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Help with A/C questions

Discussion in 'The OT' started by fluffybear, Jul 15, 2012.

  1. Rich

    Rich DBSTalk Club DBSTalk Club

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    In an ideal world that's how it's calculated. Not in the real world. Right now, when Fluffy is having his problems we're in the middle of a miserable heat wave. The readings I asked for are the same for him as they are in my home.

    Suppose you buy a 35 year old house, how are you going to know what rating the insulation is? I know how, they guess.

    Rich
     
  2. trh

    trh This Space for Sale

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    By volume? Maybe when homes didn't have insulation in the walls or attics the estimate was based on cubic feet and with a little tweak based on 'experience,' but not since the adoption of energy codes. You are required by code to calculate the load based on how the house was (or is going to be) constructed.

    There are tables for older houses and the insulation in use at that time. 35 years ago? Depending on your location, possibly no insulation. In FL in 1979 the standard house had no wall insulation and R17 in the ceilings. Now walls are at least R11 and ceilings are a minimum of R30. But yes, the tables are a guess. But if I were doing an energy audit on a house, I'd pull out some electrical outlets/wall switches and inspect behind those, plus get up in the attic to look at any insulation in the attic and exterior walls. I'd also use a thermal camera to check to see how effective the thermal barrier is.

    EDIT: Blog discussing system sizing Green Building Advisor
     
  3. fluffybear

    fluffybear Hall Of Fame DBSTalk Club

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    Right now it is 73.3 inside the house and the air coming out of vents is 52.6

    These were taken using a digital kitchen thermometer and not a wet bulb.

    When the house was built, I suspect it had large enough unit but our adding on last summer is what caused the original unit to no longer be sufficient.
    We have vaulted ceilings in part of the house but for the most part, the ceilings are standard height.
     
  4. Rich

    Rich DBSTalk Club DBSTalk Club

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    So, how did Fluffy end up with a 3 ton unit and I ended up with a larger one? Using the Internet as a resource, as you seem to do, is not the same as real life, hands on experience. Have you ever worked on air conditioning systems?

    Rich
     
  5. Rich

    Rich DBSTalk Club DBSTalk Club

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    You're kidding, right? Don't forget, I'm an electrician and doing that won't show you diddly. Pull out a receptacle or a switch and you'll get a great view of an empty box. What's that gonna tell you?

    I've participated in energy audits using thermal cameras and we saw what we expected to see.

    Rich
     
  6. trh

    trh This Space for Sale

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    His AC unit could be smaller based on the construction of his house (insulation, high performance Low-E windows), orientation, surroundings (trees or buildings providing shade) and a whole other list of possibilities. Your unit could also be oversized, which is very typical.

    No, I've never worked on an AC unit. But real-life experience? I'm a nationally certified RESNET Home Energy Rater and a Class 1 Home Energy Rater for the state of FL. I've rated close to 1,000 houses in the SE (TN, GA, AL, NC, SC and FL) in the last 19 months. In all those houses, I did the Manual J's which determined the proper size of the AC for that specific house.

    And my whole point on this has been you can't accurately determine the AC size based on volume. Too many other variables. But the OP did the right thing -- he had GA Power come in a do an audit.
     
  7. Rich

    Rich DBSTalk Club DBSTalk Club

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    I use a digital thermometer too. They seem to be more accurate. How far away from the evaporator unit was the register you checked? The closer the register is to the evap unit, the lower the reading should be. Close to the evap unit you should read ~ 45 degrees. What you're reading now is more than what I get at the registers farthest away from the evap unit.

    Do you have registers near the ceilings and others near the floor? How long ago was the house built? Must have been recent to still have a warranty and I can't imagine building newer homes in GA that aren't AC ready. Do you have a ceiling fan in the room with the vaulted ceilings? They make a huge difference in those rooms.

    Yeah, that 600 square foot addition makes a big difference. Much as I dislike window ACs, I probably would have put a large unit in one of the walls. We closed in a back porch a few years ago and added about 200 square feet to our home. Insulated up the wazoo and it still gets warm if the shades on the 7 windows aren't down, even with the ceiling fan on high. If I had it to do over again I would have put a Friedrich (the very best window AC units, I think) in one of the walls.

    Anyhow, try to figure out where the closest register to the evap unit is and check that temp.

    Rich
     
  8. Rich

    Rich DBSTalk Club DBSTalk Club

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    I don't think Fluffy needs your help, what he's looking for is how to get his contractor to fix his unit so it cools his house properly.

    Rich
     
  9. fluffybear

    fluffybear Hall Of Fame DBSTalk Club

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    52.6 - What I am discovering is the system is a balanced system. According to things I have read that makes the system more efficient and might explain a lot of my concerns. I understand that can be changed with a simple $3.00 part.

    Yes, floor vents on the 1st floor and ceiling vents on the 2nd. Home was built in 1986.
    The seller was required to obtain a 2/10 (2 on the basics and 10 on the HVAC) home warranty when we purchased the home.

    With the way I designed the room to make Mrs. Fluffybear happy, I have no where to put a wall unit without taking up window space. The contractor tried to talk me into one of those ductless systems (I know quite a few people who have them in their cabins and swear by them) but Mrs. Fluffybear wouldn't hear of it.

    FYI, all the windows and doors in new area are low-E dual panes.
     
  10. Rich

    Rich DBSTalk Club DBSTalk Club

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    52 degrees close to the evap unit? You're not gonna cool down the house very well with temps like that.

    Huh. The homes like mine have the registers on the first floor high and low and the second floors are the same.

    That's nice. Don't see much of that in NJ.

    I have the place to put a wall unit, just don't remember where the wiring is and don't want to cut thru it. Never even considered a wall unit when we finished the porch.

    What's a ductless system? How do you get rid of the heat without an outlet? I saw a unit in a Home Depot that is floor standing, but requires about a 2" duct to exhaust the heat in the room. Been considering that.

    We had the old single pane windows when we moved in and replaced them all with double panes. Makes quite a difference. Can't hear anything outside with all the windows closed.

    Rich
     
  11. fluffybear

    fluffybear Hall Of Fame DBSTalk Club

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    Thanks everyone for your assistance and advice.

    I spoke with a couple of different people over the last few days and between them and the posts here, I have learned a lot.

    trh, your posts made me think a bit. When we purchased this house, there were at least a dozen more tree's near the house then today. We were forced to removed some of the larger ones to make the insurance company happy. While we have planted a number of new tree's on the property to make up for those removed, these tree's will not provide any kind of shade on the house for at least another decade.

    Rich, I do not know the mechanics of the ductless system other then there is a outdoor unit which connects 1 or 2 indoor units via a refrigerant line but that is the extent of my knowledge. As I say I do know a few people who have installed the system from Mitsubishi in their cabins.
     
  12. trdrjeff

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    Ductless just mean there is no duct system in the house, it's just an internal unit that hangs high on the wall with an internal fan blowing air across the cooled/heated (many sub as heat pump in winter called mini-splits) radiator into the room. The refrigerant is brought in directly from the outside condenser. They are fairly efficient and quiet. Aesthetics may not have a high WAF ;)

    [​IMG]
     
  13. Rich

    Rich DBSTalk Club DBSTalk Club

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    Thanx, I'd never seen one.

    Rich
     
  14. trh

    trh This Space for Sale

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    Here is an article you may find interesting oversized units. Not that I think you have an oversized unit, but i thought the portion of this article discussing design temps and impact on the AC would help you. We had a builder who recently built a new home. The house required a 2.5 ton unit. He built the same house a month later ten lots down from the first. But the second house was rotated about 135 degrees. Because of that orientation change, the AC load dropped to only 2 tons. The house has to be treated as system and there are a lot of items that impact the AC load of a house. You were very wise to have GA Power do an audit when replacing your old unit.
     
  15. fluffybear

    fluffybear Hall Of Fame DBSTalk Club

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    Actually, the audit was done last year (2011) after we completed the addition and was not per say done for the point of air conditioning ;-)
     
  16. Rich

    Rich DBSTalk Club DBSTalk Club

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    Most of the air conditioners I've worked on were on flat roofs on tall buildings and they had no problem working correctly when maintained correctly. Yes, the ambient temperature affects the air conditioning process, but if the refrigerant was at the proper levels the rooftop ACs worked very well. No shade, just really hot roofs and brick buildings that would have been so hot no one could have worked in them.

    I still think you've got a problem that shows up in your register temp readings. Basically, you're not getting the house as cool as it should be, right? What were the results of your power company's analysis?

    Rich
     
  17. Rich

    Rich DBSTalk Club DBSTalk Club

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    Let me ask you a simple question. What is an "air conditioner"? I'll wait while you search the Internet for the proper answer. It is a question most people don't answer correctly.
     
  18. trh

    trh This Space for Sale

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    Another article from Monday: Tips for Keeping Cool with a Struggling AC

    Part of the opening paragraph:
     
  19. dpeters11

    dpeters11 Hall Of Fame

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    I made out pretty good with my 1920s house with old windows, compared to coworkers with fairly new construction in subdivisons. Last year took the attic insulation from around R20 to R50, swapped out a light fixture at the top of the stars for a ceiling fan that I run all the time in summer, and didn't set the AC to a higher temp when at work. We were generally comfortable, yet my power bill was over $100 less than the other guys.
     
  20. Davenlr

    Davenlr Geek til I die

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    So its cheaper to leave it set to 76 all day, rather than 82?
     

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