Surge Device vs Replace vs POCO Fault for Repeated Equipment Damage: Decision Matrix
Why this matters
When a customer reports electronics dying repeatedly, the easy upsell is a surge protective device (SPD), but an SPD only addresses transient overvoltage. If the real cause is a loose service neutral, a utility-side overvoltage condition, or a swapped/open service connection, an SPD will not save the equipment and the damage continues, now with the contractor's name on the failed fix. The three response paths, install/upgrade surge protection, replace a failing device or connection on the customer side, or document and refer a utility-side fault, address fundamentally different failure mechanisms. Choosing wrong either leaves a hazard energized or bills the customer for the wrong remedy. The discriminator is the nature of the overvoltage: brief transients (lightning, switching) call for an SPD; sustained overvoltage or wildly varying voltage points to a neutral or utility fault that an SPD cannot fix and that may be a safety emergency. This matrix frames the three paths.
The options
Surge protective device (SPD) install or upgrade adds a Type 1 or Type 2 SPD at the service (and optionally Type 3 point-of-use units) to clamp transient overvoltages from lightning, utility switching, and internal load switching. It protects against fast, high-magnitude, short-duration events, the failure mode behind sporadic loss of electronics during storms or motor cycling.
Replace a failing customer-side device or connection addresses a sustained or recurring overvoltage/abnormal condition originating on the customer's side: a loose service-entrance neutral, a corroded main lug, a failing connection that lets one leg float high, or a damaged conductor. This is a repair, not a clamp, and it is frequently a safety emergency because a floating neutral pushes some circuits well above 120 V.
Document and refer to the POCO covers conditions on the utility side of the demarcation: a utility neutral problem, a transformer fault, or a sustained overvoltage the utility is delivering. The contractor's job is to measure, document with timestamped data, and hand it to the power company; touching utility-side connections is outside the contractor's scope at the demarcation.
When the SPD path wins
An SPD wins when measured voltage is normal and stable but equipment dies during storms, nearby switching, or large motor cycling, the classic transient signature. It wins as a layered defense (Type 1/2 at the service plus Type 3 at sensitive equipment) for customers who have lost electronics to lightning-season transients. It is the right answer only after sustained-overvoltage and neutral faults have been ruled out, because an SPD does nothing for a multi-minute overvoltage; SPDs clamp brief transients and can themselves be destroyed by sustained overvoltage.
When replace-the-connection wins
Replacing a customer-side connection wins when measurements show a sustained or recurring abnormal voltage on the customer's side: neutral-to-ground voltage rising under load, one 120 V leg reading high while the other reads low (the floating-neutral signature), or a localized voltage drop/heat at a main lug or service-entrance splice. This is the cause behind whole-house electronics death that an SPD cannot stop. It is a repair-now situation, and a floating neutral is a documented fire and shock emergency.
When refer-to-POCO wins
Referral wins when the abnormal voltage is present at the utility connection point with no added drop or fault across the customer's service entrance: a utility neutral fault, a delivered overvoltage, or a transformer problem. The contractor measures at the meter line side and at the main, shows the condition originates upstream, and refers with documentation. Referral does not absolve the contractor from first confirming the service-entrance connections on the customer side are sound.
Why an SPD cannot fix a sustained overvoltage
The physics matter here because they explain why leading with an SPD on the wrong fault is not just ineffective but counterproductive. An SPD is a clamping device, typically built around metal-oxide varistors, that conducts hard once voltage exceeds its clamping threshold and diverts the transient energy. It is sized to absorb brief, high-energy pulses measured in microseconds to milliseconds (the lightning and switching environment described in IEEE C62.41). A floating-neutral or utility overvoltage is not a pulse; it is a sustained condition lasting seconds to minutes at an elevated voltage. An SPD asked to clamp a sustained overvoltage conducts continuously, overheats, and either opens its thermal disconnect (leaving the equipment unprotected) or fails, sometimes violently. So an SPD installed against a neutral fault does nothing for the connected electronics, gets consumed by the very condition it cannot handle, and gives the customer a false sense that the problem was addressed while the real fault keeps killing equipment. That is why the measurement step is non-negotiable before any SPD is sold.
Field decision flow
Measure before selling anything. Log line-to-line and each leg line-to-neutral, plus neutral-to-ground, under load and over time. If voltage is stable and normal and damage tracks transient events, install/upgrade an SPD. If voltage is sustained-high, one leg floats, or neutral-to-ground rises, find and repair the customer-side neutral/connection fault, treating a floating neutral as an emergency. If the abnormal voltage is already present at the meter line side with no added service-entrance fault, document and refer to the POCO. Never lead with an SPD when the symptoms point to a sustained overvoltage or neutral fault.
A loose or open service neutral lets the two 120 V legs redistribute through connected loads, driving some circuits far above 120 V and destroying electronics, with a real fire and shock risk. An SPD does not protect against this and may be destroyed by it. If neutral-to-ground voltage rises under load or one leg reads high, treat it as a live emergency, de-energize, and repair the neutral before restoring service.
References
- NFPA 70 (NEC) Article 242, Overvoltage Protection (SPD types and installation)
- NFPA 70 (NEC) Article 250.24, Grounding Service-Supplied AC Systems (service neutral)
- NFPA 70 (NEC) Article 230, Services
- ANSI C84.1, Electric Power Systems and Equipment Voltage Ratings
- UL 1449, Surge Protective Devices
- IEEE C62.41 / IEEE 1100 (Emerald Book), surge environment and powering of sensitive equipment