Reddit reviews Intermatic AG3000 120/240 VAC Universal HVAC Surge Protective Device, Color

• For the whole house, I used the Eaton CHSPT2ULTRA.
  
• For outside AC and furnace, I installed the Intermatic AG3000 HVAC SPD
  
  They are very easy to install. The whole house SPD wires into its own 50A 2-pole breaker (+neutral bar +ground bar). The HVAC SPDs wire into the line-side of the disconnects (2 hot + ground). An electrician would probably charge for an hour of labor - so $80-100. They would probably prefer to sell you their SPD that they carry in their truck, which is rarely an Eaton. FYI - Steve Jenkins blog compares several whole house SPDs.

Here is a surge protector made by intermatic that you can wire into a 120/240vac furnace:
Intermatic AG3000 Surge Protector https://www.amazon.com/dp/B008VM6MXI/ref=cm_sw_r_cp_apa_i_uyqQCbBP08VTK

Here is one for your compressor unit:
Intermatic CD1-024R Compressor Defender Protects Central Air Conditioner / Heat Pump Compressors and Circuit Boards https://www.amazon.com/dp/B00L2HW9YK/ref=cm_sw_r_cp_apa_i_5AqQCbG3VEWHA

Its also a good idea to install a whole house surge protector, here is one example:
EATON CHSPT2ULTRA Ultimate Surge Protection 3rd Edition, 2.38" Length, 5.25" Width 7.5" Height https://www.amazon.com/dp/B01AQAKRSS/ref=cm_sw_r_cp_apa_i_wCqQCbTPJQEWQ

Hopefully it's just a glitch in the terminal components that physically sees the wire and you can fix it.



On all my boiler systems I include at least a surge protector for the equipment, there are easily installed ones made for hvac equipment like these:

Intermatic AG3000 HVAC Surge Protective Device, Gray https://www.amazon.com/dp/B008VM6MXI/ref=cm_sw_r_cp_apa_i_f6AYDbB51PAMR

Intermatic IG1200RC3 Surge Protector, Gray https://www.amazon.com/dp/B006FTZRF8/ref=cm_sw_r_cp_apa_i_C7AYDbADERD5E

I dont know if surges will damage the nest, not it makes sense to protect the furnace, its computer controller board ,and the nest since any surgeon the 120v will pass through the transformer and onto the 24v as well. (Stay away westom)

Keep in mind that these whole house suppressors tend to be less sensitive than the kind you put on individual appliances. Factor in the cost as well - the power strip type run you about $27 for a good one. http://thewirecutter.com/reviews/best-surge-protector/

Then, your main AC unit has a circuit board in it, and replacement costs you at least $300, often more like $600 or more (have had it fail in a couple different houses). I just have one on each AC : https://www.amazon.com/Intermatic-AG3000-Universal-Protective-Device/dp/B008VM6MXI

Now there's a bunch of lower value stuff in your house as well as stuff that might fry in a surge or might not. Ovens have circuit boards in them, every light bulb is probably an LED these days, smart switches in the walls, etc. What type of panel you have? Here's a basic device made by square D : http://www.homedepot.com/p/Square-D-QO-Surgebreaker-Surge-Protective-Device-Takes-2-Load-Center-Spaces-QO2175SB/100202111

Just $50.

I would look at your homeowner's insurance first of all. The actual risk of a lightning strike bringing a major power surge into your house and frying everything is actually pretty low. Most devices, except for extremely sensitive things like computers with cheap power supplies, handle some surges fine. Honest, even computers and other devices these days tend to have their own cheap surge protection - such as "arc gap" devices on their circuit boards for their power supplies. A direct lightning strike can blast through even devices like that Intermatic.

So this is good case for insurance - a very low risk but very high damage if it happens. That intermatic you linked is $300, plus more cost for an electrician to install it - you would need to connect the leads for that at the main terminal lugs, which are hot, and so it would be difficult to DIY an install. What's the insurance policy say?

As for the ratings - those are how many amps that can flow if the device decides to clamp a surge. Basically, during a surge, something external is trying to raise the voltage on the line. When that happens, the surge arrester is trying to short the ground, neutral, and hot phases together to stop the voltage from rising. This causes heating in the MOVs and yeah, it burns them up.

This should rarely happen, so it hardly matters if the MOVs have a finite lifespan or not. More likely, something else would fail in the device before then. It also probably provides very little marginal difference whether you buy the 240 or the 280 - again, whole house surges that fry everything are rare.

I personally have been in a house that was hit by a closeby lightning strike. In reality, the damage was :

1. An old TV stopped working
   
2. The power adapter for the cable modem and the router both stopped working (they were plugged directly into the wall with no surge protector)
   
3. The A/C stopped working. Turns out, up in the A/C unit there was a circuit board, and it had a brown mark on it from the surge. Once the board was replaced, the unit worked again - nothing else was damaged.
   
   My desktop computer was just fine, since it was on a regular surge protector.