Understanding IPLV: Interpreting Integrated Part Load Values ​​(ACs, Chillers)

iplv or IIntegrated PArt-TookOAD valu A metric used to adequately assess the energy efficiency of chillers and air conditioners in realistic conditions.

The key metric we use for the energy efficiency of any HVAC appliance is COP (coefficient of performance). The supplementary metrics include EER, SEER, CEER and HSPF ratings.

Where does IPLV fit in?

The EER rating, for example, gives you the energy efficiency of an air conditioner when operating at 100% cooling output. It is a simple metric but it is lacking to describe how an AC unit actually performs under practical conditions. This is because an AC can run on less than 5% of the time at 100% cooling output. What about other times?

This is where IPLV comes in. IPLV is used to describe the practical energy efficiency of chillers and air conditioners at various (more realistic) loads. IPLV is calculated not only on 100% Output, But this also 25%, 50%, and 75% output,

pay attention: EER and COP are, by definition, subgroups of IPLV. We talk about IPLV EER and IPLV COP.

Essentially, the integrated part load value is a Weighted average Out of these 4 loading points. This means you can estimate energy efficiency at part-load (25%, 50%, 75%); Hence the ‘part-load’ in IPLV.

How exactly do you calculate IPLV? Here is the formula:

IPLV Formula

IPLV is calculated as the weighted average of 4 loading points. Calculation assumes that a chiller or air conditioner operates (you will find the equation below),

  • 12% of the time at 25% load (D in Equation).
  • 45% of the time at 50% load (C in Equation).
  • 42% of the time at 75% load (B in Equation).
  • 1% of the time at 100% load (A in Equation).

Here is the complete formula of IPLV:

IPLV = 0.01A + 0.42B + 0.45C + 0.12D

We always use this equation to calculate IPLV. The important part is how exactly do you measure what is a realistic 25%, 50% and 75% load:

How is IPLV measured?

The cooling load at these 4 points is generally measured by AHRI, as per the existing standard AHRI standards.

When AHRI measures the load at 25%, 50% and 75%, they simply input the measurement into the weighted-average IPLV equation and calculate the IPLV.

Now, these loads have to be measured not always possible, Therefore not every air conditioner or chiller has a specified IPLV value.

Issues that may prevent IPLV from being measured adequately include:

  • Changes in the design of the distribution system.
  • different climatic conditions.
  • Unexpected temperature changes.
  • Difficulty holding the load steady at 25%, 50%, or/and 75%.

Despite these issues, we still want to measure the actual load and resultant energy expenditure of the air conditioner and chiller.

so when we can’t measure iplv enough (with a sufficiently low measurement error), we use two other values ​​to more accurately assess energy efficiency: NPLV And SPLV,

You can read a similar explanation of what is NPLV or Net Part-Load Value. To fully understand all these metrics, it is advised that you educate yourself about SPLV or specific part-load values ​​here as well.


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