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help diagnosing and fixing a system that is freezing up.

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  • help diagnosing and fixing a system that is freezing up.

    Comprehensive Details of House First then HVAC System Second then follow up with problems we are having. If you want to, skip the details and go to my problem.
    Details:
    2300 SQ FT House Built Mid Summer 1997 NE Maryland Zone
    3 Floors Basement, 1st and 2nd.
    85% Finished Basement so I can see see some of the ducting. Unit is located center house and about 5 feet towards the front .The master bedroom above the garage in the front Left of the house with the back left being master bath and walk in closet. Entry way is an open foyer. the second floor consists of 2 more baths and 4 more bedrooms 2 Beds with a Bath in between occupying the back Middle and right of house.

    First Floor is Kitchen Family and dining room in back and front is sitting room on right then foyer middle left is small office and then Garage.. Basement Finished out about 85%.


    HVAC System:
    Original to House.
    Rheem AC and LP Heating System installed July of 97.
    Consisting of:

    Rheem Classic 90 Air Handler LP Heating.
    Evaporator Coil: RCBA-6089GG24

    AC Condenser Unit Seer 10
    5 Ton RAKA-060 JAZ Mfg 4/97
    R22 Refrigerant, Electric


    Duct Work:

    Cold air return:
    Side Intake to the Air Handler goes to a 16x25x1 Filter. 1' X 2' duct makes a 90 deg bend goes to the Basement Ceiling has a sheet metal shroud that connects it to the house wall framing using the House framing for the cold air return. The cold Air system then goes straight up tthe center of the house. There is also a 8"-10" flexible ductthat attaches into the return that feeds the basement coldair vents. tissue square test shows that the piece will stick to the vent when unit is running. The first floor has one return vent that is in the ceiling between family room and kitchen it is about 24"-36" Long and and 10"-12" Wide it branches a foot or so from the center lduct column.Tissue also sticks to this one. Second floor has 2 Cold air returns. The first is in the master bedroom on the wall directly into the center line duct. It is about 1/1/2'-2' square. Tissue also sticks to this one Center line return continues up intpo the attic where it terminates into an insulated box 1 1/2" square. A 12" flexible duct attached that leads to the last cold air return which is in the ceiling just to the left of the open foyer. This vent fails the tissue tet and will not hold a tissue when running.

    Now for the Delivery Ducting:
    All registers are 4”X10” all ducts are rigid sheetmetal, attic has flexible insulated duct work.


    It starts as a 20"x22" comming out the top of the air handler. from this is one 6” round duct that goes with two 90 degs to the office above the utility room. Out the back is a 8”x 22” feeder duct attached here is one 6” round duct that takes 2 90 degree bends goes into the ceiling to a square duct and then destination is unknown. The feeder duct then ends into the main duct system that runs the centerline of the house. The middle part is 8”x14” in size thenat each end duct is then reduced to 8”x10” and is capped. Coming out of this center duct system is the rest of the 4” or 6” ductsthat feed the rest of the rooms on all 3 floors. of what I can see on the left side of the basement which is unfinished I have 7 ducts coming out of the top of the 8”x14” and 5 from the 8”x10” part all taking a 90 bend to start feeding the rooms. Except for the very last one which feeds straight up a family room vent. So then all the vents that feed the first and second floor take one 90 then a long run to the outside wall of the house and then a second 90 to a floor register on the 1st floor and a Ceiling register in the basement. The rest of the ducts then travel to the second floor. They all take a 90 bend out of the top of the center duct then another quick 90 into the wall cavity up to the second floor where they take another 90 turn to the out side wall area and then 90 again to floor registers. Both upstairs bathrooms have a ceiling vent. In the attic both ceiling vents are fed by 2 flexible insulated ducts. They have a 90 bend to the flexible duct. Then both converge and a 90 deg bend to 2 round ducts that goes down through a second floor wall cavity and then disappears aso I don’t know if they go in the centerline trunk or if they converge at the mystery duct that comes out of the feeder duct to the center line that I can not properly trace.

    So that is it. In a large nut shell.

    Now for the problems.
    This unit has been neglected for about the last 5 Years. As second owners we purchased a service contract from the company the first owners used. A Bi Annual inspection and tune up maintenance contract. 3 years into it problems with them arose we fired them. About 4 years ago we started having cooling issues. On 90+ days the house was not staying cool and a bunch of the vents were not blowing any air at all. When HVAC came out they said mechanically everything was fine and that we had full gas. They said that both the compressor return line at the Condenser and the compressor was icing up and showed us. They also showed us that the evaporator was icing up. They said could be one of two problems. The first and one that they said was likely was that the Cold Air return was of insufficient size. Second they said that there was a possibility that the Evaporator was clogged and dirty.

    They could only speculate that the air return was not enough without doing a full look at the overall system and said that with the finished house that they could do limited if any work to rectify that and that to do it right would be major if possible. Second without dissembling,degassing the unit they could not tell me if the A-frame evaporator was dirty and that was what they needed to do to clean it anyways and had to reschedule for that.

    So not real sure we just let the problem go. We have been able to limp the machine along for the last several years and have besides a warm second floor been able to live with it. If we thought the machine was running continuously and iced up we just shut it down manually for a little bit and gave it time to thaw.

    But not so this year with this last heat wave we could not get the house to cool during the day at all. During the day we could get the house down to 77F and at night it could drop to 74F to 75F. Normally we could keep it with the thermostat set to 71F between 71F and 73F. Now this is how things progressed.

    1st thing I did was hose off the Condenser coils by taking the sides off the unit and it was dirty. So I cleaned up with just water the Condenser coils.
    Then at the beginning of the heat wave I was finding the both the pump and return line was icing up regularly. With definitely the unit icing up over night and finding it iced up in the morning. Also most times the Evaporator would also be iced too. Sometimes though only one or the other would ice. As the heatwave progressed then the only time I would find the pump and return iced up would be first thing in the morning also the evaporator would show some ice during the day but not much. In the middle of the heat wave nothing would ice up except for maybe a few coils in the evaporator. Now that the heat wave has subsided we are back to this morning complete icing of both the pump and return at the condenser and the evaporator. I went to the best register in the house which was in the office and had no air whatsoever coming out the evaporator was that blocked with Ice. So I thawed everything and turned it back on at 9 and then at noon had a call that the register was blowing non cold air but was blowing air so had the unit turned off so I am assuming that the Condenser size froze.
    So that is where I stand.
    I don’t have enough confidence in or a good recommended AC company in the area to give me a good diagnosis and I am not sure how to approach this. I understand that three obvious problems stand out the two most probable are bad design return air and dirty evaporator it could be either or both. (Squirrel cage is a little dusty but not enough for it to be a factor I think.) or it could be low refrigerant. Or it could be a combination of all 3 things.

  • #2
    A/c

    I used to do maintenance on a/c units for apartment buildings. In all cases, topping off the freon at the condenser took care of the icing. as soon as I opened the access valve and started to add gas, the icing disappeared and extended well into the neoprene covering. the unit again blew cold air. sometimes air flow across the A coil was restricted with dust so a blast cleaning was necessary. Next I'd check all solder joints with an ultrasonic freon tester. to save time and fittings, freon lines are expanded with a tool that expands the tubing so that a regular size tubing will fit into and is brazed together. make sure the solder used is brazed or silver solder. this will resist the heat generated by the system. lead solder will not do! another "solder" is called sil-phos. this is a low temperature solder that needs the tubing and/or fittings heated to a cherry red before the sil-phos will flow. any a/c system vibrates, so checking for leaks is a must.

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