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Need some general input on a 20 year old Lennox compressor and a Unico system

Hi:

First off in full disclosure, I'm a homeowner that designed and installed his own high velocity Unico system just under 20 years ago. I did everything except the pressure and suction line brazing and final charge, but given that it was so long ago I'm fuzzy on the specs of some of the mechanicals. The outside compressor (air conditioner) is a Lennox although I don't recall what ton it is. Can you tell from the model number plate I'm showing? I'm curious what the life expectancy of these things are, and what replaces HCFC-22 that is compatible with the Unico coil (air handler) up in my attic. What should one expect to pay ballpark to have this replaced and charged? Does going with a larger unit improve cooling capability in the house? I'm not having any specific issues with the Lennox per say, but various appliances- including my hot water boiler- are getting to end of life and going bust. Additionally, one thing that the original tech that charged the system never did was put one of those soup can sized dryer canisters on the refrigerant line, saying it was unnecessary. Thoughts? Thank you!




Comments

  • mattmia2
    mattmia2 Member Posts: 5,512
    It could last a very long time. keep it clean and treat and stop any rust before it gets out of hand. The sealed system is likely to last decades, especially with the likely brief use it sees for a couple months in the summer.

    The capacitors for the compressor and the fan may need to be replaced every 15-20 years or so. Buy high quality made in the us caps, not Chinese caps. i think r22 condensers are still available. The heat capacity of a different refrigerant will be different so retrofitting it to a different refrigerant would require reengineering, it would be better to just keep your current system in good condition and replace both parts if something irreplaceable breaks.
    Mosherd1
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 11,992
    @mattmia2 gave good advise.

    How long they will last depends on where you are located. In the northeast 30 years wouldn't be out of the question. Down south with more run time maybe not so long.

    Keep the condenser outside clean by hosing it down keep grass clippings and leaves out of it, keep the air filters in the air handler changed

    Any technician that works on it will tell you to replace it because the refrigerant is outdated. Just keep running it.

    I probably wouldn't replace compressor in it if the compressor failed due to it's age. The only other thing is the air handler and condenser fan motors and capacitors. I would change those if they failed.

    With age the unit could develope refrigerant leaks. If it starts doing that replace the system

    I am not a lennox model # expert but it looks like 2 ton to me

    The refrigerant of choice now is R410A but that may be phased out by the time your unit fails.

    If you change the outside unit you have to change the air handler as well. The ahu coil was not designed for 410A
    SuperTech
  • bburd
    bburd Member Posts: 331
    edited March 2021
    “024” in the middle of the model number means 24,000 Btu/hr, which is 2 tons. Doing a little math on the compressor’s electrical rating confirms this approximately for a ~10 SEER condensing unit.

    One of the more annoying air conditioning industry practices is the lack of obvious (to most people) cooling capacity ratings on central systems. For window units it’s right on the nameplate.

    And @op, the condensing unit and cooling coil(s) must be matched in capacity. If you change the capacity of one, you replace both (and may need to add ductwork to move additional air; the fan laws are unforgiving). 

    Also, you do not want an oversized air conditioner; it will not run long enough to remove humidity as well as a correctly sized system, leaving the house feeling cool but damp. Moisture removal is a considerable part of the cooling load in humid climates, and the key to this is long run times. 

    Bburd
  • Ironman
    Ironman Member Posts: 6,868
    The typical life span of an a/c unit is 20 years, but as others have mentioned, it may last longer in a cooler climate with less run time and proper maintenance.

    And as also stated, when replacement time comes, you’re gonna have to do both indoor and outdoor units.

    We install a lot of Bosch units and they are rated with Unico and work great.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • mattmia2
    mattmia2 Member Posts: 5,512
    That was made after they stopped using quick connect linsets, the joints are all brazed and before the cost of copper skyrocketed and they started making it paper thin so it would surprise me if it developed a refrigerant leak without either severe physical damage or someone leaving one of the caps to the service ports loose.
  • pecmsg
    pecmsg Member Posts: 2,881
    Do you really want to put a New higher SEER condensing unit on a 20 year old coil? Thats going to be tough to size and set up. Also consider the New refrigerant is R-410A your old was R-22. R410 operates almost 2X the pressure. I doubt that coil is rated for these higher pressures.

    As @Ironman said the Bosch unit is a good match but change the evaporator at the same time!
  • JUGHNE
    JUGHNE Member Posts: 9,759
    I recently serviced a Lennox twice the age of yours, all original parts still, both caps right at marked rating, no voltage drop across contactor when running, fan motor bearing still good and had to add only .5 LB R-22 since 1980's.
    These usually outlived the gas furnace they were connected to.

    I believe R-22 or a substitute is available.
  • SuperTech
    SuperTech Member Posts: 1,792
    R-22 is still available, but getting more expensive since it's no longer being manufactured.  Replacement refrigerants are available, but only if all R-22 is removed from the system.  If it leaks, its time for replacement.  It's much too late to worry about the lack of a filter drier.  

    I agree that these are usually good systems that can last over 20 years in the northeast. I would have it cleaned and serviced annually. I'd pay special attention to the dual capacitor in the outdoor unit and the capacitor inside the indoor unit. Those are the most likely reasons for a service call.  Replace the single pole contactor every 7-10 years. Use only quality, USA made contactors and capacitors.
  • JUGHNE
    JUGHNE Member Posts: 9,759
    Who has USA made contactors?
    The Mexico caps seem to last.

    I save old USA caps, and may use for temp repair.
  • mattmia2
    mattmia2 Member Posts: 5,512
    "Titan HD" appear to be made in the US, although Mexico is probably fine too.
    https://www.supplyhouse.com/Titan-HD-PRCF30A-30-MFD-Round-Motor-Run-Capacitor-440-370V
    SuperTech
  • Ironman
    Ironman Member Posts: 6,868
    Actually, those 20 year old caps on the unit are probably made better than just about any new ones you could find. If their values are still in spec, I’d leave them alone.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    SuperTech
  • SuperTech
    SuperTech Member Posts: 1,792
    I agree that the old capacitors definitely last more than the new ones, but all capacitors these days should be tested annually.  Amrad and Titan are my preferred brands. The Amrad Turbo 200 and 200X are more expensive but do have a five year warranty. 
  • mattmia2
    mattmia2 Member Posts: 5,512
    I have a similar 2.5 ton lennox condenser from about 2002 and the compressor section of the capacitor failed in 2013.
  • Chamber1
    Chamber1 Member Posts: 1
    Thanks for all the feedback. I definitely appreciate the insight. Again, nothing is broken at the moment, just doing a little planning. I'm located in Minnesota, so we have some pretty serious run time on it from late June through early September.

    Also, nothing but respect from me for HVAC techs. Often working on beat equipment that was never maintained or cleaned, all the while dealing with sweaty crabby customers. My hats off to you all!
    SuperTechratio
  • HydronicGuru
    HydronicGuru Member Posts: 13
    This high velocity system works now, as you say your not having any problems. However, when the time comes, do yourself a favor, make the decision. Are you going to have it replaced properly or is cost the issue? Unico is a matched high velocity system. You are not going to find a "current" approved list of outdoor units containing R-22 matched for your blower assembly and coil. The unit in your attic uses a TXV to distribute refrigerant properly threw the indoor coil. This and the coil were designed to operate on R-22 refrigerant which had a far less operating pressure than todays refrigerants. I am sorry to say but expect to replace both indoor and outdoor equipment when the time comes. The indoor blower will now be CFM adjusted by manual setpoint (One time on start-up) or variable speed depending on the matched system selected. The indoor coil will be bigger then the size of your existing coil. This is to aid in dehumidification. The new coil will have a R-410A TXV. Also some, not all 2-ton systems utilized 5/8 suction line. If this is your case, you will need to also replace the copper lineset connecting the indoor to the outdoor unit. This now needs to be 3/4 suction min. for 2-Ton Unico installation, and both lines should be insulated threw the attic. Not sure if 20 years ago it was the same, but they now advise to have 6 to 7, runs per ton. In your case you should find 12-14 air distribution vents throughout your home, and one main return. Unico has a list mandating what outdoor condensers they approve to be used with their indoor evaporator coils. Not any unit can be bought and hooked up and expected to preform properly. These systems do not use average ac temp drops of 15-18 degrees. They are much higher than that. (22-28 degree temp drop)
    Find a contractor who deals with Unico. This will help in getting the best bang for your buck, and insuring a successful install the first go around. My guess for pricing may not help you much. Their are so many variables involved. What one company could do it for another would pass 10 times. Contracting is an interesting business. I would say a comfortable guess of 7500-12,000 with 10-year parts and labor warranty. Last one we installed, we ordered and waited for (4) weeks to ship in. (Again, could be way different where your located) Luckily as you, they had a boiler and this was ac only and they were being proactive.
  • mattmia2
    mattmia2 Member Posts: 5,512
    Now that i think about this a little more, likely what took out most of the 30 or 40 year old systems was not a failure of the sealed system but a failure of one of the fans or a minor refrigerant leak that went unnoticed and since the older models didn't have high and low pressure safety switches, the system was run in that state long enough to damage the compressor.