Friday, January 11, 2013

Things HVAC tecs do not want you to know!

  • Hello;                                           " Thermostats"  
  I would like to start out by saying thank you for stoping by and taking a look at what I have to offer you.  There are problems with our economy, witch we all know.  And there are companys out there that will take advantage of our lake of knowledge.   There are things that i am going to include in this blog that will tic many businesses owners mad.  The things I would like to go over with you today is you thermostat, "the brains behind it all" starting off you have many diff color of wires that controll diff things in your heating and air system.  Going over these colors will give you an idea of what colors control what in your system.  If you take the face plate off you thermostat you will see a red wire, take in mind that all these wires are 24 volts, "not enough to kill, but it does have a little bite to it."
                                           NOTE YOU ARE WORKING WITH 8 WIRES
1. "RED WIRE"=  This should always hold a  24 volt current threw it, consider it your main control voltage.  The function of the R terminal is to energize the other terminals, depending on what mode the thermostat is in, or whether the thermostat is calling for heating, cooling,  and/or fan operations.  If you see a RH and RC terminal, you will normally also see short jumper wire between them.  In most cases the heating and cooling system share a single transformer.  The only time this jumper would be removed is if the heating and cooling system both have their own transformer (this could be the case if a central AC system was added to an old home).  Depending on what type o thermostat you have some have displays like,  RH, RC, or R terminal  - usually red - The red wire is the source hot wire from the transformer on the heating/cooling equipment.  don't let that word transformer confuse you we will get to that in a later blog.  If nothing is working on your system this is one of the 1st places to check, this is where it gets important, if you don't have 24 volts on this line there is you 1st sign you don't have your control voltage, remember this is with your "face plate off."  To check take you volt meter and take one lead to the red wire, and the other lead to the other wire "C."  Witch stands for "common".  That is the wire we will go over next.

2. "BLUE WIRE/BROWN WIRE OR BLACK"=  Most technicians I have worked around have always used the blue wire for the common, but I have seen in some cases the brown and or black wire was used.  If when you open your thermostat up and notice that there is no common wire its ok.  The thermostat runs off battery's.  So in the case you cant test the 224 volts from red to common just take one lead from red and the other lead to something that's grounded like the screw that mounts your thermostat to the wall.  So this is a little on what the common does for your system.  Wire coming to the C terminal - this is the 24 volt "common."  This wire could be any color, but is usually black or blue.  This brings 24 VAC power to the thermostat.  With many thermostats, the common is required to run the thermostat (when thermostat is hard-wired), provide continuous backlight, control a humidifier, use a remote sensor.  Obviously, it's nice to have the common wire present, and it may be a necessity.

3."THE GREEN WIRE" = Notified on your thermostat as "G".  This is the wire that sends 24 volts to your blower motor inside your Air Handler.  Again another word we will get to later.  But if your not getting 24 volts from your red wire its not going to work.

4."O/B"= Recognized as your orange wire, in some cases some thermostats does not have this option because it is a strait cool unit only, it only cools, for heat, it uses heats strips electrical.  This orange wire sends 24 volts to your reversing valve that is located inside our out side unit, that tells the out side unit to cool or heat.  again we will get to the reversing valve later8).Wire coming to the O/B terminal - usually orange or blue. This terminal is used to control the reversing valve on a heat pump.  Some heat pump thermostats have both and O or B terminal.  In the case of a combo O/B terminal - it will be energized or not depending on whether or not the compressor is going to be used for heating or cooling.    It's usually possible to switch the way this terminal works using the onboard software on the thermos

5."YELLOW"= COOL 8),  this is your wire that sends the signal for your unit to cool.3).  Wire coming to the Y terminal - usually Yellow.  This is the compressor relay.  When energized, it will turn on the compressor.  This works in tandem with the O/B terminal which energizes to control the reversing valve.  If you have a heat pump, you know that the compressor runs in the heating AND cooling season.  Whether it is heating or cooling depends on the which way the refrigerant in the system is running.

6. Wire coming to the E terminal - could be any color.  This is the emergency heat relay.  In most cases, it does exactly what the auxiliary heat, but instead of energizing when the thermostat decides it can't keep up- it's more of an "on-demand" button that the homeowner decides to push.  In many cases there is jumper installed between the "E" terminal and the "AUX" terminal in instances where there is no specific emergency heat relay on the furnace.

7. 8).  Wire coming to the Y2 terminal - could be any color.  This is for the second stage of cooling where the cooling system is multistage.  Any time you see wiring connected to terminals like "Y2" or "W2" it is pretty safe to assume that you are dealing with a multistage heating or cooling system.

Wiring a new thermostat properly is really just half the battle.  Most of the higher end thermostats require system software setup for the system they are controlling.  Below is an example of the installer setup menu from a Honeywell VisionPro thermostat.  The thermostat comes from the factory set up for 1 heat / 1 cool conventional operation.  If you have a multistage system or a heat pump, you MUST set up the thermostat to control your system by switching a value in the setup menu.  This "system type" switch is just one of many in the installer setup options that allow you to customize the way the thermostat behaves.

Ok, there is the jest of your thermostat.  The reason I want to make this blog is becouse I have over 8 years of experience, I was recently laid off, and I know how the system works and if I can save you money by finding the problem before the tec arrives he can not take advatage of you and run a bill that you have to pay with your kids tuition to collage.  Threw out this blog you will be able to take care of your own AC and save money and that what I want to provide for you, share my knolage with you.  Somtimes I can fix one over the phone if we can comunicate good, I also have a sight you can call for any questions. at any time you can go to this link and I can help you out the 1st 15min or until we find out what typpe of system you have is free.  This at the bottom is  my only income but there will be more info to come
God Bless


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