Frequently Asked Questions (and answers) about air conditioners & heat pumps, set #5

These FAQs about air conditioning and heat pump systems help troubleshoot and repair AC and heat pump systems.

These FAQs are part of an article series discussing how to inspect and repair all types of residential air conditioning systems (A/C systems). Page top image provided courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].

Air Conditioning & Heat Pump FAQs #5

These questions & answers about air conditioning & heat pump systems were posted originally at AIR CONDITIONING & HEAT PUMP SYSTEMS - home

Schematic: sequence of electrical tests useful in troubleshooting air conditioners and heat pumps.

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Older Air Conditioning & Heat Pump Questions & Answers Posted Originally at aircond1123.htm

On 2011-08-08 by (mod) - typical air conditioner air temperatures

Xinhua, please see OPERATING TEMPERATURES HVAC

On 2011-08-09 by Xinhua Chen

I have a new Lennox air conditioning XC17 and have problems. I would like to know:

1. what is normal discharge air temperature?

2. what is normal supply air temperature and return air temperature? hope this will help me to know if the Ac is normally working or not. Thanks.

On 2011-08-09 by jude

My A/C units, switch themselves on when I am out of the house,last night, one switched on and ran for 7 hours in a room we dont use....can you please advise why this is happening. Thank you for taking the time to read this

On 2011-08-08 by (mod) - motors drawing high amperage

Scoot:

re motors drawing high amperage, sure, a motor that is damaged or failing but still rotating may draw excess current - that's a standard test.

See ELECTRIC MOTOR DIAGNOSTIC GUIDE (Found in INDEX to RELATED ARTICLES at our Continue reading suggestions at the end of this article)

On 2011-08-08 by (mod) - gurgling water sounds when turn the air conditioning on

Anon: regarding: "when we try to turn the air on, it wont kick on. You can hear water kinda going thru in the furnace "

bubbling or hissing in the refrigerant piping is discussed at REFRIGERANT LEAK REPAIR

Sounds like a refrigerant charge problem. Of course also take a look inside the air handler (your "furnace") to see that there is no mechanical problem like a blower fan coming apart and flopping around or a partly broken blower fan drive belt (not all units use drive belts)

On 2011-08-08 21:46:59.972368 by (mod) -

Anon: regarding

"... noticed white smoke coming out of the registers doesn't smell like smoke what could this be? "

I hope you turned OFF the system immediately just in case you in fact were facing an electrical fire.

Other possibilities:

- refrigerant gas, if escaping rapidly from a leak such as a punctured refrigerant line, would make a hissing (or louder) sound and might appear as an odorless white vapor. (this is bad and is perhaps contaminating the environment too)

- a mechanical problem in the air handler that is producing loose debris such as a failing bearing

let us know what happened - the results may help other readers.

On 2011-08-08 by (mod) -

Ramon: for evaporator coil icing problems see the article FROST BUILD-UP on AIR CONDITIONER COILS listed under a series of diagnostic articles beginning at COOLING COIL or EVAPORATOR COIL

(Found in INDEX to RELATED ARTICLES at our Continue reading suggestions at the end of this article)

On 2011-08-08 by (mod) - AC system has stopped cooling but was working before

Anon: when your AC system has stopped cooling but was working before, start by asking if anything has changed: did someone turn off a switch somewhere? If air is coming out of the supply registers but is not cold, that suggests a compressor/condenser problem or lost refrigerant.

If no air is coming out of the supply registers at all, that tells us the air handler/blower unit is not running, or the fan belt or motor has broken or stopped.

Take a look at your thermostat - is it calling for cooling? If so, then check the indoor and outdoor equipment to see what is running and what is silent.

Then take a look at our air conditioning problem diagnostic suggestions beginning at LOST COOLING CAPACITY (Found in INDEX to RELATED ARTICLES at our Continue reading suggestions at the end of this article)

On 2011-08-08 by Anonymous

My central AC System stopped cooling. The temp is set at 75. What could be the problem and what should I turn off the unit.

On 2011-08-08 by Tom

Mine isn't very Cold

On 2011-08-07 by ramon

I have a trane ac system. Even when all vents are open but its very humid outside the evaporator freezes. The temp is set to 75.

On 2011-08-07 by Anonymous

i was in the other room where there are no ducts and when i came in the rest of the house noticed white smoke coming out of the registers doesn't smell like smoke what could this be?

On 2011-08-07 by Anonymous

when we try to turn the air
on, it wont kick on. You can hear water kinda going thru in the furnace

On 2011-08-07 by Scoot

In other words...is there a reason why the equipment would be drawing a very high amperage?

On 2011-08-07 by Anonymous

The system turns off normally, and this usage is WAY higher than normal...any advice on why the elec usage could have gone through the roof?

On 2011-08-06 by (mod) - A/C system never turns off

Scott:

a system that never turns off, or equipment drawing high amperage will increase the electric bill. First check with your electric utility about the normalcy of your usage level.

On 2011-08-06 by Scott

What could be making my central air unit use WAY too much electricity? It turns on and off, and is set to 78 degrees in Cincy, OH...and my bill was $720 last month. An experiment shows it is using about 120 Khw per day.???

On 2011-08-06 by (mod) - short cycling fan/compressor unit that keeps varying the fan speed sounds

Dave, a short cycling fan/compressor unit that keeps varying the fan speed sounds like something to diagnose with some confidence before launching into new ductwork or even replacing a circuit breaker

. If your circuit breaker were defective it wouldn't cause short cycling, it would either fail to trip on overcurrent or fail to turn back on. If no one changed the indoor air handler/ductwork as part of the compressor replacement, ask the HVAC company to diagnose the outdoor problem and explain it to you (and us). We will both learn something.

On 2011-08-06 by (mod) - outside unit motor turns on but fan does not spin

Anon: if your outside unit motor turns on but fan does not spin, see the FAN, COMPRESSOR / CONDENSER UNIT article (Found in INDEX to RELATED ARTICLES at our Continue reading suggestions at the end of this article)

On 2011-08-06 Dave

WE had a new compressor installed under warrantee. Current one has trouble cooling the house, and after a few hours everything fan/compressor outside and fan inside run from low to high speed in 20 sec cycles.

The unit then trips the circuit breaker. This never happened before, they want to put in a higher circuit breaker, and create new duct work> help

On 2011-08-06 by Anonymous

outside unit motor turns on but fan does not turn

On 2011-08-06 by (mod) - A/C works except at one register

Christopher if the A/C works except at one register I figure either that register has been shut or the duct has come disconnected somewhere.

Try first removing the register cover and looking with a flashlight into the ductwork from that end. If you don't see a crimp or disconnected duct you'll need to start tracing the ductwork backwards towards the air handler until you find the problem.

On 2011-08-06 by Christopher

A/C works, but one register is not producing any air. Air is coming out of every other register. It's been 100+ for over 35 days now, and the last thing I want to do is spend wasted time in the attic looking for the issue. I was hoping you could provide a suggestion as to where to begin to look?

On 2011-08-05 by (mod) - A/C keeps tripping the breaker

Dominic, if your A/C keeps tripping the breaker there is probably an electrical current overload - could be a compressor motor failing, overheating, or having trouble starting.

Turn off the system to avoid an electrical problem or fire and get a service tech out to diagnose the issue.

On 2011-08-05 by (mod) - frost or icing on your refrigerant lines

Hezekiah:

if you see frost or icing on your refrigerant lines there must be insulation missing. Also if the icing is occurring past the end of the cooling coil the refrigerant charge may be too much - overcharged.

Take a look under the COOLING COIL article (Found in INDEX to RELATED ARTICLES at our Continue reading suggestions at the end of this article) and click on the article titled FROST BUILD-UP on AIR CONDITIONER COILS

On 2011-08-05 by (mod) - air conditioner trips breaker after 30 minutes

Bud the air handler can be located as far from the compressor as needed at a building but the installer may need to use a larger diameter refrigerant piping system to overcome resistance, and s/he will need to adjust the refrigerant total charge to account for the volume in the piping.

On 2011-08-05 by Dominic O Setshego

What causes an airconditioner to go for a short time then stripe the breaker after 30mins or so?

On 2011-08-05 by Hezekiah Thomas

Why do the pipes from the unit freeze up and have ice on them.

On 2011-08-04 by Bud Ogden

Restated: How far from the air handler can the air compresser unit be located?

How far from the air handler be from the air conditioner compresser unit?

On 2011-08-03 by (mod) - condensation building up in the larger duct

Dave I'd start by taking a careful look at the condensate drain pan, it's side height, slope, and of course it's drain - to assure it's free flowing;

Also check that the evaporator is not partly clogged with dirt and debris as those can prevent the condensate from falling down into the drip tray.

On 2011-08-03 by dave

I have alot of condensation building up in the larger duct thats connected just beyond the evaporator. It starting leaking through the seam and the insulation type "wrapping". How can I stop this?

It a Goodman Model # GMNT 060-3
thanks

On 2011-08-02 by (mod) - causes of blown fuses on A/C system

A: as you know, a fuse will blow from either an instantaneous hard short circuit or from an overcurrent that occurs over a longer period of time.

So it would seem there's either an intermittent short or an overcurrent, or an intermittent overcurrent. It would probably help to look at a circuit diagram to see exactly what that control board fuse is protecting - what's on that circuit.

On 2011-08-02 by Anthony

I have checked it, it's normal.

On 2011-08-02 by (mod) - equipment keeps blowing fuses

Anthony I think if your equipment keeps blowing fuses and there is no evidence of a short circuit in the wiring itself I'd suspect that the equipment is drawing high amps - which points to a bad motor. Ask the service tech if s/he has measured the current draw on the system.

On 2011-08-02 by Anthony

I have goodman Air handler & My blower motor contorl board keeps blowing fuses, Have replaced control board, transformer, contactor, capacitor, t-stat, breaker, disconnect, the unit was working for about 5 days now it keeps blowing fuses on the board it will work 4 about a day then blow another fuse. HELP?

On 2011-07-25 by (mod) - A/C is blowing just warm air

Duane

if your A/C is blowing just warm air you will want to see the diagnostics beginning at LOST COOLING CAPACITY (Found in INDEX to RELATED ARTICLES at our Continue reading suggestions at the end of this article) .

On 2011-07-24 by Duane

A.C blows warm air

On 2011-07-25 by (mod) - Thermostat not working

Deanna,

if the old thermostat was not damaged, and if the wires were not damaged, cut, or broken during the work you describe, another possibility is that someone shorted out the low voltage transformer that powers the thermostat.

Check for voltage on the thermostat wires. 12-14V would be normal.

On 2011-07-25 by Deanna

My daughter thought she would change the thermostat on her heat pump/air conditioner. After taking off the old one, she realized that she had purchased the wrong one. So she rewired the old one, turned the unit back on,and now it is not working properly. She lives in a double wide mobile home.

At first only one half of the house had cold air and the other half had hot air blowing from the registers. The air flow is good except for the fact that the air was HOT! So I pulled the air filter out which is in the floor. It was past dirty. Then all of the other air vents began to blow cool air except for the one closest to the filter . This one is still blowing hot air and all the others cool air. What could possible be the problem? Please help.

On 2011-07-24 by MEHMET

HI HOW CAN I WIRE UP MY AIR CONDITIONING TO MY GAS-FURNACES MODEL GHS- 100

On 2011-07-18 by (mod) - how to wire up the air conditioner to the gas furnace

Abdu Wahab

See A/C DATA TAGS where to get the basic data about your unit. (Found in INDEX to RELATED ARTICLES at our Continue reading suggestions at the end of this article)

On 2011-07-18 by (mod) - how to sort out which wires go where on my AC unit

Craig:

a service tech can reconnect your wires properly, or if you are competent to handle it you will need a wiring diagram that is either already in/on the unit or is available from the manufacturer or in the service/installation manual for your unit.

On 2011-07-14 by Craig

I have a Heil 10 Permence Series central air unit model NACO3OAKA1, S/N# L010404976. The 2 downstairs 30AMP breakers kept popping so i decided to clean out the unit outside.

When shopvaccing near the wires, I believe I accidently knocked a yellow wire connection loose.

To see if I did, I turned everything back on, set thermostat to kick in the air and I could hear the furnace unit kick in downstairs but the A/C unit outside wasn't doing anything (no fan, nothing). I see one other yellow wire connected but this other one is dangling loose. Any help or would a picture help?:)

On 2011-07-18 by charles

my unit will cool a while and then stop. I turn it off for 5-10 mins. and turn back on and start cooling again

On 2011-07-14 by abdulwahab

i need to know how many tone in centeral ac

On 2011-07-14 by Will

Pierre,

My system actually drains inside to a pump that sits on top of the reservoir (where the condensate drains to).

The pump the pumps the condensate out of the reservoir when it reaches a certain level (by using a float switch).
I don't remember the make and model but I had to replace mine and I think it was about $100 US.

On 2011-07-13 by (mod) - condensate leak solutions

Pierre: take a look at the article CONDENSATE HANDLING, A/C for details (Found in INDEX to RELATED ARTICLES at our Continue reading suggestions at the end of this article)

I've dealt with this condensate leak issue in particular at split system cooling units and other installations at which a flexible condensate drain line was installed using poor workmanship, not sloping downhill from the point of entry into the line to the exit point outdoors. If your condensate drain is not properly sloped it will clog repeatedly, risking leaks into the building and even possible water or mold damage.

It's pretty easy to clean out a condensate drain line or trap using a small brush or even a length of smaller-diameter flexible plastic tubing as a probe; but be sure the line drains properly.

Will:
Using a manual damper to re-balance air flow through your duct system would not cause damage to the system unless you so completely cut off airflow that the coil iced over. In your case you are not talking about cutting off air flow as much as trying to get the cool air where you want it.

On 2011-07-13 by Will

Thanks again. So with a manual damper I could effectively create a dual zone system by placing the damper in the ductwork that supplies the first floor. I have hot water heat so remembering to reverse the process wouldn't be a problem unless I need to cool the first floor.

Would it cause any damage to the system ? I think that will be my last question :-)

On 2011-07-13 by Pierre

I have a LG wall unit and a heatpump outside. Last year our wall unit was dripping water inside our home.

We called a technician who was there for 15 minutes, according to my wife because I was at work.

He opened the unit and cleaned the tubing (for 150$) and told us to clean the filters and shoot some anti mold product. That's what I do! Again yesterday there was a bit of water forming at the base of the unit, not as much as last year. Anyone know how I could fix it myself without paying 150$ again.

On 2011-07-13 by (mod) - need to improve air flow balance

Will:

I would focus on trying to better balance the cool air flow. If an air conditioner air handler is on a lower floor or in the basement, it's always harder to push the cool air up to the top floor than it is to push warm heat air to that same location.

During the cooling season I'd try to maximize the air delivery upstairs (the hotter area) by closing off downstairs registers or by using a manual balancing damper in the ductwork. If the same ducts are used for warm air delivery during the heating season you'll want to remember to reverse the procedure.

On 2011-07-13 by Will

My heat has two zones using baseboard radiators. My AC seems to only have one zone that can be controlled by either thermostat. However, when the downstairs thermostat reaches it's programed temperature the cooling shuts off, despite the upstairs thermostat still reading too warm

. I guess my question should be, is it possible to add something into my system (like a damper of some kind) so I can cool my bedroom without cooling the first floor. To get my bedroom to a comfortable temp would mean cooling my first floor to something like 60 - I don't think it's even possible with it being 90 outside. Unfortunately, I have skylights so it's not as easy as just putting a window AC unit in.

On 2011-07-13 by (mod) - loud pop sounds

agree loud "pop" sounds like something burning up.

if you only have one AC system and no thermostatically controlled zones, then I'm not sure what you are doing with two thermostats unless one is for heat and one for cooling. Two thermostats are not normally wired to control a single device.

On 2011-07-13 by Will

thanks for your comments.
Unfortunately I do not have the technical nous to check for partial shorts but presumably a half decent multimeter across the live(s) and neutral at the motor will provide me with the incoming voltages.

What should I be looking for, 110V or similar (as opposed to 12V or similar) ?

I still wonder what the loud pop was from my thermostat but the fan is definitely running slower than it used to so maybe it is a multi speed blower and it's stuck in 2nd gear, so to speak. It used to whistle out through the registers.

I know my AC is one system and do not know of the existence of thermostat controlled dampers (if there is such a thing). I tried closing off some registers on the 1st floor and it does increase the volume on the 2nd floor but not by much. I also read somewhere that this might cause the system to "freeze".
Is it possible to have two zone AC with one compressor, blower, coil etc. ? I would think it could be possible with two sets of ducting and some kind of damper control to close off one of the zones if required.

On 2011-07-13 by (mod) -

Will I agree with the general principle that when debugging a mechanical system we pay special attention to what has happened recently or what has changed.

If your blower fan is a multi-speed model you might check to see if your thermostat replacement wiring or a control change at the blower assembly somehow left the fan running only on slow speed; low voltage can also slow down some motors. Check the voltage level and check for partial shorts to ground.

If you have two thermostats, one for first and one for second floor, either you have two A/C systems, one controlled by each thermostat, or you have zone dampers controlled by the thermostats. If it's the former, then you have a problem to debug with your upstairs A/C system

. If it's the latter (only one A/C system) then I'd try first seeing if you can better balance the airflow through your ductwork by adjusting manual dampers or outlet registers.

Anthony, regarding condensate drain line blockage, you will want to review the A/C condensate handling system information at

CONDENSATE HANDLING, HVAC (Found in INDEX to RELATED ARTICLES at our Continue reading suggestions at the end of this article)

probably your condensate drain line is clogged.

John if your A/C and heat are not coming on at all I'd look for a power switch that was off or a thermostat that is in the wrong mode.

See the diagnostic article DIAGNOSTIC GUIDE A/C or HEAT PUMP

On 2011-07-13 14:32:52.547992 by Will

When over-riding my thermostat to cool my house before the set time I heard a "pop" from the thermostat. Since then it seems like the air doesn't blow as hard from the vents. I have since replaced the thermostat but the air speed is not back to it's earlier level. Any ideas ?

Also, I have two Honeywell thermostats, one on the first floor and one on the second. The second floor is always hotter than the first but when the first floor thermostat reaches it's target temp the cooling stops. Is it possible to make it so that the second floor thermostat has overall control of the system ? (I'll need to be able to switch it back in winter)

On 2011-07-13 by Anthony

I have a water leak (consendatiin) which the water does not come out of the PVC pipe where it it suppose to drain from, it's leaking into my system!! HELP!!

On 2011-07-13 (Mod) said - where to start if the AC won't come on at all

John, See the diagnostic article DIAGNOSTIC GUIDE A/C or HEAT PUMP

On 2011-07-13 by John

My AC unit won't come on at all. When I switch it to heat it remains off also what can I check?

On 2011-07-13 by (mod) - no cool air

Amanda:

if air is coming out of your supply vents and it's not cool, it sounds as if the outside compressor/condenser is not running or if that component is operating, that you may have lost refrigerant. Time for a service call.

On 2011-07-12 by Amanda

Hi- I have a central ac unit with a thermostat inside. My fan is running, thermostat is set to cool. There is no cool air coming out of the vents. Ideas I can check first

On 2011-07-12 by Steve Dresner

Tanya check the fan for you condensor, in attic or outside if the fan is not running the system needs to be checked.

On 2011-07-12 by Tanya

Hello, my AC (in a condo unit) stopped cooling the air. The fan turns on and off ok according to the thermostat setting, however the air that's being circulated is room temperature.

I did check that the thermostat is set for "cool", changed the batteries just in case and re-set the thermostat which made no difference. What could be wrong? Thank you.

...

Continue reading at DIAGNOSTIC GUIDE A/C or HEAT PUMP or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see AIR CONDITIONER HEAT PUMP FAQs-6 for more recent reader Q&A on fixing an air conditioner or heat pump.

Or see these

Recommended Articles

• AIR CONDITIONING & HEAT PUMP SYSTEMS - home
• AIR HANDLER / BLOWER UNITS - home
• COMPRESSOR / CONDENSER REPAIR - home

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