New house, new AC woes....


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Old 08-25-14, 06:35 PM
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New house, new AC woes....

Hi there, 1st post and looking for some help.

I've made many mistakes during this process but it is what it is, I'm stuck with a beautiful house with a poor A/C system.

We live in North West Florida, so most days between June and September are 90F+ and 70% humidity (or higher) 2000 sq ft in sun light until 3pm in the afternoon. The house was built in 1956 with a couple of additions, I know for a fact the insulation isn't what it should be but so be it.

We bought a house in July (a flip, mistake #1), seller bought the house in March 2014 and hired some crack job A/C installer who literally ripped out the existing unit and put in a brand new 3.5 ton Ruud unit and left it at that.

Home inspector noticed that the A/C was frozen, we insisted that it be checked over prior to closing, (mistake #2)same crack job A/C guy comes out and signs off on it as being fine so we proceed the sale.

We move in a week after closing and notice it is not cooling what so ever, I check the coils and see that they are frozen, then take off the front cover and boom here it is.

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Fast forward a month and every morning the coils are frozen, requiring 30 mins of fan only time to thaw it out. My wife is a stay at home mom to 4 kiddos and keeps the air low on 71F, the house stays at around 74F all day until the sun goes down, so from 11am to 9pm it runs non-stop. But our livign room which is a huge room stays at about 80F until the evening, so the room we use the most is almost unbearable to be in

I had an A/C company come out and put Freon in the system as it was low. This A/C tech seemed to think that the ductwork is too small to handle a 3.5t unit. The air at the returns register 75 and at the vents 58 so it's doing a fairly good job of cooling but the air flow out of the vent is pretty pathetic, compared to our previous house, which was 1500 sq ft 3 ton in a heavily shaded location.

There are 3 returns, 1 in the smallest bedroom (my office) the door stays open, 1 in the living room, couch is about 5 feet away and 1 in the ceiling of the hall way (it's so far away from the unit I actually doubt any air is being pulled in from this return). I use those cheap ez green filters to try and limit the restriction of air flow, we have no animals just 4 kids under 4 years old lol.

Also a point to mention, the water is pumped out of the house via an electrical pump that goes up through the roof, I'm starting to wonder if the build up of cold water collects then freezes and has a snowball (pardon the pun) effect on the entire unit.

So I'm looking for some guidance on my next step, luckily we are coming to the end of Summer so thinks will get a bit more comfortable in our living room and we can hopefully take some steps to stop the freezing.

1) Does ductwork that is too small cause daily freezing?
2) Does 3.5 ton unit in a 2000 sq ft seem undersized?
3) How can I increase air flow out of the vents?

Any questions are welcome and any suggestions are appreciated.
 

Last edited by Reznor; 08-25-14 at 06:49 PM. Reason: corrected register and vent temps
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Old 08-25-14, 06:47 PM
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Has anyone checked the static pressure of your ductwork?
I use a Dwyer dual port digital manometer but less expensive models are available.

Robot Check
 
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Old 08-25-14, 06:49 PM
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Welcome to the forums.

Can you post the model number of the air handler ?
 
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Old 08-25-14, 06:50 PM
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As of yet, no we haven't had the static pressure checked.
 
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Old 08-25-14, 06:56 PM
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Is this what you were asking for?
 
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Old 08-26-14, 05:11 AM
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A manometer is a tool that would indicate if you don't have enough ductwork.
The model number should be on the outside of the air handler panel. The E.S.P. should be listed on the same tag. (Probably 1/2" water column).

The model number can often be used to find the manual.
The manual, the motor speed tap, and the static pressure can be used to look up the airflow output in cfm.
 
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Old 08-27-14, 12:55 PM
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Main supply should be about 14x16 or 12x20 return should be 20 round or 14x20ish range. If you don't have those sizes on your ductwork you are undersized. Can you get access to the ductwork like in an attic space or basement/crawlspace. You may have some dampers closed, branch piping thats crushed, leakage, etc. those are all causes of poor airflow.
 
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Old 08-31-14, 05:26 PM
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We have 2 16X20 returns directly underneath and then another 16x20 about 20ft away above the thermostat (I doubt that this return is actually pulling any air into the system)

Here is another photo from the system, does this show what kind of blower I have?

There is no rhyme or reason to the cooling, the living room which has a return stays between 76-80, our bedroom which is at the end of the house stays nice and cool probably 70F, but the bedroom that is adjacent to us (equal distance from the ac unit) stays between the 76F to 80F range. urgh can't wait for Summer to be over.

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Old 08-31-14, 05:49 PM
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Low airflow can easily be misdiagnosed as low refrigerant charge. Low airflow can cause freezups.

With low airflow in theory you should have a high split (above 20), unless there's also another problem like improper refrigerant charge or air in the system from not evacuating the refrigerant lines properly.

Does 3.5 ton unit in a 2000 sq ft seem undersized?
Nope.
 
 

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