Comments for HVAC Energy Conservation

Comment on Quick Check for Sizing Units & Ductwork for Adequate Airflow by udarrell

udarrell — Fri, 03 Jul 2009 21:38:36 +0000

Quick Check for Sizing Units & Ductwork to Achieve Adequate Airflow

Actually, even on service calls where there are cooling problems the ductwork should have a quick Manual D performed.

Then take the ESP static pressure & compare to blower graph or chart, also take the FPM duct velocity.

Then do a quick estimate of airflow per equipment tonnage.To find area of a round duct; Duct diam is 7″; 7″X7″= 49-sq.ins., X’s .7854 = 38.04845-sq.ins divided/ by 144= 0.2672541-sq.ft. area X’s FPM Velocity 600-FPM = 160.35246-CFM X30 = 4,810.5738 each 7″ run X’s 6 branch runs = 28,863-BTUH, or airflow for 2.4-ton.

That would also be good for 2-ton; at 550-FPM velocity X’s 0.2672541= 147-CFM X 30 = 4,410-BTUH each run X 6-runs = airflow for 26,460-BTUH.
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The Return-Air & Return-Air Filter area are critical to proper airflow & system performance. The Return-Air filter area should be sized for 300-FPM velocity; quick ballpark to use is 2-CFM airflow per sq.in. of filter area. Remember even the filter grille’s free-air-area is only ballpark 75% of the listed size! I.E., 1000-CFM / 2= 500-sq.ins., X’s .75= only 375-sq.ins.

375-sq.ins., / 144= 2.6-sq.ft. | 1000-CFM / 2.6= 384-FPM or, above 300-FPM & that is without the filter! You cannot have too much filter area!

Never sell units requiring more airflow than the duct system & Blower will support! - udarrell - Darrell Udelhoven

Comment on Welcome to Energy Conservation toward reducing your heating & air conditioning costs by Michael

Michael — Thu, 28 May 2009 23:32:24 +0000

I read on your website that you recommend oversizing the coils to increase system efficiency. How much can you oversize them? Will a 2 ton condenser work well with coils designed for 3 tons? Also, what is the smallest condenser unit that you would recommend pairing with 5 ton coils?

Comment on Reply to Carmen by Brian C.

Brian C. — Wed, 22 Apr 2009 19:24:56 +0000

If I lower the velosity of air over the evaporator.
Will it raise or lower my head pressure?

Reply: It might lower it a hair, but very little. - udarrell

Comment on Welcome to Energy Conservation toward reducing your heating & air conditioning costs by Ray

Ray — Mon, 06 Apr 2009 22:53:49 +0000

I wanted to comment and thank the author, good stuff

Comment on Welcome to Energy Conservation toward reducing your heating & air conditioning costs by udarrell

udarrell — Sun, 05 Apr 2009 03:16:01 +0000

Question: Lowering CFM for increased latent heat removal, at which CFM to set the charge.

It depends on whether you are going to use the lower 850-CFM setting all the time.

If the lower setting, then charge it to that 850-CFM & at a little above the normal load conditions it will usually be operating at.

The higher the indoor humidity the higher the load through the evaporator.

Use both Superheat & subcooling to check for appropriate operation of a TXV metering device.

Use just Superheat for a fixed piston device.
Use the diagnostics in all of my Web pages:
http://www.udarrell.com/ac-trouble-shooting-superheat-subcooling.html
- udarrell

Comment on Welcome to Energy Conservation toward reducing your heating & air conditioning costs by Bruce Mart

Bruce Mart — Sun, 05 Apr 2009 02:11:09 +0000

Latent heat removal.

If you are planning on lowering the CFM across the evaporator to remove additional humidity, should you first charge the system with the nominal air flow suggested by the manufacturer ie. 1000CFM with 2.5Tons or lower the speed first ie. 850CFM and then charge.

Respectfully yours,

Comment on Welcome to Energy Conservation toward reducing your heating & air conditioning costs by udarrell

udarrell — Wed, 25 Mar 2009 22:49:33 +0000

Ed Hardy & SEO, Thank You for your comments.

Practice energy conservation and learn all you can about HVAC.

http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html

- udarrell

Comment on New Three Ton Payne Condenser by Darrell Udelhoven

Darrell Udelhoven — Wed, 25 Mar 2009 22:38:33 +0000

Thank You, Robor.

Learn all you can, we need to conserve on energy use & lower our utility bills!

http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html

- udarrell

Comment on Reply to Carmen by Darrell Udelhoven

Darrell Udelhoven — Wed, 25 Mar 2009 22:35:13 +0000

A big Thank You to Jack Robert & Jack Lester.
Always go to my website pages for all the information you need.

http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html
- udarrell

Comment on Welcome to Energy Conservation toward reducing your heating & air conditioning costs by Darrell Udelhoven

Darrell Udelhoven — Wed, 25 Mar 2009 22:30:07 +0000

Tony, sorry but I have been absent from my log.
The answers to your question & how to figure duct sizing & return air ducts, Grilles & filter racks is all on this web page.

Use the charts & click on the page anchor links for specific areas of the page.

If you need further specific help post a specific question.

http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html

- udarrell