HVAC air flow on intake vent

[Redright9]

Hello, anyone know of a simple, inexpensive gauge or meter that I can put in my house on the intake duct of my HVAC system to see what kind of suction/air flow is going into my system? My vent is located at the end of my hallway and actual system in my attic (which is a pain to get to) so I would like something that I can put on the vent.

Thanks.

 

[Deleted member 89374]

What you're looking for doesn't exactly exist, so describing your actual issue might help diagnose your problem.

I'm not an HVAC professional. However, due to financial constraints, I had to replace our entire HVAC system by myself, ductwork included, so I learned a thing or two.

 

[Redright9]

What you're looking for doesn't exactly exist, so describing your actual issue might help diagnose your problem.

I'm not an HVAC professional. However, due to financial constraints, I had to replace our entire HVAC system by myself, ductwork included, so I learned a thing or two.

I dont exactly have a problem, but more overthinking filters I am using. I just want to see what the air flow difference is between filters and new versus dirty. I feel I get conflicting information and being told to change them too often. I dont mind changing them, but seems like the time interval is getting shorter and shorter.

 

[Deleted member 89374]

I dont exactly have a problem, but more overthinking filters I am using. I just want to see what the air flow difference is between filters and new versus dirty. I feel I get conflicting information and being told to change them too often. I dont mind changing them, but seems like the time interval is getting shorter and shorter.

There is a way to check the differential pressure between input and output, but it requires drilling holes and an expensive tool to measure the pressures. I never did it on my Goodman furnace. I installed a gas furnace and a heat pump. The heat pump is for mild heating and as a backup. My home is so poorly insulated that I need to run the furnace almost full time in winter. It was built in the 80s.

Even funnier, because I didn't have room for two air filter boxes, I'm only using one, along with a MERV 11 filter. I kept an eye on the filter in the beginning and concluded that a six months schedule is good enough to change the filters. I don't know what kind of filtration system you have and how many filters, but the more significant the filter, the less you have to change it. There are many other factors, of course.

Of course, you could call an HVAC company to come out and do the measurements for you, but they will probably charge you an arm and a leg.

So let me ask you, what kind of HVAC system is it, and what kind of filtration system (filter model) does it use? Asking about square footage, ducts, windows, etc. would be useless, as I haven't done load calculations since I installed the system.

 

[KJSmith]

Change them when they are dirty.
A dirty filter is an efficient filter.
Changing to often does more harm than good.

https://www.amazon.com/AOPUTTRIVER-Digital-Anemometer-Handheld-Temperature/dp/B07NRSYNW2/ref=asc_df_B07NRSYNW2?tag=bingshoppinga-20&linkCode=df0&hvadid=80264429310837&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583863983428558&psc=1

 

[Dinoburner]

If there is only one return on the system then thats a problem. If there are others then duct statics are measured across the furnace at supply and return. Actually there are several posts on BITOG that could be useful.

 

[jhellwig]

There is a way to check the differential pressure between input and output, but it requires drilling holes and an expensive tool to measure the pressures.

Two holes, clear hose and a ruler. Only limit on accuracy is the ruler.

 

[JC1]

You can buy a anemometer to measure the output at the ducts supplying AC to the different rooms.

Search Amazon for different options.

Amazon.com : anemometers

I don't think there is equipment available for cheap that can do what you want. I guess you cannot easily seal your ductwork? I had Aeroseal done to my house in 2020 and just finished a Garage reno where I improved some of the airflow to the bedroom above the garage as well as the insulation.

Are you trying to fix a problem with your HVAC system?

 

[brianl703]

Measure the current consumption of the fan motor. If it's a PSC motor the current consumption will go down as the filter gets more clogged.

If it's a constant airflow ECM motor, the current consumption will go up as the filter gets more clogged.

If it's a constant torque ECM motor, I believe these act the same way as PSC motors. Never had one so I don't know.

You could get a digital panel mount ammeter and wire it in permanently.

 

[Redright9]

I have a small home at 1600sqft. I live in the desert and the filter is a 20x20x1. It is a Goodman system. The system (other than the AC condenser outside) are in the attic. It is an "all in one" AC and furnace unit. All ducting is up in my attic with vents in the ceiling.

 

[KJSmith]

If you want to measure the pressure drop across the filter buy a simple manometer.
You should be able to make this one work.

Amazon.com: XYF Air Easy Read Manometer | U-Tube Air Pressure Indicator (Blue) : Industrial & Scientific

Buy XYF Air Easy Read Manometer | U-Tube Air Pressure Indicator (Blue): Manometers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[Nick1994]

Use a piece of paper and see if it sucks against it. Then tape a 2nd piece to that one and see if it holds the weight. See how heavy it'll hold. Then try the new filter and go from there.

 

[CDX825]

Change them when they are dirty.
A dirty filter is an efficient filter.
Changing to often does more harm than good.

While that may be true for engine air filters, You don't want to let your furnace filter get really dirty. Lack of airflow from a dirty filter can cause lot of issues with a hvac system.

 

[Yah-Tah-Hey]

I dont exactly have a problem, but more overthinking filters I am using. I just want to see what the air flow difference is between filters and new versus dirty. I feel I get conflicting information and being told to change them too often. I dont mind changing them, but seems like the time interval is getting shorter and shorter.

Use the lowest cost pleated filter you can find. Spending the $$ on filter hype won't get you that much more. Advice from my HVAC guy.

 

[KJSmith]

While that may be true for engine air filters, You don't want to let your furnace filter get really dirty. Lack of airflow from a dirty filter can cause lot of issues with a hvac system.

If its restricted so much its causing an issue, its pat time to change it.
Same with the air filter in your vehicle.

That should be common sense.