls ASHRAE System & Equipment; Chapter 12, Hydronic Heating & Cooling System Design Manufacturer IOM: (Ex. Carrier Catalog, Fan Coil Unit). II. The following are advantage & dis-advantage of 2 & 3-Way Control Valve: PSME Sponsor 1. Advantage of 2 & 3-Way Valve a. For 2-way Valve: The 2-way valve system is self-balancing under normal operating conditions. Two-way valves result in variable flow that will reduce pumping energy. This particularly true when variable speed drives (VSD) is used on pumps. The valve is less expensive to buy and install. The need for system balancing flows is reduced or eliminated in most applications. Because the valves will only use as much chilled or hot water as required by the load. Two-way valves located on the return side of coil piping will maintain pump discharge pressure on hydronic coils to enable positive air venting from the coil return header. In many cases, the return line temperature is above dewpoint, in which case the 2-way valve won't sweat even with a poor insulation job if installed in return line and for hot water return, the water is cooler. You don't burn your fingers working on them as much. b. For 3-way Valve: The flow occurs through the circuit at all times (either through the coil or the bypass. The flow remains relatively constant through the loop which includes the pump and varies in the loop containing the coil. This works well for systems in which the supply of heat, typically a boiler, or supply of cooling, typically a chiller, requires a constant flow. The 3-way valves have no problem on handling widely varying flow rates in some chillers and boilers plant. The 3-way valve works well in hot water system operation, water that bypasses each terminal is returned to the boiler at the supply water temperature. Essentially, this arrangement prevents thermal shock by assuring that the water returned to the boiler isnt too cold. PSME SPONSOR If the system properly balanced, the 3-way valve can offer smooth & easy operation. It can offer simple low cost inline maintenance. 2. Dis-advantage of 2 & 3-Way Valve a. For 2-way Valve: The 2-way valve cannot handle widely varying flow rates in some chillers and boilers plant. The requirement for some other means to maintain flow through the equipment must be included, such as a pressure actuated bypass, VSD, or a primary/secondary pumping system. Two-way valves caused differential pressures to increase across control valves, particularly when pumps are uncontrolled to ride their pump curves. This reduces the controllability of the system and may even cause valves to be forced open by the water pressure. Putting 2-way control valve in the supply line, this will keep coil partially filled and this may even create airlock. PSME Sponsor PSME Sponsor

PSME Sponsor

PSME Sponsor

PSME Sponsor

PSME SPONSOR



An improperly sized two-way control valve may consume more water flow when open than the design calls for. b. For 3-way Valve: The 3-way valve can only be used in the last loop of terminal unit to main available flow in the variable flow in chilled water system. The flow in 3-way valve application must be balanced to ensure that the required flow is delivered to each coil. PSME Sponsor Since 3-way valve diverting the flow it wasted energy. The chilled water system can suffer from an acute case of low t (temperature difference) syndrome caused by improper staging of chillers and 3-way valves installed in the loop. Using 2-way valve in variable flow system & 3-way valve in constant flow system can both compromised comfort and operational costs. In practice, not even the most sophisticated systems always perform as promised. This is often because the mechanical design of the HVAC plant does not meet some conditions necessary for stable and accurate control. The design flow must be available at all terminals, the differential pressure across the control valves must not vary too much, and the flows must be compatible at system interfaces. I hope this short story may help you exploring deeper in control valve application in HVAC system. PSME Sponsor Regards, Engr. Cerrado --- On Thu, 3/10/11, butch wrote: From: butch Subject: [PSME-CRSA] CONTROL VALVES FOR AHU CHILLED WATER To: [email protected] Date: Thursday, March 10, 2011, 3:20 AM

PSME Sponsor

PSME Sponsor

PSME Sponsor

My Dearest brothers in PSME-CRSA, I would like to ask some few question regarding two- way and three-way control valves.. As far as I know this valves are usually mounted in outlet of AHU or FCU chilled water line, but in our present project..it was located at the inlet. My questions are: 1. It can be mounted in inlet or outlet? What will be the advantage and disadvantage? 2. If I am the designer what will be the basis, why should I use two-way instead of threeway valve? Thanks! MORE POWER PSME-CRSA TRULY YOURS, ENGR. TEODY A. DELA CRUZREPLY QUOTE

PSME Sponsor

The following user(s) said Thank You: bumangil_samuel1 year, 1 month ago

Re: CONTROL VALVES FOR AHU#18 CHILPosts:1

bumangil_samuel Fresh BoarderOFFLINE

Thanks for these informationREPLY REPLY TOPIC NEW TOPIC QUOTEPage: 1

PSME-CRSA

Main Forum

What is Engineering?... What isis Engineering? ... What Engineering?Powered by KunenaGo

Time to create page: 1.26 seconds



enter text here

Search

PSME-CRSA 2011 Riyadh, Kingdom of Saudi Arabia


Documents

Control Valves for Ahu Chilled Water