Recommendations for 3-phase “two-tier” surge protection (subpanel + rooftop RTUs)

[MDVoltage]

Hi everyone,
I’m looking for recommendations on a three-phase, two-tier surge protection approach and I’m hoping to get some guidance from those of you who do a lot of SPD work.

Project: Church with rooftop HVAC/RTUs. They had a storm last summer that took out boards and components—roughly $15,000 in damage—so they want to be proactive.

Existing electrical setup / goal:

• There’s a 200A 3-phase HVAC subpanel I’d like to protect (Tier 1 at the subpanel).
• Then add three additional SPDs at the rooftop units (Tier 2 at/near each RTU disconnect or unit feed) to protect the equipment electronics.

I had one recommendation for Transient Protection Design (TPD) equipment, but it’s pretty expensive, and surge protection is a bit of uncharted territory for me beyond the basics. ($5,650 for 4 SPU’s)

What I’m asking the group:

1. Any recommended manufacturers/models for a setup like this (Tier 1 + Tier 2) in 3-phase?
2. Any guidance on Type 1 vs Type 2 choices for the subpanel and what you typically use at the rooftop units/disconnects?
3. Any “must have” specs you look for (kA ratings, SCCR, NEMA enclosure ratings, monitoring contacts, etc.)?
4. Any practical install tips for rooftop placements (weatherproofing, mounting, lead length best practices, coordination between the two tiers)?

Appreciate any suggestions—especially what you’ve used in the real world that holds up well and doesn’t cost a fortune.


Thanks in advance,

Michael
MD Electrical Solutions, LLC

 

[zbang]

The inevitable forum questions (we're good as asking)-

Were the boards physically damaged by a surge or did something else kill them? For example, some control boards really don't like the power going off and on quickly even if the voltage never exceeds normal. An SPD won't help with that.

Did the church take a very close or direct strike, or was the damage from somewhere down the line? An SPD won't help (much) for a direct strike, either.

Is there appropriate lightning protection on the building? ("Appropriate" may be none for some buildings, OTOH steeples tend to attract lightning, and if they're not properly grounded Bad Things can happen. Also check any bonding from rooftop metal to the grounding electrode system.)

 

[MDVoltage]

The inevitable forum questions (we're good as asking)-

Were the boards physically damaged by a surge or did something else kill them? For example, some control boards really don't like the power going off and on quickly even if the voltage never exceeds normal. An SPD won't help with that.

Did the church take a very close or direct strike, or was the damage from somewhere down the line? An SPD won't help (much) for a direct strike, either.

Is there appropriate lightning protection on the building? ("Appropriate" may be none for some buildings, OTOH steeples tend to attract lightning, and if they're not properly grounded Bad Things can happen. Also check any bonding from rooftop metal to the grounding electrode system.)

I should have been more thorough in my original post. The three AC units are located on top of the school building, not the church itself. The circuit boards were fried, and while I can’t say for certain whether it was caused by a power surge or a lightning strike, your assessment is a good one.

Unfortunately, the school was without air conditioning for an entire week during a heat wave, as it took that long to obtain replacement boards. I’m not certain whether the school has its own lightning protection system; however, the church steeple does have lightning protection and is located approximately 40 yards away.


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