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  1. #1
    Join Date
    Feb 2006
    Location
    michigan
    Posts
    175

    York startup problem

    Hey everyone, I have an issue and I was hoping to get a little insight on. Ill start with my condtion then my problem. Bear with me. I have two 12 1/2 ton 410A condensers, single piped into a 25 ton evaporator. All equipment is York (Johnson Controls). Each condenser has two 6 ton scrolls that are piped in tandem but can be staged if necessary.

    I have roughly 160 ft of lineset. I ran 1 3/8" suction line and 7/8" per mfg specs. I have from the condenser going back to the evaporator in this order. 6' of horizontal pipe, 13' of vertical pipe up, 100' of horizontal pipe, 8' of vertical pipe up, 25' of horitzontal pipe, then 6' of vertical pipe down to evaporator. So essentially my evap sits about 15 above the condensers. I installed a liq line filter drier, solenoid valves, sight glasses, and txv sized for 12 1/2 ton (410a) near the evaporator.

    I have verified that driers are installed correctly and that liq line solenoids are opening.

    My problem is that I dumped enough refrigerant to get me close with my charge and I'm trying to start the condensers up and trim the charge out. What is happening, is that i will energize one condenser and the suction press will maintain about 120psi. The high side will start off at roughly 175psi then steadily climb up until it trips the hps. I then tried the other condenser, and the exact same thing happened.

    After scratching my head for a minute, I just energized one compressor on one condenser, and presto the pressures stabilized. So after I watched it run for a while, I shut it down and tried to energize only one stage on the other condenser. Same problem. head pressure starts normal then within a minute, it climbs until the high press trips. I thought at first I had a restriction, but after seeing one compressor on one condenser run pretty steadily., I'm dumbfounded Now I'm completely off in left field. I am going to try York tech support tomorrow morning but it is like pulling teeth to get a hold of them. I was looking for a little insight from my fellow workers first. Sorry for lingering on but wanted to include as much as possible. Thanks for any help that you can offer.

  2. #2
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,609
    Need to post a complete set of readings with one compressor running to see if you can get a grip on which direction to head. Are your condenser fans staging up as intended? Sight glass clear? Check for non-condensibles yet? Liquid line temp when trip occurs? Outdoor ambient temp? Superheat and subcooling need to be taken both at the condensing unit and at the evaporator to see if the lines are creating any issues in this scenario.

  3. #3
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,055
    when you give us more info on the operating conditions, tell us exactly how the units are piped, what configuration are they in..

    From your post it sounds like you have 2 seperate condensers, tee'd together at the condensers and ran with one 1-3/8" suction and one 7/8"liquid line to 1 evaporator.

    Is the evap 2 circuit? Did you run 1 suction and 1liquid line to the evap for each condenser or are the condensers tee'd together?

  4. #4
    Join Date
    Feb 2006
    Location
    michigan
    Posts
    175
    I have two two stage condensers single piped into a dual circuit evaporator. The condensers have fan cycling controls but I also tried running the consers with both fans at full speed. The only way I could get one condenser to run was have one stage of one condenser on. My readings were 130 suction and 150 on the high side. When I let the fans cycle off the control, they would maintain a head pressure of around 300 psi. I had a superheat of 15 deg. Liq line temp was fluctuating with head press control. Outdoor ambient was 38 deg. I had cranacase heaters on for over two days before startup. Could not run the other condenser long enough to get readings before head presure trip would occur.

  5. #5
    Join Date
    Mar 2011
    Location
    East Coast FL
    Posts
    1,056
    Yes as the others said , all the test data will be required here. I myself have had strange problems with commercial R-410A equipment as compared to good ol 22. Even with a seemingly perfect job , it just does not always behave predictably. I hate to say it , but Im reading a mis-application of equipment here. Tee-ing two multi-stage condensing units into one lineset sharing a common refrigerant charge is not ideal IMO. I know , I know you dont always get to do what you want in this trade. There must be a huge refrigerant charge in that system with the 160' 7/8 liquid line. The 1 3/8 suction line is not large enough. More for 7.5 and 10 tons. Im wondering about that liquid drier..core type? Large enough? Surely you performed good evacuations , so there should be no atmosphere inside , which can make the head skyrocket. Ideally you would have a two circuit evaporator and two linesets sized for the length and 12.5 tons , then with capacity reduction you may have okay oil return. But that doesnt help you now. Or a 25 ton condensing unit. I am 100% sure these guys can help you if you post every piece of data you can gather.

  6. #6
    Join Date
    Mar 2011
    Location
    East Coast FL
    Posts
    1,056
    Quote Originally Posted by dmd-marc View Post
    I have two two stage condensers single piped into a dual circuit evaporator. The condensers have fan cycling controls but I also tried running the consers with both fans at full speed. The only way I could get one condenser to run was have one stage of one condenser on. My readings were 130 suction and 150 on the high side. When I let the fans cycle off the control, they would maintain a head pressure of around 300 psi. I had a superheat of 15 deg. Liq line temp was fluctuating with head press control. Outdoor ambient was 38 deg. I had cranacase heaters on for over two days before startup. Could not run the other condenser long enough to get readings before head presure trip would occur.
    I think that suction line is your problem. Wait , with all 4 comps running I KNOW that suction line is your problem. It is too small and wont flow enough vapor. And so the high side builds up fast. Even with the low ambient.

  7. #7
    Join Date
    Mar 2009
    Location
    central illinois
    Posts
    532
    Maybe try and take your txv bulb off warm it up with your hand and leave it off and see if that helps.Sounds like it is not opening.Just a guess.
    work to live not live to work.

  8. #8
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,055
    How much gas did you throw into this system?

    Since you cant keep it online, Id be looking into taking out just enough to keep it running so you can take some pressure and temp readings and see whats up.. Who knows maybe you overcharged it.

    Why would you connect 2 seperate condensers together and run only 1 lineset?

  9. #9
    Join Date
    Feb 2006
    Location
    michigan
    Posts
    175
    I DID NOT RUN ONE LINESET! Sorry if I didn't explain it clear enough. I have one 12 1/2 ton condenser with 1 3/8" suction and 7/8" liq to one circuit on the evap. And I have another 12 /12 ton condenser with 1 3/8" suction line with a 7/8" liq. running into the other circuit n the evap. I have a 25 ton evap coil. I did the calculation from Johnson Controls piping chart and dumped around 38# into the one system. The application data said that my condenser had a 24# operating charge with matching evap with 25' lineset. Then the rest is for the reamaing 140' of lineset. But I only dumped 29# into the other system to start off and its doing the same thing. Sorry for the confusion guys.

  10. #10
    Join Date
    Aug 2010
    Location
    hampton roads, Va
    Posts
    16
    if i understand what your saying correctly and the second circuit is tripping quickly before you can get readings and the refrigerant is 410a i would recovery refrigerant in that circuit and pull vacuum and recharge with virgin refrigerant. 410a is very funny if has to much oil in it. It will hunt on the suction not stable and head with trip quickly. you said you thought you had a restriction your condenser is what both circuits have in common it would affect one side just like the other. would like some readings to be able to help more. the side that will run.

  11. #11
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    20,951
    Lessee if I am getting this: AH has a dual circuit 25 ton coil. Two 12.5 ton condensers (2 compressors in each condenser), and two linesets.

    Did I get that right?

    Initially, without any more information, here is what I see and where I would start:
    Too much head means too much heat to release through the condenser coil and fan... With a 38D ambient and fans running full bore... you manage to release the heat.

    I would recover enough juice to get the system running, and watch it... Ideal SC is around 9-10... Check your SH at the coil to see if the TXV is working properly.

    Better IMO to collect all the information requested in previous posts.... and lets see how the system is functioning.
    GA-HVAC-Tech

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  12. #12
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,055
    Quote Originally Posted by dmd-marc View Post
    I DID NOT RUN ONE LINESET! Sorry if I didn't explain it clear enough.
    No you didnt explain it clear enough..

    You said you had 2 condensers "singlepiped" to one evap. WTF are we supposed to think?

  13. #13
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,055
    Quote Originally Posted by dmd-marc View Post
    I DID NOT RUN ONE LINESET! Sorry if I didn't explain it clear enough. I have one 12 1/2 ton condenser with 1 3/8" suction and 7/8" liq to one circuit on the evap. And I have another 12 /12 ton condenser with 1 3/8" suction line with a 7/8" liq. running into the other circuit n the evap. I have a 25 ton evap coil. I did the calculation from Johnson Controls piping chart and dumped around 38# into the one system. The application data said that my condenser had a 24# operating charge with matching evap with 25' lineset. Then the rest is for the reamaing 140' of lineset. But I only dumped 29# into the other system to start off and its doing the same thing. Sorry for the confusion guys.

    Pull some of the gas and see where that gets you.. My starting point on a system like that would be around 20lb, and go from there..

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