Control Valves on the Supply or Return Chill Water System?

Author: Marina

Apr. 29, 2024

Control Valves on the Supply or Return Chill Water System?

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Control Valves on the Supply or Return Chill Water System?

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Control Valves on the Supply or Return Chill Water System?

thien2002

(Mechanical)

(OP)

18 Feb 04 13:03

My drawing indicates the Honeywell 3-way modulating Control Valves on the Supply side (modulating the return side), shouldn't the Valve be on the Return Side for Chiller Water and Hot Water System? I thought it was a drawing error. Would that effect the flow efficiency if it's located on the wrong side?

Thank you in advance.

RE: Control Valves on the Supply or Return Chill Water System?

jmw

(Industrial)

18 Feb 04 15:02

My usual concern with coolant water flow is if the medium being cooled is or can be above 100degC. In which case i don't want a fully closed valve on the discharge side trying to contain a build up of steam. It may depend if there are any safety valves in the design.
Let's see what the experts say.

RE: Control Valves on the Supply or Return Chill Water System?

pardal

(Automotive)

18 Feb 04 16:06
Diverting valve on the supply side.

Mixturing vale an the return side .

Plaese check what kind of valeve it is ,Diverting valve on the supply side.Mixturing vale an the return side .

Pardal

RE: Control Valves on the Supply or Return Chill Water System?

pardal

(Automotive)

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Unlock the Best Deals on Non Slam Check Valves: Discount Prices Inside! 18 Feb 04 19:04
Diverting valve on the supply side.

Mixturing valve an the return side .

Plaese check what kind of valeve it is ,Diverting valve on the supply side.Mixturing valve an the return side .

Pardal

RE: Control Valves on the Supply or Return Chill Water System?

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quark

(Mechanical)

19 Feb 04 04:52

Regards,

Pardal is right. A mixing valve is always installed on the return line and a diverting valve on the supply line. Though both installations are technically correct, it is better to use mixing valves(on return line). The advantages are that, you can always ensure your coil is totally filled and also as the return temperature is higher you will have less problems with valve body sweating.Regards,

Eng-Tips.com : Solving your problems before you get them.

RE: Control Valves on the Supply or Return Chill Water System?

thien2002

(Mechanical)

(OP)

19 Feb 04 13:10

Please explain:
"A mixing valve is always installed on the return line and a diverting valve on the supply line. Though both installations are technically correct, it is better to use mixing valves(on return line)."
** Please define mixing or diverting.
"The advantages are that, you can always ensure your coil is totally filled and also as the return temperature is higher you will have less problems with valve body sweating."
** What happen if valve body sweating, what consequences?

THANK YOU

RE: Control Valves on the Supply or Return Chill Water System?

pardal

(Automotive)

19 Feb 04 13:54
And the diverting valve is more expensive than mixing.

I dissagree about sweating , the return water will be always under the dewpoint of air , so it will allways sweat.

When instaling you shall locate the actuator preferible on top or by the sides , never on the bottom , because sweat water will damage the actuator.

Talking about fluid, it is hard to divert or divede than to mix.And the diverting valve is more expensive than mixing.I dissagree about sweating , the return water will be always under the dewpoint of air , so it will allways sweat.When instaling you shall locate the actuator preferible on top or by the sides , never on the bottom , because sweat water will damage the actuator.

Pardal

RE: Control Valves on the Supply or Return Chill Water System?

quark

(Mechanical)

22 Feb 04 06:13
Diverting Valve - Which diverts one stream flow into two stream flow.

The links below will give you good understanding and selection procedures.

http://www.spartan-pd.com/PDFfiles/Piping.pdf

http://www.belimo.com/IMS_DOCS/56/56189BE43C17984A862A4...

http://www.belimo.com/IMS_DOCS/21/21BD69054E68674C8BA60...

Disadvantages with sweating.

1. Energy Loss (latent heat from condensing moisture is transferred to chilled water) - Superfluous
2. May corrode your system slowly - Most Likely
3. May cost your job - If you are in a Pharma Company
4. You may have to arrange for floor cleaning frequently - Obvious

Pardal!

I agree with your disagreement (huh... so kind of me). I said that the sweating problems will be less and not that they will be eliminated.

Regards,

Mixing Valve - Which mixes two streams into one stream.Diverting Valve - Which diverts one stream flow into two stream flow.The links below will give you good understanding and selection procedures.Disadvantages with sweating.1. Energy Loss (latent heat from condensing moisture is transferred to chilled water) -2. May corrode your system slowly -3. May cost your job -4. You may have to arrange for floor cleaning frequently -Pardal!I agree with your disagreement (huh... so kind of me). I said that the sweating problems will beand not that they will be eliminated.Regards,

Eng-Tips.com : Solving your problems before you get them.

RE: Control Valves on the Supply or Return Chill Water System?

pardal

(Automotive)

23 Feb 04 12:38

Quark. If two do not want , one do not can.

Pardal

RE: Control Valves on the Supply or Return Chill Water System?

ercanbaser

(Mechanical)

25 Feb 04 07:44

I think , statement "A mixing valve is always installed on the return line and a diverting valve on the supply line" is not 'always' correct because there are applications which mixing valves used in supply line and diverting valve used in return line as can be seen at links quark's post.

first,proportional control valves should not be mixed with 2-position "3-way valve" , secondly the control logic must be considered (constant flow or cnst.temperature)and pressure drop for both sides of 3-way valve should be calculated to ensure the valve work properly. (if it is not equally ballanced valve may be %50 open but fluid flows ,lets say, %40 because it 'always' prefers the easiest way).Pump location should also be considered.

I hope , I dont 'mix' too much

Ercan

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News

The Benefits of Return Side Control Valve Installation

Control valves installed on the return side of hydronic heating and cooling coils are standard in most 2- way valve applications; the reasoning may not be as well known. A major factor behind this standard practice is coil efficiency. The first principle to understand is that the amount of air in the water at a given temperature depends on pressure. If the water pressure is reduced, the air is released. A good way to visualize this phenomenon is by opening a carbonated beverage bottle; the sudden pressure drop allows the entrapped carbonated gas to come out of the solution and quickly dissipate.

A control valve in a closed-loop circuit, Cv, is often calculated with an equal or greater than drop to than the coil. The pressure drop results in air entrapment on the leaving side of the coil. Air acts as an insulator and is a poor heat transfer media. Air-bound coils transfer thermal energy inefficiently and cause noise.

ASHRAE states that "water velocity noise is not caused by water, but by free air, sharp pressure drops, turbulence, or a combination of these, which in turn cause cavitation or flashing of water into steam" (2009 ASHRAE Fundamentals Handbook, Chapter 22). When a control valve is installed on the return side, the water is at a higher pressure through the coil, reducing off-gas, thereby lowering dissolved oxygen content compared to a supply installation. This decreased dissolved oxygen content minimizes air entrapment or free air in the coil and thus the potential for noise.

In a heating application, the water temperature leaving the coil is cooler than the supply temperature. The return side is preferable as it allows the valve and actuator to operate at a reduced temperature which can help protect valve seats and actuator electronics over the installation lifetime.

In a chilled water application, the tempered water of the return reduces the amount of potential condensate on the valve from reaching the actuator. Return side installations may not always be appropriate, as in the case of a 3-way diverting valve- these are commonly installed on the supply and is not critical to proper operation; both locations will work effectively. In supply-side valve applications, the balancing valve should be installed on the return side whenever possible to reduce air and noise problems while achieving more efficient heat transfer.

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