A tertiary pump system is not required and makes the system pumping control more complex.
The current DP sensor can be effectively used to control the secondary pump VFD if the current DP sensors set point can be reset based on Chilled Water Control Valve positions.
At least one valve position...
Variable primary pumping requires a very sophisticated and expensive controls and highly trained chiller plant operators.
Sequencing chillers on and off is very complicated with a variable primary only system
The variable primary - variable secondary flow system (VPF-VSF)system in the article...
Yes
I designed a Variable Primary Flow (VPF)/Variable Secondary Flow (VSF) flow system for an existing University Campus Chilled water system.
The design approach was published in ASHRAE Journal October 2014 Technical Feature "Simplified Chiller Sequencing for a Primary/Secondary Variable...
PS
Very good explanation of how a decoupled primary/secondary piping system arrange works.
However, you limited the system operation to a traditional constant primary flow (CPF) and a variable secondary flow (VSF) system.
You can also have a variable primary flow (VPF) and a variable...
SDTH
SDTH Question:
Why should the operator switch on additional chiller?.. He can simply run a primary pump to balance the flows.
Response:
The primary objective of a chilled water system should be to maintain the distribution supply temperature at or below the design temperature at all...
To better understand the Low Delta T issue and possible solutionS, additional information is needed on your application.
What is the piping configuration?
Primary/Secondary or Primary
What type of pumping is used?
Constant Primary Flow Pumping (CPF)
Variable Primary Flow Pumping (VPF)...
marcoh
See 16-Jan-15 comments
If the approach indicated in the ASHRAE Journal October 2014 Article " Simplified Chiller Sequencing" is used,
No costly flow meters or differential pressure sensors are required to control staging of chillers.
The indicated approach only requires four...
ZDR1985,
First of all, an air washer is not a swamp cooler.
Swap coolers rely on evaporative cooling and are used in dry arid areas to reduce the supply air temperature. Leaving air temperature will be near saturation.
Air washers deliver chilled water directly to the air washer spray...
BronYrAur
The hospital may want to consider a Variable Primary Flow/Variable Secondary Flow (VPF-VSF) system to to mitigate the Low Delta T issues.
See ASHRAE Journal October 2014 Article "Simplified Chiller Sequencing"...
ELoyRD,
The B&G Technical Manual TEH-910A discusses many issue and or concerns associated with automatic operation of a Variable Primary Flow (VPF) system.
Are you concerned that the primary pump will continue to run when the chiller shuts down and the chiller automatic control isolation valve...
See AHSRAE Journal October 2014 Article titled "Simplified Chiller Sequencing."
Link
The article describes a chiller sequencing approach for a primary/secondary chilled water system that is being used for a university campus chilled water distribution system.
The control approach minimizes...
