Additional Resources
1) MVAC performance testing and refrigerant charging:
2) ESCO 608 study guide. Study Guide
3) Air handler schematic: Schematic
4) Condensing unit schematic: Picture
5) Air handler control board: Picture
6) Does the EPA REALLY go after individuals for violations? Read this ...
I guess this means that if you plan to steal a condensing unit you better take your recovery equipment with you or you will face the Feds as well as local law enforcement!
7 CHECKING SMALL APPLIANCE RELAYS, OVERLOADS AND COMPRESSORS
The overload should have continuity.
If the appliance cycles on and off with a click, the compressor relay may be bad. Does it rattle when you shake it?
The formula for checking the resistance of the compressor windings:
S = Start
C = Common
R = Run
S & C + R & C should equal S & R. The second highest resistance is found between S & C.
Test the compressor for ground. See B below and the above page image for instructions.
8) CHECKING A REFRIGERATOR'S COLD CONTROL (THERMOSTAT)
- Remove the cold control and set it to the off position. Leave the capillary tube connected.
- Rx1 should show no continuity.
9) The sequence of steps, in their proper order, for a gas fired furnace that uses a HSI ignition are:
- Power and gas are supplied to the unit.
- The transformer supplies control voltage for all control circuits by converting line in voltage (usually 120v) to 24v.
- The thermostat calls for heat.
- The high limit and perhaps other limits are checked.
- The combustion inducer blower is turned on.
- The inducer blower closes the (air) pressure switch.
- The hot surface igniter (HSI) is turned on.
- The gas valve is opened and the gas ignites as it flows past the HSI.
- The flame sensor senses the flame.
- The blower motor starts.
10) Pressure ⁄ Temperature Chart apps for your phone or tablet
- Android phone: Search for then download "Pressure ⁄ Temp Chart" from the Play Store
- iPhone: Search for then download "HVAC PT Chart" from the App Store
11) "Emerson Check & Charge" is an app that can be used to calculate superheat and subcool values. It can be downloaded from the App Store or Play Store.
12) Checking a hot surface igniter (HSI)
Silicone Nitride(Match stick shape)
15 - 20 ohms
Silicone Carbide ("M" shape)
50 - 90 ohms
The following silicone carbide HSI is bad. Why?
13)
