new condenser, suction line warm

kg321June 18, 2008

replaced 2-ton condenser-installed new 2-ton concord condenser R22 with new line set of 3/4 in for suction line (was 5/8). A-coil was not replaced and is a Carrier 2.5 ton upflow. after running vacuum, pressures read 75 (normal) and 425 (high on high side) and suction line is warm. Air out of vents are about 78 degrees. A-coil clean, filter clean, duct work is tightly connected, no return vents blocked, no air in system. Adding addtl freon only causes high side to increase with overcharge. While running unit, evap coils get cold up until it reaches 3rd from top coil, where it is not cold (I am guessing that since the a-coil is 2.5 ton, then the freon is turning to vapor before it reaches thru all of a-coil). I thought you cold mismatch up to 1/2 ton higher for evap coil. Could this be my problem or deos anyone have any other recommendations to troubleshoot?

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You have a mismatched system, so proper performance is never guaranteed. Did you change/install a TXV?

    Bookmark   June 18, 2008 at 9:23PM
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should have matched up the system and replaced the coil didn't say if it's a piston or txv coil...If I were the tech, I'd be looking there first... you are wayyyy over-charged IMO

    Bookmark   June 18, 2008 at 9:33PM
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Okay, there is a 350-psig pressure differential between the high & low side, a normal differential is somewhere in the area of 150 to 170.

The half ton larger evaporator coil, is usually a good situation, & has no real affect on the problem stated.
Nor would a mere mismatch of condenser & A-Coil, except that a piston flow-rator must be matched to the condenser's capacity.

There is a restriction somewhere in the refrigerant lines.
If it has a TXV when they were brazing the suction line net the TXV did the TXV power element get too hot. That could shut down the TXV's ability to open properly which would starve the evaporator.

It it's a fixed orifice, it could be partially plugged. Check all the filter/dryers, etc. Solder plugged strainer screens, etc.

Because the suction line was warm they may have keep adding charge which drove the high-side pressure way up.

What was the outdoor temp, & what kind of heatload was going through the evaporator coil? That determines how fast & how high it would drive the head-pressure.

Provide more data infomation including indoor humidity level, etc. - udarrell

Here is a link that might be useful: Trouble Shooting Using Superheat & Subcooling

    Bookmark   June 19, 2008 at 8:16AM
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ok...swapped out the a-coil with a matching 2-ton 13-seer.
same problem....low side 72 high side-425. checked both air returns and clear all the way to return at furnace. Orifice is properly matched. so now have new condenser and a-coil (both 2-ton) with a new suction line ran from condenser to a-coil. Liquid line has new drier filter (on correctly) and do not see any restrictions on the liquid line. You can hear the freon flowing thru the liquid line but line is not real hot. Suction line is still warm with very little heat coming out of condenser fan. The blower motor sounds fine but could it be the blower motor speed and how can I check the speed? Can't think of anything else to check. Desperatelt need help. Out of ideas.
Thanks for the help so far.


    Bookmark   June 19, 2008 at 9:27PM
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I'm going out on a whim here, but are the shraeder cores/valves open fully? Could there be a restriction in the condenser metering device?

    Bookmark   June 19, 2008 at 9:33PM
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yes. I double checked the valves today. It's a new condenser so shouldn't have a restriction but at this point have to look anywhere.

    Bookmark   June 19, 2008 at 9:42PM
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It is obvious that something is holding back refrigerant flow (425psi head pressure and a cool liquid line) so have you gone through the copper and tried to detect where a drastic temperature difference occurs, many times with improper welding trash will accumulate either in a liquid line drier or the metering device but in either case with the head pressure you have there will be an easily detectable (20 to 50 degrees) temperature difference

Here is a link that might be useful: Air Conditioning Repair made Easy

    Bookmark   June 19, 2008 at 10:55PM
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Miken is on target, there is always a considerable temp drop & many times there will be frost at that point. It seems the restriction should have been found by now.

Be sure to let us know what you find! udarrell

    Bookmark   June 19, 2008 at 11:09PM
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i tried that. even took temp reading at 1 connection. I'll look again. Has me completely puzzled. Will update when I find something.


    Bookmark   June 19, 2008 at 11:24PM
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Still no answer after 4 hrs troubleshooting today. Checked Orifice for blockage as recommended but clear and checked to make sure in correct way. Checked all supply and return duct again. Ran 2 vacuums. Followed liquid line throughout attic, except for about 6 ft down wall cannot check, and no crimps or change in temps. Blower motor is only 1 speed and checked amps, ok.

I can hear freon flowing thru liquid line and makes a type of swooshing sound but cannot find any type of restriction or change in temp. Temp is holding about 90 degrees on both liquid and suction line.

The compressor seems to take an abnormally amt of time to kick on. I know there is a bit of a delay when power is shut off and then on, but this compressor takes about 6-7 minutes. I called supply house and asked about this and could it be adjusted, and they said delay is controlled by thermostat. I think he must've mis-understood my question. I know the guages would indicate otherwise, but could the compressor be bad or the condensor be restricted even though brand new. I am about out of options. My next option is to re-run a new liquid line-set but my gut tells me that is not the problem.

Let me know if you have any other ideas, and I will keep everyone updated with this mystery unit.

    Bookmark   June 20, 2008 at 5:16PM
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just a WAG. My new Carrier did this. The Txv was for reg freon. System was using Puron.

    Bookmark   June 20, 2008 at 8:05PM
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With both gauge hoses attached, try opening both up acting as a coil and line set bypass while unit is running and see if the pressures come into line.

This should determine where a possible restriction may be.

    Bookmark   June 20, 2008 at 8:16PM
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