RoBoTeq it doesn't really matter how I answer your questions, you have personal issues with being 100% right 100% of the time. Even in the 10 + 13 = 8 SEER, 2nd Amendment, and Abortion discussions you're the same way. Quick to attack anybody who doesn't 100% agree with you, then go insulting them. Even when somebody DOES agree with you, you still find something to insult them about. Great professionalism shown there, you must be a real pleasure to work with...
Oddly I agree with a lot of your posts on Social & Government issues..
I only have issues with those who make commentaries that are wrong about HVAC issues, and you do just that....a lot. The information that you post is never supported by any facts, just your rantings that HVAC professionals don't know how to install proper sized furnaces....blah, blah..
You have refused to respond to several specific questions I have posed to you to support comments you have made. I realize that you don't respond because you don't understand what you are posting about, yet you continue to make erroneous posts. Why are you trying to impress those of us who are professionals in the HVAC industry? Isn't it bad enough that you are giving DIYers irresponsible information on DIY sites?
Don't get me wrong, I'd love to banter with you about thermostat controls, the only thing you seem to really be involved with in the HVAC industry. But please, stop making erroneous posts about furnace oversizing and furnace internal controls. You really do not understand what you are posting about.
What other DIY sites are you talking about that I'm supposedly insulting the HVAC profession? Please let me know what they hell is going on, because I have no idea what you are talking about.
When I supported the power being disconnected from the thermostat by posting a schematic, you insult me without giving any explanation of why the schematic wasn't relevant. Do you not believe that any furnaces disconnect the power to the thermostat when they reach high limit?
MrBill, the 24V is cut to the board terminals going to the thermostat but not the boards internal CPU. The error codes work, even though there is no 24V going to the thermostat. Look close at the schematic, it's a thin "wire" from the 24V to the CPU before sending the 24V to the limit controls.
We could wire straight to the transformer to keep 24V at all times, but won't do so. If the furnace is hitting high limit they need to call their HVAC company and have them correct what's causing the problem. We'll check the air filters to see if they are dirty or the highly restrictive type, but if it's not that we let their HVAC company deal with it. Poor ductwork is to blame for a lot of the high limit problems, clogged blower wheels and a-coils account for some of them also.
You were wrong about the power to the thermostat being cut off when a furnace goes out on high limit. There is nothing in any furnace that turns off power to the thermostat due to a limit switch opening. My stating you are ignorant of furnace functions should be taken as positive criticism and not as an insult. The only thing insulting is posting things that are not accurate.
Also if you look closely to your schematic you posted, the "W" wire to the gas valve has it's own limit, between the "W" on the board and the valve.