[Kymike]

I'm using an anemometer to measure cfm. How do I I find out how much air flow I need and how much needs to be put out?

 

[schr8er]

Are you asking how to figure it in general? Or are you asking how to get your specific anemometer to tell you the cfm?

I only ask because it sounds like you've never used an anemometer.

 

[Kymike]

I have never used one. I'm wanting to know how to figure out if I'm getting good airflow.

 

[schr8er]

I saw from your post history that you're using a Fieldpiece with an anemometer attachment. It turns out that attachment has a useful how-to page about how to roughly figure CFM:

http://www.fieldpiece.com/accessory-heads/aav3

You're going to need more data to be able to figure it, with or without the equipment. Go over that page, and I'll help you out with the calculations if you need it.

 

[Kymike]

How do I figure how much airflow I need at return and supply to make sure the air flow is good. I do apartment maintenance and some residents complain that the upstairs never gets cool. I'm going to check the supply but not sure what I would need as far as cfm. I know how to figure cfm, free area of the vent x air velocity = cfm

 

[schr8er]

What made you focus on cfm for that problem? There are about a billion other things to check before even considering how much air you're moving.

 

[jimj]

What made you focus on cfm for that problem? There are about a billion other things to check before even considering how much air you're moving.

Really?

 

[schr8er]

Well, no, obviously. Just that there are other factors to consider before worrying about CFM in an apartment.

 

[Kymike]

Inside and outside coils clean. Pressures are right and superheat is correct. I've noticed that the squirrel cages are very dirty. Figured airflow could be a problem. Now that I have anemometer I'm going to clean the squirrel cage and check before and after. This was just something that I wanted to check out. I've been keeping a clean blower with me and changing them out on all my ac calls. So far no one has called and said it isn't any better. What else could be the problem? I'm still new to the trade.

 

[jimj]

Inside and outside coils clean. Pressures are right and superheat is correct. I've noticed that the squirrel cages are very dirty. Figured airflow could be a problem. Now that I have anemometer I'm going to clean the squirrel cage and check before and after. This was just something that I wanted to check out. I've been keeping a clean blower with me and changing them out on all my ac calls. So far no one has called and said it isn't any better. What else could be the problem? I'm still new to the trade.

Hard to know if pressures are rite if ya don't know if air flows are rite!

 

[schr8er]

What size HVAC units are we talking about here? I had a similar problem with some new townhouses not long ago, where the downstairs would cool off just fine, while the upstairs roasted. It turned out the units were undersized for the cooling load, because contractors around here are cheap-asses.

 

[Kymike]

I know if the airflow is completely obstructed that you can't get the correct pressures. I was taught if you feel it coming out its good. With coils being clean. I already check more than what they want me to.

 

[Kymike]

1 1/2 ton for about 1000sq ft. Trane units inside and out.

 

[Kymike]

I'm sticking with this job for about another year then try and get into the hvac trade. They have taught me the basics. And I've learned a lot on my own and in here. Maybe someone would give me a chance.

 

[schr8er]

The usual rule-of-thumb is 400 square feet per 1 ton of cooling, but there are other factors. For your region and general temps it's about 1.5 tons for 600-1000 sqft. If the buildings are underinsulated, or have a sh*t-ton of windows, this would be insufficient to cool the space, especially for upstairs apartments.

It could very well be an airflow problem, damaged ductwork or something, if it's happening in random units. Out here in central TX, a big cause of that are raccoons and squirrels in the walls and attic.

 

[Kymike]

Not sure about the insulation but there aren't a bunch of windows.