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My Hvac is not working per the setting. But when it is

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working it heating the house...
My Hvac is not working per the setting. But when it is working it heating the house properly. Why doesn’t it heat per the setting in thermostat?Earlier I worked with JustAnswer and after analysis I was told that the issue is with thermostat. I bought a new Nest and installed it last week. Initially the house was warm enough for us but I noticed the same issue with the new thermostat.What happensEarly morning I noticed that hvac will not start even if the temperature is below the requested setting. It will show a delay in hours without any activity in hvac.Both at nights and early morning when the heater is needed it used to heat for a few seconds maintain a 65 degree temperatureSuddenly hvac will start working. I have noticed that mostly in the afternoon where it will heat up to the setting.Y’day evening to this morning 11:30AM hvac was not working and the temperature inside the house dropped to 62. But the requested temperature was 73 .Around 12 noon hvac started on its own and kept heating the house and it didn’t stop even after reaching 74. I had to ask Nest to turn off the systemIt looks like hvac is working fine. I would like to detect the sensor or bare minimum part that need to be replaced. Please help.
Submitted: 8 months ago.Category: HVAC
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Answered in 9 minutes by:
11/18/2017
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago
Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 24,577
Experience: 40+ yrs. experience as a licensed oil & gas technician.
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Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

Assuming the Nest iswired properly, this sounds like an intermittent shor in the thermosta wiring between the furnace and the Nest

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HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

Then it's acting like you have an intermittent connection/short in the wiring between the Nest and the furnace.

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Customer reply replied 8 months ago
Ok. How can we confirm and fix?
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

Replace the thermostat wiring. Only way to do both

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Customer reply replied 8 months ago
You mean with a new cable?
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

Yes

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Customer reply replied 8 months ago
Why do you think a new cable would work? Again are you suspecting that the problem is with the wire?
Customer reply replied 8 months ago
Like I said I saw similar behavior with old thermostat with old cable
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

Did you run a new cable all the way to the furnace with the nest?

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Customer reply replied 8 months ago
The old cable only had two wires (white and red). New cable has white, red, green and blue. All are collected.
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

Ok then the next most likely culprit is a bad board

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Customer reply replied 8 months ago
Hmm.. if so what is my next step or option. Buy and replace? If so, need your help buying the right one first.
Customer reply replied 8 months ago
Is there any test that can be done to confirm that the board is bad?
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

Other than thermostat the board is the only thing that controls furnace operation. I don't sell product. Get in touch with these guys on Monday
http://bestbuyheatingandairconditioning.com/index.htm

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Customer reply replied 8 months ago
Ok. I’ll find out. Just hours ago when we set it to 80 hvac started heating for hours and didn’t stop. Once it hit 74, I turned it down to 73 and hvac stopped. All through this time Nest continued to say ‘in 2+ hours’I wonder if there is a miscommunication of temperatures between hvac and thermostat. Maybe a 70 in thermostat is understood as 65 or less by hvac. Is that a possibility?
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

The thermostat is essentially a simple switch. As far as the furnace is concerned it's either on or off. Nest's self monitoring is another unrelated matter. If it fails it's an issue for Nest to address.

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Customer reply replied 8 months ago
Ok. Here is some more info about the hvac behavior after my last update. This morning hvac didn’t start automatically or even after setting to 79 or even 80+. It did start couple of times and furnace was only on for 3 seconds a couple of times with a few minutes intervals.I opened the cover and noticed that the green and red lights were blinking alternatively. I looked up the wiring diagram on the door and it mentioned fault of ‘1 hour lockout’. See attached picture
Customer reply replied 8 months ago
The red pen marks were already there in the diagram . I wonder if this problem existed in the past.
Customer reply replied 8 months ago
Hope the new information is useful for your analysis.
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

Ok that explains why it won't come on not why it won't shut off (stop blowing warm air). The latter problem is related to a bad board.

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Customer reply replied 8 months ago
For some reason your answers keep confusing me. It may be because of my lack of knowledge and novice in these things.You are suspecting two problems now. Right? When you ‘latter problem’ I understand that as why my hvac doesn’t shut off. So the solution you are suggesting is to change board.What is the former problem? Is it why hvac won’t come on? What is the solution to it.
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

The solution is likely beyond your ability given your ability level. You need to call a pro

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Customer reply replied 8 months ago
Hmm.. Well that is why I reached out for JustAnswer.My problem is that I am not finding a good pro who identifies the specific problem and charge me fairly. I would like to fix it myself. So far I am not satisfied with the diagnosis. Please don’t mistake me.
HVAC Technician: Rick, HVAC Supervisor replied 8 months ago

A novice doesn't have the knowledge or skill set to fix the furnace. You're likely to make matters worse. I won't be a party to that.
I'm going to open this up to my colleagues so one of them can help. Please don't respond (even to acknowledge this post)until you get a response from us. If you respond first it will only delay your answer.

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Customer reply replied 8 months ago
Seriously?is this the quality of justAnswers?
Customer reply replied 8 months ago
Almost a week to connect to an expert.
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