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Thermostat Wiring
Hi David, hope you are having a nice day On 31-Jul-03 At About 18:56:24, David Martel wrote to All Subject: Thermostat Wiring DM 0006315 From: "David Martel" DM Peter, DM I think he answered the question. C Black/Blue - Common of 24 VAC DM transformer G Green - Fan relay if you do this you may blow your transformer. -= HvacTech2 =- ... "After they make styrofoam, what do they ship it in?" - s.w. ___ TagDude 0.92á+[DM] ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++ spam protection measure, Please remove the 33 to send e-mail |
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Thermostat Wiring
On Thu, 31 Jul 2003 17:18:34 GMT, "Travis Jordan" wrote:
Peter wrote: I'd like to find out whether there is any "standard" to the wiring between home thermostats and the HVAC equipment. The thermostats in my house are connected to the HVAC units in the basement via a 5 conductor cable. Yellow, green, white, red, blue. The blue is not connected. I *assume* that two of the other four are the main on/off and the other two are for the fan on/auto switch. Can I tell by color which is which or do I have to open up the thermostat and look? Thanks. Peter Most installers adopt the commonly used 'standard' wire color code. Here's a sample of some typical usage: R Red - Power 24 VAC transformer C Black/Blue - Common of 24 VAC transformer W White - Primary heat call relay E Brown - Emergency heat relay Y Yellow - Primary cool call relay G Green - Fan relay O Orange - Change-over to cool relay B Blue - Change-over relay to heat relay Here's as much as you will ever want to know about the various manufacturer's equipment-to-thermostat connections: http://hbctechlit.honeywell.com/tech...0s/70-6627.pdf So, which two wires are for the fan On function. Green is one, which is the other? In other words, if I wanted to run a jumper between two of the terminals to force the fan to be On all the time (as if I put the fan switch in the On position), which two terminals would it be? I assume one is where the green wire is connected. Which is the other? Peter -- **Remove Xs to reply by e-mail** |
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Thermostat Wiring
Peter wrote:
On Thu, 31 Jul 2003 17:18:34 GMT, "Travis Jordan" wrote: Peter wrote: I'd like to find out whether there is any "standard" to the wiring between home thermostats and the HVAC equipment. The thermostats in my house are connected to the HVAC units in the basement via a 5 conductor cable. Yellow, green, white, red, blue. The blue is not connected. I *assume* that two of the other four are the main on/off and the other two are for the fan on/auto switch. Can I tell by color which is which or do I have to open up the thermostat and look? Thanks. Peter Most installers adopt the commonly used 'standard' wire color code. Here's a sample of some typical usage: R Red - Power 24 VAC transformer C Black/Blue - Common of 24 VAC transformer W White - Primary heat call relay E Brown - Emergency heat relay Y Yellow - Primary cool call relay G Green - Fan relay O Orange - Change-over to cool relay B Blue - Change-over relay to heat relay Here's as much as you will ever want to know about the various manufacturer's equipment-to-thermostat connections: http://hbctechlit.honeywell.com/tech...0s/70-6627.pdf So, which two wires are for the fan On function. Green is one, which is the other? In other words, if I wanted to run a jumper between two of the terminals to force the fan to be On all the time (as if I put the fan switch in the On position), which two terminals would it be? I assume one is where the green wire is connected. Which is the other? Peter -- **Remove Xs to reply by e-mail** dont think you have to run any jumpers.. just put the switch on FAN and the fan stays on.. AUTO means automatic and the fan will come on when the compressor comes on.... and will go off when the compressor goes off. hope this helps. |
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Thermostat Wiring
Peter,
I think he answered the question. C Black/Blue - Common of 24 VAC transformer G Green - Fan relay Dave M. |
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Thermostat Wiring
On Thu, 31 Jul 2003 23:56:24 GMT, "David Martel"
wrote: Peter, I think he answered the question. C Black/Blue - Common of 24 VAC transformer G Green - Fan relay Dave M. I have yellow, green, white, red, blue wires. The blue wire is not connected to anything. There is no black wire. That leaves yellow, green, white, red. One side of the fan relay is the green wire. The other side is ??? (yellow, white or red). Peter -- **Remove Xs to reply by e-mail** |
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Thermostat Wiring
Poor Peter.. I understand exactly what he's asking, but nobody is providing,
in black and white, the answer. I don't know the answer myself, but why won'tanyone just tell him?? From all the responses to his posting, it seems everybody has at least some idea what theyr'e talking about, but nobody will let him in on their "little secret". Childish. Here's the question one more time: What two wires and their standard corresponding colors would one person/one thermostat/one HVAC tech have to short/connect together/work magic on to make that wonderful fan motor begin to turn?? The answer must be in this format to be acceptable: Black and Red. Replace the above colors with whatever color would satisfy the aforementioned question. Else, your response is unwelcome. No intro, no outro, no silly rant about asking specific questions.. Just three words in the exact format specified above. "Peter" wrote in message ... I'd like to find out whether there is any "standard" to the wiring between home thermostats and the HVAC equipment. The thermostats in my house are connected to the HVAC units in the basement via a 5 conductor cable. Yellow, green, white, red, blue. The blue is not connected. I *assume* that two of the other four are the main on/off and the other two are for the fan on/auto switch. Can I tell by color which is which or do I have to open up the thermostat and look? Thanks. Peter -- **Remove Xs to reply by e-mail** |
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Thermostat Wiring
Peter,
IF and thats a HUGE IF your thermostat is wired correctly/to the acceptable standard Red to anything turns that portion of the system on. Example: Red and Green = Fan Red and Orange = reversing valve if so equiped, could be eiter heat or cool depends on the system. Red and Yellow = 1st stage cooling Red and White = 1st stage heat You should be able to look at your thermostats subbase and confirm that it is wired correctly before jumping anything. You should have: Red to Rh and Rc (your 24v feed from the transformer) Green to G (feeds your fan relay) Yellow to Y1 (feeds your first stage contactor/time delay circuit) White to W1 (feeds your gas valve/gun/thermodisks etd etc) If it's NOT wired like that to a subbase call someone, don't mess with it. In addition, it appears that you don't know what your doing and you should stop and call a pro, plain and simple. You mess with it your looking at several hundred and could be upwards of 1000's (depending on the system) to replace the components you fry. Simple solution.....place a call to a local company for probably no more than a cnote will get you someone out there for this and they will make sure it's done right. -Brian "Peter" wrote in message ... On Thu, 31 Jul 2003 23:56:24 GMT, "David Martel" wrote: Peter, I think he answered the question. C Black/Blue - Common of 24 VAC transformer G Green - Fan relay Dave M. I have yellow, green, white, red, blue wires. The blue wire is not connected to anything. There is no black wire. That leaves yellow, green, white, red. One side of the fan relay is the green wire. The other side is ??? (yellow, white or red). Peter -- **Remove Xs to reply by e-mail** |
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Thermostat Wiring
Trevor Lowe wrote:
Here's the question one more time: What two wires and their standard corresponding colors would one person/one thermostat/one HVAC tech have to short/connect together/work magic on to make that wonderful fan motor begin to turn?? The answer must be in this format to be acceptable: Black and Red. Assuming standard wiring conventions were followed, the answer is: Greeen and Red. Although the original question indicated that we should not ask why he wants to do this, I think we should point out that any external wiring to the thermostat should be appropriated fused in order to protect the HVAC equipment. |
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Thermostat Wiring
Hvac,
I meant to write Red to Green, as Nunya has answered. I must have been 1/2 asleep when I posted. I don't understand why the transformer would be damaged by connecting it's common through the relay's coil to ground. Dave M. |
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Thermostat Wiring
On Thu, 01 Aug 2003 05:13:53 , "HvacTech2"
wrote: Hi Peter, hope you are having a nice day On 31-Jul-03 At About 12:25:47, Peter wrote to All Subject: Thermostat Wiring P From: Peter P What I actually want to do is put in a second On/Auto switch for the P fan -in parallel with the existing switch. (Don't ask why.) One P side of the new switch should be wired to the green wire terminal. P The other side of the new switch wired to what??? This would probably require a relay unless you would like to run the A/C at the same time. It will be wired to a relay which will be controlled by my home automation system. I'm just trying to double check where in the HVAC system I should wire the relay to. Peter -- **Remove Xs to reply by e-mail** |
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Thermostat Wiring
Just to clarify to anyone who may care what I am planning to do and why I
asked the original question... I wanted to know which two wires control the fan On/Auto function. I have since learned from this thread it's green and red. I *will* open the thermostat to double check that before I do anything else. I plan to connect a normally-open relay in parallel with the On/Auto switch. The relay will be controlled by my home automation system. This will enable me to turn the fan On/Auto from my automation system. I am not trying to control the heating/cooling functions of my HVAC; just the fan On/Auto. Assuming I pick the correct pair of wires (which I think I can now do even though I am not a "professional") I don't see how this will damage my HVAC system. If anyone thinks I'm wrong about that I'd certainly like to hear what you have to say. Peter -- **Remove Xs to reply by e-mail** |
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Thermostat Wiring
In alt.home.repair on Thu, 31 Jul 2003 21:28:28 -0400 Peter
posted: On Thu, 31 Jul 2003 23:56:24 GMT, "David Martel" wrote: Peter, I think he answered the question. C Black/Blue - Common of 24 VAC transformer G Green - Fan relay Dave M. I have yellow, green, white, red, blue wires. The blue wire is not connected to anything. There is no black wire. That leaves yellow, green, white, red. Someone pointed out that standard colors are only used most of the time. Do you have a thermostat connected now? And it works correctly? A voltohmmeter?. Turn off the furnace, then you can write down which wire is connected to which screw on the thermostat, then disconnect the wires. With the ohmmeter, you can find which pair of screws (and which pair of corresponding wires) has zero, or near zero, resistance between them when you have the fan switch on ON and infinite resistance between them when you have the fan switch on OFF. On the thermostat. Since one is probably green, that will likely speed things up a lot. Connect the switch in parallel to the thermostat switch, (You might want to turn on the power and test it, then turn off the power again) and reconnect the thermostat. It's wonderful and very useful to ask for help, but no one else is at your home, no one knows if for some strange reason yours wasn't wired like others. Even human organs aren't always where they are usually are. You can also get in the habit of measuring for suitable voltages before measureing resistance, and before connecting something new. One side of the fan relay is the green wire. The other side is ??? (yellow, white or red). Peter Meirman If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary. |
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Thermostat Wiring
On Thu, 31 Jul 2003 21:25:47 -0400, Peter
wrote: On Thu, 31 Jul 2003 18:07:44 -0500, jim wrote: Peter wrote: On Thu, 31 Jul 2003 17:18:34 GMT, "Travis Jordan" wrote: Peter wrote: I'd like to find out whether there is any "standard" to the wiring between home thermostats and the HVAC equipment. The thermostats in my house are connected to the HVAC units in the basement via a 5 conductor cable. Yellow, green, white, red, blue. The blue is not connected. I *assume* that two of the other four are the main on/off and the other two are for the fan on/auto switch. Can I tell by color which is which or do I have to open up the thermostat and look? Thanks. Peter Most installers adopt the commonly used 'standard' wire color code. Here's a sample of some typical usage: R Red - Power 24 VAC transformer C Black/Blue - Common of 24 VAC transformer W White - Primary heat call relay E Brown - Emergency heat relay Y Yellow - Primary cool call relay G Green - Fan relay O Orange - Change-over to cool relay B Blue - Change-over relay to heat relay Here's as much as you will ever want to know about the various manufacturer's equipment-to-thermostat connections: http://hbctechlit.honeywell.com/tech...0s/70-6627.pdf So, which two wires are for the fan On function. Green is one, which is the other? In other words, if I wanted to run a jumper between two of the terminals to force the fan to be On all the time (as if I put the fan switch in the On position), which two terminals would it be? I assume one is where the green wire is connected. Which is the other? Peter -- **Remove Xs to reply by e-mail** dont think you have to run any jumpers.. just put the switch on FAN and the fan stays on.. AUTO means automatic and the fan will come on when the compressor comes on.... and will go off when the compressor goes off. hope this helps. What I actually want to do is put in a second On/Auto switch for the fan - in parallel with the existing switch. (Don't ask why.) One side of the new switch should be wired to the green wire terminal. The other side of the new switch wired to what??? Peter This has reached the poin where you might want to take a look at the furnace and see what wires go where at that end. |
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Thermostat Wiring
Hi Travis, hope you are having a nice day On 01-Aug-03 At About 07:44:17, Travis Jordan wrote to All Subject: Thermostat Wiring TJ From: "Travis Jordan" TJ Trevor Lowe wrote: Here's the question one more time: What two wires and their standard corresponding colors would one person/one thermostat/one HVAC tech have to short/connect together/work magic on to make that wonderful fan motor begin to turn?? The answer must be in this format to be acceptable: Black and Red. TJ Assuming standard wiring conventions were followed, the answer is: TJ Greeen and Red. TJ Although the original question indicated that we should not ask why TJ he wants to do this, I think we should point out that any external TJ wiring to the thermostat should be appropriated fused in order to TJ protect the HVAC equipment. There is a lot more to it than this. the G is connected to the Y internally on most thermostats. and jumpering these out will cause the A/C to run which will damage the compressor. -= HvacTech2 =- ... URA Redneck if you think cow tipping should be an Olympic sport. ___ TagDude 0.92á+[DM] ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++ spam protection measure, Please remove the 33 to send e-mail |
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Thermostat Wiring
Hi 'nuther, hope you are having a nice day On 01-Aug-03 At About 09:01:39, 'nuther Bob wrote to All Subject: Thermostat Wiring 'B From: 'nuther Bob 'B On Thu, 01 Aug 2003 05:16:08 , "HvacTech2" 'B wrote: 'B If only it were that simple, but of course it isn't. by doing 'B what he wants to do the A/C would run at the same time which could 'B easily damage his compressor. and no, I do not give answers so 'B someone can damage their system. 'B Yeah, but he posted this in a followup: 'B "What I actually want to do is put in a second On/Auto switch for the 'B fan - in parallel with the existing switch. (Don't ask why.) One 'B side of the new switch should be wired to the green wire terminal. 'B The other side of the new switch wired to what???" 'B So, he's got a fan switch already. All he has to do is mimic that 'B switch. Sorry you are wrong. I of course cannot see what he has but most thermostats use a Y to G internal connection inside to run the fan when the A/C comes on. if you parallel that, whenever you run the new switch you will run the A/C and damage it. -= HvacTech2 =- ... "Curiosity killed the cat, but for a while I was a suspect."- s.w. ___ TagDude 0.92á+[DM] ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++ spam protection measure, Please remove the 33 to send e-mail |
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Thermostat Wiring
Hi Peter, hope you are having a nice day On 01-Aug-03 At About 01:12:17, Peter wrote to All Subject: Thermostat Wiring P From: Peter P Just to clarify to anyone who may care what I am planning to do and P why I asked the original question... P I wanted to know which two wires control the fan On/Auto function. I P have since learned from this thread it's green and red. I *will* P open the thermostat to double check that before I do anything else. P I plan to connect a normally-open relay in parallel with the On/Auto P switch. The relay will be controlled by my home automation system. P This will enable me to turn the fan On/Auto from my automation P system. I am not trying to control the heating/cooling functions P of my HVAC; just the fan On/Auto. P Assuming I pick the correct pair of wires (which I think I can now do P even though I am not a "professional") I don't see how this will P damage my HVAC system. If anyone thinks I'm wrong about that I'd P certainly like to hear what you have to say. what is the model number of your thermostat? if it is a honeywell T87?? or one of several other mechanical models this will cause the A/C to run and it will cause damage. the relay may have to be wired differently to make it work. -= HvacTech2 =- ... And now, a brief musical interlude ___ TagDude 0.92á+[DM] ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++ spam protection measure, Please remove the 33 to send e-mail |
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Thermostat Wiring
HvacTech2 wrote:
Hi Travis, hope you are having a nice day On 01-Aug-03 At About 07:44:17, Travis Jordan wrote to All Subject: Thermostat Wiring From: "Travis Jordan" Trevor Lowe wrote: Here's the question one more time: What two wires and their standard corresponding colors would one person/one thermostat/one HVAC tech have to short/connect together/work magic on to make that wonderful fan motor begin to turn?? The answer must be in this format to be acceptable: Black and Red. Assuming standard wiring conventions were followed, the answer is: Greeen and Red. Although the original question indicated that we should not ask why he wants to do this, I think we should point out that any external wiring to the thermostat should be appropriated fused in order to protect the HVAC equipment. There is a lot more to it than this. the G is connected to the Y internally on most thermostats. and jumpering these out will cause the A/C to run which will damage the compressor. -= HvacTech2 =- The poster indicated that his thermostat has the 'fan on' only feature. Also, remember that his original post said: "The thermostats in my house are connected to the HVAC units in the basement via a 5 conductor cable. Yellow, green, white, red, blue." We're assuming that the appearance of a (G) - fan relay wire means that it is functional, and also that he is smart enough to know that the current configuration does work to allow him to run the fan only (after all, that is what he is planning on doing with his new control system). Besides, even if G and Y were connected together, so what? If his external control system were to attempt to short-cycle the compressor, I would hope most modern compressors would have time delays built in. After all, there is always the momentary power outage for the HVAC manufacturer to worry about. |
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Thermostat Wiring
Hi Peter, hope you are having a nice day On 01-Aug-03 At About 10:55:28, Peter wrote to All Subject: Thermostat Wiring P From: Peter P On Thu, 01 Aug 2003 19:22:39 , "HvacTech2" P wrote: P 1. Is there any way to do this without damaging my HVAC system? P 2. If so, to what terminals on the control panel inside my HVAC unit P should I connect the relay? P it isn't that simple. you will need a single pole double throw P relay and a special hookup to do what you want. P You've convinced me that it's not as simple as just connecting my P external relay to the green & red wires. Just so I understand this P better, can you explain why that is. What "bad things" would happen P if I did that? What would happen is you would run the A/C compressor every time that relay kicked in for the fan. there is an internal connection in the thermostat between Y and G when the fan is in auto position. if you left it in the on position it would be OK but that would defeat the purpose of the relay -= HvacTech2 =- ... "It's a small world, but I wouldn't want to have to paint it."- s.w. ___ TagDude 0.92á+[DM] ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++ spam protection measure, Please remove the 33 to send e-mail |
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Thermostat Wiring
On Thu, 01 Aug 2003 17:08:19 , "HvacTech2"
wrote: what is the model number of your thermostat? if it is a honeywell T87?? or one of several other mechanical models this will cause the A/C to run and it will cause damage. the relay may have to be wired differently to make it work. I'm out of town now so I can't tell you the model number of my thermostat but I will post that here when I'm back home next week. For now I can tell you that it is a non-programmable mechanical model. Honeywell, I think but I'm not positive. Perhaps I should rephrase my original question to the following: I want to connect an external normally-open relay to my HVAC system that will paralel the function of the fan on/auto switch on my thermostat. When the relay is closed it would be the same as the fan switch being in the on position and when the relay is open it would be the same as the fan switch being in the auto position. The relay should control only the fan; it should not cause the compressor or heating system to run. Those functions should continue to be controlled only by the thermostat setting. That being the objective... 1. Is there any way to do this without damaging my HVAC system? 2. If so, to what terminals on the control panel inside my HVAC unit should I connect the relay? Peter -- **Remove Xs to reply by e-mail** |
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Thermostat Wiring
Hi meirman, hope you are having a nice day On 02-Aug-03 At About 04:51:53, meirman wrote to All Subject: Thermostat Wiring m From: meirman m I think the terminology here might be a problem. On the thermostats m I've used, if you turn the fan switch to ON**, the fan runs whether m the A/C is on or not. Think of it as a double pole single throw relay. G is common and there is R and Y, when you are in auto G is connected to Y internally so that when Y ( cooling ) calls the fan runs at the same time. when you switch it to Fan On it connects to R and disconnects from Y m The A/C might be enabled***, but unless the m house is hot enough that the the temperature setting is lower than m the house temperature at the thermostat, and the compressor is m running, I don't think most of us would say that the A/C has "come m on". See above. m ***I"m not sure the industry term for this, but I mean by "enabled" m that the A/C is ready to run as soon as the house is hot enough to m cause the thermal switch to turn it on. What is the industry term m for this? **Peter is trying to duplicate the ON setting for the fan m switch, not the AUTO setting. See above. m To us, it's hard to understand when you say it runs the fan when the m A/C comes on, if it runs the fan all the time. See above. m If there is an internal connection from the G to the Y, which is the m primary cool call relay, what would happen if that internal m connection was broken and the thermal part of the thermostat was m relied on to turn on the compressor? There is no "thermal part" to turn on the fan. again, see above. m if you parallel that, whenever you run the new switch you will run m the A/C and damage it. m Do you mean, because even though the fan and compressor are on, m eventually the house will be as cold as the A/C can make it, but it m will keep running? Would that damage it? Yes it will damage it. anything below abut 68 degrees indoor can cause the evaporator to freeze which will slug the compressor with liquid refrigerant and damage it. m If you mean that would damage it, what happens if I use my current m thermostat and set my A/C on and my thermostat to 33 degrees, and my m fan on AUTO or ON? early death for the compressor. m Even without modifying the thermostat, how come we don't damage our m A/C's when we have the A/C-Heat switch set to OFF and the Fan switch m set to AUTO or ON? see above. m Can we damage our A/C just by setting the thermostat to settings we m don't always use? I don't know what you mean here but running the A/C anywhere below a 68 degree setpoint will cause excessive wear and early compressor failure. -= HvacTech2 =- ... "Are there any questions?" - s.w. ___ TagDude 0.92á+[DM] ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++ spam protection measure, Please remove the 33 to send e-mail |
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Thermostat Wiring
On Fri, 02 Aug 2003 10:50:27 , "HvacTech2"
wrote: P OK, I can now see that just connecting an external relay to the red P and green wires is not the right answer. So, what is the way to do P what I want to do ... to switch just the fan on/off using an exernal P relay? it is a little tricky but it can be done. due to liability I don't think I should go into it. -= HvacTech2 =- Please consider this a public release from any liability you may have (probably none) for any advice you give me on how to connect an external relay to my home HVAC system to parallel the function of the fan on/auto switch in my thermostat. I'm not a lawyer but that should cover you. Peter -- **Remove Xs to reply by e-mail** |
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In alt.home.repair on Sat, 02 Aug 2003 15:20:40 GMT the_plumber
posted: Peter wrote: OK, I can now see that just connecting an external relay to the red and green wires is not the right answer. Peter Whatever you do, DON'T CUT THE RED WIRE! Why? What will happen if I d |
#23
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Thermostat Wiring
In alt.home.repair on Thu, 01 Aug 2003 17:04:11 "HvacTech2"
posted: Hi 'nuther, hope you are having a nice day On 01-Aug-03 At About 09:01:39, 'nuther Bob wrote to All Subject: Thermostat Wiring 'B From: 'nuther Bob 'B On Thu, 01 Aug 2003 05:16:08 , "HvacTech2" 'B wrote: 'B If only it were that simple, but of course it isn't. by doing 'B what he wants to do the A/C would run at the same time which could 'B easily damage his compressor. and no, I do not give answers so 'B someone can damage their system. 'B Yeah, but he posted this in a followup: 'B "What I actually want to do is put in a second On/Auto switch for the 'B fan - in parallel with the existing switch. (Don't ask why.) One 'B side of the new switch should be wired to the green wire terminal. 'B The other side of the new switch wired to what???" 'B So, he's got a fan switch already. All he has to do is mimic that 'B switch. Sorry you are wrong. I of course cannot see what he has but most thermostats use a Y to G internal connection inside to run the fan when the A/C comes on. I think the terminology here might be a problem. On the thermostats I've used, if you turn the fan switch to ON**, the fan runs whether the A/C is on or not. The A/C might be enabled***, but unless the house is hot enough that the the temperature setting is lower than the house temperature at the thermostat, and the compressor is running, I don't think most of us would say that the A/C has "come on". ***I"m not sure the industry term for this, but I mean by "enabled" that the A/C is ready to run as soon as the house is hot enough to cause the thermal switch to turn it on. What is the industry term for this? **Peter is trying to duplicate the ON setting for the fan switch, not the AUTO setting. To us, it's hard to understand when you say it runs the fan when the A/C comes on, if it runs the fan all the time. If there is an internal connection from the G to the Y, which is the primary cool call relay, what would happen if that internal connection was broken and the thermal part of the thermostat was relied on to turn on the compressor? Would not the fan either stay on all the time if the switch were in the ON position, or go on when it should if in the Auto position? if you parallel that, whenever you run the new switch you will run the A/C and damage it. Do you mean, because even though the fan and compressor are on, eventually the house will be as cold as the A/C can make it, but it will keep running? Would that damage it? If you mean that would damage it, what happens if I use my current thermostat and set my A/C on and my thermostat to 33 degrees, and my fan on AUTO or ON? Even without modifying the thermostat, how come we don't damage our A/C's when we have the A/C-Heat switch set to OFF and the Fan switch set to AUTO or ON? Or when we have the A/C-Heat switch set to A/C, the thermostat set to 100 degrees (or anything hotter than what the house is), and the Fan switch set to AUTO or ON? Can we damage our A/C just by setting the thermostat to settings we don't always use? -= HvacTech2 =- .. "Curiosity killed the cat, but for a while I was a suspect."- s.w. ___ TagDude 0.92á+[DM] +++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++ spam protection measure, Please remove the 33 to send e-mail Meirman If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary. |
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Thermostat Wiring
In alt.home.repair on Sat, 02 Aug 2003 13:51:53 -0400 meirman
posted: In alt.home.repair on Thu, 01 Aug 2003 17:04:11 "HvacTech2" posted: Hi 'nuther, hope you are having a nice day On 01-Aug-03 At About 09:01:39, 'nuther Bob wrote to All Subject: Thermostat Wiring 'B From: 'nuther Bob 'B On Thu, 01 Aug 2003 05:16:08 , "HvacTech2" 'B wrote: 'B If only it were that simple, but of course it isn't. by doing 'B what he wants to do the A/C would run at the same time which could 'B easily damage his compressor. and no, I do not give answers so 'B someone can damage their system. 'B Yeah, but he posted this in a followup: 'B "What I actually want to do is put in a second On/Auto switch for the 'B fan - in parallel with the existing switch. (Don't ask why.) One 'B side of the new switch should be wired to the green wire terminal. 'B The other side of the new switch wired to what???" 'B So, he's got a fan switch already. All he has to do is mimic that 'B switch. Sorry you are wrong. I of course cannot see what he has but most thermostats use a Y to G internal connection inside to run the fan when the A/C comes on. I think the terminology here might be a problem. On the thermostats I've used, if you turn the fan switch to ON**, the fan runs whether the A/C is on or not. The A/C might be enabled***, but unless the house is hot enough that the the temperature setting is lower than the house temperature at the thermostat, and the compressor is running, I don't think most of us would say that the A/C has "come on". ***I"m not sure the industry term for this, but I mean by "enabled" that the A/C is ready to run as soon as the house is hot enough to cause the thermal switch to turn it on. What is the industry term for this? **Peter is trying to duplicate the ON setting for the fan switch, not the AUTO setting. Replying to my own post, the line above is important, but much of the rest of my previous post wasn't. To us, it's hard to understand when you say it runs the fan when the A/C comes on, if it runs the fan all the time. If there is an internal connection from the G to the Y, which is the primary cool call relay, what would happen if that internal connection was broken and the thermal part of the thermostat was relied on to turn on the compressor? Would not the fan either stay on all the time if the switch were in the ON position, or go on when it should if in the Auto position? if you parallel that, whenever you run the new switch you will run the A/C and damage it. Do you mean, because even though the fan and compressor are on, eventually the house will be as cold as the A/C can make it, but it will keep running? Would that damage it? OK, I still can't guess what Hvac would say to this, but I've figured out what he is getting at. If you mean that would damage it, what happens if I use my current thermostat and set my A/C on and my thermostat to 33 degrees, and my fan on AUTO or ON? And I can't figure out what Hvac would say to this, but I can explain the rest of it. Hvac is referring to a connection in the thermostat, at least mechanical ones he seems to say, between the Y (Primary cool call wire) and the Auto position of the fan switch. He's saying that when the unit is on A/C and the fan is on AUTO, when the thermostat calls for cooling and closes the connection from the Red to the Yellow, this also provides power to the internal connection from the Yellow to the AUTO position of the fan, and thus runs 24 volts to the Green, so that the fan goes on. But, Peter, if you run a the switch part of a relay in simple shunt with the ON position of the Fan switch, the power will go (logically only since it is AC current) in the opposite direction, compared to the last sentence of the previous paragraph**. That is, when the relay you add sends 24 volts to the Green wire, that 24 volts would be present at the AUTO lead of the Fan switch. We know the Fan switch is in the AUTO position, because if it were in the ON position, it would be ON all the time anyhow and Peter would be asking how to turn it off, not how to turn it on. When the 24 volts reaches the Fan switch Auto position, it then goes through the switch to the common terminal of the Fan switch. And then via the internal connection in the thermostat, to the Yellow screw/wire, where it goes to the furnace and activates the cooling relay and cooling function of the AC. Peter, I think if you stop here for a minute you can figure out what you need to do, but if you are impatient, meet me after the 7 line footnote in the next line. Otherwise, pause here to think about it. **If this were DC, this could be prevented by the use of a diode, but it is AlternatingCurrent. In some devices, not necessarily Air Conditioning, one could probably just rectify the whole thing, the whole power supply, with a diode and then block the current from going the opposite direction with a well-placed diode in the opposite direction, but half wave rectification would lower the effective voltage, require a bunch of testing to make sure everything still worked, and there is no need for that here. What to do next? Use the relay you are controlling remotely to disconnect the Green lead of the thermostat from the Green lead of the furnace. In other words, take the Green lead from the furnace-AC and connect it to the common connector of a double throw relay switch. In the normal position, have it connected to the Green lead from the thermostat, as it is now.**** In the activated position, have it connected to the Red lead from the thermostat/furnace-AC. Of course you don't have to and can't cut the Red wire. You can make these connections anywhere along the wire from the furnace to the thermostat. Probably easiest near the furnace. But you know that. Don't forget, if you do a bad job or use a really inferior relay, that this could lead to the fan not running whether the relay is activated OR NOT. I guess this is what Hvac is worried about. Don't forget what you have done, if you ever have problems^^. Don't forget if you sell the house^^^ to rip out what you've done and solder the halves of green wire, or tell the next owner what you have done, and remind him to tell the owner after him. (I was once involved in a situation where I fiddled with phone lines, and years after I left, the phone company had to run a whole new wire from the basement to the second floor, becuase they couldn't figure it out. I had restored it, but not fully.) ^^I've fiddled with the wires to my stereo, my burglar alasm, my vcr and its output distribution, and my car until I've made them so complicated I can't even remember all the wiring. I have to refresh my memory every time I need to change things. The burglar alarm, at least I drew myself a schematic. (The car has notes scattered through the wiring diagram pages in the shop manual) (Hvac made a reference to needing a double throw relay, but that is not how I figured this out. It was his reference to the internal connection. Peter, feel free to sue me if you are foolish enough to connect this wrong in blind obedience to my directions, without thinking about it and being convinced on your own that this will work. How could it not if you do what I say? Anyone else, who has not released me, may sue me also. ) ****As an aside, this setup would be referred to as Fail-Safe. Not because it is a nuclear weapon where it will destroy the world if we don't have rigid precautions. But because that compound word means something specific. It means if your added relay fails, things will return to normal, the Safe situation. The odds are very very high that coil in it will de-energize and the relay will go back to its normal position, and your wires will then be connected the way they were before you fiddled with them. Of course, since this isn't an explosive, you might want to reverse those wires so if it fails the fan will always be on. ^^^I had a beautiful 1930 apartment in Brooklyn NY, with a separate pipe next to the tub which controlled draining, not draining, and overflow. In order to get a deeper bathtub, I taped up the overflow holes, and got about 2 inches more. I was happy for 10 years, never had an overflow, but I was afraid I would move out of the building without undoing what I had done. But I remembered and did so the last week I was there. Here I have a modern little bathtub and I reversed the overlow plate, to get about 1 1/2 inches more depth. I turned the overflow, inside the tub, upside down. I hope I remember to undo it before I move, although in Brooklyn, it was totally invisible -- there was no need to pull the pipe up more than a quarter inch. Here one can see the open drain at the top even before getting in the tub. Even without modifying the thermostat, how come we don't damage our A/C's when we have the A/C-Heat switch set to OFF and the Fan switch set to AUTO or ON? Or when we have the A/C-Heat switch set to A/C, the thermostat set to 100 degrees (or anything hotter than what the house is), and the Fan switch set to AUTO or ON? Can we damage our A/C just by setting the thermostat to settings we don't always use? -= HvacTech2 =- Meirman Meirman If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary. |
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Thermostat Wiring
On Sat, 02 Aug 2003 15:12:42 -0400, meirman wrote:
What to do next? Use the relay you are controlling remotely to disconnect the Green lead of the thermostat from the Green lead of the furnace. In other words, take the Green lead from the furnace-AC and connect it to the common connector of a double throw relay switch. In the normal position, have it connected to the Green lead from the thermostat, as it is now.**** In the activated position, have it connected to the Red lead from the thermostat/furnace-AC. Of course you don't have to and can't cut the Red wire. Thank you for the answer! It does make sense to me now that I've learned all that I've learned from this thread. And, I do like the "fail safe" nature of your design. The only fly in my ointment now is the relay I have (for my home automation system) is single-pole, single-throw. There is no connector on the "normally-open" side so I will have to find another relay that has contacts on both sides that will work with my home-auto system. Peter -- **Remove Xs to reply by e-mail** |
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Thermostat Wiring
In alt.home.repair on Sat, 02 Aug 2003 15:12:42 -0400 meirman
posted: But, Peter, if you run a the switch part of a relay in simple shunt with the ON position of the Fan switch, the power will go (logically only since it is AC current) in the opposite direction, compared to the last sentence of the previous paragraph**. That is, when the relay you add sends 24 volts to the Green wire, that 24 volts would be present at the AUTO lead of the Fan switch. We know the Fan switch is I guess these lines are a little backwards, relative to the Fan switch. ....the 24 volts from the Green wire would be present at the Common terminal of the Fan switch. in the AUTO position, because if it were in the ON position, it would be ON all the time anyhow and Peter would be asking how to turn it off, not how to turn it on. When the 24 volts reaches the Fan switch Auto position, it then goes through the switch to the common terminal of the Fan switch. And then via the internal connection in the It reaches the Common terminal and then goes through the switch to the AUTO terminal, and from the AUTO terminal to the Yellow screw/wire. thermostat, to the Yellow screw/wire, where it goes to the furnace and activates the cooling relay and cooling function of the AC. Meirman If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary. |
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Thermostat Wiring
Yes, you can tell. No, your guesses are incorrect.
How about call a HVAC guy to do it for you? -- Christopher A. Young Learn more about Jesus www.lds.org www.mormons.org .. .. "Peter" wrote in message ... I'd like to find out whether there is any "standard" to the wiring between home thermostats and the HVAC equipment. The thermostats in my house are connected to the HVAC units in the basement via a 5 conductor cable. Yellow, green, white, red, blue. The blue is not connected. I *assume* that two of the other four are the main on/off and the other two are for the fan on/auto switch. Can I tell by color which is which or do I have to open up the thermostat and look? Thanks. Peter -- **Remove Xs to reply by e-mail** |
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Thermostat Wiring
In alt.home.repair on Sun, 03 Aug 2003 15:33:06 GMT the_plumber
posted: meirman wrote: In alt.home.repair on Sat, 02 Aug 2003 15:20:40 GMT the_plumber posted: Peter wrote: OK, I can now see that just connecting an external relay to the red and green wires is not the right answer. Peter Whatever you do, DON'T CUT THE RED WIRE! Why? What will happen if I d Due to liability I don't think I should go into it. This is a friend of the poster Meirman. I'm very sorry to notify you that he did cut the red wire while he was in the middle of the last post. Somehow, the explosion caused his post to be sent, incomplete though it was. The trauma and burn unit says he may be discharged in about 2 weeks. |
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Thermostat Wiring
Hi 'nuther, hope you are having a nice day On 03-Aug-03 At About 15:20:11, 'nuther Bob wrote to All Subject: Thermostat Wiring 'B From: 'nuther Bob 'B On Sun, 3 Aug 2003 12:25:11 -0700, "CBHvac" 'B wrote: 'B ....and thats why you are HERE and not in the alt.HVAC 'B group....we ran your silly stupid ass out. Now you are here, tryin 'B to impress those that do not know better. 'B I don't know why you'd run him out of alt.hvac. He chanted the HVAC 'B tech mantra "not for free, not for free". It's because he doesn't have a clue. you really don't understand what we go through in this trade. just about everything we work with is extremely dangerous. I really don't want to see anyone get hurt. it isn't due to money but the danger involved. -= HvacTech2 =- ... I'm not really a cowboy. I just found the hat... ___ TagDude 0.92á+[DM] ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++ spam protection measure, Please remove the 33 to send e-mail |
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Well, I'm not a tech or trainee or even the least bit knowledgable about anything involving HVAC. I am, however, dealing with this exact same issue. I am about to move out of an apartment and do not want my landlord to charge me an ungodly damage fee for A/C that never worked in the first place. So I have been randomly connecting wires of every imaginable color hoping to win the deposit-return lottery. Am I lucky to still be alive and should I cease this activity immediately? -- dyiidiot ------------------------------------------------------------------------ dyiidiot's Profile: http://www.homeplot.com/member.php?userid=14 View this thread: http://www.homeplot.com/showthread.php?t=14329 |
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"dyiidiot" wrote in message ... Well, I'm not a tech or trainee or even the least bit knowledgable about anything involving HVAC. I am, however, dealing with this exact same issue. I am about to move out of an apartment and do not want my landlord to charge me an ungodly damage fee for A/C that never worked in the first place. So I have been randomly connecting wires of every imaginable color hoping to win the deposit-return lottery. Am I lucky to still be alive and should I cease this activity immediately? -- dyiidiot Like the handle... It is 24 volts at the t-stat. As long as you do not short the wrong ones to ground or to each other there is little danger to you. Unless your standing in a bucket of water. (following your handle). a little googling and you should be able to come up with the wiring diagram for your t-stat. |
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It's never a very good idea to go randomly shorting out wires that you have
no idea what they do. Most T-stats are wired up with a common code -- google is your friend... -Tim |
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