CONTROL VALVES FOR AHU CHILLED WATER
Hom e
A bo bo u t U s
M em e m b er e r sh s h ip ip
Gallery
Publication
Board of Directors
Forum
New s
Login Form
Username
Recent Topics
Rules
Help
Search April 2012
Welcome, Guest Username
Password
Password:
Remember me
PSME-CRSA
Remember Me
Main Forum
What is Engineering?
CONTROL CONTROL VALVES FOR AHU CHILLED WATER (1 viewing) (1) Guest
Login
REPLY TOPIC
Forgot your password? Forgot your username?
NEW TOPIC
1 year, 1 month ago
Calling 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 invites you to its MECHANICAL ENGINEERING BOARD EXAM REVIEW CLASSES.
W
T
F
S
1
2
4
5
6
7
8
9
3
10 11 12 13 14
1
Posts:2
OFFLINE
22 23 24 25 26 27 28 29 30
Latest Events
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,
Click the image below...
PSME-CRSA 5
Today
Page:
CONTROL CONTRO L V ALVES FOR AHU CH CHII#L1 L7 ED ED
beriawel_arnold Fresh Boarder
M T
15 16 17 18 19 20 21
TOPIC: CONTRO CONTROL L VALVES FO FOR R AHU CHILLED WATER
Newsflash
S Login
Forgot your password? Forgot your username?
1 05
Yesterday
98
This week
2 03
Last week
1 99 6
This month
5 932
Last month
4 443
All days
Co n t a c t U s
Events Calendar Index
Share
Career
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 control the flow of chilled chilled water in HVAC system, but also to hot water water and condenser condenser water and they have specific specific requiremen requirements ts for design includi including ng issues of safety and material compatibility.
P SM SM E S p e c i a l A w a r d e e
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.
1 7 1 8 62 References:
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
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:
PSME Sponsor
· 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.
PSME Sponsor
· 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.
PSME Sponsor
· 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.
PSME Sponsor
· 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 isn’t 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.
PSME SPONSOR
· Two-way valves caused differential pressures to increase across control valves, particularly when pumps a re 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
CONTROL VALVES FOR AHU CHILLED WATER
· An improperly sized two-way control valve may consume more water flow when open than the design calls for. b. For 3-way Valve:
PSME Sponsor
· 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 Δt (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.
PSME Sponsor
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
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,
PSME Sponsor
ENGR. TEODY A. DELA CRUZ REPLY
QUOTE
The following user(s) said Thank You: bumangil_samuel
1 8I L Re: CONTROL VA LVES FOR AHU #CH
1 year, 1 month ago
bumangil_samuel Fresh Boarder
Posts:1
OFFLINE
Thanks for these information REPLY REPLY TOPIC
PSME-CRSA
NEW TOPIC
Main Forum
QUOTE Page:
1
What is Engineering? ... ...What WhatisisEngineering? Engineering? Powered by Kunena
Time to create page: 1.26 seconds
Go
CONTROL VALVES FOR AHU CHILLED WATER
enter text here
Search
PSME-CRSA 2011 Riyadh, Kingdom of Saudi Arabia
