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Old 09-15-2019, 10:12 AM   #1
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A/C system suddenly using much more electricity?


My parents are snowbirds and spend their summers in NY. They have a condo down in Florida. Today they got their monthly electric bill from Florida Power and Light for $130 dollars. Their usual electric bill is about $25-29 for this time of year.
The power company said most likely something is wrong with the A/C system and the best move was to have someone shut off the circuit that the A/C is on for a day and see if that lowers the power usage. They did that, and the power usage went from $4.75 a day to $0.40 for the day. Clearly its something with the A/C system.
I've been trying to read what could cause the A/C system to basically use 5x the power that it typically uses. I mean when they are there using the A/C its under $4.00 a day.
When they are away they have a the thermostat set to 80 degrees and a humidastat set to 50% so the A/C only goes on if humidity rises above 50 first. Everything has been working fine with that set up for years.

Any advice on what could be causing this? About 8 months ago they had to get someone to empty the system to level the piece of wood it was on, it started to sag, then refill the system. Could low Freon cause this?

thanks for any help in advance.
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Old 09-15-2019, 10:21 AM   #2
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Re: A/C system suddenly using much more electricity?


It could have a low refrigerant problem and is running both the compressor and air handler all the time and producing no cool air. Yes, I would have a professional look at the units and determine the cause of the problem.
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Old 09-15-2019, 05:07 PM   #3
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Re: A/C system suddenly using much more electricity?


Could their "rate" have changed also?
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Old 09-15-2019, 05:52 PM   #4
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Re: A/C system suddenly using much more electricity?


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Could their "rate" have changed also?
Just checked, its the same price per kilowatt for the two months before, July and August. Both those bills total were $24 and $25. Last year the price per kilowatt was the same also.
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Old 09-15-2019, 05:54 PM   #5
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Re: A/C system suddenly using much more electricity?


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It could have a low refrigerant problem and is running both the compressor and air handler all the time and producing no cool air. Yes, I would have a professional look at the units and determine the cause of the problem.
I did call a pro to come by and check but I'd like to figure out a couple causes so I'm not going in blind and being told I need a new system or something along those lines.
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Old 09-15-2019, 07:58 PM   #6
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Re: A/C system suddenly using much more electricity?


there are too many causes to list.
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Old 09-15-2019, 08:07 PM   #7
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Re: A/C system suddenly using much more electricity?


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I did call a pro to come by and check but I'd like to figure out a couple causes so I'm not going in blind and being told I need a new system or something along those lines.
We would need more info to help you. There's many variables. If they say it's low on refrigerant, ask them to write down the super heat and sub cooling that they measured, along with the pressures. Make a note of the indoor temp and humidity, as well as the outdoor temp.

If they have a SC of zero, and a SH above 20*f, then you likely have a leak and need refrigerant.

Cheers!
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Old 09-15-2019, 08:32 PM   #8
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Re: A/C system suddenly using much more electricity?


if their place in florida has a smart meter they should be able to access hour by hour electric usage - potentially helpful in figuring out what's going on.

it may not even be the a/c - a leaky hot water tap could do it if there's an electric water heater.
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Old 09-15-2019, 09:15 PM   #9
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Re: A/C system suddenly using much more electricity?


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if their place in florida has a smart meter they should be able to access hour by hour electric usage - potentially helpful in figuring out what's going on.

it may not even be the a/c - a leaky hot water tap could do it if there's an electric water heater.
It's possible but they Already tried turning off the circuit and seen positive results for a day.

Cheers!
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Old 09-15-2019, 09:17 PM   #10
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Re: A/C system suddenly using much more electricity?


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Originally Posted by user_12345a View Post
if their place in florida has a smart meter they should be able to access hour by hour electric usage - potentially helpful in figuring out what's going on.

it may not even be the a/c - a leaky hot water tap could do it if there's an electric water heater.
I believe it is figured out. The electric water heater is unplugged. The amount of power used went from $5 dollar a day to .40 cents when the A/C circuit was shut off. Its the only device on that circuit. It has to be the A/C that's causing the problem. The only other item running is the fridge, the fridge showed one spike at 4pm when the compressor must of turned on then and then back to almost zero energy use.

With the A/C circuit on now it averages 1.6 kW per hour. With the A/C circuit off it about .04 kW per hour. And when the A/C was working correctly it used .20 kW per hour average. That translates to the A/C using 8 times more energy than it was using last month.

Included some charts to show how the energy increase from year, month, day, hours. On Aug 12 it just jumped much higher than usual. Then stayed high until the A/C circuit was shut off at 9am on Friday Sept 13th.
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A/C system suddenly using much more electricity?-year.png   A/C system suddenly using much more electricity?-aug.png   A/C system suddenly using much more electricity?-sept.png   A/C system suddenly using much more electricity?-recent.png  
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Old 09-15-2019, 09:24 PM   #11
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Re: A/C system suddenly using much more electricity?


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We would need more info to help you. There's many variables. If they say it's low on refrigerant, ask them to write down the super heat and sub cooling that they measured, along with the pressures. Make a note of the indoor temp and humidity, as well as the outdoor temp.

If they have a SC of zero, and a SH above 20*f, then you likely have a leak and need refrigerant.

Cheers!
I understand Super, impossible to diagnose without more info. Just was looking for a couple or reason that could cause a drastic increase in power consumption of an A/C system. All I can find when I do a google search is stuff like how to lower your AC bill. Or is your A/C system becoming inefficient, try cleaning filters and coils type articles. Unfortunately I'm not there to take temps readings, see if its blowing cold air, see if if the compressor is running no stop, see if the fan is on all the time. My dads friend is helping them as nobody is there. Their unit is a middle unit on the first floor. So I'm also telling them as they have conditioned units to the left , right, and above they really could wait till they get down there in a month to fix it too.
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Old 09-16-2019, 12:51 PM   #12
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Re: A/C system suddenly using much more electricity?


If no one is there, it won't hurt anything by leaving it off.

I dunno if they have aux, electric heat, but if it's stuck on, then it could be causing the problem too.

Either way, you'll want to have as much info written down as possible. It'll help us, help you.

Cheers!
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