Help! My BRAND NEW GOODMANA/C unit is costing me $275/mo in electric bills!

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  #1  
Old 06-24-15, 03:41 AM
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Help! My BRAND NEW GOODMANA/C unit is costing me $275/mo in electric bills!

Installed brand new 2 ton a/c unit 6 months ago in a 1966 Southern Florida, 800 square foot home...

Humidity hovers around 57-63% during the day and for some reason gets worse at night... averaging 60-70%

A/C worked fine when it was initially installed last August.

Thermostat ALWAYS set on same temp, 76 degrees but over the last month it doesn't remain 76 inside. By 3-4pm everyday it's anywhere from 80-85 degrees inside and it's than h*ll.
Unit does catch up at night or if it rains and cools down outside but humidity gets worse at night...

Early this morning it was 74% and it was miserable. Cool but sticky!


Coils were a little dirty but they've been thoroughly cleaned (oddly, the humidity readings actually increased after cleaning them....?)

My electric bill has QUADRUPLED last month.

Two A/C companies have come out & checked everything: EVERYTHING IS FINE...

The last company that came out is trying to tell (convince) me that my new roof, which used to have white singles and now has black shingles is the cause. (yep... they actually told me this). This is so far beyond ridiculous...

Iff this were the case I could see the electric bill increasing somewhat but it stands to reason that the unit would at least be able to cool the house down without running 24/7... right?

Can anyone please help me figure this one out? I can't stand the heat but i can at least deal with it... but my 12 year old dog cannot: she has severe heart failure and she is truly suffering.




*Black shingles.... Woohoo! Now that's some serious BS
 
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  #2  
Old 06-24-15, 03:53 AM
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Check the return air temperature at the intake grill and check it again by the furnace intake in the hot part of the day. You could have a return air leak.

Check the supply air temperature 2 feet from (after) the cooling coil.
 
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Old 06-24-15, 04:24 AM
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I can not see why anyone would have black shingles installed ?

How is your attic ventilation working ?

With the black roof , it probably needs to be upgraded / improved .

So the condenser is running just about non stop ? Or is it starting and stopping ? Are both the compressor and the outdoor fan starting and stopping together ? Is the indoor fan starting and stopping ?

Then the temperature of both of the copper refrigeration lines at the condenser and the outside air temp , and the temperatures Houston asked for .

God bless
Wyr
 

Last edited by PJmax; 06-24-15 at 06:26 AM. Reason: We DO NOT discuss pressures in an A/C system
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Old 06-24-15, 08:17 AM
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All has been checked

Everything has been checked... and I mean EVERYTHING... And I mean repeatedly with my very good friend (who spent 10 years working as an ac guy) standing along side every tech who's been here.

Unit runs all day long and doesn't stop... at night it does 'catch up' and cycles on & off normally. EXCEPT...just last night the humidity was 71%...lol... just inhaling was like breathing in soup.

Theres no leaks, everything is normal...absolutely everything is good.

Now, I didn't have this issue after new roof for a long time... even the days in which it was much much hotter than this past month (I've checked electric usage by day.(which also shows daily temps...& this just started).

This crap is literally consuming me... between this and the newly overheating, undiagnosable car I'm up to my a** in troubleshooting and HEAT!

Once again it's 80 degrees in here and it's not even noon!

Thanks so much for your help.... keep em coming!
 
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Old 06-24-15, 08:49 AM
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Easy Safe-Way to Test Your A/Cs Performance

Easy Safe-Way to Test Your A/Cs Operating Performance

If U want me to run a ballpark analysis of how your system is performing in respect to its ‘Nominal Rated Btuh’ I need at least the following numbers.

You will need to call a good HVAC Contractor to fix the performance problems we find.

Not a DIY fix; all U need is a good air-temp probe thermometer (digital reading in tenths preferable) and a low cost 'Indoor Humidity Gauge' > ACU-RITE Digital only $8.94 at Walmart or over the Internet.
This form is for anyone to use & come on here to have us analyze if U need to call an HVAC Contractor.

1) Helpful: condenser 'Tonnage' & SEER Rating of Unit &/or model number:
FIRST; We need to know the 'Indoor' % of Relative Humidity______ %

2) TXV or, orifice metering device? _______. Only if U know; not critical…

3) Outdoor condenser’s discharge-air-temperature ___°F

Subtract Outdoor air temperature: _____°F

Outdoor Condenser Air-Temp-Split ___°F

4) Need the ‘Indoor’ percent of relative humidity - in the middle of the rooms or, at Return-Air inlet grilles ___

5)Subtract Indoor Supply-Air Temperature __°F
Return Air Temp ____°F Subtract Indoor Supply-Air Temperature ___°F
Indoor temperature-split = ___°F

Indoor temperature-split ___°F

“Reply with Quote” Fill the #numbers in where the blanks were. Easy Safe testing of your A/C or heat pump cooling performance for all the visitors to use:

First, make sure the return air filter is clean, and then you should get a digital probe thermometer that reads in tenths degrees, (though U can use any mercury thermometer) and a low cost percent relative 'humidity gauge 'to check the 'indoor' humidity level.

If you have an air conditioner that was manufactured between 1992 and 2005 it will 'probably be' a 10 or 12 SEER (though some were higher SEER even back then) R-22 refrigerant units.

When the temperature reaches around + 80 to 95°F outdoors and the indoor temperature is 80°F and the relative humidity indoors' is right around 50% RH the outdoor condenser temperature split should be around 20°F above the outdoor temperature.

If the indoor temperature is 75° and the relative humidity is 50% then the air discharge temp-split off the condenser should be around 17°F.

The indoor temperature split between the return-air at the supply air grille closest to the air handler should be a 18 to 20°F temperature drop with either an 80°F or 75°F indoor temperature. This is also the indoor split with the higher SEER units at 13 SEER or above.

If the indoor temperature split is too high may have very low airflow which needs to be brought up to its normal CFM Rate.

If the outdoor condenser split is too high your air handler may be drawing hot outdoor air into the return from the attic causing the high condenser discharge air temperature; or it has dirty coils or lack of ambient airflow through the coils, check for cottonwood if trees are in the area.

On the new air-conditioning systems & any systems at 13 SEER or higher, the outdoor condenser split is lower than it is on the 10 to 12 SEER units; the indoor temp-split is the same according to the humidity level.

New 13-SEER units have a 'condenser' temp-rise 'at above conditions' of close to 17°F; a 16 or 18-SEER usually around 9 or 10°F need model numbers for more definitive temp-numbers.

If the temps are within +/- a degree or two, that air-conditioner is performing fairly well; if not, call an HVAC service contractor (in your case the installing contractor) and show them your test results; tell them you want it to pass their Delivered Performance Test.

If they don't know how to perform those tests call to find someone in your area hopefully that can do those tests; with modern test instruments they are not that difficult to do.
----------------------------
Another source of humidity is the infiltration of outside air into your home. This is mostly wind driven and operation of air moving devices. What things are contributing moisture & heat in your home? You need a complete indoor air change in 4-5 hours to purge indoor pollutants and renew oxygen.

If the dew point of outside air is +65-70°F and you want 75°F, 50%RH inside, you need to remove 2-4 lbs. of moisture per hour. At 3 lbs per HR= 2.88 pints or 1.44 quarts per hour. Please do this...!
 
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Old 06-24-15, 11:17 AM
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Why don't you provide us some numbers so we can help you. Like intake air temperature, return air temperature, in house humidity at that time, also hand feel the outside (near condenser) both large and small pipes, are they warm, cool, or cold ? You said everything has been checked, any check results ? did he check the following --- delta-T, subcool, or super heat ?
 
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Old 06-24-15, 07:17 PM
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How were you cooling the house before?
What was the difference in temperature between the intake grill and the return air inlet to the furnace?

It sounds like something has been overlooked.

If you don't provide us more information we cannot provide much help.
 
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Old 06-27-15, 04:46 AM
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Does the unit have a thermostatic expansion valve ?

Is the small line leaving the condenser unit warm / hot ? What is the temperature ?

Is the large line leaving the a-Coil cool / cold ? What is the temperature ?

What is the temperature of the air being blown vertically by the condenser ?

What is the Outside Air Temperature ?

God bless
Wyr
 
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Old 06-28-15, 10:27 AM
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Do you have the invoices? Were pressures, temperatures, etc written down? If they were, post them.

Were they checked? Did you see what was done.

I'm thinking major duct issue if flex or performance problem.

Post the model number and temp split across the condenser -> we can ballpark heat removal. (plug temp split and cfm into a formula)

------------------
When you got this new roof put in, is it possible that they took out the old vents when ripping the shingles off and never installed new ones?

Maybe the attic temp should be measured on a hot day and posted here, might give a clue - not sure what it should be to be honest.
 
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