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Duct blast machine
who owns one? is it worth the money?
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Duct blast machine
I own one, if you test correctly you can really answer some important customer questions like "so I have duct leaks it can't cost that much right?" You can show them not only how much it leaks but also how much the leaks cost them, you can verify your own ducts, and you could also do duct testing for customers of other companies for 3rd party verification. All very good for the customer and very good income streams for your business.
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Always do whats right.
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Which one do you have? What's the price range?
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About $1000 for retrotech without manometer
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A Duct presurization/depressurization device can be a good tool depending on what you want to do with it. If you are working utility jobs that require duct leakage info or if you are testing new duct systems to meet some spec, then it's kind of necessary. From a sales perspective, you could quantify the amount of leakage in a system to justify duct repair/sealing. The tricky thing though, is that you would need to quantify the leakage to the exterior of the building. Sealing duct leaks inside the thermal/pressure boundary of the building are not going to save you any money unless they are creating pressure imbalances in the building which may increase infiltration/exfiltration. Typically, a blower door is used in conjunction with your duct device to determine how many of the leaks are to the exterior. (another expensive tool) Without any ducts in the attic/crawl or structure being used as return - it is pretty much useless. And if you have ducts outside, you should seal them anyway - but, I suppose you could quantify the amount of leaks you have before you seal them.
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I have the variable blower machine. Did not buy the manometer yet. I made some simulations with the machine and feel I have a good way of testing a duct system without using the $1000 manometer. I will post some of my test results later if anyone is interested. My first post did not go through.
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We test all of our ducts to check our work before finish (other trades) that way we now our job is tight and when the LEED test is needed or Inspector wants a cert of performance we don't worry.
Additionally if a client wants to know if their ducts need replacement this test can help for some of the process.
We use the "Duct Blaster".
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Blowerdoor , dust blaster IR are must tools even if not required in your area...diagnose the home, not just the heat transfer machine. Know where the heat is coming from and going to
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Originally Posted by
lkapigian
Blowerdoor , dust blaster IR are must tools even if not required in your area...diagnose the home, not just the heat transfer machine. Know where the heat is coming from and going to
Do you have more than one? We certify ours every year. I have two guys that perform the test.
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Originally Posted by
Fan Curve
Do you have more than one? We certify ours every year. I have two guys that perform the test.
We have 1 set of everything, we only have 1 full time testing all of our systems. Our utility provider does have a great lending library when we need additional, and our HERS rater for backup
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Originally Posted by
7X
A Duct presurization/depressurization device can be a good tool depending on what you want to do with it. If you are working utility jobs that require duct leakage info or if you are testing new duct systems to meet some spec, then it's kind of necessary. From a sales perspective, you could quantify the amount of leakage in a system to justify duct repair/sealing. The tricky thing though, is that you would need to quantify the leakage to the exterior of the building. Sealing duct leaks inside the thermal/pressure boundary of the building are not going to save you any money unless they are creating pressure imbalances in the building which may increase infiltration/exfiltration. Typically, a blower door is used in conjunction with your duct device to determine how many of the leaks are to the exterior. (another expensive tool) Without any ducts in the attic/crawl or structure being used as return - it is pretty much useless. And if you have ducts outside, you should seal them anyway - but, I suppose you could quantify the amount of leaks you have before you seal them.
This used to be what most techs thought. But since the residential code started requiring duct leak test in 2009 - you need a way to test or you have to hire a 3rd party to do the tests. Most people (myself included) were very very surprised at how much our ducts leaked when we first started testing. Now that we have been testing our own work for a while we generally get it right the first time. But there are still surprises.
BTW - all duct leaks, even to inside the building, cause problems. Either you can't get the required airflow to a zone or the leaks cause pressurization problems. At least that is my experience.
If "I have always done it this way" is a good reason to do it again, how many times do I have to do something wrong - before it becomes right?
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Here's an example of how I did my own house with duct blaster without the manometer: use the small ring at 125 cfm and used a magnahelic gauge to measure 25 pascals. First try could not obtain found my ceiling leaks by too much air loss between ceiling grills and boxes. Afte correcting problem was able to maintain my 25 pascal at 125 cfm. I have a 1600 square foot house which means my maximum duct loss at 6cfm would be 96cfm. I don't think I would have more than a 30 cfm loss. What do you think about my fuzzy math?
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Some thing that is interesting about maintaining the .10 inches of water column on your duct system: section 403.2 talks about testing with a pressure differential across the entire system. In chapter 1, page 2 of the introduction to Minneapolis duct blaster, it says 25 pascals is mist commonly used test pressure and pressurized to a standard test pressure and does not mention differential across the entire system. Just thought that was interesting terminology.
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Originally Posted by
Sammtillman
Here's an example of how I did my own house with duct blaster without the manometer: use the small ring at 125 cfm and used a magnahelic gauge to measure 25 pascals. First try could not obtain found my ceiling leaks by too much air loss between ceiling grills and boxes. Afte correcting problem was able to maintain my 25 pascal at 125 cfm. I have a 1600 square foot house which means my maximum duct loss at 6cfm would be 96cfm. I don't think I would have more than a 30 cfm loss. What do you think about my fuzzy math?
Very fuzzy math- Did you pressurize your house or ducts? If your house you would be @ 50Pascal If you did the ducts the square footage of your house would not come into play. How did you come up with the CFM without a DG700 or EQ? .... . .1" is awful small to measure with a magnehelic unless you have one in the 0-.2 range. What is the design CFM of the unit, you need to compare leakage to that in a %
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I have the dg700 machine but haven't purchased the manometer yet. Basically I'm trying to figure the duct leakage using static pressure instead of differential pressure. Using the small ring on the machine delivers 125cfm. If I can maintain a static pressure of 25 pascals delivering 125 cfm into the duct system I feel I would have a duct leakage way below 96 cfm/which is the maximum amount of loss the code allows in a 1600 square foot house. 6cfm per 100 square foot.
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Originally Posted by
Sammtillman
I have the dg700 machine but haven't purchased the manometer yet. Basically I'm trying to figure the duct leakage using static pressure instead of differential pressure. Using the small ring on the machine delivers 125cfm. If I can maintain a static pressure of 25 pascals delivering 125 cfm into the duct system I feel I would have a duct leakage way below 96 cfm/which is the maximum amount of loss the code allows in a 1600 square foot house. 6cfm per 100 square foot.
The DG700 is a manometer... Your DG700 will tell you the leakage or are you saying you bough the duct blaster without the DG700?
Not sure where you are but duct leakage is not based off of square footage, but design CFM of the system
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Would believe there are two critical elements for the testing: surface area of duct work and the design pressure class of its build. Up to 2" of static testing is usually just the Transverse Joint, over 2 inches you need to include the longitudinal seam as well as damper shafts and stiffener class penetrations. Both supply and return are critical; supply for the waste of the systems expended resource and the return for inducing heated air if in an attic, or pollutants (IAQ Type) into the distribution system. Tight ducts= happy customers...
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We use the Minneapolis Duct Blaster kit which we have been using for 4 years and I would easily recommend it. In 2010 we were doing mostly energy star homes which had to be tested for certification, and now since the 2012 energy code all new duct systems have to be checked. We saved ourselves a lot of money by getting our own, when an independent verifier wasn't needed. And its nice to be able to do it in front of customer so they can see if they need a new duct system and if its new, then they see how tight it is.
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A Duct Blaster is a great tool for determination of duct leakage - if you are required to do it for some reason. And maybe one of those reasons is to check your work. The point I was making earlier is that if your ducts are interior to the thermal/pressure boundary of the building and there are no comfort/delivery issues and there are no pressure imbalances being created - there are no savings associated with duct sealing. If the occupants are comfortable and you measure the main body/duct zones and there are no pressure imbalances, then why spend the money to make the ducts airtight?
If I was putting in a new system, then I would want tight ducts. But, in a retrofit application where you are intimating that there is a savings potential for sealing ducts - I would be more careful.
If I was installing a system that was "outside" the building, then I would seal the piss out of them - even a small leak costs you money.
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