Recent Questions & answers on how to diagnose, repair air conditioners & heat pumps.

This article series describes how to inspect and repair all types of residential air conditioning systems (A/C systems). Information for home buyers, owners, and home inspectors about A/C or heat pump system problems. Page top heat pump operating schematic provided courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].

Air Conditioning or Heat Pump System FAQs Set-2

The questions and answers immediately below were posted originally

at AIR CONDITIONING & HEAT PUMP SYSTEMS - home. Be sure to see the recommended topics and articles given on that page.

[Click to enlarge any image]

On 2019-06-16 by (mod) - can I just pump in R407C in an R22 system?

Jimmy

You can compare refrigerant gas properties and allowable substitutions in our article on REFRIGERANT GASES & PIPING inspectapedia.com/aircond/Refrigerant_Gas_Guide.php

On 2019-06-16 by jimmy z

Having to change out my condensing unit with R22 and wondering to save a $ if using 407c, I'm to the understanding that this gas works to the same pressure as R22 so wouldn't have to change out evap coil and just flush sys throughly will this work. Can someone help ? #to good to be true

On 2019-06-13 by (mod) - My A/C won't start up

Tony:

Please check where we have already replied to your identical question at

https://inspectapedia.com/aircond/Air_Conditioner_Wont_Start.php - please take a look at that page.

On 2019-06-12 by tony

Im in office building. each unit has own ac unit outside. turned on work for two days no problem. Today stop cooling. fan inside on but no air flow. air unit outside nothing. no sound when turned on. I check panel for trip switches. On left side label A C right side had two single switches together. label a c and heat. look this switch was tripped.

On 2019-06-11 03:37:05.687103 by (mod) -

Rick I think we have several things mixed up here. The outdoor compressor fan does not remove Frost from the indoor evaporator coil. It's air movement across the coil that does that.

In general if a air conditioning system can't get the humidity level down then the system has been oversized. Course there could be other problems such as a cooling coil that's becoming blocked by Frost or dirt. Sounds like you need a competent service tech on site.

On 2019-06-10 22:00:46.886583 by Rick Z

Sorry, comment immediate below is from Rick Z.

On 2019-06-10 21:59:29.183465 by Anonymous

Also, this new system, installed last August 2018, has never been able to get the humidity lower than 60%. In fact, while it cools the condominium well, the humidity will actually sometimes rise while it's running. Now I suspect that's because the blower fan is running after the compressor has shut down, thereby taking residual moisture off the evaporator coils and returning it back to the home. The system is sized correctly @ 2 tons blowing at 850 cpm, for a 1700 sq ft condominium on 2nd floor of 4 story building.

On 2019-06-10 11:20:18.615582 by Rick Z

Just to clarify... The blower motor in the furnace keeps running even when the cooling has stopped. However, the compressor fan is also running without providing cooling. This is happening frequently, but randomly, throughout the day.

On 2019-06-09 01:05:05.737413 by (mod) -

Sometimes when a fan keeps running it's because the system is entering a defrost cycle. However I would expect the compressor to stop.

On 2019-06-08 13:18:52.376088 by Rick Z

The fan on my A/C continues to run after the cooling stops. I have a temp probe in a vent and watch the air temp climb until the next cooling cycle and the temp drops again. This symptom is not consistent, because often the fan shuts off about a minute after the compressor stops. What I have noticed is that when the fan continues to run, the compressor also seems to be running, which doesn't make sense because the vent temp is rising. Perhaps it's just the compressor fan that continues to run, not the compressor itself. If the compressor fan runs, would that keep the blower fan running?

On 2019-06-02 23:44:16.421030 by (mod) -

You're welcome to post comments and pictures together, you can include one photo per comment. You also should be able to look at the label or data tag on your equipment and Elsewhere on the equipment for the manufacturer's brand and model.

On 2019-06-02 23:36:45.320545 by MG1

if i send pics can you tell me which one it is?

On 2019-06-01 01:22:38.014812 by (mod) -

I'm sorry I can only give rather vague advice because I just don't know a thing about your installation. But in general if you found a fuse blown you would rule out a short in the wiring or in a control and then assume that there's a problem with a failing motor that's drawing High current. You could also have a bad start / run capacitor

On 2019-05-31 21:32:56.922237 by MG1

i'm having a problem with my Trane AH motor (TWE049E13FB2). sometimes it starts and sometimes it doesn't. obviously when it doesn't the unit freezes up. i replaced the circuit board, found a blown fuse (5amp). with the door open (no safety switch 2004 model) i have got it to start by turning the breaker on and off (i know, not the best way to do it). right now i have the fan on continuously so it doesn't freeze up. i'm curious what starts the motor (i didn't see anything that looked like mine throughout your site.

On 2019-05-22 20:38:05.303238 by (mod) -

Otis,

Am I right that we're talking about your outside compressor/condenser unit?
Is it only the outdoor condenser unit fan that's not running or is its compressor motor also off.

It's possible that the root problem is the compressor motor itself or a control board in that unit.

See the simple diagnostic steps starting at COMPRESSOR/CONDENSER REPAIR https://inspectapedia.com/aircond/AC_Compressor_Repairs.php

On 2019-05-22 20:34:35.213945 by Otis gabriel

The fan on the 3 ton air conditioner does not rotate when the unit is turned on. The fan on the furnace blows air from the vents but the air is not cooled. Electricity is going to the ac unit because the fan housing is very warm but the fan does not spin.

On 2019-05-19 18:11:05.386917 by (mod) -

Thanks for commenting, Tom.

On 2019-05-19 18:00:07.786438 by Tom

Re: Tan/brown gummy substance. This may also be a seam sealer or caulk to prevent leakage along a pan joint. If it won't wash off with water, I'd recommend you leave it alone.

On 2019-01-28 15:14:31.405726 by (mod) -

I can't say for sure what thee debris is in your photo Evelyn, but it looks to me like there is a combination of corrosion (white mineral salts on metal) from leakage or clogged or blocked condensate drainage, AND a mixture of house dust and dirt and water.

The system ought to be inspected and cleaned by a service technician.

On 2019-01-28 13:17:19.313102 by Evelyn

I would like to know what the tan/brownish gummy substance is that I see in my HVAC's condensate drain pan. Thank you: looking forward to the responses. ET
- image lost

On 2019-01-22 00:50:06.093173 by (mod) -

Reader adds that he found this sketch online

We OPINED

That looks reasonable, and very simple - it does not appear to me to show all of the pipe connections in the manuyal. Apologies, but I may be the only one who responded to you but that does NOT make me an expert on hooking up a chiller unit. I'm very disappointed if the manufacturer won't answer basic hookup questions from you by phone - if that's the case I ought to add that observation where we list that company's contact information.
- image lost

On 2019-01-22 00:47:44.057308 by (mod) -

If the manufacturer doesn't have piping diagrams that you requested, I infer that it's because the specifics of how pipes are routed to and from the chiller depend on the physical properties of the installation site and perhaps have nothing to do with the operation of the unit itself, a long as the flow rates meet the design specifications.

I'd expect that the installation and operation manual for the unit would at least give the basic requirements for water flow rates or capacities.

Those two statements lead me to wonder if perhaps the root trouble here is just how you are phrasing your question or request. Perhaps if you go to the manufacturer with specific questions they can be of more help. After all they have a great interest in the successful installation of their product.

Do you have an IO manual for the equipment? If so I'd like to see a copy.

Reader follow-up:

Thank you for getting back with me. This is what I received from the manufacturer ( see attachment). I am a plumber by trade but I've never piped one in before and I'm the only one at the embassy capable of doing it. I know it should have a bypass installed before the shut offs on both supply and return lines... but what comes after that? I hope I made my question at least a little clearer. I know there are controls, strainer/drain port, filter, and I'm sure I'm missing something....and in what order do they go?
Thank you for your help

See MULTIAQUA A/C, Chillers, Fan Coil Units at

https://inspectapedia.com/heat/HVAC-Manuals-Air-Conditioners-Boiler-Furnaces-J-O.php#MultiAqua

The company gave this advice:

It was a pleasure speaking with you. Attached is the IOM for the MHCFC4W for your review.

Unfortunately, we do not have or provide piping diagrams for this unit. When installing control valves, I would suggest installing them in the supply line, so when the unit satisfies, water flow through the coil will be stopped. Please ensure that the control valves are 24V, drive open/spring closed.

On 2019-01-21 by Thomas

I work overseas at one of our many U.S. Embassies. I have been tasked to install a

MultiAqua chilled water cassette 2- pipe fan coil unit and I can't seem to find a piping diagram for supply and return lines, with all the valves and controls in the proper sequence, anywhere. Not even the manufacturer could supply this info

. Can you please help? I want to make sure that this unit operates proficiently.

Thank you

Desperate for info

On 2019-01-20 10:27:21.261753 by Lit Zeno

Ac coils freezing over after cleaning filter n adding antifreeze can’t afford repair man so trying to fix it myself i think it’s something simple not sure any info help!

On 2019-01-06 19:59:57.224441 by (mod) -

Checking out the A/C Control Board

Start with a visual inspection for signs of overheating: burn marks, melting components

If you are qualified, trained, and can do so without getting shocked or killed, you would check the current draw of the unit when the A/C motor is trying to start up.

PS

I would much like to see some photos of the burned contactor - both the whole device and closeups of the actual damage.

On 2019-01-06 19:40:00.686686 by (mod) -

Daunne

Well my goodness!

More on why an air conditioner's compressor / condenser unit might be burning up or welding contactor or relay component

I most-respect the tech who answered "I don't know" rather than making up an explanation or offering to just throw money at the unit.

What's disappointing is getting answers without the slightest effort at inspecting and troubleshooting the unit. NOBODY can give a completely-reliable answer to your AC unit welding contacts over the telephone.

What's wanted is an on-site inspection by an experienced HVACR technician. Call an established service company, ask to speak with the service manager, and politely explain that you've been getting lots of opinions and no help, and that you would be grateful for and glad to pay for an inspection and diagnosis and repair by one of their senior, experienced technicians.

Regarding the fire ant in the air conditioner problem, yes it's true that fire ants sometimes nest in outdoor compressor/condenser units AND it's possible that insects can invade and short circuit or damage electrical components.

Most likely, even a moderately-careful visual inspection will tell you - or your senior technician - whether or not there are ants or other invaders inside the compressor/condenser unit. Look for ants, an ant mound of debris, insect fragments.

If you find an ant invasion the unit can be cleaned - often simply by hosing it off, taking care not to soak electrical components. If the invasion is extensive or recurrent you'd get help from a pest control expert who will apply an appropriate pesticide around the unit and elsewhere if needed.

More details about fire ants and their control is in this U.S. USDA Fire Ant Manual
inspectapedia.com/exterior/Imported-Fire-Ant-Manual-USDA.pdf original source: US Department of Agriculture, USDA, www.aphis.usda.gov/import_export/plants/manuals/domestic/downloads/fire_ant.pdf

The manual does not discuss invasion of air conditioners but does give help identifying and controlling imported fire ants.

About installing a "hot start" device, most likely referring to a hard-start capacitor, that's not an unreasonable guess but some additional explanation, in which I am GUESSING at what that service tech was thinking, would have been helpful to both of us.

I suspect she was thinking the following: if a compressor motor is faililng and having trouble starting, we can add a hard-start capacitor that gives it an extra high voltage kick to get the motor going. A hard start motor can sometimes draw high current that in turn might burn a contactor or switch. However if a compressor motor is failing, while adding a hard-start capacitor may keep it running for a time, we ought to realise that we may have to replace a failed compressor motor ($$$) soon.

Details are at

CAUSES of HARD STARTING ELECTRIC MOTORS inspectapedia.com/electric/Motor_Hard_Start_Causes.php

and at

CAPACITORS for HARD STARTING MOTORS inspectapedia.com/electric/Starting_Capacitors.php

On 2019-01-05 15:18:25.245011 by Daunne

Thanks for your time and advice. I have contacted three techs.and gotten the following answers: I don't know - - You may need to install a hot start device - - you may a have a fire ant problem. Rather than pay one of these techs to come out, I did the following to keep from buying contactors. I installed a 3 phase 40 amp relay to split the compressor load current to make it thru the winter. It is working fine now. I will soon remove this relay and inspect the contacts. I realize this is probably only a band-aid approach, however will try for a different tech later this year. Also, would like an explanation of how to check out the control board. Again thank you for your time and diagnosis.

On 2019-01-04 20:02:14.398322 by Daunne

I have a 5 ton Rheem heat pump/ac system that is 13 years old. About 9 months ago it started burning and welding the contacts on the in the condensing unit about every 3 to 4 months. The thermostat would turn off the air handler but the condensing unit would keep running and ice up the suction line back to the evaporator coil. At this time the heat pump operation is fine. I'm sure there is an answer to this problem. Any help you can provide will certainly be appreciated.

On 2019-01-06 by (mod) - 13 y.o. Rheem heat pump contacts keep burning or welding

Daunne

Well my goodness!

Shown here: SUPCO A/C or heat pump temperature sensor used to detect freezing conditions or coil icing. Opens at 35 degF to permit the compressor motor to run at safe outdoor temperatures.

More on why an air conditioner's compressor / condenser unit might be burning up or welding contactor or relay component

I most-respect the tech who answered "I don't know" rather than making up an explanation or offering to just throw money at the unit.

What's disappointing is getting answers without the slightest effort at inspecting and troubleshooting the unit. NOBODY can give a completely-reliable answer to your AC unit welding contacts over the telephone.

What's wanted is an on-site inspection by an experienced HVACR technician.

Call an established service company,

ask to speak with the service manager, and politely explain that you've been getting lots of opinions and no help,

and that you would be grateful for and glad to pay for an inspection and diagnosis and repair by one of their senior, experienced technicians.

Fire Ants Causing Trouble in the A/C Compressor Unit?

Regarding the fire ant in the air conditioner problem, yes it's true that fire ants sometimes nest in outdoor compressor/condenser units AND it's possible that insects can invade and short circuit or damage electrical components.

Most likely, even a moderately-careful visual inspection will tell you - or your senior technician - whether or not there are ants or other invaders inside the compressor/condenser unit. Look for ants, an ant mound of debris, insect fragments.

If you find an ant invasion the unit can be cleaned - often simply by hosing it off, taking care not to soak electrical components.

If the ant invasion in your air conditioner unit is extensive or recurrent you'd get help from a pest control expert who will apply an appropriate pesticide around the unit and elsewhere if needed.

More details about fire ants and their control is in this

U.S. USDA IMPORTED FIRE ANT IDENTIFICATION & CONTROL MANUAL [PDF] retrieved 2019/01/06 original source: US Department of Agriculture, USDA, www.aphis.usda.gov/import_export/plants/manuals/domestic/downloads/fire_ant.pdf

The manual does not discuss invasion of air conditioners but does give help identifying and controlling imported fire ants.

Hard Start Motor causing Welded Relay Contacts?

About installing a "hot start" device, most likely referring to a hard-start capacitor, that's not an unreasonable guess but some additional explanation, in which I am GUESSING at what that service tech was thinking, would have been helpful to both of us.

I suspect she was thinking the following: if a compressor motor is faililng and having trouble starting, we can add a hard-start capacitor that gives it an extra high voltage kick to get the motor going.

A hard start motor can sometimes draw high current that in turn might burn a contactor or switch.

However if a compressor motor is failing, while adding a hard-start capacitor may keep it running for a time, we ought to realise that we may have to replace a failed compressor motor ($$$) soon.

Details are at

CAUSES of HARD STARTING ELECTRIC MOTORS inspectapedia.com/electric/Motor_Hard_Start_Causes.php

and at

CAPACITORS for HARD STARTING MOTORS inspectapedia.com/electric/Starting_Capacitors.php

Checking out the A/C Control Board

Start with a visual inspection for signs of overheating: burn marks, melting components

If you are qualified, trained, and can do so without getting shocked or killed, you would check the current draw of the unit when the A/C motor is trying to start up.

On 2019-01-05 15:18:25.245011 by Daunne

Thanks for your time and advice. I have contacted three techs.and gotten the following answers: I don't know - - You may need to install a hot start device - - you may a have a fire ant problem. Rather than pay one of these techs to come out, I did the following to keep from buying contactors.

I installed a 3 phase 40 amp relay to split the compressor load current to make it thru the winter.

It is working fine now. I will soon remove this relay and inspect the contacts.

I realize this is probably only a band-aid approach, however will try for a different tech later this year.

Also, would like an explanation of how to check out the control board. Again thank you for your time and diagnosis.

On 2019-01-04 23:18:05.066112 by (mod) - 13 y.o. Rheem heat pump contacts keep burning or welding

We need some help from an on-site service technician to find out why the contacts were being welded.

I don't know if that's because of motor is failing and drawing high current, which would be an explanation, or because there is a problem with a control board.

On 2019-01-04 by Daunne

I have a 5 ton Rheem heat pump/ac system that is 13 years old.

About 9 months ago it started burning and welding the contacts on the in the condensing unit about every 3 to 4 months.

The thermostat would turn off the air handler but the condensing unit would keep running and ice up the suction line back to the evaporator coil. At this time the heat pump operation is fine. I'm sure there is an answer to this problem. Any help you can provide will certainly be appreciated.

...

Continue reading at AIR CONDITIONING & HEAT PUMP SYSTEMS -topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• AIR HANDLER / BLOWER UNITS - home
• COMPRESSOR / CONDENSER REPAIR - home
• DIAGNOSTIC GUIDE A/C or HEAT PUMP - home for diagnostic procedures

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