MOOP vs MOPP in IEC 60601-1: Insulation Diagrams and Table Lookup

Electrical safety work on active medical devices soon runs into two abbreviations from IEC 60601-1: MOOP and MOPP. Before testing, design and regulatory teams need to know whether a barrier protects the operator or the patient, whether it needs one means of protection or two, and which table holds the creepage, clearance and dielectric strength requirements. Following the clause structure of IEC 60601-1 Edition 3.2, this article covers the assessment logic, how to draw an insulation (isolation) diagram, two common mistakes, and where SUNGO does this work under which accreditation. We quote no limits or test voltages; take all values from the standard itself.

Key points

• IEC 60601-1 divides MEANS OF PROTECTION against electric shock into MEANS OF PATIENT PROTECTION (commonly MOPP) and MEANS OF OPERATOR PROTECTION (commonly MOOP). Patient-side creepage distances and air clearances are in Table 12; operator-side ones are in Tables 13 to 16.
• The logic starts from single fault safety. How many means of protection a barrier needs, and of which kind, is decided under 8.5; in Edition 3.2, Figure 40 gives an identification example.
• An insulation diagram shows every barrier between the mains part, secondary circuits, internal power sources, applied parts, accessible parts and protective earth, each marked with the protected person, count and working voltage, before any table lookup.
• Two common mistakes: treating IEC 62368-1 reinforced insulation as 2×MOPP, and looking up requirements with the mains voltage while ignoring the peak working voltage.
• IEC 60601-1, EN 60601-1 and GB 9706.1 are all within the Hefei laboratory's IAS accreditation (TL-1119), listed as whole standards with no edition year.

Standards and scope

Three designations and their editions

IEC 60601-1 is titled "Medical electrical equipment – Part 1: General requirements for basic safety and essential performance". The IEC Webstore lists consolidated Edition 3.2, published 2020-08-20, combining the 2005 third edition, Amendment 1 (2012) and Amendment 2 (2020). The third edition's foreword says it replaced the 1988 second edition as a technical revision, further aligned the electrical requirements with IEC 60950-1 (information technology equipment) and added a risk management process requirement.

GB 9706.1-2020, the Chinese mandatory national standard with the same title, was published on 2020-04-09, took effect on 2023-05-01 and fully replaces GB 9706.1-2007 and GB 9706.15-2008. China's national standards platform lists it as a modified adoption of IEC 60601-1:2012 (Edition 3.1), so it does not include the 2020 Amendment 2.

EN 60601-1 is the European designation. EN 60601-1:2006/A2:2021 adopts IEC 60601-1:2005/A2:2020 without modification.

The standard covers the basic safety and essential performance of medical electrical equipment (ME equipment) and medical electrical systems (ME systems). Its introduction notes that where particular standards exist, the general standard should not be used alone.

The relevant clauses in Clause 8

Clause 8 deals with protection against electrical hazards from ME equipment. Three subclauses matter most for MOOP and MOPP:

• 8.5 Separation of parts: where the kind and number of means of protection are decided. In Edition 3.2 it contains Figure 40, "Identification of MEANS OF PATIENT PROTECTION and MEANS OF OPERATOR PROTECTION", and Figure 41, "WORKING VOLTAGE measurement". Neither appears in the Edition 3.1 table of contents, where the identically titled figure sits in Annex A as Figure A.12. Figures 9 and 10 (test voltage application for defibrillation-proof applied parts, see 8.5.5.1) are also here.
• 8.8 Insulation: contains Table 6, "Test voltages for solid insulation forming a MEANS OF PROTECTION", and Table 7, "Test voltages for MEANS OF OPERATOR PROTECTION".
• 8.9 Creepage distances and air clearances: contains Tables 8 to 16 and Figures 22 to 31 (creepage distance and air clearance, Examples 1 to 10).

Read alongside: 8.1 (fundamental rule of protection against electric shock), 8.6 (protective earthing), 8.7 (leakage currents), 4.7 (single fault condition), 4.8 (components), 5.9 (determination of applied parts and accessible parts) and 15.5 (mains supply transformers and transformers providing separation in accordance with 8.5).

MOOP and MOPP: concepts and assessment logic

What each kind covers

As the names say, MOPP protects the patient and MOOP protects the operator; the formal definitions are in Clause 3 and the original text governs. GB 9706.1-2020 uses the same concept, for example in its note to definition 3.49 (mains part).

The foreword and introduction show that the operator side links up with IEC 60950-1. The introduction to Edition 3.2 states that the requirements for solid insulation forming a MEANS OF OPERATOR PROTECTION in 8.5.1.3 were incorporated by normative reference to IEC 60950-1:2005. These referenced requirements sit mainly in Clause 8, including many tables used to determine requirements for means of protection, primarily operator protection and insulation coordination. Amendment 2 addressed these references, and the normative references of Edition 3.2 list both IEC 60950-1:2005 and IEC 62368-1:2018.

The patient side has its own creepage distance and air clearance table, Table 12. Patients touch equipment through applied parts, which GB 9706.1-2020 definition 3.8 describes as the part of ME equipment that, in normal use, needs physical contact with the patient for the equipment or system to perform its function. For any barrier, start by asking who touches the part on the far side, and how.

How 1× and 2× combine

Engineers write 1×MOOP, 2×MOOP, 1×MOPP and 2×MOPP to show how many means of protection a barrier provides, and of which kind. "Two" comes from single fault safety. GB 9706.1-2020 definition 3.116 describes a single fault condition as one where only one means for reducing a risk is defective, or only one abnormal condition is present. Interpretation Sheet ISH1:2021, included in the Edition 3.2 consolidated version, states that ME equipment is to remain single fault safe, or the risk is to remain acceptable, throughout its expected service life. For every path from a hazardous voltage to an accessible or applied part, ask: if one means of protection fails, what is left?

In general electrotechnical terms, two levels of protection can be two independent measures, or a single insulation that gives equivalent protection. The International Electrotechnical Vocabulary (IEV) defines double insulation as insulation comprising both basic insulation and supplementary insulation (195-06-08). It defines reinforced insulation as insulation that provides protection against electric shock equivalent to double insulation (195-06-09). GB 9706.1-2020 equipment classes follow the same logic: Class I adds protective earthing of metal accessible or internal metal parts to basic insulation (definition 3.13); Class II provides double or reinforced insulation, without protective earthing or reliance on installation conditions (definition 3.14). The count and kind for each barrier are decided under 8.5 and Figure 40.

Protective earth and Y capacitors

• Protective earth: Class I equipment uses protective earthing as an additional safety precaution on top of basic insulation. The protective earth itself has to meet 8.6, and Annex A includes Figure A.13, "Allowable protective earth impedance where the fault current is limited". Whether, and under which conditions, a protective earth connection counts as a means of protection is set out in 8.5 and 8.6.
• Y capacitors: IEC 60384-14:2023, 3.1.4, defines a Class Y capacitor or RC unit as one suitable for use where failure of the capacitor could lead to danger of electric shock. The normative references of IEC 60601-1 Edition 3.2 include IEC 60384-14:2005. Mark each bridging Y capacitor on the diagram with the means of protection it bridges (count and kind) and check that its class and certification match; IEC 60601-1 governs. AC current flows through it, so also check its selection against the leakage current results under 8.7.
• Transformers and optocouplers: also common across barriers. The normative references include IEC 60747-5-5:2007 (photocouplers) and IEC 61558-2-1 (separating transformers); component evaluation is in 4.8, and transformers providing separation are also covered by 15.5.

How to draw the insulation diagram

The standard prescribes no format for an insulation diagram; it simply puts the assessment under 8.5, 8.8 and 8.9 on one page for design checks and lab verification. Informative Annex J, "Survey of insulation paths", is a useful cross-check while drawing. A later article on medical power adapters will use the same method. Suggested order:

1. Divide the device into zones: the mains part, each secondary circuit, any internal electrical power source, the applied parts (grouped by patient connection), the enclosure and other accessible parts, protective earth, and external signal or data interfaces. Per the notes to GB 9706.1-2020 definition 3.49, the mains part includes all conductive parts not separated from the supply mains by at least one means of protection, and the protective earth conductor is not part of it.
2. Draw every barrier: draw and number every isolation between zones, such as transformer primary-to-secondary insulation, optocouplers, Y capacitors, PCB isolation spacing, enclosure insulation and cable insulation. Include internal power sources; Annex A Figure A.23 shows the means of operator protection needed between internal power source terminals and a subsequent protective device.
3. Mark the protected person and the count: mark a barrier MOPP if it protects the patient (for example, one toward an applied part) and MOOP if it protects the operator, then mark 1× or 2×. Whether patients might touch an accessible part depends on the use scenario and risk management; when in doubt, check 8.5 and Figure 40.
4. Establish the working voltage: for each barrier, record both the RMS and peak working voltage across it, and whether each was measured or calculated. Figure 41 shows the measurement.
5. Look up and record the basis: write the table number, the parameters used and the resulting requirement next to the diagram. Take the values from the original text.
6. Map to the tests: dielectric strength is under 8.8, creepage and clearance measurement under 8.9, leakage current under 8.7, and protective earth under 8.6.

A barrier list can follow the format below; the rows only show how to fill it in.

You need to identify the applied parts and their type (B, BF or CF) before you can draw the MOPP barriers. See How to Classify ME Equipment and Identify Applied Parts.

Where to find the values

The table below lists only the table numbers and titles from the Edition 3.2 table of contents. It contains no values.

Tables 6, 7 and 12 to 16 have the same titles in the Edition 3.1 and Edition 3.2 tables of contents. GB 9706.1-2020 is based on Edition 3.1, so for the GB version, check table numbers and content against the GB text.

The IEV defines the two distances. A clearance is the shortest distance in air between two conductive parts (581-27-76). A creepage distance is the shortest distance along the surface of a solid insulating material between two conductive parts (151-15-50). For common measurement failures, see Electrical Safety Failures: Creepage, Earthing and Leakage Current.

Two common mistakes

Mistake 1: treating IEC 62368-1 reinforced insulation as 2×MOPP

Bought-in power supplies often carry an IEC 62368-1 report or certificate. IEC 62368-1 is the safety standard for audio/video, information and communication technology equipment, and the certificate covers insulation assessed against it. IEC 60601-1 Edition 3.2 lists IEC 62368-1:2018 as a normative reference, and its Annex A Table A.6 discusses typical scenarios for using such equipment in ME equipment. Even so, patient-side creepage distances and air clearances come from Table 12, and solid insulation test voltages from Table 6. Compare the two sets of requirements item by item; "reinforced insulation" cannot simply be relabelled "2×MOPP".

Mistake 2: looking up requirements with the mains voltage only

Tables are entered with the working voltage across the barrier. Table 14 gives additional air clearances for mains-part insulation whose peak working voltage exceeds the peak of the nominal mains voltage. Peaks across switch-mode transformers, inverters or boost stages can exceed the mains peak, so using the nominal mains voltage alone may underestimate the requirement. Record RMS and peak values, and how each was obtained, for every barrier.

Accreditation scope

The table lists the entries in the Hefei laboratory's IAS scope (TL-1119) that are relevant to this article. MOOP and MOPP assessment and the related tests are part of the general standard. The scope lists the standard as a whole, without individual clauses.

Where SUNGO performs this work and under which accreditation

• Laboratory: the Hefei laboratory in Zipeng Town, Feixi County, Hefei, Anhui Province.
• Legal entity: Hefei SUNGO Medical Technology Co., Ltd., an independent legal entity.
• Accreditation: IAS accreditation, certificate TL-1119, with the scope effective from 2026-06-04. IEC 60601-1, EN 60601-1 and GB 9706.1 are all within the Hefei laboratory's IAS accreditation (TL-1119).

Keep three points in mind.

1. The IAS scope lists standards by number, without an edition year. State the edition you need when you place the order, for example IEC 60601-1 Edition 3.2 or GB 9706.1-2020, and confirm the edition with the laboratory before an IAS report is issued against it.
2. Whether a report will be accepted for registration or certification in a given market should be confirmed with the relevant regulator or notified body in advance.
3. The same IAS scope also includes the collateral standards IEC 60601-1-2, IEC 60601-1-8 and IEC 60601-1-11 (with their EN versions and YY 9706.102, YY 9706.108 and YY 9706.111), the oxygen concentrator particular standard ISO 80601-2-69 (with EN ISO 80601-2-69 and YY 9706.269) and the technical specification IEC TS 60601-4-2. The oxygen concentrator group is the only ME equipment particular standard in the scope. IEC 60950-1, IEC 62368-1, IEC 60384-14, IEC 60747-5-5 and IEC 61558-2-1 are mentioned here for background only. None of them is within SUNGO's accreditation scope. The scope of Shanghai SUNGO Medical Technology Co., Ltd. (laboratory at 958 Kangqiao East Road, Pudong, Shanghai) does not include the standards in this article.

Preparing for testing

• Insulation diagram and barrier list: in the format above, showing the protected person, count, working voltage and table used for each barrier.
• Circuit and layout documents: schematics and PCB layouts, with isolation zones and slots marked.
• Critical components list: models, ratings and certificates for transformers, optocouplers, Y capacitors, fuses, power supply cords and appliance inlets, plus transformer construction details (windings, insulation layers, lead-outs).
• Bought-in power supply or adapter: model, applicable standard and report, plus a note on which barriers it provides in the overall diagram.
• Applied parts: which parts are applied parts, their type (B, BF or CF), whether they are defibrillation-proof, and how patient connections are grouped.
• Classification and conditions of use: Class I, Class II or internally powered; rated mains voltage and frequency; intended operating altitude.
• Documents and standards: instructions for use, technical description, risk management records on electric shock protection, target markets and required standard editions.

FAQ

Which is stricter, MOOP or MOPP?

Do not assume. Each has its own tables: Table 12 for the patient side, Tables 13 to 16 for the operator side, and Tables 6 and 7 for solid insulation test voltages. Compare the requirements at the same working voltage using the original text.

Can a power adapter with an IEC 62368-1 certificate be used directly in a medical device?

The certificate shows compliance with IEC 62368-1, not automatically with the patient protection requirements of IEC 60601-1. Check MOPP barriers item by item against Tables 6 and 12. IEC 62368-1 is not within SUNGO's accreditation scope.

Do GB 9706.1-2020 and IEC 60601-1 Edition 3.2 give the same results?

Do not assume so. GB 9706.1-2020 is a modified adoption of Edition 3.1 without the 2020 Amendment 2; Figures 40 and 41, for example, are not in the Edition 3.1 table of contents. State the edition you need when ordering.

Should the insulation diagram be submitted with the samples?

We recommend it. It is the basis for checking 8.5, 8.8 and 8.9, and lets both sides agree on each barrier before testing starts.

Requesting a quote

If you are preparing an electrical safety evaluation for a medical device, start with our medical electrical safety testing service. When you ask for a quote, include the product name, model, equipment classification, applied part details, target markets and the editions of the standards you need. If possible, attach the insulation diagram, schematics and critical components list. Send your request through our contact page.