How to Ground a Furnace? (Tim’s Expert Answer)

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Grounding the furnace in your home is very important, mainly for safety purposes. Especially since grounding will provide protection in case any insulation failures take place inside your heater.

But did you know that good grounding also allows for a higher electrical efficiency? That’s because it provides unwanted electricity with an easy path to the ground.

So you must be wondering, how to ground a furnace?

You can ground a furnace in 4 simple steps. First, locate the electrical outlet where all the wires are present. Then, you have to locate the ground wire. After that use a conductor to connect it with the metal heater housing. However, don’t forget to test the ground in case of any poor connections!

Stick with us and we’ll tell you all the details! Just scroll down for more on grounding furnaces!

How to Properly Ground a Furnace?

If you’re wondering how to ground your furnace, we can help you out with that.  

But keep in mind that this is how an expert technician would do it. And it’s best to consult one for grounding the furnace in your home. 

Grounding serves two general purposes, safety and maintaining signal integrity. So, based on those, we can guide you through the process. But first lets go through the steps on grounding your furnace.

One of the main purposes of grounding your furnace is for safety purposes. Especially in case of a short circuit. 

Short circuits are common in case of any insulation failures inside the furnace. It will also help to prevent any contact of the user with dangerous voltages. 

You can do that by the help of metal parts which are exposed but also connected to the ground. 

Let’s go through 4 simple steps to help you ground your furnace.

Step 1: Locating the Electrical Outlet

The first thing that you need to do is to locate the electrical outlet or panelboard where all the wires are kept. Without locating the wire you can’t ground the furnace. 

Step 2: Find the Ground Wire

Inside the electrical outlet, look for a ground connection, which is usually a green wire. You’ll know it when you see it. Just when you see the green wire, you can be sure that you’ve found the ground wire. 

Step 3: Connect Conductor Between Ground Wire and Metal Heater

The next step is to connect the conductor between ground wire and metal heater. You’ll need a conductor for this which is properly rated at first. 

The purpose of the rated conductor is to ensure a particular activity. It is when the current flows to the ground, the resistance is pretty low. That way you can avoid any voltage drops. 

Not all conductors are appropriate for this. Only certain conductors can get the job done. Here are some conductors that you can use for this: 

ConductorWhere To Get
Metra MC918-20 20-Feet Nine-Conductor 18 AWG Twisted Multi-UseBuy Now from Amazon!
22 Gauge Wire, 65.6ft/20m Low Voltage Landscape WireBuy Now from Amazon!

Now, connect this conductor between the ground connection with the metal heater housing. And you’re all set!

But be careful of the grounding wire as not keeping it in check can cause this to happen-

So, despite whatever current you supply, the path to the ground can handle it. Moreover, it can easily stay at zero potential throughout, even in cases of short circuits. 

Regardless of how large of a current has been produced, none of it’ll lie on the heater case. Hence, it won’t be able to harm you.

Step 4: Practice Caution 

And you’ve successfully attained grounded safety for your furnace! But that doesn’t mean you shouldn’t be cautious regardless. 

Make sure to test the ground wire that you’re using is good quality, besides being of low resistance. Because your personal safety relies upon this. 

This is just in case of a poor connection to the ground. As you go further down along the electrical circuit. 

And if you’re doing this yourself, have an expert technician come and check on it instead. 

Common Furnace Grounding Issue While Grounding

A common furnace grounding issue is reliant on signal integrity. So, let us get into that immediately.

Grounding Your Furnace for Better Signal Integrity

It’s important to maintain proper signal integrity due to the difference between “no voltage difference” and “zero voltage”. 

Thanks to ground loops, even though it often reads zero on a meter. The voltage isn’t necessarily zero. And that makes it unreliable. 

What happens in ground loops is any ground current can affect the voltage. And set one up on your ground circuit. Now this current could be leaking far away from where you are working. 

And therefore, affect your signal integrity. While typically these ground loop currents are low, they could also be fairly large. And that’s what makes them so dangerous. 

But there’s a fix for this too. So let’s get into that real quick. 

Quick Fix for Ground Looping Issues

Use different grounding systems, for different components of an electric system. To safely ground high current systems, use a facility power grid ground.

And for signal equipment which are sensitive, go for a very low resistance but isolated ground system. And you’re good to go!

Do look into grounding and line polarity faults to learn more about the furnace grounded game.

Will a Generator Damage my Furnace?

Yes, a generator can damage your furnace sometimes, but it’s actually dependent on some factors. Main factor being the starting wattage of your generator. So, you’ll need to get a generator with a high starting wattage. Otherwise, you’ll end up damaging your system electrically.

Therefore, in this case, small portable generators are a complete no-go. Those are more suitable for powering little things. And not suited at all for large electrical systems.

So before connecting your furnace to a generator, make sure you get your wattage calculations right. Unless you end up acquiring more expenses, in an attempt to be cost-effective.

Try to learn about the size of furnace blower motor you need for better generator wattage calculations.


Do you Have to Ground a Furnace?

Yes, you do have to ground a furnace. There’s always the safety issue primarily. But, then modern furnaces actually require some independent ground, in order to work efficiently. Plus, without it, the electrical board ends up picking up disturbances. And that will cause the harmonics to lock out on your furnace.

How to Ground a Gas Furnace?

To ground a gas furnace, first locate the grounded outlet and put a jumper over it.Then you need to hook together the grounding wire and the neutral wire. The grounding wire is green in color and the neutral wire is white. In the end, connect the ground wire to the gas line and you’re all set!

How do you Ground a Portable Generator to your House?

You should not ground a portable generator to your house separately. It should be tied into your house ground like other appliances. Because it’s risky to use a separate ground for the generator. Especially in case of lightning strikes. Instead, simply connect it to the electrode grounding system.


That’s all we had for you on how to ground a furnace. Hope we were able to help you out!

It’s usually a good idea to consult an HVAC contractor with any issues related to furnaces. Always better to be safe than sorry.

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