Help me understand the Testo 435

[DesMech]

I am in need of a micromanometer and a hot wire or mini vane anenometer. I like the Testo 425 or the 416, but I don't have any experience with a mini vane. Are they accurate? Also, I have been looking at a TSI dp calc micromanometer, which I have used an older version of. I know TSI makes good stuff, but I am wondering about the Testo 435. It seems this tool will do both jobs. Does the 435 have the resolution and accuracy of the dp calc? I tried looking at the specs, but I can't tell how many decimal places the manometer will show (I need at least thousandths of an inch of water). If I understand the 435, I buy the unit, and then have to buy each probe I need seperately. I found a lot of differently priced 435's and I can't quite figure it out. Anyone know what this thing is about?

[mark beiser]

The 435 won't take the place of a micro manometer for applications where you really need a micro manometer.

[weber]

The 435 is an excellent instrument!

You need to look at the different models and kits. They come with different probes and features, so make sure you buy the right one for what you will be doing.

The minivane is excellent and is of higher quality over the hot wire due to there is no need for a correction factor due to the density of the air.

[DesMech]

Thanks guys. In the brochure for the 435, they show the differential pressure resolution as 2" H2O. Huh? How can that be? Do either of you guys know how many decimal places this thing goes to? At this point, I think I am leaning toward the tsi and a seperate anenometer.

[jim bergmann]

For residential airflow measurement, the vane anemometer is the ideal airflow measurement tool. Vane anemometers operate within the ideal measurement range, are non-density dependent, and by design vanes are less influenced by turbulence than thermal probes or Pitot tubes. A fan is a constant volume machine; it will move the same CFM of air no matter what density of the air. If a fan will move a constant CFM, it will also measure a constant CFM. This is the primary reason behind the design of a vane anemometer. A vane anemometer is a miniature fan that is moved by airflow instead of moving air. This provides a cost effective solution for a quick and highly accurate airflow measurement in residential and light commercial systems. Vane anemometers have several advantages over any other method. The primary advantages are cost, speed, accuracy, and ease of use. Pitot tubes and hot wires both require calculation of air density for correction of the velocity measurement, and many hotwires are calibrated only for standard air and do not provide a means for compensation of the measurement. To measure velocity or volume of air, vane anemometers do not require air density compensation due to variations in air temperature, humidity, or atmospheric pressure – vane anemometers simply measure the air speed directly. Different size vanes are available for each step in the commissioning procedure. Remember, if you are using air measurements obtained with a vane to calculate cooling or heating capacity, air density will still have to be considered for accurate calculation involving the true mass flow rate across the heat exchanger or coil. A fan is not a constant mass flow machine. Therefore, mass flow changes as the density changes. The mass flow is directly proportional to density change, while the volume flow (CFM) remains constant. As air density decreases, mass flow decreases and the effective cooling or heating will diminish proportionately. Therefore, equivalent mass flow is needed for equivalent cooling and heating calculations

The mini-vane anemometer is the ideal tool to measuring airflow in a duct, across a heat exchanger or evaporator coil as required in the commissioning process. The mini vane allows for a full duct traverse with an automatic calculation of the CFM in the duct (as the duct dimensions and the free area are input into the instrument before the measurement is taken). If done carefully the measurement error will be less than 3%, and often less than 1% error. Changes in yaw and pitch of the probe head in the duct by as much as 10% will result in less than 1% error in the measurement making the mini-vane an ideal probe for field in-duct air measurement. Because of the larger probe size compared to a Pitot tube tip or hot wire, stray eddy currents will have little effect on the final measurement.

At the grilles/registers, a 4” diameter vane anemometer may be used to determine air velocity leaving at each terminal outlet. Again, no air density compensation is required, it is a simple one-hand operation, and most are easy to carry and operate. Another advantage is a more accurate average of true airflow over the sample area. The 4” vane does not respond to local stray eddy air currents created at grills that a hot wire probe or Pitot tube may. Many times 4-6 trucks can be equipped with a large vane anemometer for the equivalent cost of one of the more expensive options previously mentioned. For residential and light commercial technicians balancing of air velocity will be adequate due to the limited resources on hand and limited knowledge of original system design available to them in the field. Duct leakage should be determined using alternate methods as studies have shown most of the methods including capture hoods mentioned above are not accurate enough to measure duct system leakage. For residential applications, grille/register face velocity should be 400-600 FPM. Higher air velocities may be noisy and lower velocities may not provide proper spread and throw leading to problems with air stratification and comfort issues. The quantity of air delivered is a function of the blower performance, duct and branch size and finally the register performance. A branch can be delivering the correct CFM, but if the register selection is incorrect, and the throw and spread are not adequate, the air will not mix with the room leading to problems with space comfort.

So in a nutshell, go with the 416 and possibly the 417 if desired and get a good micro manometer. The testo 512 will work for a manometer, 0560 5126 it is reasonably priced

http://www.testo-international.com/online/abaxx-?$part=PORTAL.INT.ProductCategoryDesk&$event=show-from-menu&categoryid=10423729

[weber]

See, I knew Jim would be around sooner or later to answer your question.

[davidr]

I still have concerns over a vane that is that compact in size.

Larger vanes no issues as the blades can't be tweaked that easily.

[weber]

Here are some links to the site that I highly recommend.

http://www.trutechtools.com/cart/index.php?main_page=product_info&cPath=8&products_id=207

http://www.trutechtools.com/cart/index.php?main_page=product_info&cPath=2&products_id=43

[jim bergmann]

I have been using a vane in the classroom for over two years, *(Used by 40+ high school boys 20-30 times a day) 416, 417 both, never had it damaged yet. I have had the calibration verified twice in our labs, and it is still perfect. The mini-vane is very durable and had a two year warranty. Have you ever worried about your hot wire, it is a lot more subject to damage.

[davidr]

Have you ever worried about your hot wire, it is a lot more subject to damage.

Sure I do that is exactly why it gets recal every year and treated like fine china.

The minivane might just be the next best thing since sliced bread for airflow but I still see it as no reason to discredit proven technology.

The readings we take in the field are exactly that field readings and are going to have a varying degree of error whether we want to acknowledge that or not.

If anyone is using a hot-wire they absolutely need to be aware of the variables surrounding it's use.

You want a real winner Jim put dry bulb/wet bulb capability along with the minivane in one probe. :)

[weber]

You want a real winner Jim put dry bulb/wet bulb capability along with the minivane in one probe. :)

They have that, but its a little hard to get into the duct work.

I dont think anyone is discrediting a hotwire, just stating that there are alternatives that are more reliable, less sensitive, and less correction factors.

[jim bergmann]

They have that, but its a little hard to get into the duct work.

I dont think anyone is discrediting a hotwire, just stating that there are alternatives that are more reliable, less sensitive, and less correction factors.

David,
I am not bashing the hot wire, after all we sell them. Just saying that the vane is much more robust. Our hot wire is adjustable for air density, temperature pressure and RH compensated. Most are not. This leads to a lot of uncorrected airflow measurements Airflow can be as much as 10% off if left uncorrected.

We use the vane and wireless probes to calculate true mass flow rate and BTUH in the capacity calculation. With the 435 we can correct on the fly. Two probes required though, the vane and the RH/temp.

We do have a hot wire, rh and temp probe available, but not in the vane.

[weber]

David,
I am not bashing the hot wire, after all we sell them. Just saying that the vane is much more robust. Our hot wire is adjustable for air density, temperature pressure and RH compensated. Most are not. This leads to a lot of uncorrected airflow measurements Airflow can be as much as 10% off if left uncorrected.

We use the vane and wireless probes to calculate true mass flow rate and BTUH in the capacity calculation. With the 435 we can correct on the fly. Two probes required though, the vane and the RH/temp.

We do have a hot wire, rh and temp probe available, but not in the vane.

410-2 is a vane that also does DB WB :)

[davidr]

We do have a hot wire, rh and temp probe available, but not in the vane.

Is the vane with a temp/rh probe a possible option for the 435 in the future?
That would be a wonderful option to have available.

Thanks for the clarification and response Jim.

[mark beiser]

410-2 is a vane that also does DB WB :)

I'm pretty sure he means in a minivane.
You can't exactly do a duct traverse with a 410-2. ;)

[davidr]

I'm pretty sure he means in a minivane.



Lol.......Yep. :D

[weber]

I'm pretty sure he means in a minivane.
You can't exactly do a duct traverse with a 410-2. ;)

LOL, thats why I said it doesnt fit in the duct very well;)

[weber]

Is the vane with a temp/rh probe a possible option for the 435 in the future?
That would be a wonderful option to have available.

Thanks for the clarification and response Jim.

With the cost of these probes, I think I would perfer them to be seperate probes.


Right now I use my 435-4 not only for airflow but also just as a wireless meter that measures delta t and delta h. So I like having the probes seperate so I dont have to always have the minivane in the ductwork and traversing to have a reading.

I could only imagine the price of the minivane that also measures wb/db.

[jim bergmann]

I will forward your request/idea to Germany for consideration. Why not it makes sense. :D

[DesMech]

Thanks Jim, and everyone else for the response. Jim, I am curious, you said the mini vane is good for residential and light commercial, why not heavy commercial? Also, it appears the mini vane is not good for measuring face velocity of grilles and diffusers? This is one of the things I was hoping to use this tool for. This is why you also recommend the 417? By the way, I am still curious about the resolution of the 435-4's differential pressure measurements.

[jim bergmann]

The mini vane can be used for any duct up to about 25 inches in depth, then you run out of handle for the probe. When I think of large commercial, I am thinking of a duct system that I can walk in. So if the duct has a dimension that is less than 25". the mini vane Will work flawlessly.

For reference,
Hot wires are ideal for less than 0-5 m/s (0-984 FPM)
Vanes 5-40 m/s (984-7874)
Pitot Tubes 40-100 (7874-19685)

The Testo 416 is accurate from .6 to 40 ms (118-7874), the vane easily measures in the hot wire range, however the ranges listed above are the ideal. You can see that the ideal range is the common velocity range for most air distribution systems.

This will cover you for every application I can think of, and obviously the CFM is a calculation of FPM x Area in Ft2, so that is no an issue.


For face velocity the large vane is better because it less susceptible to the eddy currents created as air leaves the grills. We make a large and mini vane for the 435

Resolution for the 435 is 1 pascal or .01" H20, the micro manometer posted in an above post has the resolution you are looking for.

Probe type Differential pressure
Meas. Range 0 to +25 hPa
Accuracy ±0.02 hPa (0 to +2 hPa)
1% of mv (remaining range)
Resolution 0.01 hPa (= 0.004 inch of water [4 °C])

435 full specs
http://www.testo-international.com/online/abaxx-?$part=PORTAL.INT.Applications&$event=show-from-content&externalid=opencms:/Products/MeasurementParameters/velocity/Messgeraete/testo_435-4/Englisch.product

[davidr]

I will forward your request/idea to Germany for consideration. Why not it makes sense. :D

I've got a good sized list to give to Bill in Atlanta in September. :D

[vajranata]

I am new to the forum. I think my question is okay in this thread, as it is directly applicable.

Balancing residential airflow is new to me. I have decided to start balancing the systems I design/install despite the fact that local code doesn't care one bit.

My question is this:
I am installing a new system in a new house. I have installed dampers in every branch line. Is it necessary to mount all the grills and registers before balancing the system?

I am not sure if this question is a stupid one or not. My feeling is that if the airflow is balanced at each branch line takeoff, and the delivered volume is less than the rating on the register, then having the registers mounted may not have that big of an impact.

I could just conduct the experiment myself to answer the question, but I thought some among you may already have the answer. Many thanks.