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Thread: Brand-new split system, terrible results, am I over-expecting? Did I under-buy?

  1. #1
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    Brand-new split system, terrible results, am I over-expecting? Did I under-buy?

    Hi all, brand new member although I used this site to do a ton of research before buying my new system. I have a "Cape" house on Long Island, previously using a mix of hole-in-the-wall units and a couple of window units. Finally took the plunge and bought a 42,000 BTU external unit and 5 air handlers. The company we went with is A rated on Angies List, and service has been relatively good. However...

    I had the install a couple of weeks ago, as soon as they guys left it took about 45 minutes to cool. We played with the five remotes and found (a) setting everything to 70 made the house uncomfortably cold. Which was amazing! Such power! So we tweaked all the units up until it felt comfortable, ended up at 73 in one room, 74 in another, generally found a nice set of settings to get an amazingly cool, dry home. Very happy. Ecstatic even.

    I was in the house for two days, then had to leave for a week on business. I set all the units to 85 and left. I came back seven days later, and I cannot cool the house. The main unit in the downstairs, a 15k BTU unit, is clearly the poorest performer. The best I can get is around 78 degrees on the digital room thermometer I use. Humidity is high, I can feel the moisture on the wood furniture, in the carpet. The other four are cooling to some degree, but nowhere near the day one feel of the house.

    I immediately called the company, and they sent someone over pretty quickly, he said he found a small leak where the lines connect from outside to inside (three lines run throught the basement and up the far side of the house) which he fixed and then topped up the refrigerant. The system worked well, albeit degraded from the day one experience, but after about three or four hours I had one unit pumping pretty much room-temp air, and the other four doing a relatively poor job of cooling.

    I called them again and they sent someone over within a few days. This time the original installer was accompanied by a more senior guy from the company who had a heat probe. He told me the Delta on these units should be about 15 degrees, hinting that it was simply too hot for the units to cool to my desired temp. However, he also hinted that the 15k unit had a Delta of 10 and was under performing. Generally the chap was talking along the lines of "this is about as good as you can expect", which is bizarre to me as my old, presumably inefficient units did a great job of cooling the house (the upgrade was more about diminishing noise than improving the cooling, I had a nicely comfortably cool home prior to this.) I'm now waiting to hear the outcome of his findings tomorrow.

    The whole time, I know full well that the guys coming out are looking at me in a hot house during a heatwave and thinking I'm complaining about the heat in an uneducated fashion, but I'm adamant that these units are severely degraded from their day one capability. I don't know enough to know how much I'm over thinking this, so I'm looking for a few bits of advice. I asked all the following questions of the guys that came over (except q1) and did not really get clear answers to my questions, lots of vague responses.

    1. Should I get an independent company to come out and inspect the system?
    2. Should I be expecting this system to cool the house as cold as my old individual units did? Have I under-bought?
    3. Should the lines going in to the external unit be alternately hot/cold? The guys who have come out to fix the system have removed insulation - I presume to feel the lines. For me, I can plainly tell that in and out lines are the same temperature, neither is hot nor cold. Plenty of condensate on the copper though.
    4. The fan on the outside unit turns very slowly, even if I max out all five indoor units. Should I expect that external fan to ramp up if all units are on?
    5. There seems to be a lot of water coming from the outside condenser unit, I've not seen this at other people's homes. Is this normal?
    6. Conversely, there seems to be next to no condensate coming out of the five exhaust lines coming from the handlers, on day one i recall these plastic pipes were exhausting a significantly higher amount of water. Is this normal?
    7. As a last resort, I've now set two of the units to 61 and turned the others off. There has been a slight dip in the temperature in the room I'm measuring, from 79.7 degrees to 77.8 as measured by a room thermometer.

    Thus far the after sales service has been prompt and friendly, but I'm having a hard time understanding how this company isn't 100% next to me saying "holy heck, you're right, this house is not cooling". Even if they were to change the one 15k unit, I don't feel that that's going to get me back to my first day experience, as the four other handlers are similarly straining to get rooms down to the mid-70s.

    I know that's a wall of text and a lot to ask, hence question (1), if the advice is to get a second opinion from a reputable company then I'll jump over to the Find a Pro forum and do that. If you read all this, thanks! Mainly I want to continue with this company, but I don't want to be so under-informed that I end up losing a chunk of change to have a warmer and noisier house.

    System specs:

    Condenser Mitsubishi MXZ 5C42NA
    Handlers/Evap: Mitsubishi MSZ GL15NA x1 GL12NA x1 GL09NA x3

    House is 1800 foot, 15k and 9k handlers downstairs (one open plan live/kitchen area, one office), 12k and two more 9s upstairs (three bedrooms). Thanks in advance!

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  2. #2
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    Those units have specific amounts if refrigerant required based on heads and line lengths. They need to remove all the refrigerant and recharge with new.

  3. #3
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    I'm going to suggest that you have an independent contractor come out to look at the system. Mitsubishi units are amazing & should have NO problem keeping your house cold. I suspect 2 things.
    1- The leak wasn't really fixed.
    2- You're low on refrigerant.
    It would be worth it to have someone come out to evaluate this, then go back to the other company who installed it to fix whatever problems & have them fix it. If they become argumentative or uncompromising, the best thing to do is have someone competent fix the problem. How you handle it from there is up to you. Shouldn't work well one day & then just quit.
    Also, if you do go away, set your thermostats to 78. That will help keep the latent humidity out of the air. I'm a native Long Islander (lived in Port Jefferson Village) & the humidity is too much to turn your units to 85, they won't keep the house dry. Once it's inundated with humidity, the unit will be fighting to remove all of that humidity that soaked into walls, carpets, etc. A few dehumidifiers set to 45-50% when you go away would help, but either way you're using electricity. The Mitsubishi, if set up & charged correctly, are EXTREMELY efficient and will keep your house dry when away. This is better than turning them up to 85 & having them work like crazy to get the house back down. Properly sized units need to dehumidify the air to around 50% before they will actually lower the air temperature significantly

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  4. #4
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    42000 btu serving 1800 sf. You did not under buy and you are not over expecting. You purchased the best brand but your contractor has let you down. I don't know the details of your house, but that unit is most likely way to big for your home. It should be able to cool your home at any temperature. As the previous post said, you can't just add refrigerant to those units.

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  6. #5
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    Thank you all for the informative replies! Is there a reference somewhere I can point to that shows the way to calculate the correct refrigerant levels by head/line length? And @hedrash thank you for the very helpful tip on the settings while absent. This all helps me understand my problems and allows me to deal with the contractor professionally, so thank you again, very very much appreciated.

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  8. #6
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    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486 Instructor & Service Technician

  9. #7
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    Quote Originally Posted by hedrash View Post
    I'm going to suggest that you have an independent contractor come out to look at the system. Mitsubishi units are amazing & should have NO problem keeping your house cold. I suspect 2 things.
    1- The leak wasn't really fixed.
    2- You're low on refrigerant.
    It would be worth it to have someone come out to evaluate this, then go back to the other company who installed it to fix whatever problems & have them fix it. If they become argumentative or uncompromising, the best thing to do is have someone competent fix the problem. How you handle it from there is up to you. Shouldn't work well one day & then just quit.
    Also, if you do go away, set your thermostats to 78. That will help keep the latent humidity out of the air. I'm a native Long Islander (lived in Port Jefferson Village) & the humidity is too much to turn your units to 85, they won't keep the house dry. Once it's inundated with humidity, the unit will be fighting to remove all of that humidity that soaked into walls, carpets, etc. A few dehumidifiers set to 45-50% when you go away would help, but either way you're using electricity. The Mitsubishi, if set up & charged correctly, are EXTREMELY efficient and will keep your house dry when away. This is better than turning them up to 85 & having them work like crazy to get the house back down. Properly sized units need to dehumidify the air to around 50% before they will actually lower the air temperature significantly

    Sent from my SM-G920V using Tapatalk
    I'm looking for a means to PM you about your suggestion, but not finding the option...

  10. #8
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    [QUOTE=rider77;23396561]Was this a diamond dealer?


    Yes, that is my understanding.

    Edit: I checked your link and confirmed, yes, Diamond Dealer.

  11. #9
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    That doesn't mean much. Could just mean they sell a lot of Mitsubishi equipment

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  13. #10
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    Quote Originally Posted by mynameismonkey View Post
    Thank you all for the informative replies! Is there a reference somewhere I can point to that shows the way to calculate the correct refrigerant levels by head/line length?.
    Yes. On the side of the unit where the model and serial number is. It shows factory charge and amount to add over a specified distance of line set.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
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  14. #11
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    Quote Originally Posted by pacnw View Post
    Yes. On the side of the unit where the model and serial number is. It shows factory charge and amount to add over a specified distance of line set.
    Doesn't mean much if the unit is leaking & you have no idea how much charge is actually in it.

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  16. #12
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    Diamond dealer has to have at least one guy in the company go to the training. How to use the software for getting total charge is part of the class. So is the required leak checks to be done before the service valves are opened. Obviously they didn't follow the training.

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  18. #13
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    Quote Originally Posted by pacnw View Post
    Yes. On the side of the unit where the model and serial number is. It shows factory charge and amount to add over a specified distance of line set.
    I think that is partially right and partially wrong. The plate will show the factory charge. However the amount to add for longer line sets is not on the plate.
    *********
    https://www.hvac20.com/ High efficiency equipment alone does not provide home comfort and efficiency. HVAC2.0 is a process for finding the real needs of the house and the occupants. Offer the customer a menu of work to address their problems and give them a probability of success.

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  19. #14
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    Quote Originally Posted by martyinlincoln View Post
    Diamond dealer has to have at least one guy in the company go to the training. How to use the software for getting total charge is part of the class. So is the required leak checks to be done before the service valves are opened. Obviously they didn't follow the training.
    Exactly. When I left my old company on Long Island they lost several certifications because I went to the school... not them. Think they lost 8 total.

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  20. #15
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    Just a little update, I turned off all the clearly poor-performers, I have two of the units on right now and the fan outside is now at full speed, the two exhaust lines are producing a ton of condensate runoff, the air coming out of those two units is considerably colder, and the humidity in the room with the 15k which is now off, has dropped from 65% humidity to 55% with the unit _off_.

  21. #16
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    Quote Originally Posted by mynameismonkey View Post
    Just a little update, I turned off all the clearly poor-performers, I have two of the units on right now and the fan outside is now at full speed, the two exhaust lines are producing a ton of condensate runoff, the air coming out of those two units is considerably colder, and the humidity in the room with the 15k which is now off, has dropped from 65% humidity to 55% with the unit _off_.
    You've got problems in the middle of a major heat wave.
    Until things settle down continue to run just the units that work.
    Give the contractor a little time to make it right but not much.
    3 1/2 -Tons is a lot for that Sw ft.

  22. #17
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    Sounds as if your system is definitely undercharged. Mitsubishi units use "flare" connections not a brazed connection (essentially a welded connection) & they are VERY prone to leaks if not done correctly. The technicians need to use a good 410A flare tool & confirm with high pressure nitrogen leak test. I'd almost bet one of the flares are leaking. Turning a few of the units off will allow the system to come up to full capacity (well, at least the maximum capacity you'll get with low refrigerant) & work well. Insist on a few things from this "diamond dealer."
    1. - recover all of the R-410A into a proper recovery can & weigh that refrigerant to find out how much was actually in the system.
    2. - Perform a 300psig nitrogen leak check. This should hold for at least 2-3hrs without budging.
    3. - Have them find & fix any leaks
    4. - Have them triple evacuate the system
    5. Have them charge the unit to Mitsubishi's specs.

    This is work intensive but you paid good money for a system that works. If it worked, then didn't & you cut down the capacity & it's working well now, it's DEFINITELY undercharged & could have a leak still.
    Hope this helps & hopefully the company is receptive to your wishes.

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  24. #18
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    Quote Originally Posted by hedrash View Post
    Sounds as if your system is definitely undercharged. Mitsubishi units use "flare" connections not a brazed connection (essentially a welded connection) & they are VERY prone to leaks if not done correctly. The technicians need to use a good 410A flare tool & confirm with high pressure nitrogen leak test. I'd almost bet one of the flares are leaking. Turning a few of the units off will allow the system to come up to full capacity (well, at least the maximum capacity you'll get with low refrigerant) & work well. Insist on a few things from this "diamond dealer."
    1. - recover all of the R-410A into a proper recovery can & weigh that refrigerant to find out how much was actually in the system.
    2. - Perform a 300psig nitrogen leak check. This should hold for at least 2-3hrs without budging.
    3. - Have them find & fix any leaks
    4. - Have them triple evacuate the system
    5. Have them charge the unit to Mitsubishi's specs.

    This is work intensive but you paid good money for a system that works. If it worked, then didn't & you cut down the capacity & it's working well now, it's DEFINITELY undercharged & could have a leak still.
    Hope this helps & hopefully the company is receptive to your wishes.

    Sent from my SM-G920V using Tapatalk
    Mitsubishi wants the pressure tested at 600 PSI.
    *********
    https://www.hvac20.com/ High efficiency equipment alone does not provide home comfort and efficiency. HVAC2.0 is a process for finding the real needs of the house and the occupants. Offer the customer a menu of work to address their problems and give them a probability of success.

    Find contractors with specialized training in combustion analysis, residential system performance, air flow, and duct optimization https://www.myhomecomfort.org/


    Site member map HERE!

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  26. #19
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    Quote Originally Posted by kdean1 View Post
    Mitsubishi wants the pressure tested at 600 PSI.
    Yup. I was talking at a minimum. Usually you'll see a leak at 300psig on a flare. A LOT of companies are still using plumbers flare kits, not 410A rated flare kits. Really sad this is a "diamond dealer."

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  27. #20
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    Please post something on the R-410A special flair

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