Balancing my heating system


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Old 12-11-16, 02:38 PM
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Balancing my heating system

I bought a house 4 years ago. The 1st floor is 1700 sf; mainly the kitchen, family room, dining room, master bedroom and master bath. The upstairs is 800 sf and is three bedrooms and 2 bathrooms. The basement is about the same as the 1st floor.

There are 4 heating runs, one for the living room, master bedroom and master bath. One for the living room and kitchen. One for the upstairs, and one for the basement.

I shut off the basement ducts because the basement was too cold the first summer. It left it too cold in the winter, but that's what jackets are for.

The master bedroom and bath were too cold and too hot in the summer. I put and electric heater in the bathroom and that made it livable. Finally I decided I can't go on like this, and decided to call a heating contractor in to see if they could do anything to improve it.

But first I thought I would try balancing it. Yesterday I opened up 2 ducts in the basement, and closed all the ducts going to the first floor except the ones going the master bedroom and bath. Today it is 25 out, and the whole house is 72.

Did I do the right thing, or will shutting all the vents to the 1st floor come back and bit me somehow.
Should I get a pro in, or live with it a while and see how it goes.

A related question... I was always told that you leave the fan on auto with heat, but continuous with A/C. I initially tried leaving the fan on with the heat, thinking it would even the temperatures out, but apparently the humidifier it tied to the fan so it also ran continuously. Advice?
 
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Old 12-11-16, 06:33 PM
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Leaving the fan on On in cool mode can grow mold in your ductwork.
I recommend Auto for Cool mode.

Shutting off grills entirely can grow mold around the grill in cool mode.
I recommend leaving at least a 20% opening at the grills that you want to damper down.

I would shut and seal any vents to an unfinished basement but except for River Oaks, we don't have many basements this far south.
 
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Old 12-11-16, 07:07 PM
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Just going by feel, if I shut off a duct, it reduces the air flow to about 25% of what it was open. Is that enough to prevent mold?

To get 72 everywhere, I have to close 9 of the 20 vents. But as I say, there is still airflow when they are closed. Is that okay for the system?

Right now I am just concerned about heating. I will revisit the problem when it warms up.
 
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Old 12-11-16, 07:34 PM
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Probably be okay but the temperature difference across the unit should be measured.

Furnaces have a minimum and maximum heat rise. ( I see 35 to 65 degrees Fahrenheit on many furnaces) If you exceed the maximum heat rise it can shorten the life of the furnace or trip limit switches.

With the number of supply air registers that you have this may not be an issue.
 
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Old 12-12-16, 07:12 AM
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You had me worried about my solution.
I called the guy who installed and maintains the system and asked him if it was okay to close down the ducts; I didn't want to damage the heat exchanger. He said they leak enough that it won't do any harm. I asked if I should have him come out and look at it. He didn't think that was necessary.

Assuming the same balancing works for the A/C, is it safe for the A/C also?
 
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Old 12-12-16, 09:06 PM
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A $10 digital meat thermometer from Walmart is a small investment to see the delta tee in heat and cool mode.
 
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Old 12-13-16, 07:25 AM
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I watched a bunch of video and the temperature rise thing; seems easy enough. You test the air temperature in the air going out and aircoming in.
Below is a photograph of my furnace, a Trane XR90 TUX080C9423D.
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Is drilling a hole at the purple tape right?
Do i have to drill a hole in the return, or can I just assume it is the same temperature as the air in the rooms it is returning from?
 
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Old 12-13-16, 11:06 AM
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I try to get it 12" after the coil. That spot is OK. The return air temperature will usually be a little different at the furnace. You may be able to insert the thermometer where the stat wire enters the furnace at the blower section to avoid drilling a second hole.

The rated heat rise is listed on the furnace nomenclature (tag). It is usually in the burner section.
 
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Old 12-13-16, 11:46 AM
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I found a natural hole where a duct is attached to the main body. Terrible picture, but you can see the silhouette of the dial just below the round duct.
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I turned the temperature down to 68 degrees; it took 3 hours to drop 3 degrees at 34 outside. I then turned it back to 72.
I measured a output temperature of 125. (I tested the thermometer against 3 others in hot water, so i think it is reasonable accurate) There are no convenient holes for the return, but assuming it it pretty much has to be 70-75, that gives delta of 50 to 55. The manual says it is good for 35-65.
So it ought to be good?

It takes an hour to back up 3 degrees. That seems pretty slow; what do you think?

When looking for someplace to get the return temp, I noticed the humidifier. It takes hot air, runs it through the humidifier and into the return. Presumably it causes the return air to be warmer and reduces efficiency. Where would I measure the return air? Way before the humidifier, or after it? If after, my delta T would be rather lower wouldn't it?

I moved the setting on the humidifier to summer, and the temperature on the out air went down 5 degrees to 120. Is that what you would expect?

I sincerely appreciate your help on this!
 
 

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