Primary-Secondary chilled water system

[Timothi]

Hi experts,

HVAC related books say, in a primary-secondary chilled water system, the flow is controlled by the 2-way valve in the coil return side and the pressure in the supply pipe shoots up which is sensed by the dpt and dpt signals the secondary pump vfd to reduce pump speed.

If this is right what parameter controls the 2 way valve? How does it open and close automatically?


Thanks in advance?

 

[willard3]

Primary secondary pumping does not have to be variable flow either in the primary or secondary.

You should do some more search of Bell and Gosset as this is is a forum and not a fluids class

http://bellgossett.com/training-education/training-manuals/

 

[Timothi]

I meant constant primary-variable secondary chilled water system

 

[DRWeig]

The two-way valve is typically controlled to discharge air temperature from the unit to which it is attached.

Best to you,

Goober Dave

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[Timothi]

Thank you very much

 

[sprinkler1000]

Timothi:

The variable that controls the two-way valve is room air temperature. Room thermostat then calls for open valve or close valve, to let water enter the coil.

 

[willard3]

If the secondary is variable speed, you won't need any control valve unless there are multiple controlled units serving different uses.

 

[DRWeig]

Sprinkler1000 is also correct -- small units serving individual zones will have room temperature as the valve control point; air handlers for VAV (for example) systems will control the discharge air by modulating the valve.

Best to you,

Goober Dave

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