System freezing/capacity issue question


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Old 09-13-13, 06:34 AM
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System freezing/capacity issue question

We have a Bryant 383KAV042091AGJA heater/air handler with a Model 561CJ036-E Prod 561CJX036000AEAA AC compressor/condenser. The ratings for this unit near as I can find is 1170cfm heating and 1360 cooling. Rated at 88K btu input and 71K btu out. We have 4 returns to the air handler, 3 upstairs(2 large one small) and 1 small one in the basement. When operating, the unit seems to have very little air flow at the registers. By little I mean the registers 50% distant from the air handler can barely blow a sheet of paper off the top of themselves. If I take that same piece of paper and place it over the basement air handler (basically 4" from the air handler) it sucks very hard.

Since we bought the house we have had the unit serviced several times and the r-22 checked twice. Nothing seriously amiss. The problem is when the AC runs if it runs hard it tends to freeze up, completely blocking the evaporator and eventually freezing the connection out on the condenser. My theory is the airflow is too low or this unit is just under sized for the house because when its 85 and above outside the AC runs non stop to keep the house cool and even then in the afternoons it slowly pushes up. On a 92 deg day by 8pm it will be 78 - 80 in the house with the thermostat set at 75. The air coming out the registers is very cold, just not blowing with any force. It doesnt freeze up all the time maybe just 2-3 times a year.

Any thoughts or opinions on how to get things working better? I really don't have the cash to replace this system at this time but today for the first time it broke down (waiting on repair person now). When I got up the AC was trying to run but the fan on the condenser was not working and the plate its mounted against on the top of the unit was hot (was still dark out so it wasn't sunlight). The house is about 2800-3000sq ft climate controlled space. I have considered adding a mini split to my office in the basement, it gets quite warm due to lots of electronics, computer and such.

From a heating standpoint the system is fantastic. Runs very little and keeps the house quite warm.
 
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Old 09-13-13, 07:00 AM
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How old is the blower fan ? Ask the repair person to check the fan speed. Also you said register air is very cold, how cold? get a delta T (cold air temp - room temp).
 
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Old 09-13-13, 07:04 AM
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As far as I know the blower is original, the house was built in 99. I will try to get a register temp once we get back up and running. I have one of the point and shoot IR thermometers would that be good enough for the register temp? I know playing with the thermometer yesterday the register face in my office was 50deg F. The office at that time was overall 76deg.

My one personal issue with this unit is the horrible filter setup. https://dl.dropboxusercontent.com/u/7490029/filt.jpg
 
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Old 09-13-13, 07:17 AM
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Point and shoot thermo is not good for air temp. Any old type thermo will be better. 76-50=16 is fine if the air speed is normal. So check the blower fan and go from there, usually you should feel the cold air from at least 8-10 feet away. A cheap filter may help.
 
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Old 09-13-13, 12:21 PM
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The failure today was a bad relay/contactor and/or capacitor. The tech showed me both, the capacitor was badly bulged at the top and the contacts on the relay looked like crap. The markup on those parts was utterly obscene ( $240 for the two parts alone, I can order each for under $30 online ). Wife decided she wants them to come out and give us an estimate to replace the whole system. So we will see what comes about on Tuesday.
 
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Old 09-13-13, 03:01 PM
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Wait, does not make sense. If those parts failed, your AC should not even run. From what you said, your AC was running and blow cold air, just not enough cooling power, that has nothing to do with contactor, capacitor, etc.. If you can start your AC, then do not blame on contactor or capacitor. call another tech....
 
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Old 09-14-13, 06:15 AM
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Sorry I likely made this a bit confusing as I was dealing with two issues.

Issue #1 The issue you and I were talking about with the low flow/ freezing etc is something I had been dealing with ongoing for the past couple years.

Issue #2 was I got up yesterday morning to a dead unit, the fan on the condenser was not running though the blower inside was. Thats what the repair issue and parts were for.
 
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Old 09-14-13, 12:12 PM
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OK, I understand now. Hopefully the new system will fix both problems. You should get a 410a system, and talk to your tech to see if you can use the old line set. Good luck to you.
 
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Old 09-23-13, 06:12 PM
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Just an update in case anyone was curious. We canceled the estimate because the wife and I both came down with strep throat. The AX worked until Friday night. We had them come look at it Sat morning and the compressor was seized. The tech they sent was one of their techs able to do the load calcs so he spent an hour going over the house and then recommended a 4 ton system. He pointed out that the heater we had was more than we needed but the AC that the home had originally had installed was only suitable for a max of 1700sqft or so. He also pointed out even with the 4 returns we were still too restricted. With the house topping 3000sq feet he wasnt surprised to hear about the issues we had been having. We picked a XC14 lennox system and they installed it today.

The difference frankly is AMAZING. When the blower kicks up to max you feel it nearly everywhere in the house as a light breeze and its quieter. They still are coming back tomorrow to install another register in the living room where they say we have too few for the room size and the one register in there is 9 feet from a return so he believes it creates a short circuit with the cold air going right back into the return.
 
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Old 09-25-13, 08:36 AM
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Okay, it appears you have a 3.5 ton air conditioner on 3 ton air handler; I don't think the duct system is set up probably with sizing that will handle a 3.5 ton air conditioner.

Undersized AC's do not cause the icing of the evaporator, however, an oversized air-conditioner with extreme lack of airflow can cause the evaporator coil to freeze-up.

Okay if you have a fixed orifice flow rater feeding evaporator coil; a refrigerant under charge will cause low suction pressure & low liquid pressure, high superheat, low sub cooling and low amp-draw; you'll also have poor humidity control.

If the evaporator is fed by thermostatic expansion valve, & the refrigerant is under charged, it can have normal looking pressures if it's not under a real heavy load; liquid line pressure will be low; the superheat if you don't have full load on the coil can appear normal; sub-cooling will be low; amp-draw low; relative humidity control could be close to normal.

With a low evaporator airflow; suction pressure will be low with a fixed orifice; normal with a TXV. Sub cooling will be normal with TXV; sub-cooling will be low with a fixed orifice device & normal with a TXV.

Amp-draw will be low with either device; relative humidity control will be pretty much normal with either device.

I would definitely 'NOT' go to a higher tonnage A/C; if anything stay with a 3.5-Ton to match the air handler & then improve the duct system to help the condenser deliver a higher % of its Btuh to & from the rooms. Didn't notice the 3000-sf of your home so wouldn't go lower than 3.5-Ton...so the edit...

What state do you live in, & what large city do you live near? Very important for us to know...

You can do many things to reduce the load on the A/C system; a load-calc will help you in this respect; try it on your own with this Free online Whole House Load-Calc
 
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Old 10-02-13, 06:43 AM
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@HVAC RETIRED
We had the new 4ton system installed already. The original system had horrible airflow, and at this point in part we will never know why. I can tell you that the only modification that has been made on the intake side was the basement return was increased in size from about 10x14 to 15x22 with new ducting fabricated between it and the air handler. Other than that they added one more 6" or 8" duct into another location in our living room. The airflow from the new system is several orders of magnitude stronger. The old system if you put a piece of 8x11 paper on top of the floor registers, you'd be lucky if it blew off, and if it did it would barely float itself off the top of vent by 1/8" and just drift to the side. You could not feel the airflow with your hand directly above the register at 48". So low airflow was likely our biggest factor. When they pulled the old system out the evaporator had corrosion on it and some dust but not significant amounts. They said likely it might have impeded airflow by as much as 10-12%.

We live in Villa Rica Georgia, 27mi give or take west of Atlanta. The home is better than 90% unshaded.

The new system they installed, mentioned in post #9 is;
FURNACE LENNOX SL280UH090V48B-03
COIL LENNOX CX34-44/48B-6F Coil/3.5-4Ton/Cased
AIR CONDITIONER LENNOX XC14-047-230-04

The airflow from the same vents I mentioned before where it couldn't be felt at 48" now blow the same sheet of paper around at 48". So while the system doesn't blow air as cold as the old R-22 system did (nor does it dehumidify nearly as well in my opinion) it moves massive amounts more air so we have far fewer hot pockets in the home, with one exception, my office ( looking for suggestions in this post on that Problem room gets too hot - DoItYourself.com Community Forums ).
 
 

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