A/C gone bad

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DADoES

DADoES

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May 21, 2001
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TX, U.S. of A.
 
My 17+yo Carrier heat pump has gone kablooey.  Service says a couple+ small leaks on the evaporator and the (scroll) compressor isn't pumping properly, probably worn out.  It has been horribly noisy for ~14 years but continued to perform OK until now.  They added 2 lbs of R22 10 days ago. I (and they) hoped it'd be reasonable for a couple/few months until fall weather but it's doing essentially nothing since yesterday evening so I shut it off.  Previous bit of re-up on refrigerant was in 2010 (different servicer).

Problem with replacement now is choices are limited.

I've always thought 5 tons is a bit oversized for this house (2350 sq ft) ... which premise is kinda supported by a borrowed 6K window unit covering the kitchen, living room, dining, office room, hallway & 1/2 bath area (not the master BR/bath wing or the 2nd full bath and two bedrooms) had attained 76°F in the early morn hrs and is currently managing 77.7°F in early afternoon.  The HVAC outfit thinks 5 tons is correct, although there hasn't been further discussion of it.

RJ has a spare 18K window unit (Whirlpool, serial May 2004) from one of his rental refurbs that probably will be swapped in later today or tomorrow.  He already has a homemade extension to run it off a dryer outlet from use a couple times when his system was down, needs to be extended on length to reach from my dryer outlet to the target living room window (not as far as it sounds).
 
A reputable HVAC company should run a load calculation to determine the correct tonnage if the current size is questionable. This includes many things such as insulation types and values in ceilings and walls and types of doors and windows and the direction they face, etc. Warranties definitely matter these days in the sense that you want to make sure it is from a company that you believe will be there for you through the warranty period. A lot of the lower end units these days have major issues within several years even when installed correctly. I haven’t looked in a long time but consumer reports in the past wouldn’t rate central HVAC systems due to the installation being too high of a variable in the longevity of these systems. I’m sorry you are having to deal with this at this time.
 
It might also depend on what you have for a cooling coil in your air handler. These were sized to work together with the 5 ton unit. I went through this 5 years ago when our outside unit had some leaks in it. It was almost a 2 month wait to get another 4 ton unit. When I questioned maybe putting in a 3 ton unit they said it would not match up correctly. Don't know if this is truth or not so I waited till the new 4 ton unit came in. During the meantime I put 2 10,000 btu units in and they also did a good job keeping the 1st floor comfortable.
 
 
Melvin, yes I'm aware of Manual J.  I doubt that any local HVAC services do those.  My parents have had two system changes by two different companies, dad never showed to me or mentioned it.  I had a new system done at my previous house, no mention of it.

Neighbor has had two systems installed on rental refurb houses that didn't originally have anything, two different installers, no mention of Manual J.  He had trouble with both of them so I'm aiming to avoid those companies.  One of them installed smaller auxiliary heat strips (on a heat pump system) than was stated on the details ... which was not an "ooops, we made a mistake on ordering the strips" or "oops, we pulled the wrong ones from stock" ... they had to redo the wiring for the larger capacity when he caught them on it.  There's also an ongoing problem with the condensate drain there, it has leaked through the ceiling twice due to design issues.

The company I plan to use, I intend to ask them about Manual J when they present the quotes to see what is their reply.

Dan, I don't monitor the humidity level other than an el-cheapo thermometer/barometer/hygrometer in the master bathroom, which is not a good reading for the overall house condition.  I've never seen it at or below 50% ... usually mid/upper 50s to 60%.  40% is highly unlikely to happen in this area without considerable effort.  My parents have a 2-speed Lennox with humidity control and a fancy thermostat that mystifies and scares them.  Dad kept complaining about the 2°F overcooling allowance at which it was configured ... why does it get down to 74°F when set on 76°F?  I found on investigation that humidity was set at 45% and that was never attained ... usually between 56% and 52%.  I set humidity at 52% and 0°F overcooling.  Last time I was there it was reading 58%

Jon, the evaporator coil has refrigerant leaks.  The entire system is being changed, not just the compressor/condensor.

We swapped out the 6K window unit for the 18K window late yesterday afternoon, put the 6K in the larger spare bedroom (master BR windows aren't conducive).  I discovered the thermostat on the 18K doesn't work, the compressor never shuts off.  Left running all night AND with the central blower on to circulate through the house ... the living room area was 73.6°F this morning, the smaller east-end bedroom (not with the 6K unit) 77°F, and the west-end master bathroom 78°F with the hygrometer reading 56%.
 
 
HVAC outfit called yesterday.  I asked about Manual J, he said they have a guy with a program to do that, can look up the details on "satellite maps."  !!??  I told him the sq ftage and the ceiling height varies at 9' and 10', double-pane windows.  He said the guy could come onsite if he needs more info.

He called again this morning.  Said only regular 14 SEER models are immediately available, they're on the waiting list for 2-speeds, could be 2 weeks or 2 months.  He mentioned Manual J again.  I said that I found an online calculator that asks for bunches of parameters such as insulation values, window sq ft and roof overhang for exposure, exterior wall sq ft for N-S-E-W facing, etc.  He said "the program will handle all of that."  (uhhh, yeahbut dontcha hafta come over here to get the measurements?)

I put the hygrometer in the living room yesterday.  It varied between 54% and 58% with the 18K running continuously.  I put it in the refrigerator for a couple hrs, reads 34%.
 
Our vintage

1988 Bryant High Efficiency 2.5 tonner worked all summer until Monday evening. It was just the two outside box fuses again. Tech tested the start-up draw amperage. It's fine. Drawing just 12 amps. on each side. He said keep spare fuses. It's not ready to die. He said it was top of the line when new. It has a heater around the compressor so refrigerant doesn't pool up, and a start capacitor/relay. New ones don't.
He said new ones are not nearly as durable, and a or s.e.e.r. rating higher than 16 is a waste of money for this climate. 13 is the low end. The control boards are huge and expensive at the higher end.
 
Dual stage system is the answer

A dual stage system is the answer BUT, dual stage systems are all "communicating" systems these days I think and they can be troublesome and any out of warranty repairs are $$$$.
They do an amazing job maintaining humidity levels though.
 
Our 11 year-old Armstrong had a blower fan motor failure in the hottest part of the summer. It took more than four weeks in the hottest part of the summer, (more that a week of 100+ temperatures) to get a replacement motor and start capacitor. The motor arrived the same week the temperatures dipped to normal. At least now I know whether or not I wanted and indoor sauna.
 
On hot humid summer days

the humidity in my house with the AC set to 72 is like 57%. My unit is also 17 years old this month.

I know people who leave their AC T stat to 76 or 77 and sometimes even 78...I couldn't live in those conditions. LOL
 
 
This morning with the 18K window unit off for 6 hrs, the living room temp is 80°F and the el-cheapo hygrometer reads 60%.  Outdoor temp was lower than usual yesterday due to a couple rains but outdoor humidity was quite high.  Lowest the living room temp reached was 76.8°F and humidity 54%.  The 18K thermostat doesn't work so I manually turn it off if/when the temp reaches below 78°F if I'm paying attention, back on at 79°F-80°F, and now off when I go to bed.

Electric bill for August is 2,488 KWH, $283.90 (includes a 1% rate increase as detailed below).  That usage is 200-ish KWH higher than the previous year for August (2020 = 2,266, 2019 = 2,318), attributed to the system not functioning very well until it went to failing completely on 8/26 (end of the billing period), which day had the highest daily usage (107 KWH) for the period.  I had the temp set at 79°F for the month.  There's no way I could afford to maintain 72°F or 68°F or 65°F as some folks do even with an A/C working properly. 

I had it running until late afternoon on 8/27 when I realized it was failing so shut the central off and installed the 6K window unit in the living room.  8/28 late afternoon swapped the 18K in and moved the 6K to a spare bedroom.  Had the central blower running for a few days for whole-house circulation but then turned it off for a couple floor fans aimed from the LR toward the west end and the office room.

8/27 = 104.17 KWH
8/28 = 51.29 KWH
8/29 = 83.5 KWH
8/30 = 85.96 KWH
8/31 = 58.21 KWH (central blower off & 18K off at night)
9/1 = 53.17 KWH
9/2 = 53 KWH

August Billing
Generation
  Energy: 2,488 KWH @ 0.04688 = $116.64
  GCRF*: 2,488 KWH @ 0.02700 = $67.18
STEC Transmission, Distribution & Ancillary Services
  Energy: 2,488 KWH @ 0.1633 = $40.63
  TDCRF*: 2,488 @ $-0.00700 = $-17.42
Coop Distribution
  Customer Chg = $19.83
  Minimum: 475 KWH @ $0.03855 (1% increase) = $18.31
  Over-Minimum 2,013 KWH @ 0.01924 (1% increase) = $38.73

*CRFs are adjustment factors that vary based on costs charged to the Coop (which is a non-profit, member-owned entity) to maintain operating margins.  Member capital credits are applied biennially.
 
If folks can run a central ac system in Texas below 70 degrees when it is 100 outside then their ac system is oversized. It’s not a huge problem when it’s so hot but during the couple of months when it gets a little cooler here it will not take the humidity out without running below 70 due to the fact if the ac isn’t running enough there is no way to remove humidity. Any progress on the new system?
 
Again ~ Dual stage system is the answer

The beauty of the dual stage is you can oversize it and if the extra capacity is needed it'll bring it on and when it isn't needed it ramps down capacity and fan speed maintaining humidity levels in the process.
Great for comfort but they can be trouble...
 
Are there full-size ACs with inverter compressors?

Have heard both great and horrible about inverter heat pumps over here.

With certain situations they can be great as they can reduce short cycleing which can happen in climates like ours during the transition months.

If things go bad on these it's usually the inverter drives.
That can be a good thing as an inverter replacement is still cheaper than a premature compressor exchange. And with technology advancing and unification of system components, drives have come down in price.

Bad experiences have been either installation error or drives going out over and over.

And with 2.5k kWh usage a month (which would be insane for any household 3 people or less over here - really still can't wrap my head around that - and how cheap that is) going for an efficient system might be worth it.
 
The inverter systems have been here for some time now but at close to double the price of a standard system a lot of folks pass on these. There was one that came out in the early 2000’s but due to cost, complexity, and poor quality they didn’t last very long and left a bad taste in mouth of those who sprung for them. Central ac systems are like anything else these days. The lower cost ones are built shoddily and usually the fly by night companies put a lot of them in and then are no where to be found in the short period of time when problems start to occur.

The best advice I can give is to buy from a reputable company who has been around long term and has good reviews or references in the community. Someone you think will be right there when you need them and competent enough to fix issues with ease.

I know that’s asking a lot these days.
 
If you want REAL trouble get an inverter system.

The base dual stage systems are fairly reliable but if you want REAL trouble get an inverter system.
You may get lucky but they are often a nightmare.
 
 
No further word from the HVAC outfit.  No info on the Manual J, no one has been here to take measurements.  No info or quotes on a system, which perhaps they can't provide until choices are available.  I have not yet checked with other services.
 
 
Quotes from first contacted service.  $10,450 for 1-speed Lennox, 14 SEER (not stated but previously mentioned).  $14,000 for 2-speed, 15 SEER stated.  Only 1 point increase??

Awaiting quotes from another service.  Fellow said Trane 1-speed should be 16 SEER, 2-speed maybe 18.
 
I'd bet 3.5-4 ton would be more than enough for that house. I'd be looking at the ductwork, particularly the return air to make sure it's not undersized, that will always make an oversized system perform like it's undersized. I believe a 5 ton system should have at least 2 18" returns.

13 years ago when I did our upstairs system, it was practically unheard of for contractors to offer Manual J here. I went with the one that did, but he fudged the numbers so much in the software that we ended up with an oversized system anyway.

Second time around, 8 years ago, I solicited bids again for the downstairs system and everyone was offering Manual J. I ended up going with the contractor who wanted to downsize our furnace from 100k to 60k, we kept the same 2.5 ton condenser as that was already sized correctly. The furnace has no issues keeping up and it runs nice LONG cycles in 1st stage and 2nd stage doesn't kick in until it's below 10º outside.
 
 
I have two 20" x 25" (grill/filter size) returns.

Second quotes.  Single-stage 15 SEER Trane (4TWR6060H1, TEM6AOD60H, 81-0703-01), $10,216.73.  Two-stage 17 SEER (4TWR7060A1, TEM6AOD60H, 81-0703-01), $11,718.27.  Does not state if sales tax is included but I assume not.  It is included on the first quotes.
 
I'm not sure about your market plus things being the way they are lately, but those prices around here for a simple changeout seem kinda high. That said, that 17 SEER two stage quote isn't a whole lot higher, I'd be tempted to go that way but I'd downsize it to 4 ton. Was there ever a time when your 5 ton would run continuous to maintain setpoint or even not keep up? A proper sized system would run continuous at design outdoor ambient (which IIRC is around 97-102º depending on which part of TX) with an indoor target of 75º.
 
July 2020

 

<span style="font-family: helvetica;">Our A/C went out and we decided to replace the entire system because it was 18 years old.  The Heat Exchanger and Compressor were replaced around 2014ish from what I could find in the paperwork.  The system is Trane with a 16 SEER 4 ton compressor and a two stage furnace.  All in it was $7318.20.   We put a two stage in the old house and really loved it so we went with the two stage here as well.  I don't recall the difference in price.</span>

 

<span style="font-family: helvetica;">We had an interesting situation in this house.  It's 2400 sq ft. and the family that built this house had a zoned system put in.  It didn't make a lot of sense because one zone was most of the house and the other two zones were each of two smaller bedrooms at the other end of the house.  That needed to be replaced or removed when we put in the new system.  It would have been about $2,000 to replace or $800 to remove.  Since it didn't really buy us much in this house we had it removed.  We paid the $800 to have them remove the unneeded ductwork in the attic and air balance the system.  No regrets.</span>
 
Zoning forced air is usually an act in futility getting it to work right, particularly when they’re small zones like that. And it murders your systems efficiency. The only way it works is if each zone can individually handle the full airflow that the equipment requires, or if it’s two stage and each zone can individually handle the airflow needed for the 1st stage. Or if it’s a communicating zone system like Carrier Infinity or whatever Trane calls their version where it can adjust the blower CFM according to how many zones are calling, and it all works even better if you’re using a modulating furnace and modulating inverter condensing unit.
 
no fan of zone control

I have a Honeywell Zone Control System, three Honeywell Modulating Automatic Round Dampers (MARDs) and a Honeywell Universal mini-zone controller box. It's been problematic since day one. The primary problem are the MARDs. All dampers move to the open position when the system is off. Depending on which zone calls for heating or cooling causes some of the MARDs to close. The dampers are prone to sticking or they leak air. The zone controller developed cold solder joints causing all kinds of erratic behavior. I reflowed several connections years ago and no problems since.

Had the original installer out twice to fix the leaking air problem. The result was the tech fried one of the zones on the controller board. Moved the zone to an unused port but now have no spare. Right now I'm sure all zones blow air even when one of the zones should be closed. I gave up on the system years ago. In theory zone control sounds good, but in practice you will be buying a constant source of problems.
 
I have 2 heating and a/c systems in my house. The 1st is in the basement, there is one zone down there and the 2nd zone does the 1st floor. The 2nd unit is on the 3rd floor. 1st zone is on the 2nd floor and the 2nd zone does the 3rd floor. They were installed 15 years ago and no problems with the zone features on either unit. Also had both systems balance for airflow when installed and all rooms in all zones keep target temps set. Very please the way they work.

Jon
 
Zoned systems

 

<span style="font-family: 'American Typewriter', serif;">We have had zoned systems in the past and have been happy with them but in all those cases it made sense.  The man who built this house was a contractor who built this house for he and his wife who had become empty nesters.  His daughter said since he was a contractor, he had access to lots of cool upgrades and added the zoned system just because he could.  The house is filled with many upgrades that make sense but this one didn’t.  It’s 2400 sq. ft. with large rooms except for these two small bedrooms at the opposite end of the house.  They zoned the entire house as 1 zone and then each of the two small bedrooms were a separate zone.  It worked as designed for a while, but we started having issues with damper motors as it was 18 years old.</span>

<span style="font-family: 'American Typewriter', serif;"> </span>

<span style="font-family: 'American Typewriter', serif;">If we could have easily made the Master Bedroom and Bathroom a separate zone then we would have replaced the zone system along with the new A/C and furnace.  With this setup we could heat/cool just the bedroom at night vs. the entire house, but the way the ductwork was done it would mean ripping out what was done on that end of the house and redoing it.</span>

<span style="font-family: 'American Typewriter', serif;"> </span>

<span style="font-family: 'American Typewriter', serif;">So, we made the decision to remove the Zoned system altogether and have been happy with it.  I think it depends on the brand and how the system is designed.</span>

 
Split System?

 

<span style="font-family: helvetica;">I don't know what a Split System is but here in the South if you have a two story home you really need two separate systems to cool the upstairs.  My condo complex when I moved here in 2002 was built in two phases.  They were all two story units, bedrooms up.  The first Phase was built with 1 system for the entire unit.  The second Phase (where I was) was built with two systems one up and one down.  The people in the old Phase did nothing but complain about cooling the upstairs.  The complex didn't allow for air conditioners in the windows so it was an issue for them.</span>

 

<span style="font-family: helvetica;">Since then both houses we've had have been single story, LOL.</span>

[this post was last edited: 11/12/2021-12:44]
 

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