A/C Cycling too much?


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Old 07-20-08, 10:03 AM
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A/C Cycling too much?

I have an a/c unit that is about 10 years old. It was serviced (freon added) last year. I think it is cycling too much while not keeping the house cool.

Temps outside: high 90s
thermostat set to 81
A/C cycles on for 10 minutes or so and off for about 5 minutes.

house is 1100 sq/ft single story
only about 5 inches of insulation in attic

small line outside is warm to touch, inside not as warm
large insulated line is cold and wet, inside cold and wet

At the unit in the closet where the small line goes in to the unit there appears to be condensation (or liquid of some kind) where the metal tape covers the entry point.

From my description, do things seem normal?

I have a Home Warranty (American Home Shield) so I can always call for repair. However, a local contractor is offering a "complete A/C rejuvination" for 90.00 and he guarantees no breakdowns this year or repair is free.

I am just concerned about the constant cycling. My electric bill is killing me.

Any advice appreciated

Mitch
 
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Old 07-20-08, 10:15 AM
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What is the temperature going into the return and out of the supply closest to the air handler/furnace?...should be around 17 to 20 deg. split.
 
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Old 07-20-08, 10:20 AM
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You say freon was added last year. Freon never goes away unless there is a leak, so I'm curious if a leak was ever brought up?
 
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Old 07-20-08, 10:31 AM
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Originally Posted by tinmantu View Post
What is the temperature going into the return and out of the supply closest to the air handler/furnace?...should be around 17 to 20 deg. split.
I have no way of checking the temps right now. Would have to buy a thermometer.....any suggestions on what I should buy? Just need something cheap but functional
 
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Old 07-20-08, 10:46 AM
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Wal-Mart or Home Depot would have a cheap digital thermometer, I'm sure. Even if it werent' 100% calibrated, it would give you a temp. differential fairly accurately. It's just one of a few things a homeowner can check before having to call in a pro.
 
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Old 07-23-08, 02:10 AM
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Well, I cleaned the inside of the coil. Gosh that thing was dirty. I had been spraying the outside but didn't know I was supposed to take the top off and clean it from the inside out. Seems to be cooling better.

Went to Walmart yesterday. Only digital thermometers I could find were in the pharmacy, others in hardware were much to big. will check at Lowes and Home depot tomorrow and post temps then.
 
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Old 07-23-08, 03:27 AM
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Air Conditioning Repair

You said the small line was sweating outside your air handler is it doing this at a device (brass threaded fitting or steel bulb like cylinder) if so you may have a restriction make sure it is not just getting moisture on it due to its proximity to the suction (cold) line
 
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Old 07-23-08, 10:11 AM
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Originally Posted by mike n View Post
You said the small line was sweating outside your air handler is it doing this at a device (brass threaded fitting or steel bulb like cylinder) if so you may have a restriction make sure it is not just getting moisture on it due to its proximity to the suction (cold) line
It appears the moisture is coming from the suction line just above it. I'll have to watch it for a day just to be sure.
 
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Old 07-23-08, 12:48 PM
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Originally Posted by hmc1570 View Post
Went to Walmart yesterday. Only digital thermometers I could find were in the pharmacy, others in hardware were much to big. will check at Lowes and Home depot tomorrow and post temps then.
Look in the home hardware or garden section of just about any department store for an indoor / outdoor digital thermometer with a wired outdoor probe. Many available for less than $20. Use the outdoor probe up close to the return air or supply grilles. These thermometers may not be the most accurate but they are repeatable and mostly what you are interested in is the differential temperature.
 
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Old 07-23-08, 02:39 PM
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Thanks Furd, will give you an update later today or tomorrow.
 
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Old 07-23-08, 02:45 PM
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Don't forget the kitchen gadgets area......
 
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Old 07-24-08, 09:28 PM
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temp readings from vents

Outside temp 102 degrees at about 4:30pm

Thermostat ste at 81 degrees

Living room vent (closest vent to closet) (used to be a garage) 67.5 degrees

Air return in living room 81.1 degrees

Air return in laundry room (directly below closet, no ac vent in this room) 80.2 degrees

Vent in bedroom (farthest room away from closet) 70.3 degrees

I do suppose there is a margin of error on these readings but a ballpark at least.
 
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Old 07-26-08, 10:23 AM
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A C Repair

Your temperature difference is kind of low should be between 15 and 20 degrees but because your suction line temperature is close to being right going by your description (you would need an accurate line temp reading to be sure) you don't want to immediately assume refrigerant issues in this case I would start looking for air infiltration in your return is your ductwork in the attic? You can easily air infiltration by taking an air temperature reading at the air handler/ furnace if the temp is higher then you have a significant leak in your duct if not then you probably have a refrigerant circuit issue (low charge, metering device malfuction or bad valve in compressor)
 
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Old 07-26-08, 11:25 AM
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Room T-stat with on/off differential settings or one adjustable cycles/hour

Originally Posted by hmc1570 View Post
I have an a/c unit that is about 10 years old. It was serviced (freon added) last year. I think it is cycling too much while not keeping the house cool.

Temps outside: high 90s
thermostat set to 81
A/C cycles on for 10 minutes or so and off for about 5 minutes.

house is 1100 sq/ft single story
only about 5 inches of insulation in attic
"There should be a lot more insulation in the attic." - udarrell

small line outside is warm to touch, inside not as warm
large insulated line is cold and wet, inside cold and wet

At the unit in the closet where the small line goes in to the unit there appears to be condensation (or liquid of some kind) where the metal tape covers the entry point.

From my description, do things seem normal?

I have a Home Warranty (American Home Shield) so I can always call for repair. However, a local contractor is offering a "complete A/C rejuvenation" for 90.00 and he guarantees no breakdowns this year or repair is free.

I am just concerned about the constant cycling. My electric bill is killing me.
Any advice appreciated Mitch
Is there a supply air register throwing air at or near the room T-stat?

The fact that it runs only 10-mns & is off only 5-mns, tells me the room T-stat is improperly located.

You could also buy a room T-stat with a on/off differential setting, or one adjustable for so many cycles per hour.

With at 50% RH, & a large 20" fan to keep air circulating you will be comfortable with a 3-F or more degree room temp variation. HVAC RETIRED - udarrell
 
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Old 07-26-08, 01:45 PM
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Udarrell,

The thermostat is in the hallway at about the center point of the house. No vents near it. However, the wire leading to the thermostat runs through the wall into the closet where the water heater is, runs up the wall and through a hole in the ceiling then along the attic floor to the a/c closet.

Is the thermostat in the optimal location or should it be moved?

More insulation is in the future. Had planned on it in april but broke my foot and had to postpone. When I bought the house there was no insulation over the living room (former garage). I crawled up there and put some cellulose down, seven bags total with most of it over the living room.

I don't think there is any insulation in the exterior walls.

No trees for shade so sun beats on the house all day.
 
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Old 07-26-08, 01:51 PM
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Originally Posted by mike n View Post
Your temperature difference is kind of low should be between 15 and 20 degrees but because your suction line temperature is close to being right going by your description (you would need an accurate line temp reading to be sure) you don't want to immediately assume refrigerant issues in this case I would start looking for air infiltration in your return is your ductwork in the attic? You can easily air infiltration by taking an air temperature reading at the air handler/ furnace if the temp is higher then you have a significant leak in your duct if not then you probably have a refrigerant circuit issue (low charge, metering device malfuction or bad valve in compressor)
Duct work is in the attic. It appears to be large insulated tubing. So I understand, should I put a thermometer in the air handler closet to check the temp? or am I crawling into the attic?
 
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Old 07-26-08, 02:34 PM
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The idea is to rule out the attic by taking temp in the air handler itself before the plenum goes into the attic. You have to find some place to get say a skinny 5" probe thermometer in there somewhere between where the cooling coils are, and before it enters the attic where it is hot. If there is no such place, I'd drill a small about 1/8th inch hole in the plenum and stick the 5 inch skinny probe in there. (Of course you want to be somewhat downstream of the coils as to not drill into them, as unlikely as that should be.)
 
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Old 07-26-08, 03:09 PM
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Originally Posted by ecman51` View Post
The idea is to rule out the attic by taking temp in the air handler itself before the plenum goes into the attic. You have to find some place to get say a skinny 5" probe thermometer in there somewhere between where the cooling coils are, and before it enters the attic where it is hot. If there is no such place, I'd drill a small about 1/8th inch hole in the plenum and stick the 5 inch skinny probe in there. (Of course you want to be somewhat downstream of the coils as to not drill into them, as unlikely as that should be.)
In the closet where the air handler is and where the plenum goes into the attic, there is an open space about 4" by 18" into the attic. this space is blocked by a wire screen. Will take the temp there?
 
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Old 07-26-08, 03:56 PM
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Temp must be taken -IN- the plenum, no matter how you figure or describe it.
 
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Old 07-26-08, 04:07 PM
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Understood.

Is that hole into the attic a concern?
 
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Old 07-26-08, 04:12 PM
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It is not ductwork

The complaint is: Short cycling. ( This does not include cold air from a register blowing on the thermostat - Clearly by the homeowner its not the case.


If the ductwork were degredated in any way, it would cause loss of cooling.... and longer running periods - It does not seem like it is loss of cooling in the conventional sense - just not cooling long enough...

More information is needed in order to make a logical judgement. Without it...its simply guessing, however, I think I can assume that the system worked ok in the past - That eliminates install problems. It also seems that the refrigerant is boiling properly as it returns to the compressor (Wet-cold vapor line).

It sounds like it might be a thermostat problem. - Possibly the differential is set too close. ( I agree with udarrel)Beyond that without clear information - it would be just guess work.
If this problem is to be uncovered in a forum - need spacific temps and pressures such as superheat - subcooling - suction and discharge pressures - ambient outdoor temps - indoor return temp - supply temp in the plenum.

You might want to take the thermostat off the wall and short out the - red - green- and yellow wires(A/C) ...add the orange wire to the bunch if it is a (heatpump) (unless): it is anything but a rheem heatpump... Short them all together for 1 hour. See if the A/C - Airhandler/Furnace units cycles! If it remains on...and begins to cool - I think you know where I am going with this!
 
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Old 07-26-08, 04:12 PM
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Why? Is it open around it where attic air can come into the living space, and vice-versa?
 
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Old 07-26-08, 04:20 PM
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Originally Posted by ecman51` View Post
Why? Is it open around it where attic air can come into the living space, and vice-versa?
yes. this opening is directly above the air handler. I can see into the attic. there is a door on the closet (which stays closed).

If the screen were not there, I could put my hand up into the attic. Checked the temp at that opening - 106degrees.
 
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Old 07-26-08, 04:26 PM
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If it is a furnace

Are you sure its an "Airhandler"? Homeowner never gave model # of the units in question. A good question jarredsdad always askes!

If its a furnace - The combustion air (During heating season) is being brought in through the attic (Very common in alot of states) - The closet door would have to be sealed - This attic heat would not affect the operation of the unit providing all the connections to duct were tight and all the panels were tightly secure - as if it were located in the attic itself as in a horizontal install.

* It would be a problem if the closet door had vanesian slots in it though - and as I said - I assume it worked in the past as the homeowner stated!
 
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Old 07-26-08, 04:35 PM
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Originally Posted by The Real Deal View Post
The complaint is: Short cycling.


If the ductwork were degredated in any way, it would cause loss of cooling.... and longer running periods - It does not seem like it is loss of cooling in the conventional sense - just not cooling long enough...

More information is needed in order to make a logical judgement. Without it...its simply guessing, however, I think I can assume that the system worked ok in the past - That eliminates install problems. It also seems that the refrigerant is boiling properly as it returns to the compressor (Wet-cold vapor line).

It sounds like it might be a thermostat problem. - Possibly the differential is set too close. ( I agree with udarrel)Beyond that without clear information - it would be just guess work.
If this problem is to be uncovered in a forum - need spacific temps and pressures such as superheat - subcooling - suction and discharge pressures - ambient outdoor temps - indoor return temp - supply temp in the plenum.

You might want to take the thermostat off the wall and short out the - red - green- and yellow wires(A/C) ...add the orange wire to the bunch if it is a (heatpump) (unless): it is anything but a rheem heatpump... Short them all together for 1 hour. See if the A/C - Airhandler/Furnace units cycles! If it remains on...and begins to cool - I think you know where I am going with this!
I appreciate what you are saying. But I don't have the equipment or expertise to do all those tests.

I can short the thermostat wires. but See if the A/C - Airhandler/Furnace units cycles! If it remains on...and begins to cool - I think you know where I am going with this would this mean the thermostat is the problem or something else.

I realize you can only evaluate with the information I provide. I am just trying to find out if this repair (through American Home Shield) or just a "system rejuvination" as advertised by a local contractor.

Bought the house in 2006. Its been like this since we moved in and I have done as much as I can to insulate and undraft the house.

As I am typing, it is 100 degrees outside. the thermostat is set to 81 degrees. Until the sun got to the back of the house, A/C was cycling as I had described. about 45 minutes ago the temp on the thermostat rose to 82 degrees and the A/C has been running ever since. Temp has not dropped.
 
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Old 07-26-08, 04:46 PM
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Erroneous ?

You said: "small line outside is warm to touch, inside not as warm- large insulated line is cold and wet, inside cold and wet" - "I am just concerned about the constant cycling. My electric bill is killing me." - "It was serviced (freon added) last year. I think it is cycling too much while not keeping the house cool."

I assumed it had worked before - or you would have fixed it last year?

These are very important indicators.

Could this be erroneous? It is now starting to sound more like a refrigerant problem... We dont even know if its a furnace or airhandler - Heatpump or A/C - Model numbers of nothing - There is just not enough info - I cant help you without it. Sorry!
 
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Old 07-26-08, 05:07 PM
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model numbers

As you can tell, I am clueless.

Here are the model numbers

Inside unit where the coil is on top of the furnace
519DXS036000MAAA
Carrier

Outside unit
590ANX036000ABAA
Carrier

Furnace
394CAD036075
Don't see manufacturers name anywhere. day&night lable on front
 
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Old 07-26-08, 06:14 PM
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Home shield

You said: "I have a Home Warranty (American Home Shield) so I can always call for repair."

Since you are covered by this homeshield warranty program - Simply dial their number and call for service. I dont think that would be a bad idea.

I doubt that you would DIY if you infact found a solution to your problem. You cannot provide data necessary to complete a logical synopsis. It turns out without the data to be more of a guessing game.

I think it is fruitless to try and figure out this problem when you have a warrany to boot!

If the problem is the homewarranty program cant fix the problem - Call another company for the diagnosis and then give it to the homewarranty company to reemburse you as they fix the problem.

What more could be easyer?
 
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Old 07-27-08, 02:29 PM
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I was just trying to detemine if it was "broken". I didn't want to call AHS for a non-repair issue.

If I get the "rejuvination" service from the local contractor and he finds a need for repair problem then I'll call AHS and pay the service charge for the repair.

I just needed help making a decision. I didn't mean to waste anyone's time.

Thanks

Mitch
 
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Old 07-27-08, 04:19 PM
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Originally Posted by hmc1570 View Post
I was just trying to detemine if it was "broken". I didn't want to call AHS for a non-repair issue.
And that is a very legitimate reason. On another forum here, just the other day I read, someone was about ready to call an appliance repair outfit or electrician or ? (can't recall the forum) but the problem the homeowner ended up finding, just before making the call to the repairman, was almost as equivalent to finding someone had unplugged an appliance and calling out the repair man to take a look!
 
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Old 07-27-08, 04:37 PM
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Originally Posted by hmc1570 View Post
. . . a local contractor is offering a "complete A/C rejuvination" for 90.00 and he guarantees no breakdowns this year or repair is free.

Mitch
I can guarantee you that if this contractor has to fix something that costs them money, they'll make you pay for it. That price sounds about right for regular maintenance if nothing major is found.
 
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Old 07-27-08, 04:42 PM
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One thing to look for would be loose connections. If the call for cooling is interrupted, many thermostats and some condenser units have a built-in delay even if the call was interrupted just for a second. The delay is often 5 minutes.
 
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Old 08-08-08, 03:12 AM
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Update

Well, I called American Home Shield and told them the situation. They put me on a three way call with the contractor who recommended just coming to look it over. If any problems found, they could fix it.

System is working properly. The numbers he wrote down for me are:

125 degrees F 78psi at 97 degrees F outside temp. He said that is within normal range.

Temp coming from vent is 47 degrees.

We had a long discussion about factors involved and he recommended I turn off the ceiling fans as they were pushing warm air down (all three fan motors were radiating temps around 110 degrees).

I am using cheap see through filters and he recommended a better quality filter.

going to see how things run for a week or so. Will post back then.

Thanks for all your suggestions. At least now I know my A/C unit is OK.

Mitch
 
 

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