How to adjust dampers

teddycMay 16, 2009

I am in the process of adjusting the dampers in my 1250sqft, 50 years old, 1 story home. They have been all open since I moved in a year and a half ago. I plan on getting some thermometers, calibrating them to the thermostat and checking each rooms temperature. I figured I would start with AC because heat is less demanding on airflow etc. If anyone has a better way to do this, please let me know.

I have a few questions on the proper way to do this:

A friend mentioned when he did his house he closed the doors for the bedrooms with returns. Do I want to do this? Or should I leave the doors open?

The main bathroom is 8Â X 4Â and has its duct coming right of the plenium. I would assume this one will need to be adjusted.

The master bathroom is about 4Â X 4Â. I think this one will need to be adjusted too.

Thanks

Teddy

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maryland_irisman

You should be using an air flow meter.

    Bookmark   May 16, 2009 at 7:52PM
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zl700

An airflow instrument would be good of course, and the best way if you knew the CFM required for each outlet based on a detailed heat loss/heat gain.

Comfort balancing is often a term used for simple balancing of areas to equalize temps as best as possible.

Starting with all dampers and diffusers open, if cooling start closing down the areas that are cooler, or if heating the areas that are warmer. Do this a little at a time (days) to achieve the comfort in the different areas that you wish.

Of course you cannot restrict airflow too much otherwise you will cause havoc on your system and create inefficiency.

    Bookmark   May 17, 2009 at 9:59PM
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teddyc

Thanks for your help, zl700. I realize an instrument would be ideal, along with a manual J calc.
Just curious, if I partially close the dampers in the small bathrooms, is it a correct assumption that the air that would have been going to the bathrooms will go to another room?

Also, when I do my temperature tests in the bedrooms should I have the doors closed or open?

Teddy

    Bookmark   May 18, 2009 at 8:48AM
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zl700

"Just curious, if I partially close the dampers in the small bathrooms, is it a correct assumption that the air that would have been going to the bathrooms will go to another room?"

Yes to a point. Total minimum CFM must be maintained though for proper performance, safety and efficiency of the system when shutting dampers. Not knowing your system, I'm not aware of how much capacity you have to deliver the air elsewhere.

"Also, when I do my temperature tests in the bedrooms should I have the doors closed or open?"

You would want to do it in the situation that is most often and when comfort is most desired, open or closed. Again, I'm not sure if you have proper returns, jumper grills or could benefit from trimming bottom of doors.

    Bookmark   May 18, 2009 at 11:27AM
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teddyc

Thanks for your help. I currently have returns in every room except the bathrooms and kitchen. As far as having them sized right, that I am not sure. I do not plan on partially closing to many dampers. Thanks

Teddy

    Bookmark   May 22, 2009 at 10:59AM
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