Wondering if a manual transfer switch is worth it for your home?
A manual transfer switch is a great way to safely use a generator during an emergency. It allows you to easily, conveniently, and safely disconnect your house wiring from the electrical grid, so you can have power from your portable generator when you need it most and connect it back.
Installing a manual transfer switch is a simple process that can be completed in just a few hours. And, once it’s installed, you’ll have peace of mind knowing that you’re prepared for any emergency.
Learn more about how a manual transfer switch works and find out if it’s the right solution for you.
What is a Manual Transfer Switch?
Transfer switches are electrical devices used to transfer power from one electrical power source to another. The two sources can be electrical feeds from two different transformers, or one utility power and the other the backup power from a generator, UPS, inverter, etc.
If the transfer switch has to be operated manually to transfer electrical loads between two power sources, the switch is called a manual transfer switch (MTS). In this article, the grid power and the generator are the two sources.
Can you use a generator without a transfer switch?
Using the generators without any manual transfer switches is possible by running multiple extension cords to your house. In RVs and while camping, you do not have access to any grid power and have no option but to use the cord and plug system.
It is a simple, go-to, and possibly the only option if you are caught off guard and want an easy solution. But, it has some serious limitations, like:
- The built-in lighting and other devices hardwired to your house wiring will remain off. To power them, you will have to disconnect these services one by one from the wiring system and find a way of connecting them to the cords. You need to turn off the main circuit breaker before doing this.
- In addition, you will have to undergo a reverse process once the grid restores.
- This is considerably less safe with a reasonably high probability of backfeed.
- Cords will enter the house through windows and doors, which can’t be closed.
- You must have the extension cords of proper length and ratings to power the load you intend to feed.
What is the difference between an MTS and An ATS?
An automatic transfer switch (ATS) operates automatically in response to the failure of the primary source of power like the utility grid by switching to the backup power and back to the primary power on restoration. As you know by now, this operation has to be done manually in case of an MTS.
ATS is used more for standby power generators or for large portable generators, where the intent is to provide automatic standby power for the whole house. You need to hook these generators to a permanent source of fuel like natural gas, propane, or diesel. The typical transfer time for an ATS is 10 to 30 seconds.
ATS have many advanced features like generator load center, power management, different switching transition types, etc, which have been discussed in detail in our separate article on Automatic transfer switch for generator.
Requirements And Ratings
While purchasing your generator, you would have already decided if you are going to power your entire home or certain critical circuits only. The selection and installation arrangement will depend on this decision.
Second important decision is whether the transfer switches will be installed outdoors or indoors in your garage or basement. If you select an indoor installation, you can go for NEMA-1 type of transfer switch which is more affordable, but for outdoor installation you will have to purchase NEMA 3R weather resistant quality transfer switch.
UL listed Manual transfer switches are available with UL 98 and UL1008 listings, with UL1008 being the more stringent of the two, hence expected to provide a longer and reliable service.
There are few important things which you need to consider during planning and installation of an MTS in your electrical panel.
Important considerations while going for an MTS
- You might be running the portable generator with a plug and cord system without a separate ground rod. Once you go in for power transfer switches to feed your electrical systems, you need to install a separate ground rod without any exception.
- You need to check from your owner’s manual if your portable generator has a bonded neutral or a floating neutral (neutral not connected to the frame). As per NEC article 250, neutral can only be grounded at one point at a nearest possible location. Hence in a neutral bonded generator you cannot transfer the neutral from your main panel. Hence, a double pole MTS will be sufficient. However in a floating neutral generator, since the neutral is not bonded, you need to transfer the neutral from your house wiring panel. In such a case you require a three pole transfer switch, two poles for hot lines and one for the neutral.
- Presence of GFCI outlets: For GFCI outlets to function, the generator must have its neutral bonded to the frame. Floating neutral generators cannot have GFCI outlets. In the previous point, we stated that you can use two pole MTS for neutral bonded generators. However, the neutral is also grounded at the transfer switch which will cause a portion of the neutral current to flow through the ground lead of the generator cable, causing a tripping in the GFCI outlet. As a result, you need to again transfer the neutral by going in for a three pole MTS in this situation also.
How to Determine the Manual Transfer Switch Size
To select the perfect manual transfer switch for your needs, calculate the maximum wattage you need from your generator. Check the amperage of your generator’s largest outlet. The selected switch must match this current capacity. Other features include the availability of a built-in power meter that shows the actual power consumption by the loads and helps you in ensuring that your generator is never overloaded.
How much does it cost to install a manual transfer switch?
The installation costs of a MTS, including all the material, an installation by a qualified electrician, permits, and other incidental costs, should be in the range of $900 to $1500.
Manual Transfer Switch Installation
It is convenient and better to connect your generator cord to an outdoor type power inlet box in a location nearest to your existing electrical panel. Installation of an MTS includes:
- Switch feeds the entire house – You need to first check if the main breaker and the load circuit breakers are located in the same or a different panel. If they are in different panel or if there is inadequate space between the two, you need to remove the existing connection between the two and install your MTS between the two. Hence additional wiring work is required to install the MTS before the load breakers.
- Using a Sub panel for essential lines: This method avoids the generator overloading and you do not need to operate individual breakers. The additional subpanel contains the transfer switch and circuit breakers for the selected circuits. With normal power, the subpanel feeds the essential loads while the main breaker box powers the other loads. This method is more expensive than the previous one but has its own benefits.
How do you wire a manual transfer switch?
The electrical power feed diagram for both the scenarios discussed above is shown below to provide you a detailed understanding of the connections and the operation.
Can I install a transfer switch myself?
It is recommended to get the installation done through a qualified electrician as this is normally the requirements of the local authorities before issue of the required permit and of the insurers, in case you require any discount in your homeowners insurance.
How does a manual transfer switch work?
The steps involved in operation of an MTS in two scenarios, when used to provide the generator power for the entire house and when using a subpanel to feed only the critical appliances have been described in detail in our separate article on “How To Hook Up Generator To House.“
A manual transfer switch is an important piece of equipment for anyone who owns a generator. It allows you to safely connect your generator to your home’s electrical system and use it during a power outage.
While they are not required by law, most insurance companies will give you a discount on your homeowner’s policy if you have one installed. They can be expensive to install, but the peace of mind they provide is worth the cost. If you are considering purchasing a generator, I recommend installing a manual transfer switch.