A Y2 safety capacitor sits in the EMI filter of every grid-tied rooftop inverter, and Walsin Technology (Walsin) lists 351 X1/Y2 parts: 186 disc and 165 surface-mount; a 4,700 pF Y2 brief returns 14, in both forms. Venatech is Walsin’s authorised distributor in Hong Kong and quotes every one.
Venatech Limited, an authorised Walsin distributor in Hong Kong, wrote this for an inverter or EMC engineer, or a buyer, in Tainan, Taiwan, choosing the line-to-ground (Y) and line-to-line (X) capacitors of a rooftop solar inverter’s input or output filter. We parsed Walsin’s disc capacitor export, Walsin_DiscCap_ALL.xlsx (929 rows), its MLCC export, 00_ALL_MLCC_parts_combined.xlsx, and our stock list as at 23 September 2026. Every part number is real.
What did a Tainan industry association report about Taiwan’s rooftop solar rules in July 2026?
More rooftops by rule. A Tainan industry association’s press page reported on 16 July 2026 that Taiwan’s installed solar capacity had not yet reached 17 GW against an original 20 GW goal for 2025, that a rooftop solar requirement for new buildings takes effect on 1 August, and that more than 2,000 new buildings a year could add an estimated 660 MW.
The same report describes proposals to let factory rooftops in industrial parks host limited solar for self-use, and to speed up agrivoltaic approvals. The figures are national and they are the association’s, not ours. The engineering consequence for southern Taiwan’s power-electronics makers is direct: hundreds of megawatts of new rooftop systems mean many small string and hybrid inverters, and each one carries several Y2 capacitors in its EMI filter.
Why does a rooftop solar inverter need Y2 safety capacitors?
Because they sit between a live line and earth. A Y capacitor connects a line to protective earth to divert common-mode noise, so its failure must never create a shock hazard; that is why it must be a safety-certified Y class part, and Walsin offers 186 Y2-rated disc capacitors and 165 X1/Y2 surface-mount MLCC for it, by our count.
Y2 suits equipment on mains up to 250 Vac or so, which covers Taiwan’s grid connections at the inverter output; Y1 is the higher class used where reinforced insulation is required. X capacitors sit line to line, where a failure is not a shock hazard. Each Walsin disc part carries both an X1 and a Y rating in the export. Our guide to X1/Y1 against X1/Y2 safety capacitors explains the classes, and Y capacitor selection, disc against chip S2 compares the two forms.
How many Walsin X1/Y2 safety capacitors are there, and in which forms?
- We counted 186 Walsin disc safety capacitors whose rating includes Y2, across five AC series variants, and 165 surface-mount X1/Y2 MLCC in the S2 series, for 351 X1/Y2 part numbers.
| Walsin family | Form | Y2 working rating in the export | Part numbers |
|---|---|---|---|
| AC series and AC small size | Leaded disc | X1 440 Vac / Y2 250 Vac | 57 |
| AC series and AC small size | Leaded disc | X1 440 Vac / Y2 300 Vac | 57 |
| AC series 500 V and 500 V small size | Leaded disc | X1 500 Vac / Y2 500 Vac | 49 |
| AC series Auto | Leaded disc | X1 440 Vac / Y2 300 Vac | 23 |
| S2 series | SMD MLCC, 1808 to 2220 | X1/Y2, see datasheet | 165 |
The disc parts run from 10 pF to 10,000 pF. The S2 parts come in 1808, 1812, 2211 and 2220, split 81 NP0 and 84 X7R. For the S2 series, take the X1 and Y2 working voltages from Walsin’s datasheet, not from the export’s voltage column, which states a different test figure. The disc capacitor range lists every family.
Which Walsin parts match a 4,700 pF Y2 inverter filter brief?
Fourteen do. We filtered for 4,700 pF with a Y2 rating and found 11 disc part numbers and 3 S2 surface-mount parts; a brief for a 230 V or 220 V inverter output asking for Y2 at 250 Vac or more is met by all of them.
| Walsin part | Form | Rating in the export | Dielectric | Tolerance | Match / mismatch with 4,700 pF, Y2 | Your incumbent |
|---|---|---|---|---|---|---|
YU0AC472M120 |
Disc | X1 440 Vac / Y2 250 Vac | Y5U | 20% | Match | |
YU1AC472M120 |
Disc | X1 440 Vac / Y2 300 Vac | Y5U | 20% | Match, 300 Vac Y2 | |
YU5AC472M120 |
Disc | X1 500 Vac / Y2 500 Vac | Y5U | 20% | Match, 500 Vac Y2 | |
YU7AC472M120 |
Disc, Auto series | X1 440 Vac / Y2 300 Vac | Y5U | 20% | Match, automotive series | |
YU0AC472M100 |
Disc, small size | X1 440 Vac / Y2 250 Vac | Y5U | 20% | Match, smaller body | |
YV0AC472M100 |
Disc | X1 440 Vac / Y2 250 Vac | Y5V | 20% | Match, check temperature drift | |
S255B472K502 |
SMD 2220 | X1/Y2 | X7R | 10% | Match, surface mount | |
S255B472J502 |
SMD 2220 | X1/Y2 | X7R | 5% | Match, tighter tolerance | |
S255B472M502 |
SMD 2220 | X1/Y2 | X7R | 20% | Match, surface mount |
Y5V loses more capacitance over temperature than Y5U, and an inverter on a hot roof runs warm, so check the curve. Lead spacing and body diameter are on Walsin’s datasheet, not in the export. Confirm against both datasheets, and confirm the safety certificate for the exact part number with your compliance team.
Which Walsin safety capacitors did Venatech hold in Hong Kong on 23 September 2026?
Two S2 surface-mount lines. Our stock list as at 23 September 2026 held S242B102K502, a Walsin S2 X1/Y2 MLCC at 1,000 pF in 1808, and S252B222K502 at 2,200 pF in 2211, both X7R at 10 percent.
They are a mismatch on value against the 4,700 pF brief, but 1,000 pF and 2,200 pF are common Y-capacitor values in smaller inverters and optimisers, and they suit prototypes. The 14 parts in the table are quoted to order: request a quote and we source them through our authorised Walsin channel. The ready-stock list is a dated snapshot, never live-synced, and we give no stock or lead-time promise. We hold no ISO 9001 or IATF 16949 certificate of our own and give no legal or certification advice; confirm with your compliance team.
How Venatech helps: how can a Tainan inverter team cross its safety capacitors?
In one paste. VenaMatch decodes 18 manufacturers’ part numbers and crosses 800,000+ parts to Walsin, marking each field as a match or a mismatch, so a Tainan team can check its Y2 and X capacitors against Walsin’s 351 X1/Y2 part numbers in seconds.
Use the cross-reference tool or upload the BOM for the whole filter board. Venatech is Walsin’s authorised distributor in Hong Kong; Stackpole and Viking are lines we supply. We serve small lots from Hong Kong and you request a quote through the site.
The short version
Taiwan’s rooftop solar requirement for new buildings took effect on 1 August 2026, with more than 2,000 new buildings a year estimated to add 660 MW, per a Tainan association’s July report. For the EMI filters of those inverters, we counted 351 Walsin X1/Y2 safety capacitors, 186 disc and 165 SMD; a 4,700 pF Y2 brief returns 14.
Send us your X and Y capacitor lines with the grid voltage and insulation class, and we will return Walsin crosses with every field difference marked. Is your inverter’s Y capacitor rated for the hottest day on the roof?
Related reading
- X1/Y1 against X1/Y2 safety capacitors
- Y capacitor selection: disc against chip S2
- Disc capacitor safety classes AH, AC and AS
- VenaMatch cross-reference tool and ready-stock snapshot
Last reviewed 11 Nov 2026.
Sources
Fetched 11 November 2026.
- ICC Tainan press page, Solar PV 20GW goal postponed; association suggests relaxing installation regulations, 16 July 2026: https://icctainan.com/en/press-news-en-2026/association-chairman-lin-hsin-pao-suggests-relaxing-installation-regulations-en/
- Walsin disc capacitor export, Walsin_DiscCap_ALL.xlsx, Walsin MLCC export, 00_ALL_MLCC_parts_combined.xlsx, and Venatech stock snapshot as at 23 September 2026, all re-measured by Venatech on 11 November 2026.
Frequently asked questions
How many Y2 safety capacitors does Walsin offer for solar inverters in Tainan, Taiwan?
We counted 351 Walsin X1/Y2 safety capacitors: 186 leaded disc parts in the AC series and 165 surface-mount MLCC in the S2 series. Venatech, Walsin’s authorised distributor in Hong Kong, quotes all of them.
Which Walsin Y2 capacitor matches 4,700 pF?
Fourteen parts match, including the discs YU0AC472M120, YU1AC472M120 and YU5AC472M120 and the surface-mount S255B472K502, S255B472J502 and S255B472M502. Confirm against both datasheets and confirm the safety certificate for the exact part with your compliance team.
What is the difference between a Y1 and a Y2 capacitor?
Both connect line to earth. Y1 is the higher class, for reinforced insulation and higher voltages; Y2 is for basic insulation on mains up to about 250 Vac. Walsin’s disc range offers both, and the S2 series is X1/Y2.
Should a solar inverter use a disc or an SMD Y2 capacitor?
Disc parts suit through-hole filter boards and offer more values; S2 surface-mount parts suit reflow-only boards in 1808 to 2220. Take the S2 working voltages from Walsin’s datasheet, and check creepage on your layout either way.
Did Venatech hold Walsin safety capacitors in Hong Kong stock?
Our snapshot dated 23 September 2026 held S242B102K502 at 1,000 picofarad and S252B222K502 at 2,200 picofarad, both S2 X1/Y2. Other parts are quoted to order through our authorised Walsin channel; we give no stock or lead-time promise.
What did the Tainan report say about Taiwan’s rooftop solar?
On 16 July 2026 it reported national installed solar below 17 GW against a 20 GW goal, a rooftop solar requirement for new buildings from 1 August, and an estimated 660 megawatts a year from more than 2,000 new buildings.