NAFA Guide to Air Filtration.

Chapter 13Owning and Operating Cost

By Dirk ter HorstApril 19th, 2012

Another Approach….Air Filter Comparison

OUTLINE

Objective Energy Cost Calculation: 2 approaches Calculation Example & Methodology Comparison Total Filtration Cost Tool’s presentation Conclusions

Objective

Present a practical and easy approach to air filter evaluations + operation based on: End user/customer experience (Pressure drop

and filter life) Standardized filter life indicator (ASHRAE 52.2

DHC) All air filtration associated costs Use of software

Assumptions and considerations

NAFA

Customer experience (Pressure drop and Time)

Constant environmental conditions

Average pressure drop Straight Line

New approach

Customer experience (Pressure drop and time)

Constant environmental conditions

Time vs. Pressure Drop Time vs. ASHRAE DHC Air filter Pressure Drop vs.

DHC Signature

Linear Pressure Drop Approach

Considering the pressure drop changes linearly with time the energy consumption is expressed by:

fof tPPQ

E21000

𝐴=∆𝑃𝑜𝑡 𝑓+12

(∆𝑃 𝑓 −∆𝑃𝑜 ) 𝑡 𝑓

Where:ΔP0 = Initial Filter pressure drop [Pa]ΔPf = Final Filter pressure drop [Pa]tf = operating time[hrs] = average pressure drop

Filter Pressure Drop vs. Time Approach

Considering the pressure drop of the filter versus time, the energy consumption is expressed by:

ftdtP

QE

01000

𝐴=0

𝑡 𝑓

∆ 𝑃 𝑑𝑡

Energy Cost

The energy cost is calculated by:

Linear pressure drop vs. time:

Filter pressure drop vs. time:

fof tPPQ

tcosEnergy21000

ftdtP

QtcosEnergy

01000Where:E = energy consumption [kWh]Q = airflow [m3/s]ΔP = pressure Drop across the filter [Pa]t = the time is operating the fan [hrs.]η = system efficiency (fan, motor & drive) [%]

Same results…

$273/360X365=$277$301.2/360X365=$305.4

Linear vs DHC curve..For 100 filters

This example:Difference/year: $5,863.59 (22.5%)

Transposition…

+ =

Assumption:Air filters of the same efficiency and media type

have captured the same amount of dust if they are exposed to identical environmental conditions over

the same period of time

Two filters to work with… Example

Filter A: MERV 14. 24x24x4 Box type. Initial pressure drop: 0.35 inch H2O DHC at 1.5” H2O: 67grams. ASHARE Dust 2000 cfm $70.0/unit

Filter B MERV 14. 24x24x4 Box type Initial pressure drop: 0.3 inch H2O DHC at 1.5” H2O: 143 grams. ASHRAE Dust 2000 cfm $70.0/unit

Linear approach… for 100 filters

Two different filters without DHC considerationLinear approach:

US$ 701.74/year

Two different filters with DHC considerationLinear approach…

US$ 9,682,90/year

Curve approach… for 100 filters

Two different filtersWith DHC considerationCurve approach

US$ 9,173.82/year

Optimization Linear approach..

Pressure Drop of filters at change-out time for financial optimization:

0.85inch w.g.

Cost reduction: $9,712.03/year

(for 100 filters)

Optimization… DHC curves.

Pressure Drop of filters at change-out time for financial optimization:

0.60inch w.g.

Cost reduction: $10,134.13/year

(for 100 filters)

Compare Apples to Apples…

Filter Type Filter depth Frame type Frame material Filter media material Face screen Incinerable Filter brand/make Test standard Air flow Maximum final pressure

drop Efficiency Test dust

Test Laboratory Test filter procurement/source Age of test report UL 900 compliance

Fan type Reasons for change out time Other considerations

Practical approach to TFC

Easy calculation….Let’s see a software tool:

http://filtrationcost.lpdtechnologies.com

LC 67 vs LC 143 Base

LC 67 vs LC143- High Energy Cost

LC 67 vs LC143-Low Energy cost

LC 67 vs 143 Base- Money Maker

LC 67 vs LC143- Production loss

Conclusions

Use the ASHRAE 52.2 DHC curve information when evaluating the financial impact of air filters.

Calculate the recommended filter change out pressure drop (optimization).

The cheapest filter nor the filter with the lowest initial pressure drop are necessarily the best solution.

There is a WIN-WIN opportunity for the customers and the industry!