In this module, we'll explore the advantages and disadvantages of the variable primary circuit and the constant primary/variable secondary circuit when using Distributed Pumping in data centres, as well as how we look at the primary and secondary circuit differently with Distributed Pumping.

Distributed Pumping provides versatility by seamlessly adapting to the existing systems of data centres, be it a variable primary or constant primary/variable secondary set up.

Let’s take a look at the advantages and disadvantages of using both circuits in data centres with Distributed Pumping. The variable primary circuit is known as the energy-optimised design. This is because it:
Has a lower capital cost
Saves space
Has a lower energy consumption

As data centres need newer, more sustainable space-saving solutions to help them be more energy efficient, the advantages of this circuit are appealing. But it does come at a cost. The disadvantages of the variable primary circuit are: It’s a complicated design. There’s a risk of bypass malfunction. It’s difficult to commission. It’s difficult to define the critical index circuit. The constant primary/variable secondary circuit is known as the conventional design. This circuit makes it easier to:
Design
Commission
Balance
Maintain.

But the ease of this circuit also:
Has a higher capital cost
Needs more space.

Now let’s take a closer look at the specifics of a Distributed Pumping system in a data centre. With Distributed Pumping, we adopt a unique perspective on the primary and secondary circuits by utilising the decoupling line, which is also known as the bypass. This element allows us to: Control the primary and secondary circuits. Optimise their balance. Control the Delta T of the system.

Let’s explore how this works, starting with the primary circuit. In data centres, the primary concern is the safety of the chiller. Signals sent from the chiller control valve inform the MPC Controller that the chiller is running. By using differential pressure sensors across the chillers, we measure the flow rate across each chiller. If the minimum flow isn’t met, the primary modulating pumps increase the speed. Once the minimum flow is secure, the primary and secondary circuits can be balanced. The secondary circuit needs to provide enough chilled water to meet the load on the Computer Room Air Handler (CRAH) units, while the primary circuit needs to provide the exact amount of chilled water to meet this demand. Temperature sensors are installed on the primary and secondary loops to balance the flow across the circuits.

By monitoring differential temperatures, the system ensures balance, which is critical for preventing bypass flow. Any discrepancies prompt the pumps to swiftly adjust. Under pumping triggers a speed increase in the primary pumps. Over pumping prompts a reduction in the primary pump flow. A balanced system ensures that just the right amount of chilled water is provided, helping the data centre to save energy across the whole system.

Distributed Pumping showcases its benefits by eliminating bypass flow and enhancing chiller efficiency, thereby optimising energy consumption within data centres.

Now let’s look at the secondary circuit. The secondary circuit provides chilled water to essential components, such as the CRAH units, and assesses the load being absorbed by the data halls. This ensures that the system responds accurately to the needs of the data centre. The distributed pumps on the secondary circuit operate autonomously, each dimensioned for the load of the CRAH unit and the corresponding piping. These pumps modulate their operation, adjusting the flow to provide the exact amount of chilled water required for the connected CRAH unit. The circuits stay balanced through constant communication between the pumps and sensors.

If a data centre needed to expand and add extra circuits, the system’s balance would remain unaffected. This adaptability is the result of each pump adapting its performance based on feedback received from its specific circuit. Distributed Pumping marks a paradigm shift in how we approach primary and secondary circuits within data centres. Its impact translates into cost savings, efficient space utilisation, and a significant reduction in energy consumption.