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  1. #27
    Join Date
    Apr 2007
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    6,285
    Quote Originally Posted by The Tucson Tech View Post
    Thanks hvacrmedic! It's nice to know there are some people in this world who are not so ignorant. I am a Tech from Tucson but I will keep my time in service off record. I have found that years of experience has nothing to do with know how. Not just in this trade but in life all together. Post count and member status doesn't seem to be the key either. I think the key is to listen to others when they speak...
    Some of the others in the Pro forums are more than worth it to listen to....so member status does become a factor.

  2. #28
    Join Date
    Jul 2005
    Posts
    5,380
    Quote Originally Posted by bell3156 View Post
    ttt... I like the way you think and I totaly agree with you about some of the people on here, there are some real pills. You can explain till your blue in the face...I do believe the unit will work and be efficient...You absolutly need the txv... I think the problem you will have is when the house does get sold and the compressor goes out on the unit, the tech will order the compressor off the condenser model number and put a 5ton compressor in. I would remove the condensor model and serial number and write in the contol panel 4 ton unit...I would write it everywhere on the units....Good luck
    Well, if I happened upon a system like this and found the compressor bad, when I notice that the compressor is a full ton smaller than the unit size, then I'm going to know that it's the wrong size compressor for the unit. I'll then go inside and look at the evaporator coil size. If it's a five ton coil, then I'm probably going to either put a five ton compressor back in it, or suggest they replace the entire system, because a 5 ton system is too big for this house. If they aren't interested in that, then I'll suggest putting another four ton compressor back in it, by then suspecting that this is why the tech put a four ton compressor in it in the first place. Either to reduce the capacity, or to improve the efficiency, or both. With the TXV, either compressor will work fine in this system. I'd leave it up to the HO what they wanted to do.

    Would I think the tech who put that 4 ton compressor in there is a hack? No, I wasn't there, I don't know what his real reasons were for doing this. I don't even care why he did it, to be honest. He made it more efficient, I have no reason to condemn his choice. Also, I'll have no idea whether he installed this system, or just replaced a compressor in it. I wouldn't bad mouth the guy all over town. What would I say? Even if I knew all the details, the tech who did this used to own the house. So? I guess he can do with his own system what he wants to. He should have explained the system to the buyers, and if he didn't, then my only advice to them would be "well, did your contract specify anything about the hvac system?" Either it was illegal what he did, or it wasn't. I don't see any moral dilemma there.

    Laws may prohibit that kind of thing in some places, I don't know. Might be a good question if somebody here has any answers to it.

  3. #29
    Join Date
    Jul 2005
    Posts
    5,380
    Quote Originally Posted by The Tucson Tech View Post
    Thanks hvacrmedic! It's nice to know there are some people in this world who are not so ignorant. I am a Tech from Tucson but I will keep my time in service off record. I have found that years of experience has nothing to do with know how. Not just in this trade but in life all together. Post count and member status doesn't seem to be the key either. I think the key is to listen to others when they speak...
    Just so you'll know, it'll work fine. Better than fine. Leave the condenser air flow right where it is. Reducing it will reduce efficiency, increasing it won't help enough to put up with the extra noise. Use a 4 ton blower. I used a condenser that already had an 825 RPM motor in it. That eliminated the problem of matching a blade to it. The system I built like this measures an actual EER of 13. A true watt meter and YJ digital psychrometer were used to take the measurements. Measurements were taken three times and were consistent. Cfm was measured using the heat rise method (strip heat). Blower and other loads were added to the total watts before calculating EER. I don't know what SEER that would work out to, but in any case it beats the crap out of an 8 SEER.

    My electric bill dropped dramatically. Yes, this system is on MY house. I hope that nobody wants to tell me it's too complicated to do, or that it won't work. I'm fine with the point about selling the house, because that isn't going to happen anyway
    Last edited by hvacrmedic; 03-19-2008 at 03:09 AM.

  4. #30
    Join Date
    May 2006
    Posts
    122
    I agree if you put either compressor in it will work but..he does not know which coil he was going to use, also the airflow would be set for 4 tons of cooling so the guy that did replace it with a 5 ton might have some issues...just a thought, i would just leave as much info for the next guy aas I could...Just splitting hairs here

  5. #31
    Join Date
    Jul 2005
    Posts
    5,380
    Quote Originally Posted by bell3156 View Post
    I agree if you put either compressor in it will work but..he does not know which coil he was going to use, also the airflow would be set for 4 tons of cooling so the guy that did replace it with a 5 ton might have some issues...just a thought, i would just leave as much info for the next guy aas I could...Just splitting hairs here
    A four ton blower on a five ton system would most likely be an issue. But it would still work. There are a lot of systems running right now with only 320 cfm per ton, mostly due to undersized ductwork. But they work. In fact, around here if you corrected air flow on some of these they'd complain about the humidity or the higher supply air temp. The last one that I "fixed" like this was met with "You need to come back out here and fix this right. My air isn't coming out as cold as it used to."

    Sigh.

  6. #32
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,767
    The system I built like this measures an actual EER of 13. A true watt meter and YJ digital psychrometer were used to take the measurements. Measurements were taken three times and were consistent. Cfm was measured using the heat rise method (strip heat). Blower and other loads were added to the total watts before calculating EER.


    If you measured the CFM by heat rise. Did you deduct CFM for the coil in cooling mode.
    A wet coil will have a higher pressure drop, increasing the TESP.
    Could be a 50 CFM decrease, or it could be a 250 CFM decrease.

    Makes a big difference in that BTU and EER calc.
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  7. #33
    Join Date
    Jul 2005
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    5,380
    Quote Originally Posted by beenthere View Post
    The system I built like this measures an actual EER of 13. A true watt meter and YJ digital psychrometer were used to take the measurements. Measurements were taken three times and were consistent. Cfm was measured using the heat rise method (strip heat). Blower and other loads were added to the total watts before calculating EER.


    If you measured the CFM by heat rise. Did you deduct CFM for the coil in cooling mode.
    A wet coil will have a higher pressure drop, increasing the TESP.
    Could be a 50 CFM decrease, or it could be a 250 CFM decrease.

    Makes a big difference in that BTU and EER calc.
    That's a very good point. But I also measured it in cooling mode with a vane anemometer. But I couldn't get consistent readings with it. It showed a little less cfm, but there was no way to put a reliable number on it. So I may be getting only 12.5 EER or so at standard test conditions. I assumed only a slight decrease in total efficiency due to the dry-evap reading, so I figured it would still be closer to 13 than to 12.5. Could have been way off on that assumption, you're correct. But even with only 12 EER that wouldn't be too bad either.

  8. #34
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,767
    you may be close or far off as you stated.
    Hard to tell without an acturate control method.

    As long as it works, and is doing better then the one it replaced. Your good to good.
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  9. #35
    You will have no problems getting this setup to cool your 1600sqft home. The addition of the TXV should take any guess work out as far as metering referigerant into the evap ccoil. If you run the higher seer evap coil, you may run into clearence problems, depending on the particulars of the install.

    I am also a srvc tech. in Tucson, AZ. PM me if you have any questions.

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