Is it safe to replace the thermostat when furnace is shut off?


When your furnace thermostat malfunctions, it’s time to replace it. Check the type of thermostat that you have and purchase a new one just like it. Determine the number of wires and types of terminals in the unit so you purchase the proper replacement unit. Write down the number and types of terminals and the color of wire attached to them. Also consider replacing your old thermostat with a programmable one; and a unit that has a battery backup that will retain the information if the power goes out. Using programmable thermostat lets you set the temperature according to the time of day, saving you money in heating costs. And by replacing your thermostat yourself, you’ll save on a costly service call. As always, follow the thermostat manufacturer’s directions for installation for the brand of thermostat you...

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[HVAC] AC always runs after thermostat replaced, never shuts off

I replaced my old mercury type thermostat with a new programmable Honeywell RTH2300. Soon after I realized that when the desired set temperature was reached, the unit will still continue to run. Always. Also sliding the "cool" switch to off makes no difference. My ac runs and never shuts off. (The actual compressor runs, not just the fan).

I only had 2 wires to begin with. Red and white. After pulling my hair out a quick call to Honeywell had me switch the red wire to R )removing the existing jumper) and the W wire to Y. (I had previously had R to R and W to W with a jumper factory installed between R and Rh). But this didn't make a difference. Finally, they had me pull the thermostat from the wall but it didn't matter, my system is always on and can only be shut off from the breaker. Touching the 2 thermostat wires together and pulling them back apart does nothing. Honeywell told me the problem lies...

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Though most furnace problems should be handled by an HVAC professional, you can take care of a few tasks yourself.

If your heater doesn’t heat or works poorly, this guide will help you troubleshoot and fix typical problems.

Need furnace help NOW? Get a Local Heating Pro Fast!

Though forced-air furnaces are normally quite reliable, they can break down and, when they do, getting them fixed quickly is usually critical. With a little do-it-yourself experience and the proper guidance, you can troubleshoot and repair a variety of furnace problems yourself.

Once a year, vacuum out the area around the furnace’s blower. If possible, slide out the fan unit, clean each fan blade with a toothbrush, and then vacuum with a brush attachment on a vacuum cleaner. Look for oil ports on the motor, normally located near the motor shaft. If the motor has these, apply two to three drops of non-detergent motor oil into each...

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by Jeff Patterson

It’s remarkable how many ways you can lower your utility bills.

Add more insulation, install better windows, get a more efficient HVAC system, etc.

Improvements like these cost just a bit of money though!!!

For real, I recently priced out a medium grade window and it cost $250.

Last week I had to run over to help my tenant Rich because his thermostat was on the fritz. After 15 minutes he had a new programmable thermostat at his figure tips.

I wanted to show you this tutorial so you could see how easy this project is to do.

The programmable thermostat I installed cost all of $25. You can get the same one and instantly start saving money. Let me show you how

Here’s the funny thing about today’s tutorial: I shot the video while Rich watched Germany play Brazil in the World Cup.

Amazing game, if you’re a Germany fan.

Some how I got the video done without a hitch, haha. There are several...

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Install the replacement wall plate.

Use the new wall plate as a template to mark where the holes you need to drill for the screws will be. Use a level if necessary. Then, drill the holes, and screw the replacement wall plate into its new position on the wall.

/b/ba/Replace a Thermostat Step 7.360p.mp4

If your new thermostat has a mercury tube (that is to say, if your new thermostat is rather old school), your device needs to be completely level or it won't render accurate readings. Using a level is very important in this scenario and is not just for aesthetic reasons. Make sure you're drilling holes that match the size of your screws. A 3/16" drill bit is fairly standard. Your thermostat...
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Dirty filters are the most common cause of furnace problems. Dust and dirt restrict airflow—and if the filter gets too clogged, the heat exchanger will overheat and shut off too quickly, and your house won't warm up. If the blower is running but no heat is coming out, replace the filter. A dirty filter also causes soot buildup on the heat exchanger, reducing the efficiency of the furnace and shortening its life.

The owner's manual shows where the filter is and how to remove it. Change inexpensive flat filters at least once a month. Make sure that the arrow points toward the furnace. Inspect pleated filters once a month. Hold them up to the light and if you can't see the light clearly through them, replace them. Manufacturers say pleated filters are good for three months, but change them more frequently if you have pets, kids or generate lots of...

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Common Thermostat Problems...more advanced to follow, but start with the basics first.Work with the power off whenever possible.When a furnace does not work it may be caused by problems with the furnace or the thermostat.

Before troubleshooting your thermostat, check to see if all filters are clean and all hoses to and from the units themselves are free of wear.
If these are not causing problems, then it is time to look at specific thermostat issues and possible solutions.

Your thermostat could have aging wiring that is faulty or the transformer may require replacing.

A thermostat may need cleaning to eliminate erratic operation.

Accumulated dust is a common culprit.

First, you should have a small paintbrush, a screwdriver, and a voltmeter.

anticipator is a small metal tab positioned in front of an arcing printed scale. Give it a light push in both directions. This easy step may solve the

Give the thermostat's...

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This thermostat replacement guide will take you step by step through the process of selecting and installing a new unit. A call to a hvac dealer to do this would cost at least $100. With the help of an experienced hvac technician, you can do it yourself and save. You can watch a professional do it on the player below and even shop for a new thermostat.


We will only look at installing digital units here because there is really no benefit to installing a mechanical unit.

Problems with your existing thermostat?

If you are having problems with your furnace or air conditioner, you can check the thermostat for proper operation.

To begin, shut the power off to the furnace and/or ac unit and switch the fan from auto to on mode.

Then, if you are having furnace problems, you can disconnect the r and w terminals at...

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The short answer is no, it's not OK - you increased your risk of electrocution and that's never a good thing specially for a DIYer. Now that being said, everything is working and you didn't burn down your house, so you got off OK, but generally speaking, this was a bad idea.

The Nest happens to run 24V systems so there isn't too much electricity there (though you can still get zapped - car batteries are only 12V after all), but some systems are line voltage, in which case, you would have been in for a really rude surprise. In the USA this is typicall 120V but it could be over 200V in Europe or in some other systems - that could give you serious burns or even kill you!

The other risk was that you could have shorted something out and damaged the controller in your furnace; this would likely be a costly repair and left you without HVAC until it is...

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Hi, my name is Erick Noack. I'm an HVAC technician for ABC Plumbing, Heating, Cooling, and Electric. And we're here for Today I'm going to show you what to look for if the blower motor won't shut off on your gas-fired furnace.

Thermostat Affects Blower in Gas Furnace

So some of the things that you might look for if the furnace fan is running continuously, first of all is the switch on the thermostat. The first thing that you want to check is the fan switch on the thermostat. In this case, it's up here in the display and it says "auto." Now, "auto" means that the fan should only be running to try to heat or cool the home to try to match the thermostat setting. If you see the thermostat fan switch set to "on," or in this case "low," "medium," or "high," then you're going to have continuous fan operation.

Check Filter

Next thing that's important to look at is your filter. If you find a severely clogged filter, it may have caused damage to the...

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WHEN the furnace shuts down or will not start, puzzled homeowners often panic. But you will be doing yourself and utility personnel a favor, particularly in storms or cold snaps when service crews are strained, by trying to restart the furnace yourself.

To start a furnace, no disassembly is required, and the instructions can usually be found on the furnace. Naturally, do not hesitate to call for professional service if you feel unsure about how to proceed or if you suspect a dangerous situation.

First, if your furnace stops or will not start, check the thermostat. Notice the thermometer reading on the thermostat, which indicates the present temperature in the room. Then note the setting of the thermostat control knob or dial. If the control is set at a temperature less than on the thermometer, set it several degrees higher than the thermometer reading. The furnace should come on.

If it does not, remove the cover from...

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