HVAC Energy Conservation

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HVAC Energy Conservation

Reducing Energy Usage & Lowering Utility Bills

Quick Check for Sizing Units & Ductwork for Adequate AirflowJuly 3rd, 2009

This page does not explain everything you need to know about proper duct sizing a system foroptimal comfort, but provides some general guidelines and concepts.

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*You could ballpark the CFM using the static test & the air handlers graph. You couldmeasure the CFM delivered to each room with a hood Alnor Balometer, its usually the best

instrument to use, but not cheap. Anemometers are reasonably priced & should be used forchecking velocity from diffusers.

Measuring the air velocity from diffusers is a bit tricky because you should use the diffusermfgers data which you should always have with you.You can usually get the diffuser mfrsdata, say its a 1.5-Ton system that already has 6rd branch duct runs, to achieve enough CFMairflow, you need close to 700-FPM velocity in the ducts.

I would want to use a diffuser with a little more free open sq.ft area than the 6 duct whicharea is 0.19635-sq.ft., say middle of the room in the ceiling; Hart & Cooley 2-way curved blade126 has Ak .235-sq.ft. Free-Air-Area delivering 140-CFM at 600-FPM - diffuser face velocity.

This would help lower the velocity of the duct through the diffuser & reduce air noise.Throw is7.5-ft toward each wall. Terminal velocity at the occupant level is 75-FPM.

If one diffuser face-velocity were to yield 135-CFM times 5 outlet runs - yields 675-CFM *Xs26.666-BTUH per CFM =


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have to balance, & they do work!

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Quick Check for Sizing Units & Ductwork to Achieve Adequate Airflow Actually, even on service callswhere 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; 7X7= 49-sq.ins., Xs .7854 = 38.04845-sq.ins divided/ by144= 0.2672541-sq.ft. area Xs FPM Velocity 600-FPM = 160.35246-CFM X30 = 4,810.5738 each 7run Xs 6 branch runs = 28,863-BTUH, or airflow for 2.4-ton.That would also be good for 2-ton; at

550-FPM velocity Xs 0.2672541= 147-CFM X 30 = 4,410-BTUH each run X 6-runs = airflow for26,460-BTUH.Never sell units requiring more airflow than the duct system & Blower will support! -

udarrell

Tags: airflow,blower, CFM, ductwork, equipment, ESP, FPM, sizing, velocityPosted in Uncategorized | 1 Comment

New Three Ton Payne Condenser

August 10th, 2008

I Installed a NEW 3 ton Payne Condenser with driers. Charged the system.

Low side line is sweating good, high side line luke warm. Temp coming out of vents are 69 degrees.

I removed the entire inside system outside and cleaned the coils with evap cleaner. cleaned Blower Motor

and Squirrel cage.

Replaced it.

Evacuated the system and re-charged system.

Low side would not rise above 70 lbs pressure, but high side continued to climb to 350 lbs pressure still

not cooling sufficiently.

Check ducting for leaks, all looks good.

Do you have any Idea what it could be. Rodger Touchette

Copy the data chart in the prior post, & fill out as much as you can.

NEED: Outdoor temp; indoor temp & Relative humidity.

Approximate airflow.

A shot in the dark, it sounds like a partial restriction somewhere in he refrigerant circuit.

I more information to make any meaningful judgments.

No actual data, only a shot in the dark guesses.

AC Energy Conservation http://udarrell.com/udarrell_hvac_blog/

6 10/7/2009 12:47 PM


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A liquid line, including metering device, restriction would show high head & low suction pressure.

If there is a liquid line restriction somewhere you may have overcharged the system causing the high head

pressure.

- udarrell

Posted in Uncategorized | 7 Comments

Reply to Carmen

August 1st, 2008

Carmen Said:

I came across this site last night, after searching the web for answers. We just installed a TRANE 16Seeron our 2100 sf home. Compared to last year, at this time, my bill has doubled. Last year during summer(with 2 MasterCools installed, one running 24 hours, the other about 10 hours), my bill was under $200.

This year, with our new HVAC, in addition to new windows all around the house, my bill was over$300.

What am I doing wrong? - Carmen============================Hi Carmen,

I am new to blogs & blogging. My web site is my main stay.

I do not have enough information to do any kind of analysis, however, it could be a poor install & setup of

the equipment, refrigerant lines & the ductwork system.

Your unit is costing you a fortune, the first thing to look for is hot air getting into the Return Air ductsystem, that would overload the evaporator & condenser & run your costs way up. What is theF-Temperature rise/split from the outdoor condenser above the outdoor temperature. it appears that youlive in a dry climate.

So, your unit is costing you a fortune, I need to have the temperatures below, - that you can easily take forme:

Copy only the data portions & paste in your Word-Processor, make a couple hard-copies, then

send me what you take, & get as much of this data as your Tech will provide for you. You candelete the (You &/or Tech) before you make hard copies for your Tech.

This is very important: Always tell the tech that you want all the data he takes, clearly recorded with yourbilling!

I can run the temperatures data you take with an accurate CFM Airflow & ball-park the Nominal BTUH

your new A/C is delivering, at those conditions.

TROUBLE SHOOTING DATA - (You or Your) HVAC Tech

For my information concerning summer design & your climate, provide your state & nearest large city

__________TONNAGE of Unit oroutdoor condenser model number: ___________ You

TXV or orifice metering device? _______You or Tech, - not real critical to this analysis

Outdoor condensers discharge-air-temperature _____YouOut-Door temperature: ____You


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Condenser air Temp split _____You

Indoor Total-ESP - External Static Pressure _______Tech

All Supply Air velocities in FPM: ___TechIll do the math for the total CFM:

Suction line pressure ___TechSuction-Vapor line temperature: ___Tech

Saturated Suction Temp Gage - Suction Saturated Temperature. ___TechSuperheat ______Tech

Head pressure _______Tech

SCT Gage - Saturated Condensing Temp _______TechSmall Liquid line - temperature: _______You

Subcooling: _______Return Air temp DB &, WB or %RH: _______YouSupply Air temp DB &, WB or %RH: _______You

With the information data below and an accurate CFM airflow + sea-level height, I can ball-park its

BTUH outputReturn Air temp DB &, WB or %RH: ____ ____YouSupply Air temp DB &, WB or %RH: ____ ____You

Take a cotton cloth & wet with room temperature water, wrap it around the thermometer & use it for thewet bulb temps above.

Except for the Pressures, Superheat & subcooling you can take most of the other Temp readings for me.

My advice: to every user, get a low cost humidity gage at a local hardware store & see what thepercentage-RH is in your home, I can cross-reference that to the wet bulb depression so you could use thehumidity gage instead of wet or use both.

If you want to save money you will take the time when it is hot & warm in the house to take all thistemperature data!

Please Respond, ASAP.

Anyone is welcome to use the Data Collection for use as they see fit!

Copy only the data portions & paste in your Word-Processor, make a couple hard-copies, then

send me what you take, & get as much of this data as your Tech will provide for you.

My monthly electric bills run $50.00 or less, & I keep very cool, in a 1937 farm home, even in 104-FHeat Index!

Are your electric bills too high?

Visit my many HVAC web pages at:

http://www.udarrell.com/airconditioning-sizing.html

For Techs a Trouble Shooting chart, for HVAC Techs & HVAC Users a Service Data Chart tocheck BTUH Performance:

http://www.udarrell.com/ac-trouble-shooting-chart.html

I am here to help you Conserve Energy & save a lot on your monthly utility bills.


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A high percentage of HVAC systems are operating way under their Rated Efficiency!

Visit the HVAC links at the bottom of the pages.

Edit: 08/03/08, Carmen, your initial post is in the unnoticeable uncategorized comment section!

udarrell - Darrell, Retired HVAC Tech & Contractor from mid 1970s


Welcome to Energy Conservation toward reducing your heating &

air conditioning costs

July 12th, 2008

Welcome to Energy Conservation toward reducing your heating & air conditioning costs & to ask allkinds of questions.

Feel free to post about anything related to HVAC and/or Energy Conservation.

There are many areas where your air conditioner or heat pump may be losing efficiency, together we can

achieve optimal efficiency of operation.

This is valuable free information being offered to you so you can save on your energy usage costs, &practice Energy Conservation for America. Visit my many Energy Saving HVAC web pages at:

http://www.udarrell.com/airconditioning-sizing.html

For Techs a Trouble Shooting chart, for HVAC Techs & HVAC Users a Service Data Chart to check

BTUH Performance:

http://www.udarrell.com/ac-trouble-shooting-chart.html

I am here to help you Conserve Energy & save a lot on your monthly utility bills.

A high percentage of HVAC systems ar operating way under their Rated Efficiency!Practice Energy Conservation it Pays Big Dividends forn you & for your country.

Visit the HVAC links at the bottom of the pages.

Darrell Udelhoven - udarrell.com


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