Saunier Duval Primary Bithermal Heat Exchanger ThemaClassic C25E Ref. S1059900
If you notice that the domestic hot water is lukewarm or has fluctuating temperatures, a technical diagnosis should confirm whether you need the Saunier Duval bitermic primary heat exchanger ThemaClassic C25E. This part is responsible for transferring heat from the primary circuit to the hot water instantly. When it fails, it can also reduce the flow of domestic hot water, affecting your daily comfort. It is compatible with models from the ThemaClassic range, such as the ThemaClassic F 25 E, among others. A technician should confirm through diagnosis whether it needs to be replaced when you start noticing these symptoms to ensure an adequate supply of hot water.
- Type of part
- Primary heat exchangers
- Status
- Refurbished
- Catalogue reference
- S1059900
- Warranty
- 1 year
Saunier Duval boilers compatible with reference S1059900
Primary heat exchangers with reference S1059900. A verified compatibility: ThemaClassic F 25 E.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval ThemaClassic F 25 E | ThemaClassic | Contrasted |
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 the part S1059900 is the one for your boiler
The part reference, model, and equipment revision must be verified against the manufacturer's documentation.
- Find the reference printed on the installed part and check whether it matches the catalogue reference S1059900. If it is not visible, do not identify the part from its shape alone.
- Check the full boiler model on its data plate and look for it in the model associations on this page.
- Compare the connections and physical body with the original part before installation.
- If anything is unclear, send us a photo of the marking via WhatsApp before placing your order.
Symptoms that require diagnosis in primary heat exchangers S1059900
Common symptoms and faults
- 01
The hot water comes out intermittently while you are showering.
Cause: The copper fins of the heat exchanger are clogged with scale, preventing the water from heating continuously.
Check the cold water inlet pressure and inspect the sediment filter before assuming that the fault is with the heat exchanger.
- 02
Water or moisture is leaking from the bottom of the boiler, near the heat exchanger.
Cause: The copper coil gets perforated over time due to corrosion or the buildup of scale.
Dry the area, pressurize the circuit, and check that the leak is coming from the heat exchanger and not from a nearby fitting.
- 03
A knocking or bubbling noise is heard when heating, especially when hot water is requested.
Cause: The accumulated scale between the copper fins causes hot spots and microbubbles.
Associate the noise with the exact moment when the domestic hot water is activated; if it always coincides, reinforce the diagnosis before replacing the part.
- 04
The heating works well, but the domestic hot water is faulty, or vice versa.
Cause: The heat exchanger distributes heat between both circuits; a partial obstruction first affects one of the services.
Check that the 3-way valve switches correctly between heating and domestic hot water before considering the replacement of the heat exchanger.
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: Saunier Duval S1059900 heat exchangers
- Catalogue reference
- S1059900
- Uniclima internal SKU
- ITBTMACLC25E
- Brand
- Saunier Duval
- Type of part
- Primary heat exchangers
- Units in stock
- 6 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- Delivery time shown at checkout
- Return
- 14 days
Manuals and technical documentation
Official documentation of the boiler, useful for locating the part and cross-referencing the fault codes.
- Saunier Duval Themaclassic F 25 E Manual (PDF)Document © Saunier Duval, provided as a technical reference.
Frequently asked questions: primary heat exchangers S1059900
Is the part that the Saunier Duval ThemaClassic C 25 E uses a plate heat exchanger?
Does this heat exchanger fit a Saunier Duval ThemaClassic F 25 E?
When should the heat exchanger of the ThemaClassic C 25 E be replaced?
What is the reference for the bivalent primary heat exchanger of Saunier Duval for the ThemaClassic C 25 E?
How many models are compatible with this heat exchanger?
Are there documented fault codes for this product?
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