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  1. #14
    All good responses. Thanks for all the input everyone. In response to some of the potential issues...

    I'm certain the problem is not leaky ducts. I've spent many hot afternoons in the attic tracing down each trunk, and duct to ensure there are no major leaks. In an attempt to fix the situation, one of the techs removed ~18 inches of dead space off the top of my plenum... Now the air in the house is much more balanced. But the problem isn't fixed.

    The contractor has pulled a vacuum on the system and replaced with virgin refrigerant 2-3 times. So if there are incondensibles, they are hanging on tight.

    The fan speed being set wrong is something that I'll suggest they check out. The house is kind of humid (~60%). However, I'm not sure if that is far above normal.

    As for speaking with the owner of the HVAC company... I've dealt with him on many occasions. In fact he feels so comfortable with me that he has yelled at me over the phone on a couple of occasions.

    **Update** After the last "fix" several days ago, my system has started making a very loud noise upon start-up that sounds like a furnace starting up or gas escaping (thats the best I can describe it). But we don't have any natural gas...

    I'm going to call the contractor one last time today...maybe they will replace the whole thing. Over four visits in the last 3 weeks and the problem is worse (because of the noise) than when we started. And since the manufacturer informed me the contractor can be reimbursed for labor if the system needs to be replaced, I think replacement is a good option.

  2. #15
    Join Date
    May 2009
    Posts
    272
    Quote Originally Posted by tedkidd View Post
    I'd be careful about posting hvac complaints until you know the culprit is the equipment.

    Maybe there is missing panning, a thermal bypass above a stairway or soffit, or some other unknown deficiency causing/contributing to the problem.

    Hvac is not always the solution, and it's not always the problem.

    If you think the hvac wasnt done right in your new house, why do you think everything else was done right?
    Gee Tedd, do you think the company coming out and replacing random parts and the system giving a 11-12 degree delta T might possibly indicate he has an AC problem?

    Of course he has an AC problem. Sounds like the techs have a competence problem.

  3. #16
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,722
    Gee Chase, sounds like you prefer to assume the problem is equipment without stepping back and getting much of an overall picture. Guess in your world it can't be duct work, can't be problems or changes to envelope, gotta be equipment. You prefer to solve one problem at a time, and slam people for suggesting there may be other issues?

    I'm not a tech, and I understand tech's inclination to quickly solve the problem in front of them and move on (homeowners don't appreciate 4 hour service charges). But are you sure delta t is enough to diagnose the problem? Wouldn't you want other information? Like, wouldn't major duct problems be a potential contributor? (HO indicated duct inspection after my post. Besides, visual inspections are not equivalent to having measured leakage).

    Assumptions about duct work are analogous to disconnect about building performance in general and how people can head down the wrong path.

    Common approach:

    MYOPIC "fix what's in front of me" approach: You have 2.5 tons of duct work and need 4 tons ac, so we have to replace the ductwork so we can install 4 tons. (Possible de-humidification problems, big energy and equipment cost penalty, and bigger oversize problems if they decide to weatherize later. In my opinion you've hosed this person and their home.) For some reason people seem to think the load is what it is, it's cast in stone.

    This is the approach I'm an advocate of:

    STEP BACK and THINK approach: How can we reduce your load to 2.5 tons so your duct work is sufficient and we can install less expensive equipment, not spend money on duct work, and cut your energy bill big time? This approach brings things back into balance.


    If you don't step back, look at things from different angles, and MENTION opportunities to do things a different way, are you really serving your customer? Rush, get it back up and running and move to the next? Is it really just about collecting a paycheck?

    I prefer to serve people, knock their socks off with energy savings and comfort improvement. For me that means investing effort into think time and talk time. With this approach I've found you sometimes avoid "solving" problems unnecessarily. Like fixing duct work without touching duct work, by simply curing the homes deficiencies. With this if the homeowner selects the quick fix, unanticipated consequences of not being comprehensive are ON THEM, not on me.

    My approach is not always the HVAC sales guys friend. Often you don't get to sell new duct work.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  4. #17
    your asking one of the most complex questions in this field...

    First post, and I plan on helping and asking for help, from fellow service techs...

    First of all I keep hearing leaky ducts.. Is it just me or is a proper delta T, done from the return plenum and supply plenum?? Not much duct work their.. What is the heat load? This is important... Then maybe you can start talking ductwork, on the return side.. MAYBE..

    Evap coil has been replaced because the txv? That is scary.. What was wrong with the evap coil? Leaking? Was the system low, on diagnosis?

    Fan speed set properly? What is the saturation temperature? If it is over 50, its never going to work right. Is their oil in the suction side, that looks like hot marshmallows? Refrigerant maybe bad.. What is the amp draw on the condenser? What is the make and model? Subcooling, superheat? Is the txv sluggin back?? Is the txv insolated? Inside the air handler or outside?

    You see, how complex our err my job is? hvac service technicians have to be scientists, electricians, and plumbers. If your td is 12-13 and everything is running right and you have had a evap. coil changed If I had to guess, I am guessing something is up with the refrigerant... Or the txv is not mounted properly...


    get the technician or so called service technician back out there,and ask him or her those questions I just asked...

  5. #18

    Update

    Another update... The contractor came back out with a distributor rep. and did a major diagnostic on it. Final conclusion: Bad TXV. So the contractor replaced the TXV. The system worked fantastic! Cooled the house from 78 to 73 in under two hours, and maintained 73 degrees the whole next day without a problem. However, the next day it ran all day without being able to maintain 74. Keep in mind the weather was pretty much the same on all these days mentioned.

    Yesterday the system ran for 14+ hours and finally topped 77 degrees at 8:00 last night (thats right, 8 PM). The best I can guess is that a bad TXV is the problem since the system operated great after the last two were replaced.

    What I don't understand is why these TXVs keep going bad. The second TXV lasted a week and a half, and the third one only 2 days...

  6. #19
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,722
    brazed without nitrogen?
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  7. #20
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,633
    i think the problem is the service company doing the work

  8. #21
    Join Date
    Mar 2010
    Location
    Houston
    Posts
    98
    Quote Originally Posted by Orion45954 View Post
    What I don't understand is why these TXVs keep going bad. The second TXV lasted a week and a half, and the third one only 2 days...
    It definitely sounds like some particulates loose in your system. They work their way through to TXV during cycle off (equalized pressure) then cycle on state change(differential pressure). The TXV is in fact a valve, a quite small orrifice atomizes the refrigerant with a small piston opening and closing the tiny valve based on evaporator temp. It is imperative that these valves remain very clean or they block and disrupt performance. There are filter/driers that can and should be used on refer lines to help avoid this but sometimes the garbage, like soot from brazing without nitrogen flowing, or countless other funk, needs to be flushed from the system. Usually that will do the trick. I'm just theorizing here, but it's unusual to have TXV's fail one after another without help. All it takes is one little bit of copper shaving to muck up the works. Diagnostics will tell quickly if the TXV or some other restriction is present. All this assumes tight properly evacuated system with proper charge of course.

    Please do follow back with the outcome and let us know.

    GL

  9. #22

    Follow up...

    2 days after the second replacement TXV was put on my system (third TXV overall) the delta T GRADUALLY dropped to around 6 (Keep in mind that by this point I'm having my wife maintain hourly records of the Delta T and other measurments around the house). Contractor came back and and said it was a leak, but he couldn't find it. He injected dye in the system and came back two days later.

    After 20 minutes looking for dye he couldn't find anything and basically accused me (or some kids in the neighborhood) of stealing my refrigerant. After I explained how the systems performance GRADUALLY declined he still didn't believe me. He put the line under 350 psi of nitrogen, which held for 20 minutes. After arguing with me and touting his 30 years of experience he agreed to come back in two days to check it out.

    The next day I brought home a halogen "sniffer", not that I needed it, because I immediately saw a nice neon yellow puddle in the compressor pan. I called the tech to tell him I found the leak, but he just told me that was dye he spilled. So I cleaned it off and what do you know, 20 minutes later, more dye. The source of the leak is coming from one of the lines going into the compressor.

    NEW QUESTION: The tech had temp gauges that were off by 20 degrees, which caused him to overcharge my system the previous 5 times he worked on my unit. He informed me of this when he got new gauges and replaced the second TXV. Could overcharging cause a 19 month old system to leak/damage the compressor?

  10. #23
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,327
    Quote Originally Posted by ac in fl View Post
    Ive seen taped lines full of water that literally pour out.
    If I came across something like that, a vacuum pump wouldn't even cross my mind. A bottle of nitrogen, brazing materials, and a Schrader stem would. Blow the water out and keep blowing to give the line a good sweep. THEN go for the vacuum pump.

    also your right vacum pump will remove moisture by boiling into vapor and removed by pump but will not remove water dont care how long you run pump.
    I dehydrate building fire sprinkler manifolds, that has standing water in the piping, with a vacuum pump . We drain the manifolds the best we can at first, but there are always dead legs and horizontal runs that won't let go of all their water. So we fire up the vacuum pump and let it all boil off. Works just fine. We've opened up these same sections after the fact and found them bone dry.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  11. #24
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,327
    Quote Originally Posted by tedkidd View Post
    brazed without nitrogen?
    Could be a combo of brazing without nitro and cooking the crap out of the valve when sweating it in.

    And I hear no mention of a new liquid line drier going in each time the TXV is replaced.

    Pretty sorry that an OEM rep had to find a bad TXV. Any service tech worth a hill of beans should be able to find that. Measure the superheat, folks! Even if it's a TXV and even if you're not charging the unit! There's not a system I touch where refrigeration capacity is suspect that I do not get BOTH superheat AND subcooling readings. You can't "see" what's going on inside the system without them.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  12. #25
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,327
    Quote Originally Posted by Orion45954 View Post
    NEW QUESTION: The tech had temp gauges that were off by 20 degrees, which caused him to overcharge my system the previous 5 times he worked on my unit. He informed me of this when he got new gauges and replaced the second TXV. Could overcharging cause a 19 month old system to leak/damage the compressor?
    Cause a leak? Not likely. Damage the compressor? Possible. Most of the time, no. I've pulled five pounds overcharge out of systems that had been running like that for quite some time before I got there.

    Lines inside the condensing unit can start leaking due to vibration. A weak brazing joint, two or more lines rubbing together, etc. You've seen the dye on the condenser pan floor. Now see if you can locate where the dye is emerging from the line. Show it to the tech and accept no excuses.

    I once argued with a seasoned guy when I was a greenhorn in the trade that an evap coil inside an apartment unit was leaking. He wouldn't believe me. I told him I could smell compressor oil out of the supply register in the bathroom right as the system fired up. Still wouldn't believe me. I pressed on him until we yanked the coil out, took it outside, sealed the ends off, gassed it up with R22 (this was pre-EPA days, mind you) and set it on the sidewalk.

    I put my ear to the coil and could hear it hissing, in several places. I told him so. I'll never forget his response. "That's just vibration coming up from the sidewalk." I gave him an ugly glare, snapped the coil up from the sidewalk, and said "Follow me!". We went into a vacant apartment (I worked there) and I filled up the bathtub. Tossed the coil in, still pressurized. Not just one fine stream of bubbles emerged, SEVEN of them did! It was only then that he conceded the fight and I won. We got a new coil installed that week.

    This guy was claiming all along he had "x" amount of years experience, implying that I was just a dumb know-nothing kid (for the most part, I was...just knew that particular time I was right). He ate some humble pie that day. I'm not saying you need to be an in-your-face know-it-all to your tech, but you do need to stay on the installing company's case that you know there's a leak and you won't disappear until it is resolved.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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