Modern Pump Selection Part 3: Impact of Constant Fixed Head On Pump BEP

Modern Pump Selection Part 3: Impact of Constant Fixed Head On Pump BEP

In our last blog we explained why in real life HVAC applications, variable speed pumps almost never operate at zero speed.  Even at no flow, the impeller must be spinning enough to produce some amount of pressure at the 2-way valve in order to quickly establish full flow at the critical circuit IF demand suddenly occurs. Here's a silly way to think about it....

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Modern Pump Selection Part 2: Theory Vs. Real World Operation of Variable Flow Pumping

Modern Pump Selection Part 2:  Theory Vs. Real World Operation of Variable Flow Pumping

In variable speed pumping systems, does zero load ever result zero pump speed?

Practically speaking, the answer is no.  In closed hydronic systems with 2-way valves there is almost always some amount of differential pressure created by continuous impeller rotation – even when....

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Modern Pump Selection Part 1: What Are Efficiency Islands?

Modern Pump Selection Part 1: What Are Efficiency Islands?

It makes sense to select a pump based on a wide range of operating conditions, not just peak load.  This will yield more savings than a pump selection based on the singular sweet spot of Best Efficiency Point (BEP).  Instead of focusing on that point where the system curve intersects with the BEP, we need to look at a broader operating range, the boundaries of which form what is called an “Efficiency Island”.  Efficiency Islands are.... 

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Solving Balance Issues with A Differential Pressure Controller

Solving Balance Issues with A Differential Pressure Controller

What are your options when unbalanced circuits in an existing hydronic system are creating comfort issues due to underflow or overflow through coils?  We just spent the last twelve blogs describing the various methods for balancing a start-up system but do those same methods apply to existing systems and retrofits? 

The short answer is....

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Hydronic Balancing Part 11: Variable Flow Pumping

Hydronic Balancing Part 11: Variable Flow Pumping

Throughout our Hydronic Balancing Series, we’ve been slowly and meticulously making our way to the more complex control systems that we see today.  We walked you through the steps of proportionate balancing a simple 3-zone system and taught you how to trim an impeller in accordance with ASHRAE 90.1.  Today, we’re going to see what happens when we add variable speed drives to the system. 

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