Electrical - Whole house power surge arrestor
In a sub-panel, I think it is best use a surge protector that dumps the spike into the earth rather than the neutral. This avoids the spike having to go all the way back to the main panel before getting to earth.
You want a unit that mounts so that you can see the LED indicators. This means you want it mounted on the outside of the electrical panel.
If the product has an earth wire and a neutral wire, you need to make sure the two are not connected because it a sub-panel they must not be connected.
New building code requires connecting to a 50A breaker. This is called a Type 2 surge protector.
EATON CHSPT2ULTRA Ultimate Surge Protection 3rd Edition, 2.38" Length, 5.25" Width 7.5" Height
Square D by Schneider Electric HEPD80 Home Electronics Protective Device
Includes an LED indicator
NEMA 4X rated for outdoor/indoor use, 80,000 amp Surge Current Rating, 25,000 amp SCCR.
CSA and UL 1449 3rd Edition Type 1 SPD
Can be mounted to an brand of residential load center
Product warranty of 5 years and 50,000 residential downline warranty
I currently have a Tytewadd but this is no longer available.
Used to be available from for about $150 plus shipping from Tytewadd. The model you need is called a "C1". Ordering can be done by sending mail to Rick Towe email@example.com . They accept credit cards, but you will need to phone 417-736-4500 to give the card details (no web site ordering).