AC / Heat Pump Compressor Diagnostic FAQs

Cool the HVAC Condenser Unit with Air or Water?

Would blowing a stand alone fan onto the condenser coils reduce the compressor workload?

Does using a stand alone fan blowing into the coils of a condensing unit reduce the units head pressure thus reducing the workload of the compressor?

I am not too keen on using those water misters because of my concern of calcium build up on the condensing coils.

Where I live, electrical power is very cheap so I am not concerned if my electric meter spins a little faster. On 2018-06-27 by kimball t rader

Reply by (mod) -

Interesting idea. Sounds to me as if it could work *except*

Watch out: if the direction of your fan's airflow is blowing against the condenser unit's own internal fan direction you will in fact interfere with proper condenser operation and make matters worse not better.

You might however have a booster fan blowing into the air intake, often at the top of the condenser unit.

And the installation of your supplemental fan would also have to be appropriately weatherproof and wire for electrical safety.

Followup by Kimball

Thanks for your advice. The way I have the fan situated so it is blowing in the same direction with the main fan on the top of the condensing unit.

I am first a retired electrician but over the years I have acquainted myself on some of the mechanics of how an air conditioner works but obviously I am not an expert.

The auxiliary fan I am using is placed right by the condensing unit blowing into heat rejection coils so the air I am blowing in is blowing in the same direction as the units main fan. Thanks again.

Question: does it help to spray the compressor/condenser coils when it's hot outside?

Does it help to spray water on the compressor coils when the outside air temp. is 100+? The inside air is going up in the afternoon to 82. - Greg Warner

Reply:

Some readers have reported that their compressor was overheating and ran ok when water cooled - this is perhaps a diagnostic step but not a reasonable repair.

Watch out: don't soak electrical components or you may damage the equipment or make it unsafe.

Question: compressor won't run until it's cooled down

When unit is cold it will start and run. After an hour the cooling fan stops but the compressor continues for a short time then quits. It will continue to start but will not start and run until it cools down.
Any ideas? Wayne

Reply:

Look for an overheating fan motor, relay or control board or possibly a refrigerant metering valve that is sticking.

Question: Split AC system cools OK at night but not in afternoons

Any body tell me what is the problem with my split ac It gives perfect cooling in night and morning but in afternoon its compressor turn on and off every after 15 minutes it can not give cooling from 2PM TO 6PM..

I checked gas, capacitor and connection and voltage its ok but I dont know whats the problem if you have any idea plz share with me Knight

Reply:

Knight, as afternoon is the time the system works hardest I suspect the compressor motor is shutting down on thermal overload. If cooling it off with a water spray (DO NOT spray electrical components) that's likely to be the problem.

HVAC System Energy Use Monitoring

Question: how to monitor energy use on a shared AC unit so that each tenant pays their fair share of the cost

I live in an apartment, a home that was converted to two units.

We share the outside AC unit. We each have our own thermostat.

Is it possible to seperate so that each of the two units pays for their own electricity with that one AC unit?

I mean can the power be split so to speak so that each apartment unit only pays for the cooing for their apartment? Michelle Mell

Reply:

Michelle

In Europe energy use monitoring by individual apartment is required by law.

If you live in the U.S. or Canada or Latin America that requirement is not given.

A landlord could add equipment to monitor the time your thermostat calls for coolingh but that'd be an uncommon level of detail.

We've published some suggestions on energy use monitoring at

• BTU MONITORS & HEATING COST APPORTIONMENT
• ELECTRICAL POWER ANALYZERS
• ENERGY USE MONITORING, SOLAR

 

Phased Zone Heat Pump Efficiency

Question: Phased zone heat pump to improve efficiency - my contractor keeps adding costs

Zone v. Phase

I have a heat pump. It is set up and has always operated as a two-zone system. One zone is upstairs and the other is down stairs. Each zone has a separate thermostat.

I just purchased a replacement pump for $7,000. I purchased a SEER-18, which is a high efficiency system.

I understand that what makes it efficient is that is operates in two phases. Initially, it starts up at a lower power before powering to a higher power, thus saving energy and money.

The installer now tells me that he needs another $1,500 to get the phases to work.

First, he said the new system did not have a zone board (zone issue), which I priced on the internet for $169.

Now, he says he needs to install dampers, which only controls the amount of air flow to a space (zone) and cost less than $75 (Home Depot).

Dampers really just control the amount of air in a particular zone of the home. These are already in my home. They relate to air zones and not start-up power.

In my case, they control the air flow alternatively for the air upstairs and downstairs.

What am I missing? Am I being conned? - Edward Bunn

Reply: Explanation of Phased Zone Heat Pump Efficiency vs. Heat Pumps using Single Phase vs. Three Phase Electrical Power

Phased zone heat pumps

use phase change materials (PCMs) to store energy either by warming the PCM or cooling it, later retrieving the energy from the same storage cache.

The benefit of a phased zone heat pump system, then, is that by storing extra energy and then retrieving it later when needed, the overall efficiency of the system is increased, and the delivery of heating or cooling is more consistent as outdoor temperature varies through the day.

Experts describe phased zone heat pumps as having a higher COP or Coefficient of Performance than a standard heat pump system.

Single phase vs. three phase electric heat pumps

refers to the design of heat pumps using two different electrical power types, single phase electrical power (one live electrical wire and one neutral wire) vs. three phase electrical power (three live electrical wire, each delivering alternating current that is 120 electrical degrees apart from the other two), is a completely different topic.

Smaller heat pumps and air conditioners are usually single phase while larger heat pump systems are more-often designed to use three phase electrical power and are more-often commercial heat pumps.

The main advantages of using three phase electrical power for a heat pump are:

1. Electrical power to the compressor motor is more consistent in comparison with single phase power that is more vulnerable to voltage fluctuations in the electric company's power line system.
2. A three phase electrical power supply is more efficient, able to transmit three times as much power than a single phase or single wire system over the transmission lines.
3. For a given amount of electrical power (say measured in watts), a three phase wiring system can deliver that power using less total electrical conductor (wire) material than a single phase wire.

Sources:

• Fluke, What is the difference between single-phase and three-phase power? [Web article] Fluke Corp., Technical Support: my.fluke.com/en-US/new-request/ Tel: 0044-1603-256613 - retrieved 2025/01/05, local copy saved as Single-vs-Three-Phase-Power-Fluke.pdf
• Sprsun, Single Phase vs. Three-Phase Heat Pumps [Web article] Guangzhou SPRSUN New Energy Technology Development Co., Ltd., Tel: 0086-20-82181867 / 0086-18933985692 - Email: inquiry@sprsunheatpump.com - retrieved 2025/01/05, local copy saved as Single-vs-3-Phase-Heat-Pumps-Sprsun.pdf

Question: oil in the capillary tube? - recurrent cap tube clogging

i have replaced my compressor from company and when I started it was giving cool air but the copper pipe out side (large) was not cool enough and after 40 mints its timer light flashes and after 10 more mints its down automatically.

It happens again and again I sent back it to company technician is looking into it.

He said oil was in capillary and it needs flushing so he will replace its capilary since after cleaning its not fixed. do u think there is no fault in compressor? or what possibly is the problem.. - Wagar

Reply:

You'll want to check the installation manual to find the control light decoding for your brand and model of cooling equipment. Could be a control or control board problem too. It's just about impossible to flush a cap tube so replacement is normal.

But if there is debris in the system, or excessive oil, the new cap can clog as well; good practice would be to empty the system, pull a vacuum, flush the whole system, install a filter dryer, replace the cap tube, and recharge.

Question: what causes warm suction lines in an air conditioner or heat pump system? Warm A/C suction line (should be cold) and zone control dampers that stopped working

JMONTE said: warm A/C suction line question: After my condenser is turned on for about 4 minutes the suction line starts to get warm to the touch. can you tell me what the problem may be

Reply:

JMONTE: If the HVAC suction line gets warm, you may be out of refrigerant, or the system may be running in heating mode if it's a heat pump.

See OPERATING TEMPERATURES HVAC.

Becky, If a motorized HVAC zone control damper is not opening or closing, most likely the motor has failed, or the thermostat that operates that zone control is off or set in an incorrect position.

See ZONE DAMPER CONTROLS

Becky said: motorized air conditioning zone dampers not working

My house has "zone" control with dampeners to close off the upstairs over the garage room unless that thermostat is on - the room is not cooling. I have located the damper under the house. What are some causes for the damper not opening and how to repair them? condensation, motor to damper? silicon glued properly?