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Old 07-02-2012, 03:00 PM   #31
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70 degree Supply Air


Oh and for other loads in the house... most we ever have running would be computer in my room, TV in living room and maybe the xbox. Rule of the house is that neither my roommate nor myself can use the dryer or the oven during the heat of the day. As far as lights... we have CFLs and have 1 23 watt bulb that stays on in our living room most of the time. I have darkening blinds too.

As far as energy saving when it comes to power I have it all pretty much down except this whole AC issue. I guess my next step is to re-insulate the attic with spray foam and cellulose. That is waiting till winter though because I AM NOT staying up there in this heat. heat + fiberglass = death haha

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Old 07-02-2012, 05:51 PM   #32
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70 degree Supply Air


Ryan when you recheck those temps use the thermometer as is on supply and return then check again with a damp sock over it. A piece of cotton shoe string works in a pinch. With dry bulb and wet bulb readings on both supply and return we can tell you what the capacity is. Get outdoor dry bulb temp at the same time.
Six inches of insulation is mighty weak. Throw another layer of R20ish batts up there the next cool morning that you have time. With the room mates help you'll be out of the attic before it gets too hot. Took mine from R20ish to R 48ish and it made a lot of difference.
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Old 07-02-2012, 06:26 PM   #33
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70 degree Supply Air


Thanks Marty. If i threw another layer of R20 batts up there you literally wouldnt't be able to move in my attic. That's the crappy part. It almost makes it so that I have to put an inch or 2 of spray foam down first to get a nice R14 base then throw them on top.

Ill get those temps as soon as I get back. Thanks for the help
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Old 07-02-2012, 06:40 PM   #34
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70 degree Supply Air


Ryan, we keep a pillar fan in our living room, so that we can move some air towards the seating area. Our house is between 72-73 all of the time, but with our Plasma on, it gets warm. As for the attic, 125 is too hot. Ours gets maybe at the highest that I have seen, 110 for just about a half hour at peak, then starts cooling down by 6pm. And we even have dark shingles on our roof, but have it well ventilated, and sealed from the conditioned space.
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Old 07-09-2012, 06:00 PM   #35
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70 degree Supply Air


Ok so AC guy came out and hooked up the gauges and my pressure was too high apparently. Pushing 80 psi. Looked at the service manual with the outside unit and pressure supposed to be at 70 which is what it is. Other pressure was 200 which he said was good as well.


Of course today is a much cooler day.
Air coming out the vents before he got here 63.5.
Air coming out of the vents when he left 62.5.
Air temp in the plenum at air handler 58.5
Air temp going into air handler 74
Air temp in the attic 95.

At night I have had the temp at the vents be 59 degrees but during the day it goes up to 70 coming out of the vents.

I'm going to get a wireless thermometer and put it inside the plenum to see if that temp goes up as well on a hot day. Bad part is... it's not supposed to be all that hot for the rest of the week.

He also mentioned that he expansion valve was making a weird sound that he had never heard before but that since my AC appeared to be working correctly he did not want to tear it apart.
Could that expansion valve cause any issues?
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Old 07-09-2012, 06:21 PM   #36
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70 degree Supply Air


Yes it could. And he should have checked charge by SC on a TXV.
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Old 07-09-2012, 08:51 PM   #37
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70 degree Supply Air


Air temp in the plenum at air handler
Air temp going into air handler

The difference temperature between this two points should be no less the 15. Call a Pro to check SH or SC

If the temperature air coming out of the vents are way high of the air temp in the plenum at air handler you should check you ducts, attic etc....It's no a AC unit issue
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Old 07-09-2012, 09:27 PM   #38
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70 degree Supply Air


Two ton moves 24,000 BTU's with 20-25% of that being moisture removal. Of that 18,000 BTU left for temp drop you're losing 5184 in the supply duct alone
(4 degree temp diff between plenum and vent x 1200cfm x 1.08). Figure the return is picking up that much or more heat means the AC is only removing 7600 btu's of heat an hour from the house and the rest is lost to the duct work.
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Old 07-09-2012, 09:42 PM   #39
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Two ton moves 24,000 BTU's with 20-25% of that being moisture removal. Of that 18,000 BTU left for temp drop you're losing 5184 in the supply duct alone
(4 degree temp diff between plenum and vent x 1200cfm x 1.08). Figure the return is picking up that much or more heat means the AC is only removing 7600 btu's of heat an hour from the house and the rest is lost to the duct work.

The return would pick up, as the temp difference to the attic is less.
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Old 07-09-2012, 10:12 PM   #40
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70 degree Supply Air


Thanks for the input but all i have to say is this is wack! Why the heck do I have to tell a tech what he needs to do? Shouldn't he figure this crap out!? I mean that is his job lol. If someone brings me a PC and says it's slow I don't expect them to tell me whyy.

Marty... it's just a 4 degree change because it was cloudy outside. The other day it was 70 coming out of the vent but then again maybe the temp at the air handler was different too. I have a hard time believing the temp is increasing that much in that 2 foot return run.

Guess i have to do some more recording.
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Old 07-10-2012, 04:33 AM   #41
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70 degree Supply Air


Quote:
Why the heck do I have to tell a tech what he needs to do? Shouldn't he figure this crap out!?
Yes, he should figure this out. A true HVAC technician will understand that you cannot properly check the charge on a TXV system using pressures alone. You must use SubCooling to do this. In fact, that's pretty much HVAC 101.

Note that some units have a chart to do this, but if the tech didn't check the temp of the small copper line (the liquid line) at the outdoor unit, then there's no way he could check SC.

Just like it can be hard to find a good computer guy, it can be equally as difficult to find a good HVAC technician. There are many "gauge monkeys" out there who have no clue how to actually troubleshoot refrigerant system issues. If you're not dealing with established, reputable companies, and are instead shopping around based solely on price, then you'll have a very difficult time finding a true technician.

If it were me, I'd just ask the guy if they will check Subcooling and Superheat. Do this on the phone, BEFORE you setup the service call. Tell them that you simply won't pay for the service if they don't check those things, and be firm about it. Many will just hang up on you - they don't really like dealing with informed consumers - but eventually you'll find one who will do their job correctly.
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Old 07-10-2012, 06:27 AM   #42
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70 degree Supply Air


There was a chart that I found on the service manual for the unit when he was working on it. It had the pressure curve on it based on the outdoor temp and indoor temp and the pressures he had were right on the money.

He didn't check the temp directly just grabbed the small line to make sure it was warm. he does work for the government so i guess thats "good enough for government work" haha.
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Old 07-10-2012, 07:12 AM   #43
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70 degree Supply Air


Sounds to me like you've still not hired an actual HVAC tech to come out and look at your system (or if you did, you contacted the wrong one, based on the wrong factors). If you continue to work with the "magnetic sign brigade", or go with the cheapest guy in town, then you'll keep getting the same results. Those are gas-n-go guys. They just want to drop a few lbs of R22 in the thing and call it a day. They don't bother to actually troubleshoot the system, since they have no reason to do so (and generally don't have the experience, tools or expertise to do so).

You're an IT guy - do your research and find a company in your area with a good reputation for technical expertise, and contact them. They'll generally be expensive, and will probably have a bit of a backlog. They may not tell you what you want to hear (unit might be over/undersized, compressor might be shot, ductwork wrong, etc etc) but at least you'd know.
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Old 07-10-2012, 11:37 AM   #44
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70 degree Supply Air


I don't want to hire an actual HVAC tech...hence being a member of a DIY forum
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Old 07-10-2012, 12:05 PM   #45
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70 degree Supply Air


Quote:
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I don't want to hire an actual HVAC tech...hence being a member of a DIY forum
Things like HVAC are not meant to be DIY. Especially when it comes to check line charges, etc.. You just have to know where to draw the line between what is a DIY job, and what is not.

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