Routine Maintenance: Residential Systems: Chapter 4
Condensing Unit
In this module, we will look at how to measure refrigerant pressure at condensing unit. We will also look at how to inspect and clean a condensing unit. Skip to quiz!
Inspecting Refrigerant Pressure
We use the manifold gauge to measure the pressure of the refrigerant inside the HVAC system. A manifold gauge is a pressure-checking system and one of the most basic HVAC tools. Let us learn more about manifold gauge and how to work with it.
A manifold gauge consists of:
a manifold block,
2 pressure gauges,
2 hand valves, and
3 refrigerant hoses.
A manifold gauge is used to test the pressure in the HVAC system. We compare high-side and low-side pressure readings with the specified values by the manufacturer.
A manifold gauge must match the refrigerant inside the HVAC system. Every HVAC system will have a nameplate showing which refrigerant to use. We have to make sure that we are using the right gauge for the right refrigerant reading.
For checking the refrigerant pressure, we need to make sure that the valves of the manifold gauge are closed. Then have to connect the blue hose to the high side and the red hose to the low side of the condensing unit.
Next, we have to turn on the HVAC system and let it run until readings in the manifold gauge stabilize. We have to take both pressure readings in the manifold gauge and compare them with the manufacturer specified values.
If the pressure readings are too low, this means that the coil may have a leak somewhere. We have to find the leak and repair it. Then we have to fill the refrigerant.
If the pressure is too high, this means that the condensing unit might be dirty. We have to clean the condensing unit.
Inspecting Condensing Unit
Recall that condensing unit is part of the air conditioner or heat pump. It is placed outside the house. Compressor, condenser coil, and fan are the main components of condensing unit.
Before starting the inspection, we first disconnect the power supply to the condensing unit. We need to check any debris on the condensing coil. After opening the condenser fan grill, we also need to check for debris inside the condensing unit.
We should inspect condensing coil fins to see if they are bent. We should observe the copper tubing for leakage or damage and also for its insulation. Recall that copper tubes have insulation to reduce heat transfer to the outdoors.
Cleaning Condensing Unit
For cleaning the condensing unit, we first turn off the power supply and remove the fan grill. We then need to clean the debris at the bottom of the condensing unit. We have to adjust the fins of condensing unit with the fin tool if they are bent.
We have to spray the coil cleaner onto the condenser coil and let that sit for ten minutes. We then rinse the condenser coil with a water hose from the inside out. We also need to clean the outside of the unit and reassemble the fan grill. After turning the power back on, we then check its working. A manifold gauge is a pressure-checking system.
We have to connect the blue hose to the high side and the red hose to the low side of the condensing unit. We inspect condensing coil fins to see if they are bent while cleaning the condensing unit.
Question #1: How many pressure gauges are there in the manifold gauge?
1
2
3
4
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Answer: 2
There are two pressure gauges in the manifold gauge. The high side pressure gauge is represented by red color. The low side pressure gauge is represented by blue color.
Question #2: What will be the pressure readings in the manifold gauge compared to the manufacturer’s specified values if the condenser coil got leaks in it?
High
Equal
Low
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Answer: Low
If the pressure readings are too low, this means that the coil may have leakage somewhere. We have to find the leak and repair it. Then we have to fill the refrigerant.
Question #3: What do we observe in the condenser coil during the condensing unit inspection?
Leakage
Damage
Insulation
All the above
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Answer: All the above
The condenser coil is part of the condensing unit. So, we have to inspect the condenser coil during the condensing unit inspection.
Question #4: We have to rinse the condenser coil with a water hose from the ______ .
inside out
outside in
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Answer: inside out
We have to rinse the condenser coil with a water hose from the inside out. This is because dust and dirt deposits outside of the condenser coil while the condensing unit is running.