Pump Component for Isofast, Isomax, and Thema Boilers Ref. 0020037988
The pump of the Isofast, Isomax, and Thema boilers circulates water through the heating circuit, ensuring its flow. When it fails, you may notice cold radiators, strange noises, overheating, or blockages due to lack of circulation. This component is compatible with several Saunier Duval boilers, such as Thema NOx F25 B, Themafast F25 E, among others. It is advisable to replace the pump when these symptoms occur to prevent further damage to the heating system.
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Consult via WhatsAppSaunier Duval boilers compatible with reference 0020037988
Circulating pump with reference 0020037988. 13 verified compatibilities: Thema NOx F25 B and Themafast F25 E.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Thema NOx F25 B | Saunier Duval | Contrasted |
| Saunier Duval Themafast F25 E | Saunier Duval | Contrasted |
| Saunier Duval Themafast F30 E | Saunier Duval | Contrasted |
| Saunier Duval Themafast Condens F30 | Saunier Duval | Contrasted |
| Saunier Duval Sémia Teck F24 | Saunier Duval | Contrasted |
| Saunier Duval Sémia C 24 | Saunier Duval | Contrasted |
| Saunier Duval Thema Condens F25 | Saunier Duval | Contrasted |
| Saunier Duval Thema C 25 E | Saunier Duval | Contrasted |
| Saunier Duval Themaplus C 25 E | Saunier Duval | Contrasted |
| Saunier Duval Themaplus F30 E | Saunier Duval | Contrasted |
| Saunier Duval Isotwin Condens F30 | Saunier Duval | Contrasted |
| Saunier Duval Isofast Condens F30 | Saunier Duval | Contrasted |
| Saunier Duval Isomax Condens F35 | Saunier Duval | 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 ref. 0020037988 is the part for your boiler
What determines it is not the boiler model, but the reference printed on the part you already have installed.
- Find the reference printed on the installed part and check whether it matches the catalogue reference 0020037988. 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 and faults that the circulator pump 0020037988 resolves.
The circulation pump circulates the water in the heating circuit. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The radiators farthest from the boiler do not heat up or take a long time to do so.
Cause: The pump is not pushing water correctly through the circuit due to blockages or wear.
Bleed the radiators and check the circuit pressure before considering that the pump is faulty.
- 02
There is a water leak where the pump is mounted, especially when the boiler is in operation.
Cause: The body and gaskets of the pump may be worn or damaged, causing leaks.
Dry the area and check if the leak reappears after a heating cycle, ensuring that it comes from the pump and not from a nearby fitting.
- 03
A buzzing or rubbing noise is heard from the pump when the heating is turned on.
Cause: Lime deposits or dirt in the hydraulic block are rubbing against the moving parts, causing the noise.
If the boiler has been stopped for a while, try to unlock the pump shaft before replacing it; often, that is enough.
- 04
The heating is not working, although the boiler turns on and does not show any faults.
Cause: If there is no water circulation due to a blockage in the pump, heat does not reach the radiators.
Check that the pump is running, listening for a soft humming sound, and make sure that the integrated bleed valve is not closed or stuck before replacing it.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F.75 | The control does not detect an increase in pressure when the pump starts (lack of water/pressure or pump/sensor fault). | If the circulator (block 0020037988) is blocked, does not start, or does not respond, the pressure sensor does not detect the expected increase and the boiler locks out with F.75; check electrical/PWM start-up, consumption, and that the rotor spins after bleeding. |
| F.23 | Safety shutdown due to excessive temperature difference between flow and return. | A blocked pump or one working at minimum power prevents circulation, increases the ΔT, and triggers F.23; check that the circulator is rotating, its consumption and flow rate, and bleed the primary. |
| F.24 | Safety shutdown due to excessively rapid temperature rise. | If the circulator of block 0020037988 is seized or has insufficient power, the water does not dissipate heat and the temperature rises quickly; check the pump's rotation/consumption, PWM signal, and bleed the circuit. |
| F.20 | Safety shutdown of the temperature limiter (overheating). | The lack of circulation due to a blocked pump in block 0020037988 causes overheating in the heat exchanger; check the start and flow of the circulator, free the shaft if it is seized, and bleed. |
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.
Data sheet for the Saunier Duval circulator pump 0020037988
- Catalogue reference
- 0020037988
- Brand
- Saunier Duval
- Type of part
- Pumps
- Units in stock
- 1 unit
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- 1-2 business days
- 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 Themafast F30 E Manual (PDF)Document © Saunier Duval, provided as a technical reference.
Frequently asked questions about the circulator pump 0020037988
Is this pump component suitable for an Isomax Condens F 35?
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