Why Multiple Switching Power Supplies Trip an RCD: Build a Leakage-Current Budget

Name the branch before blaming a model

Give the RCD and monitored branch a unique identifier, then list every AC-DC supply and connected device inside that boundary. Record state changes because the active equipment population can differ between observations.

Schneider Electric's UPS example describes input leakage as the sum of UPS leakage and leakage from all connected load devices. It is not a WEHO specification or a universal RCD rule; it supports only the conservative practice of accounting for all equipment behind the same RCD.

XP Power likewise states that, when multiple power supplies are implemented in one application, the overall system earth-leakage current must be considered for safety-standards compliance. Both sources support the accounting boundary; neither selects the RCD or supplies a WEHO leakage value.

Use one row per physical unit. Units with the same model name can serve different loads or states, so preserve unit tags and conditions.

Open the two-record workbook

Review boundary: the worksheet organizes evidence; it does not prescribe energized testing, probe placement, grounding changes or protective-device selection. Those decisions belong to qualified personnel using the exact installation and controlled requirements.

Show which values are documented, observed, unknown, and assigned to an owner; do not fill gaps with guesses.

Use four labels. A per-equipment entry is a nonnegative magnitude for one identified unit with its conditions. The equipment-budget upper bound is the scalar sum of comparable entries. A whole-branch residual-current observation is a separate record for one boundary and state. Fault or insulation-event evidence remains an incident record, never an ordinary budget input.

Keep different conditions in separate records. Mark unavailable values “not yet verified,” name an owner, and request the missing evidence.

For each observation, retain the authorized method, instrument, time, operating state and responsible person.

Calculate the screen; preserve the observation

For each state, choose the evidence path first. In a documentation-led screen, let each comparable per-equipment magnitude be |I_device,i|, with identity, conditions, and source attached. The conservative bound is:

I_budget,max = Σ |I_device,i|

The worksheet has two records with different meanings. The calculated bound shows the equipment counted; the branch observation records the actual boundary and state.

Preserve a whole-branch observation as its own record for the exact boundary, state, method, and instrument. Never add it to the per-equipment bound or add device entries to it. A difference between the paths is an investigation prompt, not permission to alter RCD coordination or grounding.

Use a compact worksheet:

Repeat the table for each relevant state. Give a transition its own event record, and distinguish a missing value from an observed zero.

Câu hỏi thường gặp

Why can several power supplies be associated with one RCD trip?

Do not infer cause from unit count. Account for the complete monitored branch, then review the actual installation evidence; the cited UPS example supplies only that conservative accounting principle.

Request the RSP-200 evidence that fills a row

The validated WEHO catalog identifies product 8680 as Bộ nguồn AC sang DC RSP-200 có PFC at the current RSP-200 product page. This establishes identity and the inquiry link only.

It does not establish a leakage-current value, authorize multiple units behind one RCD, or select that RCD. Request the controlled model-specific evidence and its conditions, then keep the response revision and unit identity with the worksheet.

For readers who need background before building the worksheet, WEHO also publishes What Is a Switching Power Supply? How SMPS Works and a separate discussion of whether a power supply should be grounded. These are context links; they do not replace installation-specific leakage evidence or qualified RCD review.

Send a question packet, not a request for reassurance

Ask for reproducible evidence instead of whether a model is “safe with an RCD.” Include:

• the exact product model and revision under consideration;
• the number of units and the other equipment inside the RCD-monitored boundary;
• the input and operating states that must be assessed;
• the project environment and installation context;
• the requested model-specific document and the conditions that must accompany any value;
• the current worksheet, with unknown cells and decision owners visible; and
• the project reviewer who will decide whether the returned evidence is sufficient.

When evidence arrives, preserve the new source revision, identify affected rows, recalculate relevant states, and repeat technical review.

Close the review without double counting

Use controlled project criteria; do not insert a generic threshold or rating.

Keep the RCD, branch population, worksheet revision and evidence references in the qualified review record. Neither the screening bound nor one branch observation establishes product fit, trip cause, coordination, conformity or wiring safety. Never bypass the RCD, alter protective-earth (PE) connections or energize equipment outside an authorized procedure.

Sources and evidence boundary

• Schneider Electric, RCD (Residual Current Device) on input side of the UPS [1] — source basis for the conservative accumulation screen. This is a UPS example; no threshold, RCD prescription, or WEHO conclusion is transferred.
• XP Power, Your Essential Guide to Power Supplies [2] — source basis for considering aggregate system earth leakage when multiple supplies are used; no WEHO value or RCD decision is transferred.
• WEHO Power, Bộ nguồn AC sang DC RSP-200 có PFC — product identity and inquiry URL only. The page is not used here to assert a leakage-current value or RCD suitability.