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buried line sets

Was wondering what you guys think. Last fall, I was party to a job where 2 line sets had to be buried-60 feet each approx. Don't like doing this but was only the "helper" on this job. Each 3/4-3/8 set was sleeved in 4" pvc. One pair of ends are down turned 90s to shed rain, the other ends are 4x2 pvc couplers with spray foam seal.

Well, here comes time to evac/charge etc. Both units are 410a, ones a 2 ton, other 2.5. Got the 2 ton charged with some difficulty, but it's running ok. The other....not so much. Immediate frosting on suction, head is 450 while low side practically flies into a vacuum. The compressor rattles as the suction goes below say...60.

my question is: if there was a breach in the pvc, and the pipe got filled with water, and the lineset was submerged.....what would one expect in pressure readings?

Comments

  • Dan FoleyDan Foley Posts: 1,202Member
    A kink in the suction line would be a more likely cause.

    - DF
  • TechmanTechman Posts: 2,144Member
    edited June 2015
    As Dan Foley said. How did the copper tubing get shaped to those 4" PVC 90's. That had to be difficult. I've done 45* ells.
  • JStarJStar Posts: 2,748Member
    Install a test port right at the evaporator on the suction line. If the pressure is higher at the coil than the condenser, you've got a restricted suction line. If the pressures are the same, you've got a restriction on the liquid line or expansion device.
  • Bob Bona_4Bob Bona_4 Posts: 2,083Member
    Good thoughts. It was no fun chasing the lineset, some was done when I wasn't there to supervise. 4" pvc with 45s and 90s to come up can be done in sections with some prefab of the suction line (brazing copper 90s etc). It was a miserable job and reinforcement of the saying "just because something can be done doesn't mean it SHOULD"

    This mess goes under a fresh paved driveway and big buck landscaping. Screwed.
  • Harvey RamerHarvey Ramer Posts: 2,201Member
    Sounds like a real pain in the butt, Bob. I don't think I would attempt a 4" 90 unless it was a long sweep. That might be doable.

    Ramer Mechanical
    ramermechanical.com
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Bob Bona_4Bob Bona_4 Posts: 2,083Member
    edited June 2015
    I do a lot of 90 degree bending with my rachet mandrel- even with the armaflex on it's doable to slip 4" regular 90 over that as it goes. 3" no way.

    Txv is my next examination before I condemn the burial sleeve. This is a First Co mbxb with a Heil 13 Seer. New eequipment.

    Weathers been cool here so no one is yelling yet. They've got 5 other systems so it's not like a major hardship...although this is the mbr one.
  • Harvey RamerHarvey Ramer Posts: 2,201Member
    Not by any chance an R-22 TXV? TXV get supplied by First Co?
    Ramer Mechanical
    ramermechanical.com
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Empire_2Empire_2 Posts: 2,343Member
    Providing that the system did not have any operational issues before, You have a major restriction and in MOP due to possible collapse in line under ground not from collapse or maybe because of collapse, but from possible Ice damage to lines during the winter season depending on where you are. (something seems to have damaged the line set).. If water entered the lines, You would more than likely say good bye to the compressor since it will not compress water. Valves would be gone.
    Your Q;? If the pvc had broken, I really don't care since it's just a cover, the problem lies in did it do any damage? There could be water around the line set all day with the breach in the pvc, but as long as the copper line set is undamaged it should be OK. Amazing what engineering codes cause a major potential problem with the installation of equipment. I am really surprised it was not mandatory to be thirdly encased in Titanium.........
    JStar has a great idea,... I read to fast and jumped in w/o reading.....lol. Yes it will tell you what and aprox. where your restriction is Bob.

    My .02
  • Bob Bona_4Bob Bona_4 Posts: 2,083Member
    edited June 2015
    Well guys, it was a bad txv, right out of the gate.
    Thanks for your ideas. I had wondered if the liquid line was getting cooled by possible submerging in groundwater.

    I'm red faced to admit I condemned and replaced the compressor. ..if one heard the sounds it made.

    Makes me think about First Co quality. Last year, had a 410 leaker, from the get go. Found (eventually) the nylon sealing washer at the TXV to the cap tube union was never installed. Ooops!
  • JStarJStar Posts: 2,748Member
    A faulty TXV that is failed closed will typicall show low suction pressure, high superheat, and high subcooling. Failed open will show high suction pressure, low superheat, and low subcooling. A bad compressor will usually show equal pressures at both ports of the condenser.
  • Bob Bona_4Bob Bona_4 Posts: 2,083Member
    She was failed closed. Thought the comp threw a rod too. Horrific noises!
  • TechmanTechman Posts: 2,144Member
    Is there a LoPress Safety? Is there a LLSV for pumpdown? W/ buried linesets the freon migrates to the buried linesets and kills the comp while making horrible noises.
  • Bob Bona_4Bob Bona_4 Posts: 2,083Member
    Nope no LPCO- budget Heil. The typical high and low SVs. The TXV was bad out of the gate, turns out.

    Mind wanders if the lineset sleeving is tight, I suppose there is some heat existing in it from the liquid line. Or, conversely, if the sleeve is compromised, groundwater would quench the high side particularly, creating havoc at the TXV.

    Why I Hate remote condensers and buried lines!
  • JStarJStar Posts: 2,748Member
    If the sleeve was full of water, it would transfer heat more efficiently than air, and subcool the liquid even more than the condenser does. That could flood the evaporator and raise suction pressure.
  • TechmanTechman Posts: 2,144Member
    I think there will be another comp failure, shortly.
  • pecmsgpecmsg Posts: 1,047Member
    If the line set must be buried the system becomes a pump down.

    I've used corrugated drain piping with the drain holes down seemed to allow the water to drain. (being in sand all the time helps)
  • Bob Bona_4Bob Bona_4 Posts: 2,083Member
    Hope not another comp wipeout! Been chugging away these last few weeks. Remember, the lines are in sealed (fingers crossed) 4" pvc sleeves. A possible breach and detection is my concern.
  • TechmanTechman Posts: 2,144Member
    My concern would be the lack of a "pumpdown".
  • pecmsgpecmsg Posts: 1,047Member
    Put 20' of 7/8" suction line under ground, with or without a sleeve, 1/2" or 2" wall of insulation and your going to have a 20' X 7/8" column of liquid coming back to that compressor. Just
    listen as the unit starts up.

    The pump down prevents that!
  • clammyclammy Posts: 2,376Member
    I have been watching this post as other have also ,and i was under the impression that buring a 410 a line set was a no no and voided warranty .I would agree with others on the pump down except i have heard no one talk about a liquid reciever forit to pump down or a LLS .In a past life i have done excatly what bob is doing a ran buried line set we usually installed a LLS with no pump down but did installed suction line accumalator and had installed a delay on the condenser compressor .The indoor fan and LLS would start before the compressor .Usually we would use those crappy fenco 90 s for the bends it would make it much easire also pressure testing ever joint before sleeving it in pvc.In the past i have done it with 6 in pvc for a back up remote 20 ton condenser tied into a aux chiller barrell with secondary water cooled coils on standard dx air handlers this was for a field /work out /tennis /indoor volley ball pool LOL got money to burn .Up to 15 years ago or more i was asked to remote a bunch of 410 condensers and was told by manafacture that it would void the warranty .Never did a buried 410 but plenty of 22 and unless the unit came with one (older byrant 597 and a few others used to have suction line acc built in )we would either install in the unit or mount it outside the unit.Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • TechmanTechman Posts: 2,144Member
    When we talk about a pumpdown , that means there is/should be a LLS along w/ a LP switch. I put the LLS right at the AHU so the amount of freon to be pumped down is very little thus a reciever is not needed. The Suction line would otherwise "collect freon vapor" thru migration,then the freon vapor condenses into liquid, then the comp starts, that the comp dies.

    I'm not sure about 410a not being allowed to be used w/ buried line sets as long as there is a LLSV. That same rule applies to every freon . So, present that "exception" to the rule to your supplier. Carrier agrees w/ the LLSV. As does Rheem. Good points, clammy.
  • Bob Bona_4Bob Bona_4 Posts: 2,083Member
    It's been a loong time since I've seen LLS's on res. Ac. Carrier used to include them back in the piston days.
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