Expansion Vessel Boiler Isofast C 35 E - Ref. 05733300
When the heating system of your Isofast C 35 E boiler starts, the expansion vessel is responsible for absorbing the increase in water volume as it heats up. If this part fails, you will notice that the system pressure fluctuates sharply, and it is possible that the safety valve will leak. This expansion vessel is compatible with several Saunier Duval models, such as the Isofast C 35 E1, Isofast F 35 E, and Isofast F 35 E1, among others. It is recommended to replace it if you observe these symptoms to avoid further issues.
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Consult via WhatsAppSaunier Duval boilers compatible with reference 05733300
Expansion vessel with reference 05733300. Four verified compatibilities: Isofast C 35 E and Isofast C 35 E1.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Isofast C 35 E | Saunier Duval | Contrasted |
| Saunier Duval Isofast C 35 E1 | Saunier Duval | Contrasted |
| Saunier Duval Isofast F 35 E | Saunier Duval | Contrasted |
| Saunier Duval Isofast F 35 E1 | 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 the ref. 05733300 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 05733300. 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 expansion vessel 05733300 resolves.
The expansion vessel absorbs the expansion of water when heated. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The boiler loses pressure on its own and needs to be refilled every few days.
Cause: The vessel does not absorb the water that expands when heated because it has lost the air charge or has a broken membrane, and that excess water exits the circuit through the safety valve.
With the boiler cold and depressurized, check the pre-charge pressure of the expansion vessel at the Schrader valve; if it reads well below 1-1.5 bar or shows no reading at all, the vessel has lost its charge.
- 02
The safety valve drips or releases water when the heating has been on for a while.
Cause: Without an air cushion in the tank, the increase in volume of the hot water has no place to be absorbed, and the pressure rises until the safety valve discharges it.
Before changing the expansion vessel, make sure that the safety valve is not stuck or dirty in its seat: sometimes it leaks even if the vessel is fine.
- 03
There are knocks or noises in the pipes when the heating pump starts or stops.
Cause: A vessel without air pressure does not cushion the water hammer generated by the pump when starting and stopping.
Tap the glass with your hand when it is cold and depressurized: if it sounds solid, without air resonance, it is likely full of water and without a functional diaphragm.
- 04
The needle of the pressure gauge rises significantly when the heating starts and drops when it turns off.
Cause: It is the classic signal of a vessel that no longer compensates for the expansion of water: without an air cushion, the entire increase in volume translates directly into an increase in pressure.
Note the cold pressure and the pressure a few minutes after starting; a sudden and repeated increase is typical of a bladder without charge, although it is advisable to rule out excessive filling of the circuit first.
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.
Expansion vessel data sheet Saunier Duval 05733300
- Catalogue reference
- 05733300
- Brand
- Saunier Duval
- Type of part
- Expansion vessels
- Units in stock
- 4 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- 1-2 business days
- Return
- 14 days
Frequently asked questions about the expansion vessel 05733300
What fault indicates that the expansion vessel of the Isofast F 35 E needs to be replaced?
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