Airflow

[jmeadows]

In your guys opinion what is the most practical way to check airflow on a heating and air system while in the field ? I have been a service tech for 4 years and have never seen another tech measure cfm or static pressure . The way that all of the other techs that trained me do it is by putting there hand over a vent to see if air is coming out . To me that doesn’t really tell you much . Also measuring temp split if its high poor airflow.

[Adlerberts-Protege]

In your guys opinion what is the most practical way to check airflow on a heating and air system while in the field ? I have been a service tech for 4 years and have never seen another tech measure cfm or static pressure . The way that all of the other techs that trained me do it is by putting there hand over a vent to see if air is coming out . To me that doesn’t really tell you much . Also measuring temp split if its high poor airflow.

Static pressure test and cross-referencing equipment fan-curve. Then TAB room x room with flowhood.

[rundawg]

In your guys opinion what is the most practical way to check airflow on a heating and air system while in the field ? I have been a service tech for 4 years and have never seen another tech measure cfm or static pressure . The way that all of the other techs that trained me do it is by putting there hand over a vent to see if air is coming out .

Are you familiar with the procedure of using static probes to test for external static pressure, then using the manufactures "Blower Performance Charts" to determine approximate system airflow?

If not, put an email in your profile, or send me an email (address is in my profile), and I will get some info off to you.

NOTE: You need to apply for "PRO" membership, where we go into more detail on this subject. I can also then supply you with manuals that have the blower performance charts of the systems you are working on.

[pecmsg]

Eventually you “May” get to the point that you will “Feel” the air flow and decide if a static or TESP test is needed.
There will be several other points needed along with the “Feel” method!

[jmeadows]

Thanks guys for all of the information . I have heard of static pressure and have done research on it but I have read that it is only good when you have equipment with oem parts. If you have a rescue motor then the readings would not be valid with the chart . A lot of the equipment I work on is older and doesn’t have oem motors. When I apply for pro membership it will take a few weals to get approved correct . I’m just asking because I have a unit that is driving me crazy and I have been told to add refrigerant but my superheat is high and my subcooling is normal so I don’t think that it the correct measure .

[rundawg]

When I apply for pro membership it will take a few weals to get approved correct.

The time is variable, base on the information you provide, and the back log of applications the committee has to review.

Check your email. I sent you some info.

[pecmsg]

Thanks guys for all of the information . I have heard of static pressure and have done research on it but I have read that it is only good when you have equipment with oem parts. If you have a rescue motor then the readings would not be valid with the chart . A lot of the equipment I work on is older and doesn’t have oem motors. When I apply for pro membership it will take a few weals to get approved correct . I’m just asking because I have a unit that is driving me crazy and I have been told to add refrigerant but my superheat is high and my subcooling is normal so I don’t think that it the correct measure .

Don’t see what’s the difference is. Minor if any.
Remember ALL#’s at plus or minus

[jmeadows]

Don’t see what’s the difference is. Minor if any.
Remember ALL#’s at plus or minus

What do you mean ALL#”s ?

[jmeadows]

Run dawg thank you for the information . I will now research how to troubleshoot with static pressure . Have you used this table with good results on a air handlers with pax motors ?

[pecmsg]

What do you mean ALL#”s ?

Static pressure
TESP
Amp draw
Suction pressure

[jmeadows]

Static pressure
TESP
Amp draw
Suction pressure

Ok thanks for the help I’m going to apply for pro membership. Because the questions that I now have are very specific and I don’t want to break any rules ,. Do you mind if I write you guys once that’s complete ?


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[pecmsg]

Ok thanks for the help I’m going to apply for pro membership. Because the questions that I now have are very specific and I don’t want to break any rules ,. Do you mind if I write you guys once that’s complete ?


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Ask you questions

[jmeadows]

Ask you questions

Say hypothetically you went to a unit and it was a heat pump . Say your return temp was 70 your low side pressure was 65 sat temp 37 and you had 0 degrees of superheat . However your subcooling was normal at 10 degrees. Would you measure static pressure to verify airflow because I think that the txt is having an issue but it could also be airflow. I checked the blower wheel as well as the evap coil for cleanliness .


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[rundawg]

Run dawg thank you for the information . I will now research how to troubleshoot with static pressure . Have you used this table with good results on a air handlers with pax motors ?

Static pressure readings are not exact. There are many variable that can cause minor differences in your readings - cleanliness of the blower wheel, cleanliness of the evaporator coil, turbulence in the area where the static probe is inserted, and the basic technician and meter errors.

These errors may equal 0.10” wc, but will still give you a pretty good idea of the airflow the system is operating under. After market motors will fall within this margin of error.

I have always felt, it is more of trying to nail down whether you have an acceptable static pressure (0.50” wc to 0.80”wc), or a static pressure that is out of the ball park (0.80” wc and above).

I always want to know the approx. airflow before I start trying to charge a system, or determining if I have sufficient airflow in heating, based on the type of equipment (Natural Draft, Induced Draft, or Condensing units).

Having TESP numbers, will also help you decide if you have return, or supply side duct issues.

[Adlerberts-Protege]

Ya, static pressure test isnt the final picture but it'll get you close.

Now, taking a garbage bag that is X cubic feet and seeing how long it takes to fill up? That will tell you all you need to know about airflow .

[jmeadows]

Do you guys put the unit into cooling or just turn the t-stat cool . Because I know that if the coil is wet there would be a difference .

[Adlerberts-Protege]

Do you guys put the unit into cooling or just turn the t-stat cool . Because I know that if the coil is wet there would be a difference .

The coil submittal sheet will have wet and dry coil statics.

[rundawg]

Do you guys put the unit into cooling or just turn the t-stat cool . Because I know that if the coil is wet there would be a difference .

The "Notes" in the blower chart will usually state if the data is for a "Wet" or "Dry" coil.

It may also give you the "correction factor" for a "Wet" coil, if the data is for a "Dry" coil.

[Adlerberts-Protege]

The "Notes" in the blower chart will usually state if the data is for a "Wet" or "Dry" coil.

It may also give you the "correction factor" for a "Wet" coil, if the data is for a "Dry" coil.

Still nice to know the actual pressure drops so he can rule out a dirty coil .

[jmeadows]

Ok guys great I will have to get a manometer . Any suggestions?