Replyhow do you determine the proper size unit for MY home?
correct answer= manual J load calculation, followed by manual D to determine duct size
Regular Member
I'm planning on going to the local home show and look for a contractor to install a new heat pump and ductwork. What questions should I use to weed out potential contractors?
Professional Member*
how do you determine the proper size unit for MY home?
correct answer= manual J load calculation, followed by manual D to determine duct size
It`s better to be silent and thought the fool; than speak and remove all doubt.
Professional Member*
Posted by Skippedover a few years back
HOW TO SELECT AN HVAC COMPANY
It needs to be realized that there are both professional HVAC companies and fly-by-night companies or individuals, as there are in many other professions. Since the average HVAC job will be installed and used for many, many years, it behooves the prudent shopper to acquaint himself or herself with some basic methods that can greatly reduce the potential to end up paying thousands of dollars for what could end up being at least an uncomfortable system and at worst an unsafe, even life threatening system. Below are some suggestions on how to choose a highly qualified company, as well as some editorial information about each of these suggestions.
1. Using the media of choice, go right down the list of each HVAC company and telephone them. Your goal is to ask just one basic question, the answer to which produces significant information about the company. The question to ask is,
“How would your company determine the size of the (heating or cooling) equipment for my house?”
There is only one correct answer to this question. (ed. The DOE and every major product manufacturer all recommend the same method. How the company answers this question therefore tells you whether they follow federal government and manufacturer ‘best practices’ or not. Those that do are far more likely to deliver a properly sized system or equipment to the job. Improperly sized equipment can lead to discomfort, short cycling, higher energy costs and shorter equipment life. Therefore, there is a definite value to selecting a company that answers this one question properly.
Acceptable answers: “By Manual ‘J’ calculation”; “By an engineering analysis”, “By a room-by-room load analysis”; “By measuring and calculating the load for each room”; “By ACCA (Air Conditioning Contractors Association) software”; “By using a computer design” or similar methods that specify an actual mathematical calculation based on solid science.
These companies have spent the time to educate their sales, installation and service staffs. The mere fact that they know how to do the sizing correctly tells you that they care about their reputation and your comfort. The education and materials needed to do the job correctly are a represent a substantial investment in both their business and your comfort. Do not expect any company of this caliber to cheap. In fact, the added value they bring to the table will likely put their quote substantially above a company that guesses at sizes. But wouldn’t you rather know what you’re getting than to have someone guess at the size and gamble several thousand dollars that they guessed correctly with your money?
Unacceptable answers: “By square footage”; “By looking at the size of the existing equipment”; “I’ve got XX years in the business and know how big it needs to be”; “By years or experience”; “By the thousands of units I’ve installed over the years” or variations thereof that say “I guess at the size”.
These are the companies that know only one thing. That is, how to cut corners to the point that they are the low bidder on a job. The first corner to be cut is the time it takes to measure the entire house, room-by-room, window-by-window, check the insulation, determine construction techniques and calculate the actual heat gain or loss of the house and each individual room. If they measure at all, they use a multiplier “rule of thumb” to determine the size of the equipment. They may be right or wrong. It’s your gamble as to which. After all it’s your money right, not theirs? Obviously if they’ll cut that very first corner that you should know they’re cutting, can you just imagine what corners will be cut in areas where you have no knowledge?
2. When you’ve found a company or two that will answer question #1 correctly, invite them into your home and enjoy the presentation. A good company will spend as much time as is needed to make you totally comfortable with the process of what’s happening, why it needs to happen and what you should expect to follow. Comfort comes in many guises and your emotional comfort with the process is paramount to a good company. Please do not be offended when they ask to have all the people involved in the decision present. There’s a huge amount of information to be digested, all of it representing added value this company will bring to the table. To expect one person to relate it all to another is just not going to happen. So please have everyone present who needs to be there. Opinions can vary, questions will arise. All of these issues need to be addressed to everyone’s satisfaction.
3. Once the size of the equipment has been determined (do not expect the sales person to share the equipment size with you until after an agreement has been signed. They’ve been burned too many times by customers who get them out to determine the size of the equipment and then use that information to get a lower price. In the end, the client gets the right size but a hundred other corners were cut, leaving the homeowner once again, cheated) you should expect the duct system to be designed according to Manual ‘D’. That is the ACCA method of designing a duct system that will deliver the proper airflow without excessive noise. It’s important to note that the ducts can’t be sized until the equipment is properly sized. That once again would lead us back to the importance of that question you’ll be asking in item #1.
4. Finally, after the equipment and ducts are properly sized (or in the case of ducts, reviewed as to current condition and sizing) it’s time to select the equipment itself. Brand is not normally very important and many companies can offer more than one brand. All manufacturers have both successes and failures of equipment most importantly based on the installing company. Once again, the installation company that follows the proper procedures will deliver the anticipated result to you. If corners are cut, you can expect discomfort and problems.
http://www.eere.energy.gov/consumer/.../mytopic=12340
http://www.energystar.gov/index.cfm?...zing.showIntro
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Great info. thanks. I don't want to get into a ductwork debate but depending on using metal or duct board what else should be required? Dampers on each supply etc...
Professional Member*/ARP Committee
Damps on each supply could depend on where your duct is located.Originally Posted by ku
I am against dampers in each supply if the ductwork is in an attic.
In an open basement, sure, although some may say it's overkill.
The ductboard/metal debate is a longstanding one. Personally, I'm more of a metal guy in a basement, and a ductboard guy in attics.
The problem with ductboard, is finding an installer that can do it correctly. Out of 8 installers at our company, we have 2.
If in an attic, I'd want all ductwork insulated to a minimum of r-8.
All ductwork sealed.
No deep boxes, no "toe kicks".
Warranty, warranty, warranty.
That's the name of the game right now.
I don't care who makes it, as long as they stand behind it.
Obviously, check out the contractors credentials. A #1 warranty, installed by a #10 contractor, isn't worth anything.
By the way, don't ask them pricing. It's offensive, because there is no answer.
I too, am going to the home and garden show today. Gotta go make fun of the bosses.
"Better tell the sandman to stay away, because we're gonna be workin on this one all night."
"Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."
"Just get it done son."
Dad adjusted
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I went to our local home show today. Glad I had free tickets because it was not worth the $10 admission. So anyways I figured I would ask some questions of the HVAC company's that were there just to see if they new anything about doing the right things.
Out of the five none do manual J most had no clue. Then I asked how do you know what size equipment that I need? All five said they use the numbers off the old equipment. Your kidding me right? They had no idea how to size ductwork either.
I have to say that if these company's were good they really would not have to go to a home show to drum up business. They best way to Find a great contractor is word of mouth from happy customers.
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Curious what home show did you go to? What state and of town? As for me we do (2) home shows a year with good results! I have been asked the same questions you asked of the dealers that were their.
My answers are simple and to the point. I say that I would need to come out to your home and review over ductwork, insulation, windows etc... Then preform a manual j load cal. Along with manual d for duct sizes. After that manual s is to follow if the customer is serious buyer.
I just don't understand this day in time that hvac contractors don't do load cals or even have someone who can size duct work right? In the last 5 years it has been even easier to do so with wrightsoft manual j moblie.
After the home show, I received 8 quality leads in which we have sold and installed 4 systems easily paid for the show $$$ with the 1st job installed. While some say home shows are a waste of $. I say bring it on. I spend (2) weekends out of the year to get business for years to come.
Shoot if my company covered a wider area and or did new construction those numbers would be higher. The funny thing is I had another hvac company approach me and offer me a job to come work for them. Needless to say they don't do load cals and really don't have a clue. I thanked them for the offer but stated that I am happy with the company that I work for. This was with my boss standing right their listening to competitors offer me. Now they didn't no that my boss was their.
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