Saunier Duval Hydraulic Block Pump Isofast F 35 EA Ref. 0020037988
The hydraulic block of the Isofast F 35 EA pump from Saunier Duval is responsible for directing and distributing water between the circuits of the boiler. If it has faults, you may notice leaks, loss of pressure, or issues with the production of domestic hot water. This part is compatible with boilers such as Isofast Condens F 35 E, Isofast 21 Condens F 35-B, and Themafast F 30 E H-MOD, among others. It is recommended to replace it upon detecting symptoms of malfunction or when receiving fault codes such as F.75, F.23, F.24, or F.20.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference 0020037988
Hydraulic group with reference 0020037988. 12 verified compatibilities: Isofast Condens F 35 E and Isofast Condens F 30 E.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Isofast Condens F 35 E | Isofast Condens | Contrasted |
| Saunier Duval Isofast Condens F 30 E | Isofast Condens | Contrasted |
| Saunier Duval Isofast 21 Condens F 35-B | Isofast Condens | Contrasted |
| Saunier Duval Isofast 21 Condens F 25 | Isofast Condens | Contrasted |
| Saunier Duval Isofast F 30 E H-MOD | Isofast (non-condensing) | Contrasted |
| Saunier Duval Isofast F 35 EA | Isofast (non-condensing) | Contrasted |
| Saunier Duval Isofast F35E H-MOD | Isofast (non-condensing) | Contrasted |
| Saunier Duval Themafast Condens F 24E | Themafast Condens | Contrasted |
| Saunier Duval Themafast Condens F 30E | Themafast Condens | Contrasted |
| Saunier Duval Themafast Condens F 30 H-MOD | Themafast Condens | Contrasted |
| Saunier Duval Themafast F 30 E H-MOD | Themafast | Contrasted |
| Saunier Duval Themafast F 25 E H-MOD | Themafast | 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 hydraulic group 0020037988 resolves.
The hydraulic group includes the valve, the by-pass, and the water connections. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The domestic hot water is coming out fine, but the radiators barely heat up.
Cause: The block distributes the flow between domestic hot water and heating; if the heating part fails, the domestic hot water can continue to function.
Check if the fault affects both circuits or just one before replacing the entire block.
- 02
The pump does not rotate or is difficult to start, especially after a period without heating.
Cause: The shaft gets stuck due to internal deposits or prolonged inactivity.
Try to free the shaft with a screwdriver through the front slot before declaring the pump blocked.
- 03
A metallic vibration or noise can be heard in the area of the block while the system is running.
Cause: It may be due to trapped air in the circuit or a damaged impeller inside the block.
Bleed the heating circuit properly and repeat the test before concluding that it is the part.
- 04
There are damp spots or dripping under the boiler.
Cause: The internal gaskets of the block lose tightness with use.
Dry the area and check after a complete cycle to confirm that the source is the block and not another nearby fitting.
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 hydraulic group 0020037988
- Catalogue reference
- 0020037988
- Brand
- Saunier Duval
- Type of part
- Hydraulic units
- Units in stock
- 7 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- Delivery time shown at checkout
- Return
- 14 days
Frequently asked questions about the hydraulic group 0020037988
Is this hydraulic block compatible with the Isofast Condens F 35 E?
Can I use this hydraulic block in the Isofast 21 Condens F 25?
How many models are compatible with this hydraulic block?
What fault codes are documented for this product?
What is the reference for this hydraulic block?
Spare parts related to Saunier Duval Isofast Condens
