Caleffi 540000 Safety Valve · 3 Bar · Junkers ZWBC 24-2 C 23 and 25-2 C 23
The safety valve protects the boiler's water circuit: it opens and discharges water when the pressure exceeds its setting, which in this part is marked at 3 bar. It is suspected when water comes out of its discharge or when the original needs to be replaced due to a fault.
- Type of part
- Safety valves
- Status
- Refurbished
- internal SKU
- VSEG008
- Warranty
- 1 year
VAT included Stock · 9 units
Caleffi boilers compatible
Safety valve. Two confirmed compatibilities: Junkers ZWBC 24-2C 23 and Junkers ZWBC 25-2C 23. There are two other models that we are still verifying.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| CALEFFI Junkers ZWBC 24-2C 23 | Caleffi | Contrasted |
| CALEFFI Junkers ZWBC 25-2C 23 | Caleffi | Contrasted |
Models pending verification
These models are associated with this reference, but we have not finished verifying them yet, so we do not consider them compatibleIf your boiler is one of them, send us a photo of the part you are going to replace and we will verify it before you purchase.
| CALEFFI Junkers ZWBC 24-2C 31, ZWBC 25-2C 31, ZWBC 28-2C 23, ZWBC 28-2C 31, ZWBC 30-2C 23 and ZWBC 30-2C 31 | Caleffi | Unconfirmed |
|---|---|---|
| CALEFFI Junkers ZWBE 25-3C 23, ZWBE 25-3C 31, ZWBE 30-3C 23 and ZWBE 30-3C 31 | Caleffi | Unconfirmed |
Can't see your model or have questions? The printed reference takes precedence. How to check it · Send us a photo via WhatsApp.
How to check if it is the part for your boiler
The part reference, model, and equipment revision must be verified against the manufacturer's documentation.
- Look for the Caleffi valve code "540000" and the setting marked "3bar".
- Compare them with those of your original valve: brand, complete code, and setting. Do not confuse it with the Junkers 87161064310 or with the Caleffi series 540 (fuel cut-off, 540 040 to 540 090).
- Check the exact model on the rating plate of your boiler: Confirmed: for the Junkers ZWBC 24-2 C 23 and ZWBC 25-2 C 23. The other ZWBC and ZWBE variants on the list are yet to be verified.
- Any questions? Send us a photo of your part's label and the boiler's rating plate from Contact.
Symptoms that require diagnosis in the safety valve
The safety valve releases pressure when the circuit exceeds its setting. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
Water is leaking from the safety valve discharge.
Cause: According to the Junkers manual, the valve opens when the maximum pressure is exceeded with the boiler at maximum temperature. First, check the pressure gauge (the technical manual states 1 to 2 bar as the minimum filling pressure when cold) and the expansion vessel.
- 02
The boiler stops and shows E9.
Cause: Lack of flow or pressure, air in the circuit, pump stopped or heat exchanger calcified.
Check the pressure on the manometer. If it is low or not stable, have a technician check it.
C fault codes from CALEFFI that require diagnosis
| Code | Fault | Technical checks |
|---|---|---|
| E9 | Temperature limiter of the heat block triggered (overheating). | There is usually a lack of flow or pressure, the pump is stopped, or the heat exchanger is calcified. Have a technician check it. Sources also mention the safety sensor or the differential pressure switch. |
These symptoms can have more than one cause. If your boiler displays a fault code, send it to us via WhatsApp along with a photo of the labeling, and we'll tell you if this is the part.
Technical sheet: CALEFFI safety valve
- Uniclima internal SKU
- VSEG008
- Brand
- CALEFFI
- Type of part
- Safety valves
- Units in stock
- 9 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- Delivery time shown at checkout
- Return
- 14 days
Part data and available documentation
Contrast the label codes, PCB, and revision with the installed part; they are not necessarily equivalent references.
- Marked calibration
- 3bar
- Inventory — Indicated reference
- 540000 SD00103
- Inventory — Application indicated in inventory
- Equipment indicated on the label: ZWBC 24 2C 23 · ZWBC 25 2C 23. Documented compatibilities, pending verification with the specific variant: ZWBC 24‑2 C 23 · ZWBC 24‑2 C 31 · ZWBC 25‑2 C 23 · ZWBC 25‑2 C 31 · ZWBC 28‑2 C 23 · ZWBC 28‑2 C 31 · ZWBC 30‑2 C 23 · ZWBC 30‑2 C 31 · ZWBE 25‑3 C 23 · ZWBE 25‑3 C 31 · ZWBE 30‑3 C 23 · ZWBE 30‑3 C 31
- Technical sheet: Marked setting
- 3bar
- Inventory data — Indicated reference
- 540000 SD00103
- Inventory data — Application indicated in inventory
- Equipment indicated on the label: ZWBC 24 2C 23 · ZWBC 25 2C 23.
- Inventory data — Application indicated in inventory
- Documented compatibilities, pending verification with the specific variant:
- Inventory data — Application indicated in inventory
- ZWBC 24‑2 C 23 · ZWBC 24‑2 C 31 · ZWBC 25‑2 C 23 · ZWBC 25‑2 C 31 · ZWBC 28‑2 C 23 · ZWBC 28‑2 C 31 · ZWBC 30‑2 C 23 · ZWBC 30‑2 C 31 · ZWBE 25‑3 C 23 · ZWBE 25‑3 C 31 · ZWBE 30‑3 C 23 · ZWBE 30‑3 C 31
Before purchasing
- Fill the heating circuit only with the cold boiler: this is indicated in the Junkers manual.
- The technical manual from Junkers recommends checking the expansion vessel once a year (DIN 4807).
- To confirm: Junkers ZWBC 24-2C 31, ZWBC 25-2C 31, ZWBC 28-2C 23, ZWBC 28-2C 31, ZWBC 30-2C 23, and ZWBC 30-2C 31 — Documented, pending verification with the variant. Without additional external confirmation, it links to 540000; it gives Junkers 8716106431.
- To be confirmed: Junkers ZWBE 25-3C 23, ZWBE 25-3C 31, ZWBE 30-3C 23 and ZWBE 30-3C 31 — Documented, pending verification with the variant. Without additional external confirmation, it links to the 540000; it provides the Junkers 8716106431.
- Do not confuse: 87161064310 — Junkers safety valve assigned to the ZWBC 25-2 C 23 (also to the 24-2 C 23). It gives 8716106431, a 10-digit code, which is not listed as the same code — Another reference; without additional confirmation, it links to Caleffi 540000, so we do not assume the equivalence.
- Do not confuse: 87186434270 — 3 bar safety valve Bosch/Buderus/Junkers for other series (Ceraclass, CerapurSmart, Logamax plus GB042); like Caleffi — No page links it to 540000 or to ZWBC/ZWBE.
- Do not confuse: 540 040 to 540 090 — Caleffi fuel shut-off valves (series 540, set at 98 °C) — Different function; the 540000 indicates a setting of 3 bar and is not listed on that official sheet.
- Do not confuse: 314430 — Caleffi safety valve 3 bar with pressure gauge (1/2'' M x 1/2'' F) — Another Caleffi code; the page does not associate it with 540000.
- SD00103 is the confirmed reference; without additional external confirmation, the quote has been read.
- Codes and boilers ZWBC 24-2 C 23 and ZWBC 25-2 C 23 confirmed. Without additional external confirmation read, it does not name 540000 nor link it to a boiler, which is why the external level is 0.
Frequently asked questions about the safety valve
What code does the part have and what should I compare with my original gas valve?
The part is marked with the Caleffi code 540000 and the setting "3bar". It is confirmed as "540000 SD00103"; the SD00103 does not appear without additional external confirmation that we have read. In the 540 series, Caleffi writes some codes with a space (e.g., "540 040"); the 540000 is not written that way in any documentation. Compare the brand, the complete code, and the setting with your original valve.
Is it compatible with the Junkers ZWBC 24-2 C 23 or the ZWBC 25-2 C 23?
Yes. Confirmed: for the Junkers ZWBC 24-2 C 23 and the ZWBC 25-2 C 23, which are the ones on the label. The official Junkers manual for the ZWBC 24-2 C 23 (item 7 736 900 799) does not mention the Caleffi 540000: that confirmation is it. Any questions about your variant? Send us a photo of the part's label and the boiler's PCB from Contact, or call 911 17 77 77.
Is it compatible with other variants, such as the ZWBC 28-2 C 23 or the ZWBE 25-3 C 23?
It has documented ten more variants (ZWBC 24-2 C 31, 25-2 C 31, 28-2 C 23 and 31, 30-2 C 23 and 31; ZWBE 25-3 C 23 and 31, 30-3 C 23 and 31), but pending verification with the specific variant. Without additional external confirmation, it links them to 540000. It assigns the Junkers valve 8716106431, without mentioning 540000. Send us a photo of your boiler's PCB from Contact or call 911 17 77 77.
Is it equivalent to the Junkers safety valve 87161064310?
We cannot confirm it. They assign 87161064310 to the ZWBC 25-2 C 23 (also to the 24-2 C 23). It assigns 8716106431, a 10-digit code that is not listed as the same. The Turkish one lists it alongside 87186434270 as "Caleffi OEM." No page relates it to the 540000. Before considering them interchangeable, compare brand, setting, and connection.
What does the setting of 3 bar mean and does it match the pressure of my boiler?
To confirm: The setting is the pressure at which the valve opens and discharges; it is not the cold filling pressure. The Junkers user manual requests not to exceed 3 bar at maximum temperature when the safety valve opens. The technical manuals provide a maximum operating pressure of 2.5 bar, lower than the marked setting, and "optimal filling pressure 3 bar" without clarifying which setting it refers to. The manuals do not provide the setting of the original valve, but the Turkish description lists the Junkers 87161064310 as 3 bar; for the ZWBC 24-2 C 23 and the ZWBC 25-2 C 23, compatibility is confirmed. Consult a technician for the data of your boiler.
If water is coming out of the gas valve discharge, does it need to be replaced?
Not necessarily. The Junkers manual explains that the valve opens when the maximum pressure is exceeded with the boiler at maximum temperature. First, check the pressure gauge (the technical manual states 1 to 2 bar as the minimum filling pressure when cold), fill only with the boiler cold, and check the expansion vessel, which the manual recommends inspecting every year. If the pressure is correct and it continues to drip, then it is reasonable to suspect the valve.
Can I install it myself or should a technician do it?
It is advisable to have it installed by a qualified technician: it is a safety element of a circuit with pressurized water. In the ZWBC 24-2 C, the safety valve of the heating circuit has a discharge hose, and the technical manual indicates ensuring the discharge of the safety valve. Then, it is filled with the cold boiler and the tightness of the connections is checked (the technical manual states 2.5 bar as the maximum test pressure on the manometer).
Caleffi 540000 Safety Valve · 3 Bar · Junkers ZWBC 24-2 C 23 and 25-2 C 23