Is my system undersized?

[timmahh]

AHH!! I Just spent 20 minutes writing my post and when I hit post it asked me to login!

Ok so here I go again.. but I don't remember exactly what I said so hopefully I have the same details/info..!

Here are all the specs/details:

- House built in 2005
- Split-zone system (thermo up/downstairs)
- Front of houses faces east
- No shade to protect house from heat
- 379 sq. foot of windows; Philips Vinyl Double Pane Low E2
-- Front: 6 windows
-- Left: 7 windows
-- Back: 8 windows (1 in garage), 1 SGD
-- Right: 4 windows

- Ceiling insulation is blown in, permit says R-30
- Cooling equipment is Carrier, model 36CKC036 w/ TXV
- SEER 10.0
- Duct location is the attic
- Duct R-Value is 6.0
- Cooling load 24,553 BTU/hr
- Cooling cap. 32,800 BTU/hr


Leak tests:
http://www.fuzi0n.com/imgz/envtest.JPG
http://www.fuzi0n.com/imgz/cfmleaktest.JPG


I think that's all the techie/details.. here's what I know as a homeowner:

First.. I know little to nothing about HVAC/sizing/etc.; but I do know I'm tired and honestly cannot afford to continue shelling out $400+ a month to keep my house at a temperature that is comfortable for me (I like it cold). When I moved in I ran some wiring in the attic for speakers/network; so I know i've compacted areas of the insulation and that can cause an efficiency problem. While I was up there I was looking at the ducts/equipment and found spots where I could feel cool air blowing into the attic; the builder uses big ducts that lead to custom made junctions that then feed smaller ducts that go to the individual rooms; one of these was blown apart so I bought a roll of the metal duct tape and repaired, along with taping areas that I felt cool air coming out of.

The system is located above the master bathroom. The primary return is located at the top of the stairs outside the master bedroom and is 20x25. The secondary return is 14x14 and is located about [ceiling-distance] 5 feet on the other side of the door/wall. The thermostat is on the wall below the 14x14 return. The master has two vents; one near the 14x14 and the other on an angle [vaulted ceiling] that seems perfectly lined up to blow cool air into the 20x25 return. The remaining rooms/areas of the house have one vent per room/area.

Yesterday it was about 106 outside, in the morning (about 8) we set the upstairs thermostat to hold at 74 degrees; by noon the system was on non-stop and was struggling to keep it at about 78-79. It was definately cooler inside than it was outside, but for me it's too hot and not comfortable.

At night i've got to have it like a freezer.. for some reason I like having a cold room but being warm in my blanket.. not sure why.. don't ask.. i'm weird like that. Anyways, at night i'll drop it to 72 or so, it kicks on and off at night but the only room that is cool is the master bedroom - the rest of the rooms are significantly warmer and downstairs [system is "off" down there] is 78 - 80 degrees. My thought is with the thermostat, vents, and returns all being within a few feet of each other the bedroom cools down and the rest of the house doesn't really get a chance.

So, as a dumb home owner who is HVAC challenged, based on the info above would you say my system is sized correctly? Should I look into upgrading? I know i've been to smaller houses than ours and sometimes they have condensers that are twice the size - even our smaller single story house a few blocks away has a larger condenser outside. When the a/c kicks on the vents in the master bedroom and bathroom are pumping out cool air like there's no tomorrow, but the rest of the vents have some airflow but it doesn't seem like it's enough to cool the room.

Is it possible to upgrade the blower to something that has more airflow?

Again, sorry for all the questions and the giant thread but when the PG&E bill is close to your car payment there is a problem! :)

Thanks for any info/input guys n gals!

[tlchvac]

I dont think anyone could or will read your entire post...good luck thou

[udarrell]

Always hilight & copy before you preview or submit your post.

I had that happen too many times, & redo is never as good as the first post was.

I'll have to look at your post later, got to do something else right now.

Be sure to check the condenser discharge air temp & compare to outdoor temp.
Might be pulling hot air from attic into Return.

According to the load figures, it is not undersized.

One inch water column (IWC) equals 248 pascals(PA); click udarrell.
- Darrell

[timmahh]

I dont think anyone could or will read your entire post...good luck thou

Why is that..?

I know it's a bit long but i'd rather give as much info as possible the first time, rather than have a thread full of questions :)

udarrell - thanks for the response I look forward to seeing what else you have to say after you read my giant thread

[tinknocker service tech]

at 106 outside and 78 or so inside i would tend to think you are doing ok.
increasing the blower for more air flo may cause other problems or make thing worse. You may also need to increase the tonage and ductwork for the ammount of air.
increasing the tonage way also cause humidity control problems on cooler days because the units run time will be less and to large.

It may be better served to find ways to improve the envalope or tighten up the house more

[DanW13]

Hard to understand

[HVACJOEK]

Thank You, it was a hard trying day at work, your "joke post" really uplifted my day:cool:

ps i hope you have a sequel for tomorrow.

[udarrell]

NYC summer design 89-F dry bulb & 73-F wet bulb, or around 44% relative Humidity.
If it was 106-F in the shade? What was the Heat Index? That temp is way over the summer design for NYC, so relax a little.

If the system is not keeping you comfortable enough. Have the unit checked for its nominal BTUH performance.

If the equipment performance is okay, I would not make any equipment changes, I would do more weatherization so the system will keep you comfortable.

The condenser unit's capacity has to be matched by the evaporator, airflow, duct system & air handler's capacity! - Darrell

[Roscoe]

Jeeez after reading the title I thought H-Talk started a Personals section..........:eek:...........:D:D:D

[timmahh]

:(

I just got my eletric bill for this month.. The system is set to 78 during the day; from 6AM until 4:30PM. At 4:30 it changes to 75.. but it doesn't really matter because by 4:30 the house is already over 80 degrees


My bill is $622.26. If anyone has any recommendations I would greatly appreciate it; do you think it would be wise to have someone check the system?

[fitz2180]

:(

I just got my eletric bill for this month.. The system is set to 78 during the day; from 6AM until 4:30PM. At 4:30 it changes to 75.. but it doesn't really matter because by 4:30 the house is already over 80 degrees


My bill is $622.26. If anyone has any recommendations I would greatly appreciate it; do you think it would be wise to have someone check the system?
If you are hotter inside than it is outside, there is a problem... I would have it checked. That bill is crazy! How large is your home?

[tlchvac]

It is not a matter of if its undersized or not, it is a question on wether it is working. What are the pressures, temps out of vents ect ect..I would bet that it is out of gas or something. Spend a 100 bucks and find out. You would be cool by now.gezzzzz:eek:

[udarrell]

:(

I just got my eletric bill for this month.. The system is set to 78 during the day; from 6AM until 4:30PM. At 4:30 it changes to 75.. but it doesn't really matter because by 4:30 the house is already over 80 degrees

My bill is $622.26. (WOW!) If anyone has any recommendations I would greatly appreciate it; do you think it would be wise to have someone check the system?
Well, your case is extreme, so I'll provide some links to other updated linked pages of mine you can print & use along with your Tech(s).

There is a good chance its pulling hot air from somewhere so checking the condensing temp even with a thermometer will tell you if it's above the normal split, indicating hot air entering the Return Air.(?)

http://www.udarrell.com/ac-trouble-shooting-superheat-subcooling.html

http://www.udarrell.com/ac-trouble-shooting-chart.html

http://udarrell.com/udarrell_hvac_blog/

Follow directions, copy & paste in your word processor, then Collect the temp & relative humidity data, etc., paste it back here for us to evaluate. - Darrell

[timmahh]

Thanks guys - Darrell i'll print those and see what I can come up with when I get home today.

fitz - the house is 2276 sq feet w/ a split zone system.

One of the things I still don't understand, which i'll take a picture of later, is the tray setup - everyone has the a/c water tray under the system that drains, great, and it also has a drain higher up incase it gets blocked - well i have a tube that shoots out off of it, with a hole drilled in it, that is just letting cool air into the attic - granted it's not a large amount but still what the heck is the purpose of a pvc pipe with a hole in it that vents cool air into the attic?

[crzymtrbiker]

WEll You need a service cause the last time something like this happened I had an element in an electric furnace stuck on so it was trying to cool the air and the element..that is if you have an electric furnace....

[tinknocker service tech]

you do have some problems going on here. What they are can only be seem by a tech.

the pan under your unit should NEVER have water in it except when there is a problem

The tray that is incased is the one that should be draining and only that one if all is working properly

you bill is also pointing to a problem

Time to stop asking how or what and call someone out to find your problems and fix them

[timmahh]

you do have some problems going on here. What they are can only be seem by a tech.

the pan under your unit should NEVER have water in it except when there is a problem

The tray that is incased is the one that should be draining and only that one if all is working properly

you bill is also pointing to a problem

Time to stop asking how or what and call someone out to find your problems and fix them

The tray doesn't fill up with water that i've seen [though we do have a ton of discharge from the drip line].. I'm having someone come out tonight or tomorrow night to look at it

[tinknocker service tech]

The tray doesn't fill up with water that i've seen [though we do have a ton of discharge from the drip line].. I'm having someone come out tonight or tomorrow night to look at it


it is a nice change to see someone who knows what they need to do
hope the tech can solve all your question and problems

please let us know how it works out

[rbeck]

I would think the unit is large enough. At 106 you can only expect a 20 - 25f drop from outdoor temps. There may still be duct leaks but as far as sizing it is OK. The electric bill seems high. My house is 2500 sq ft and has a three ton built in 1978. Added attic insulation. Summer bills average about $160 a month. I am not a real fan of attic ductwork as it gets extremely hot up there and even 6.0 duct it still changes the internal air temp some. This is not a huge issue so this also is not your problem.

[timmahh]

Well I had someone come out.. He took temp readings at the intake and at the outlet in the various rooms. Average temp at the vent is 17-18 degrees cooler than the intake temp.

He checked the condenser, wasn't too dirty but he cleaned it. He checked amperage loads on the fan/compressor and nothing was out of place there. I asked him about the charge and he said if the return pipe was extremely hot or the intake pipe was frozen that would indicate a problem, but the system was working ok and he doesn't like to hook up gauges if he doesn't have to because each time we loose a little bit of gas.

His thoughts are that the builder did the standard calculation for the model and then installs the same unit in every house that's the same plan - not taking into account shade on the house or what direction it faces. I asked him about the ducting and he said we had good airflow, and again the temp difference was pretty optimal so the system is installed correctly and working correctly, however due to the size and the fact that we have absolutely no protection from the sun [not even a house behind us to help in the afternoon], it cannot keep up with the solar heat the house is generating/holding.

So I guess I have a few options:

1) Install a whole house fan and see if that helps
2) Go back in the attic and look for duct leaks that I can repair
3) Add more insulation in places where it has compacted
4) Try to talk to builder who will probably hang up
5) Look into upgrading condenser/coils & evaporator

I called the California Energy Dept. to talk to someone about Title 24 compliance and what builders are required to do. They ARE required to meet energy efficiency, but apparently that means "we installed an energy efficient unit". They are apparently NOT required to perform load calculations and adjust the system accordingly (atleast that's what the guy thought). So, great, we have an energy efficient (SEER 10) system, but due to the position of our house and size, it's unable to cool it in an efficient manner and requires more energy than a system tailored to the house would need.

[DanW13]

I would definately get up in the attic and have a look around, also go by some fast growing trees, and some nice trees that are native to the area that will provide plenty of shade where it's needed. Also might want to invest in some window canopy's for the east, and west sides of the home to leessen the load the best you can. Check the rest of the house for air leaks and see what happens over the course of the remainder of the summer.

[jerryd_2008]

... Also might want to invest in some window canopy's for the east, and west sides of the home to leessen the load the best you can. ...

We get a surprisingly hot heat load from the east in the morning with the rising sun. We just turn the blinds on that side to block the direct sun through those windows as we do in other rooms that get sun.

Also have a whole house southern exposure in the rear. We added a large 20'+ awning a few years ago that covers about 30% of the brick wall and most over the kitchen/dining area. We extend it enough to block the sun on the brick down to the deck. Helps. Couldn't believe how warm brick gets in that situation and it how long it will retain it into the night.

[sktn77a]

1. Where do you live ? (I wish people would put their location in their profile). I'm guessing it's California, either LA or central valley with those temps. Well, at least that's a dry heat so all 3 tons are going to sensible cooling.
2. You mention duct leaks in your attic! That's probably stealing 25%+ of your cooling capacity!

I'm surprized the tech didn't note the duct leaks if they are as big as you say they are. California has duct leakage specifications/requirements - I'm surprized they didn't mention this to you when you called them (this and "at least that's what the guy thought" leads me to believe you spoke to the wrong person). And I'm surprized the tech didn't put a gauge on the unit - I know they're a bit wiggy about the environment in CA but when there's a problem cooling, you need to know the cause.

Might want to get a few more responses from this site but you need a proper heat gain calculation done before you let someone put in a larger system (which they will gladly take your money for). May also help your negotiations with your builder if the unit wasn't sized correctly (has it been like this since 2004)? Sounds like you also need the airflow rebalanced in favor of the other rooms that aren't being cooled enough.

[timmahh]

One of the items I attached is a duct leak test; the big thing I noticed when I moved in was the junction/distribution box that was blown open.

The house was built in 2005; bought it last year - this is my first 'full summer' in the house.

Unfortunately it was completed before the SEER 13 / newer Title 24 requirements came into effect; so the system is sized based off of the 2001 Title 24 requirements.

I'm a little north of Sacramento, we get 2 - 3 degrees hotter on avg and no delta breeze. :(

To give you an example of our weather - current forecast:

Wed 99
Thurs 101
Fri 101
Sat 105
Sun 105
Mon 107

[radiodoctor]

Tim,


I am in the same boat here in NJ.

4200 sq ft home built in 2005. Two story home. Two-story foyer and open center hall. 20x20 two-story family room with lots of windows in the rear of the home which faces west. Front of home faces east, rear (with the FR windows) faces west. NO trees anywhere near the home. The rear of the home just bakes in the sun all day. Front facade is brick.

Upstairs unit is a Goodman 3-ton system. Downstairs is a Goodman 3.5-ton unit. I checked the ductwork, all looks intact. The home is in the sun ALL day long! At night I can cool the home fine, but in the day, even if it is only 75deg outside, the upstairs unit runs all day long just to maintain 75deg inside.

My downstairs zone works like a champ. It blows cool air and cycles on and off as expected. But the upstairs zone just runs and runs. If it gets over 85deg outside, the upstairs is lucky to maintain 75deg, with the unit running constantly.


I spoke with a few owners of identical model homes in the neighborhood. None claim they have any issues cooling their upstairs. Most of them have trees or shading, and have different sun exposure angles.

My bet is that the contractor did a cookie-cutter installation, and failed to calculate the additional window package at the rear of the home, the full sun exposure, and other variables.

I recently bought an HVAC style thermometer, and checked the air flow temps. The downstairs unit will produce air output at around 62 deg at all times, while the upstairs one varies. One a hot sunny day, the upstairs unit will be lucky to output 67-69deg air, while yet on a cloudy day, or in the evening, it will get as low as 64-65deg.

Now recently I have been having another issue. A few times I have come home to find the outside condenser line frozen, and the upstairs registers not producing any airflow, yet I still hear the unit running. If I shut the unit down for an hour or two, it will be fine for a few days. Not sure if the inside coil is freezing first, or if the fan is failing, causing it to freeze. Right now I am running the thermostat on FAN ONLY for the day to see if I can get the circulator blower to fail.

I feel your pain. This was our dream home, and it has turned into nothing short of a nightmere. The original installer doesn't want to return calls.

I am about ready to pull my hair out. Anyone know of a fair/KNOWLEDGEABLE/reasonable HVAC contractor in the southern Ocean County NJ area? Preferrably someone who is a true engineer who knows how to perform and analyze a load study?

If I need to trash this builder's grade system and install a larger more adequate system for my solar heat load, then so be it. But I am tired of getting the runaround from my original installer, and $650 electric bills in the summer.

Thanks for listening!!!

[timmahh]

Tim,


I am in the same boat here in NJ.

4200 sq ft home built in 2005. Two story home. Two-story foyer and open center hall. 20x20 two-story family room with lots of windows in the rear of the home which faces west. Front of home faces east, rear (with the FR windows) faces west. NO trees anywhere near the home. The rear of the home just bakes in the sun all day. Front facade is brick.

Upstairs unit is a Goodman 3-ton system. Downstairs is a Goodman 3.5-ton unit. I checked the ductwork, all looks intact. The home is in the sun ALL day long! At night I can cool the home fine, but in the day, even if it is only 75deg outside, the upstairs unit runs all day long just to maintain 75deg inside.

My downstairs zone works like a champ. It blows cool air and cycles on and off as expected. But the upstairs zone just runs and runs. If it gets over 85deg outside, the upstairs is lucky to maintain 75deg, with the unit running constantly.


I spoke with a few owners of identical model homes in the neighborhood. None claim they have any issues cooling their upstairs. Most of them have trees or shading, and have different sun exposure angles.

My bet is that the contractor did a cookie-cutter installation, and failed to calculate the additional window package at the rear of the home, the full sun exposure, and other variables.

I recently bought an HVAC style thermometer, and checked the air flow temps. The downstairs unit will produce air output at around 62 deg at all times, while the upstairs one varies. One a hot sunny day, the upstairs unit will be lucky to output 67-69deg air, while yet on a cloudy day, or in the evening, it will get as low as 64-65deg.

Now recently I have been having another issue. A few times I have come home to find the outside condenser line frozen, and the upstairs registers not producing any airflow, yet I still hear the unit running. If I shut the unit down for an hour or two, it will be fine for a few days. Not sure if the inside coil is freezing first, or if the fan is failing, causing it to freeze. Right now I am running the thermostat on FAN ONLY for the day to see if I can get the circulator blower to fail.

I feel your pain. This was our dream home, and it has turned into nothing short of a nightmere. The original installer doesn't want to return calls.

I am about ready to pull my hair out. Anyone know of a fair/KNOWLEDGEABLE/reasonable HVAC contractor in the southern Ocean County NJ area? Preferrably someone who is a true engineer who knows how to perform and analyze a load study?

If I need to trash this builder's grade system and install a larger more adequate system for my solar heat load, then so be it. But I am tired of getting the runaround from my original installer, and $650 electric bills in the summer.

Thanks for listening!!!

That almost sounds like a refrigerant charge level.. based on things i've read that's what tends to happen. Your "A" coil/evaporator could be freezing up causing an air flow restriction(?); or maybe the system detects a problem and shuts the blower off.

At our first house we couldn't get the temp below 82; and when we turned it on it got worse - turns out the TXC was in backwards and the system was over charged.
-----------------------------

Update re: my original post; I contacted the builder asking what method they use to calculate the load for the houses or if they have a generic blanket calculation that is "good enough" for the model. They said a customer care rep will be calling me in a few days..

[pstu]

If possible would you state your electric bill in KWH rather than in dollars? I know that electric cents/KWH varies widely from state to state, my own is 13.2 cents/KWH in TX. I am a homeowner and know electric rates better than I know AC issues but have heard wild stories about the prices you pay per KWH in CA.

There are a number of things which can rob your system of capacity, duct leaks in unconditioned space can be a huge waste. Your duct leakage report, does that date back to original construction? Surely it does not reflect the state of the ducts when you moved in, with that fall-apart you mentioned.

Best of luck -- Pstu

[timmahh]

pstu - 2,095 kw/H. The leakage report is pre-anyone living in the house back in 2005 (not sure how long the duct had been blown apart; I have one record from the previous owner showing a service request due to insuffucient cooling - in theory they "checked" the ducts.)


Here is the kw/H breakdown:

Electric Charges $612.95
Baseline Quantity 511.50000 Kwh
Baseline Usage 511.50000 Kwh @ $0.11531
101-130% of Baseline 153.45000 Kwh @ $0.13109
131-200% of Baseline 358.05000 Kwh @ $0.25974
201-300% of Baseline 511.50000 Kwh @ $0.37866
Over 300% of Baseline 560.50000 Kwh @ $0.44098


I guess the way it works is the CPUC (Cal. Public Util. Commission) determines.. (on a monthly basis?) This is the baseline quantity that the average person will use this month.. Whether it's a 500 sq foot apartment or 5000 sq foot house..

[wildbill99]

pstu - 2,095 kw/H. The leakage report is pre-anyone living in the house back in 2005 (not sure how long the duct had been blown apart; I have one record from the previous owner showing a service request due to insuffucient cooling - in theory they "checked" the ducts.)


Here is the kw/H breakdown:

Electric Charges $612.95
Baseline Quantity 511.50000 Kwh
Baseline Usage 511.50000 Kwh @ $0.11531
101-130% of Baseline 153.45000 Kwh @ $0.13109
131-200% of Baseline 358.05000 Kwh @ $0.25974
201-300% of Baseline 511.50000 Kwh @ $0.37866
Over 300% of Baseline 560.50000 Kwh @ $0.44098


I guess the way it works is the CPUC (Cal. Public Util. Commission) determines.. (on a monthly basis?) This is the baseline quantity that the average person will use this month.. Whether it's a 500 sq foot apartment or 5000 sq foot house..


There is lots of cost factors, plus lots of politics, that get into setting the rates.

Idealy you should have a fixed cost that pays for billing, meter reading and the like.

And a base rate that pays for basic construiction and operating costs. And above that usage level charges based on incremental cost. Which might include using less efficient gnerators and purchasing more expensive purchased power. And possibly cost for up sizing transmission systems. Commerical users have peak charge adders for the reason.

But instead recovering the pure cost the PUC also gettings into political relms and do things like wanting to punish high users and use that to reduce the cost for poor income users.

In my area during the 4 summer months there incremental rates increase about 10% for higher usage. And that is mostly reflective of the higher operating expenses for the peaking units and purchased power.

During the other months the system is lightly loaded and incremental loads need to basically just pay for the fuel used. If you are on electric heating rates they get down to .0415 kWhr. It is 5-6 cents without the electric heating rates.

[pstu]

Thanks for the KWH info. That compares to my older (circa 1955) house in Houston which was approximately the same size, both in size and energy consumption. But it was exposed to Texas weather which is humid and does not cool down at night nearly as much as Sacramento CA. My old house was an energy hog and I think yours may be too. The nice way to look at it is, perhaps there is some "low hanging fruit" type of projects to reduce your energy consumption.

With your 55-63F overnight low, it would seem a whole house fan might work well in your climate. And if your ductwork is built large enough (doubtful), you can ask your technician about running higher airflow perhaps in the 450 cfm/ton range to enhance your sensible (thermometer) cooling at the expense of latent (humidity removal) cooling. To do this well, you will need to have a measure of what your airflow currently is and that implies tools that many Texas AC technicians like to do without. At the minimum, taking a measure of external static pressure (ESP) will allow a tech to look at the CFM vs. ESP and see what airflow is expected. You might pay attention to your filters, if you are using restrictive ones like 3M Filtrete, that often leads to restricted airflow and poor performance according to pros on this site.

It is my opinion you need an AC technician with a complete set of tools plus a lot of experience. But what do I know, I am just a homeowner and amateur at figuring out problems. You need a knowledgeable pro on your team.

Best of luck -- Pstu

[timmahh]

I do use the '3M Ultra Allergen Filtrete' filter.. Not sure if I really need it but as a consumer it makes me feel better. What's a good combo of airflow and filter performance?

The probably w/ going the whole house fan route for me is that at night in the summer time it's usually not cool enough outside to run it, and if the temp does drop enough it's at like 3AM and i'm already asleep!

[pstu]

I do use the '3M Ultra Allergen Filtrete' filter.. Not sure if I really need it but as a consumer it makes me feel better. What's a good combo of airflow and filter performance?

The probably w/ going the whole house fan route for me is that at night in the summer time it's usually not cool enough outside to run it, and if the temp does drop enough it's at like 3AM and i'm already asleep!
I suggest doing a search on "3M Filtrete" for prior threads on this board. There is a definite concensus among pros that these filters are toxic to the average system. This is a case where a direct conversation with your personal HVAC expert can best guide you. Being a homeowner I would prefer not to recommend a filter for you, too many things I don't know (both about the industry and about your house).

Evidently most HVAC pros seldom actually measure ESP (external static pressure), instead they go by expectations. I wish it were otherwise. The acute problem is when ductwork is puny in the first place, coupled with small filter area (i.e. high air velocity at the filter face). That makes ESP high already, maybe out of spec for the air handler. Then a homeowner with good intentions, aggravates the problem by putting in a restrictive filter which loads up with dirt and creates excessive ESP. This reduces airflow and can create a whole list of problems.

That said, I use 3M Filtretes when it is difficult to find another pleated filter. However I am sure of having lots of filter area and have measured my ESP so can be confident there is no airflow degradation. Not many people can say that, so better to play it safe. The 3M filter is not inherently bad, but many HVAC systems are not well set up to use it.

Hope this helps -- Pstu

[radiodoctor]

Today the unit worked flawlessy. Able to maintain 74 all day long, albeit it was raining all day and only in the mid 70s. Tonight it is behaving as well.

But last night it did act up again. I determined it was the A-coil freezing. The circulator blower seems to be ok.

Last year (May) the service tech found that one of the line valves at the outdoor unit was leaking, and re-seated it. Then in July 08 the scroll compressor was replaced after it failed. The lines were pressure tested at that time and checked good. I just read another post where an installer reported numerous Goodman systems which had bad valves due to a machining issue. Maybe the valve leaked again and caused some of the charge to dissipate.


I will be calling someone out to check the charge level.




That almost sounds like a refrigerant charge level.. based on things i've read that's what tends to happen. Your "A" coil/evaporator could be freezing up causing an air flow restriction(?); or maybe the system detects a problem and shuts the blower off.

At our first house we couldn't get the temp below 82; and when we turned it on it got worse - turns out the TXC was in backwards and the system was over charged.
-----------------------------

Update re: my original post; I contacted the builder asking what method they use to calculate the load for the houses or if they have a generic blanket calculation that is "good enough" for the model. They said a customer care rep will be calling me in a few days..