Saunier Duval Hydraulic Block Pump Themafast F 25 E H MOD Ref. 0020037988
The hydraulic block of the Themafast F 25 E H pump is responsible for directing and distributing water between the circuits of the boiler. If it malfunctions, the user may notice leaks, loss of pressure, or issues with the production of domestic hot water. It can lead to fault codes such as F.75, F.23, F.24, and F.20. This component is compatible with boilers from the Isofast Condens, Isofast (non-condensing), and Themafast ranges, including models like Isofast Condens F 35 E, Themafast F 30 E H-MOD, among others. It is advisable to replace it when these symptoms or faults are detected.
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 radiators heat little or not at all even though the boiler ignites normally.
Cause: The pump of the hydraulic block does not move the necessary flow due to wear or blockage of the impeller.
Check if the pump vibrates or makes noise when starting; if there is no signal, it may be blocked.
- 02
The pump does not start after a long period of not using the heating, like at the end of summer.
Cause: The shaft gets stuck due to sediment accumulation during inactivity.
With the boiler cold, try to free the shaft with a flat screwdriver through the front slot.
- 03
Vibration or buzzing noise in the block area with the installation running
Cause: It may be due to trapped air in the circuit or a damaged impeller inside the block.
Bleed the radiators and the circuit properly before concluding that the block is faulty.
- 04
There is dripping or moisture under the boiler, near the hydraulic block.
Cause: The internal seals lose tightness with use and temperature changes.
Dry the area and check after a heating cycle to locate the exact point before replacing the part.
- 05
The domestic hot water works, but the heating does not heat well, or vice versa.
Cause: The hydraulic block distributes the flow between both circuits, and a fault can affect only one.
Note whether the problem occurs in both uses or only in one before deciding that the complete part is faulty.
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
Data read on the part and in the manufacturer's documentation
What we have not been able to verify does not appear here.
- material
- PA66-GF3
Frequently asked questions about the hydraulic group 0020037988
Is this hydraulic block Ref. 0020037988 compatible with the Isofast Condens F 35 E?
Can I use the hydraulic block HBTF25MOD in the Themafast F 30 E?
Is the hydraulic block suitable for the Isofast 21 Condens F 25?
What fault codes are common in this hydraulic block?
How many models are compatible with this hydraulic block?
Does this hydraulic block work for the Themafast Condens F 30 E?
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