Yes, you can connect two panel boards to the load side of a Manual Transfer Switch (MTS), provided the MTS is appropriately sized to handle the total load of both panels. Here's a breakdown of the considerations and how to ensure it's done safely and correctly

Key Considerations:
MTS Amperage Rating

This is the most crucial factor. The MTS must have an amperage rating equal to or greater than the sum of the main breaker ratings of both panel boards. If one panel has a 100A main breaker and the other has a 150A main breaker, your MTS needs to be rated for at least 250A. Be sure to add 20% for safety.



Generator Capacity

Both Generators must have enough capacity to handle the combined load of both panels. If they dont have enough capacity for both panels, you will have to manage the load.

Wiring

The wiring from the MTS to each panel board must be appropriately sized for the load. Use the correct gauge wire based on the amperage and distance to each panel, following electrical code requirements (NEC in the US).

Neutral and Ground Bonding

The MTS should be configured correctly regarding neutral bonding. Typically, the neutral is only bonded to ground at the main service entrance (at the utility meter). It's crucial not to create multiple neutral-to-ground bonds, as this can create dangerous circulating currents. The generator may or may not have the neutral bonded to ground, depending on its type. Refer to the generator's documentation and local electrical codes. You'll need to decide where the single bonding will occur.

Load Management

Even if the MTS and generator can handle the total amperage of both panels, you might need to manage the load when running on generator power. This means being mindful of what appliances and circuits are being used in both panels simultaneously. You might not be able to run everything at once on generator power.

Professional Installation

This is highly recommended, especially if you're not a qualified electrician. Improper wiring can be dangerous and can cause equipment damage or even fires.

How to Connect the Panels


Select an appropriately sized MTS.2.

Install the MTS

Mount it securely and wire it to the incoming utility power (or main panel) and the generators.3.

Wire from the MTS to the Panel Boards

Run correctly sized conductors from the load side of the MTS to the main lugs (or main breaker) of each panel board.4.

Terminate Connections

Make sure all connections are tight and secure.5.

Test

After installation, thoroughly test the system by switching between utility power and generator power to ensure everything is working correctly.

Important Considerations Regarding Load Calculation and Management



Calculate the Total Load

Don't just add up the breaker sizes in each panel. This will give you a very inflated number. Perform a load calculation according to NEC guidelines. This involves considering the square footage of the dwelling, lighting, appliances, and other loads.

Prioritize Circuits

When on generator power, determine which circuits are essential (e.g., refrigerator, lighting, heating/cooling) and focus on powering those. Non-essential circuits (e.g., electric oven, clothes dryer) can be turned off to reduce the load on the generator.

In summary, yes, you can connect two panel boards to the load side of an MTS, but it's essential to do it safely and correctly. Prioritize proper sizing, wiring, and professional installation to ensure a reliable and safe system. Flag for review