How can I...

Went on a no cool yesterday on a new install. Homeowner said system worked for about a week and then stopped cooling. He said that there was a noticeable difference in the amount of air coming from the supply's, said that it is a lot less. Took amp and volt draw on blower motor, had 5.4 amps and 120V. System is 3 tons at 1200cfm. Went in attic and looked for kinked ducts, etc, none found.
Made sure speed taps were on correct spades. Took cover off of A coil and looked for obstructions, none found. Touched side of motor and hello howdy was it hot. I know that is not right so I am going to replace the motor on Monday. How can you tell if the motor is putting out the correct CFM at the air handler?
One oddball thing I did find is that the return static pressure is 1.0. The return duct is sized properly but when I went in the attic I could hear the air rushing through it about two feet after the filter grill. The noise is in one spot only, not the entire duct. Before the install the duct was doing this and it was routed so that it was pinched off in two places. Had the installers re-route it and it's still making this noise. Also, the static pressure on it was 1.0 before they re-routed it. I thought it was being caused by the duct being pinched off but I guess not. If I run the system with the blower door off the static drops to 2.5, however, the airflow in the house stays the same.
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Did some of the duct liner come loose?? might be blocking the airflow.

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wrote:

I thought about that but I did not have anything on the truck to seal the duct back up if I took it off. You would think that the installers would have noticed this when they re-routed it. When I go back monday I am bringing some panduits and mastic with me.
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wrote:

I meant to say .25
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I was hoping so...
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On Sat, 22 Jul 2006 07:38:10 -0700, Al Moran snipped-for-privacy@hotmail.com wrote:

<snip>
1.0"w.c.? No, it's not.
(Amazon.com product link shortened)(3155
-zero
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wrote:

Um, yes it is.
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wrote:

My Bad! ....Your right!
LOL! Looks like you are quite comfortable with your destiny in HVAC.
Have at it.
-zero
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wrote:

Put a new t'stat on. One with a digital CFM readout.
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wrote:

Who installed it? Also, system make and model, and motor part number especially, would be useful to know here.

Rated, not measured on site, I presume, from reading below. Therefore, irrelevant in this context.

Why would they move by themselves after one week?

Measure it. :-)
Use an anemometer and multiply face velocity by duct pening face area, to get flow rate. Don't forget to convert square inches to square feet!
I'm surprised you asked that question, though.
[cut]

Check current draw against motor specs.
Measure blower speed with tachometer. Or count fins on blower wheel, use variable strobe/timing light, adjusr for stationary pattern, record flashes per second and do the math.
If the blower was runnung backwards, or was set to the wrong speed, either someone tampered with the wiring, or it wouldn't have worked for the first week.
Hot motor case + low speed = fried motor (factory defect). It's under warranty. Just replace the motor.
You ARE factory authorized, no? :-)
Also, if it's a homeowner self-install, the warranty may be void anyway. ;`(
These questions are getting ridiculous. No wonder so many flame wars ensue in this NG.
In my opinion, you don't know what you're doing, and you are "moonlighting". If so, that's illegal (and dangerous).
--
-john
wide-open at throttle dot info
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On Sun, 23 Jul 2006 13:23:12 -0700, ~^Johnny^~

So I thought this group was for professionals, not homeowners to ask hvac questions? Not moonlighting, not doing side jobs, and yes, in a lot of instances I do not have a fucking clue. I will have been doing this trade for a whopping two years in September. What skill level did you have at that point? Most of you in here have a skill level that I can only hope to attain one day, as in you've forgotten more about hvac than I'll probably ever learn. If I ask for help in here it's because I want to learn to do this stuff right. So in that vain, you can either help or not, but please, no need to be a smartass. Fwiw, if I said the name of the company I work for, everyone in here would know it instantly. They thought enough of my skill level that they promoted me to a senior tech this year. I must say that when they did, I'm thinking to myself, you've got to be fucking kidding. I have a long way to go before my skills are at that level. But hey, I took the extra money and am stepping up to the plate. I am pretty damn good for only doing this for two years now though, just not that damn good.
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Al Moran posted for all of us... I don't top post - see either inline or at bottom.

Sears?
--
Tekkie

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wrote:

Not even.
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Hang in there, Al. Don't be afraid to ask for help in here. Refresh the post for me. Is this the one you're trying to determine the air flow for? Run the furnace for 10 minutes on cooling speed. Make sure the humidifier bypass is closed, if it has one. Measure the return air temp, then the plenum temp a few feet from the top of the plenum so as not to register any radiant heat. This will give you you're delta T. Determine the output from the rateing plate (NOT the input), and multiply the delta T by 1.08, then divide the output by that number. That will give you your CFM. If it's low, remove the blower door and measure CFM again. If it increases sunstantially, the restriction is in the return air side. Hope this helps.
--
Respectfully, Bob

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wrote:

Good gravy! Good thing I DON'T know the name of the company. Probably Sears. ;->
--
-john
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