Stiebel-Eltron LWZ 604-5-8, 303, 304, 403, 404, 504 – CORE enthalpy heat exchanger
Premium enthalpy exchanger from the German brand CORE.
Product photos may not show the exact design of the heat exchanger. This enthalpy exchanger is 100% compatible with Stiebel-Eltron LWZ 604-5-8, 303, 304, 403, 404, 504 and thanks to its construction it can offer better operating performance than the original enthalpy exchanger. It is not an original OEM part supplied by the unit manufacturer.
If we have any doubts about the correct exchanger type for your unit, we will contact you before dispatch to double-check everything together.
Technical datasheets are attached to the product.
Compatibility – Stiebel-Eltron units
LWZ 303 ✔ LWZ 304 flex ✔ LWZ 304 SOL ✔ LWZ 304 SOL E CH ✔ LWZ 304 Trend ✔ LWZ 403 ✔ LWZ 403 SOL ✔ LWZ 404 flex ✔ LWZ 404 SOL ✔ LWZ 404 Trend ✔ LWZ 504 ✔ LWZ 504 E ✔ LWZ 5 CS Premium ✔ LWZ 5 CSE Premium ✔ LWZ 5 S Plus ✔ LWZ 5 S Trend ✔ LWZ 8 S Trend ✔ LWZ 604 Air ✔ LWZ 604 Enthalpie ✔ LWZ 8 CS Premium ✔ LWZ 8 CSE Premium ✔ LWZ 8 CS Trend ✔
CORE F-ERV – the latest generation of enthalpy heat exchangers
The CORE F-ERV enthalpy exchangers represent the most advanced technology level within CORE’s ERV portfolio. They use an innovative formable polymer membrane that enables highly efficient transfer of both heat and humidity back into the supply air. At the same time, viruses, bacteria, odours and mould spores are prevented from returning into the indoor environment – they are safely carried away with the exhaust air.
Thanks to reduced weight, higher efficiency and an optimised internal design, F-ERV exchangers are suitable not only for residential units, but also for large central ventilation and industrial HVAC systems. The F-ERV series is the direct successor and evolution of the C-ERV line.
F-ERV advantages compared to C-ERV
- Significantly higher efficiency in both heat and moisture transfer
- Formable next-generation membrane = lower pressure drop, improved airflow
- Lighter design → easier handling, installation and transport
- Ideal for large central systems and higher air volumes
- Reduced condensation → fewer defrost cycles and lower energy consumption
- More sustainable construction with improved recyclability
- Awarded the PLUS X AWARD for innovation, quality, ease of use, functionality and ecology
What makes CORE technology unique
- Recovers both heat and humidity, stabilising indoor climate
- High efficiency even at low outdoor temperatures
- Microorganisms, odours and mould spores do not return into the supply air
- Design prevents condensation build-up inside the exchanger
- Washable membrane, long service life, easy maintenance

About CORE
CORE is a global leader in air-to-air heat exchanger technology. Since 1994, the company has been developing high-end membrane heat exchangers for residential, commercial and industrial applications.
Production relies on laser and ultrasonic welding, robot-assisted manufacturing and proprietary patented membrane technologies.
CORE’s philosophy is simple: better air = better living.

RECUTECH are equipped with the latest enthalpic membrane METALPIC. They excel in top-class heat and humidity recovery, high resistance to pressure differences, and long service life. They are among the most advanced enthalpic heat exchangers currently available on the market.
ZERN are fully plastic enthalpic heat exchangers, very efficient, with slightly better moisture transfer, but with higher pressure loss.
No, never block the condensate drain.
Even though enthalpic heat exchangers produce only a minimal amount of condensate due to moisture transfer, in severe frost and specific humidity conditions, condensate can still occur. Blocking the drain could cause irreversible damage to your unit.
Since an enthalpic heat exchanger also transfers humidity, it might seem that the risk of mold is higher. In reality, however, all moisture is carried away with the fresh air, so there is no risk of mold growth.
Our recommendation is to never switch off the unit during the winter months, so that moisture is continuously removed. If you still need to shut down the unit, remove the exchanger, rinse it with clean water, dry it thoroughly, and only then reinstall it.
Yes, installation is simple. Just follow the instructions provided with your unit. As with a standard exchanger, it needs to be removed occasionally for cleaning – the process is the same, except that you put the enthalpic exchanger back in instead.
Feel free to contact us with any unit model. We will do our utmost to provide you with a 100% compatible exchanger, regardless of the type of ventilation unit you have.
In any case, the exchangers we supply are identical to the original parts used by the unit manufacturers, and in many cases, our exchangers are even of higher quality. However, we must clearly state that we are not official distributors of spare parts from the unit manufacturers. Transparency is very important to us.
An enthalpic heat exchanger should be used all year round. In winter, it prevents excessive drying of the indoor air, and in summer, it helps maintain comfortable humidity and temperature by reducing heat transfer and returning part of the moisture to the fresh supply air. This increases comfort and saves energy in every season.
No, caring for an enthalpic heat exchanger is no more demanding than for a standard one. Maintenance is described in the user manual and in our video guide. In short: first vacuum the exchanger with a soft brush attachment, then rinse it with clean water (max. 50 °C). Never use compressed air or a pressure washer.
After rinsing, allow all water to drain completely. Remaining moisture can be carefully blown out with a regular hairdryer, but always use cold air only. Once the exchanger is completely dry, place it back into the unit in the same orientation as before removal.
We do not recommend using chemicals for cleaning. Only if disinfection is absolutely necessary may a weak solution of peracetic acid (CH₃CO₃H) at 0.1–0.2% concentration be used, followed by very thorough rinsing with clean water.
Yes, the use of an enthalpic heat exchanger is completely safe. The membrane is designed to allow only water vapor molecules to pass through, while blocking bacteria, odors, and harmful substances. All enthalpic heat exchangers we offer are hygienically tested and certified.
An enthalpic heat exchanger will always help improve indoor humidity, as it transfers part of the moisture from exhaust air back into the fresh supply air. It cannot be guaranteed that ideal levels (typically 40–60%) will be achieved, since the final humidity also depends on other factors – such as household habits, number of occupants, natural moisture sources, and outdoor climate conditions.
However, we can guarantee that humidity will improve, because it is physically impossible for the return of moisture not to contribute to higher values.
The enthalpic plate works the same from both sides, so the orientation of the plate itself does not matter. However, it is essential that after cleaning the exchanger is always reinstalled in the same orientation, ensuring that the channels for fresh air remain for fresh air and the channels for exhaust air remain for exhaust air.
An enthalpic heat exchanger does not generate humidity – it maximizes the transfer of humidity from exhaust air into fresh supply air. If you previously used a standard exchanger, not only the air but also the building structure (walls, ceilings, floors) and porous materials became dry. This means it may take some time for humidity levels to recover, so patience is necessary.
Every enthalpic exchanger we supply is fully functional and improvement is guaranteed. We recommend keeping natural humidity sources (plants, cooking, drying clothes). If you use humidifiers, continue using them until the humidity rises to a comfortable level with the enthalpic exchanger, after which they can be reduced.
Yes. Unlike a standard exchanger, an enthalpic heat exchanger transfers part of the humidity back into the fresh air. This process is gradual, but you can speed it up by adding humidity – either naturally (plants, drying clothes, washing floors) or with humidifiers. Once the humidity has returned to a stable, optimal level, additional humidification can be reduced.
No, an enthalpic heat exchanger does not generate humidity by itself. It only transfers part of the moisture from the exhaust air back into the fresh supply air. If humidity in your home is too high, the cause lies elsewhere (e.g., insufficient ventilation, drying clothes indoors without venting, or residual construction moisture). The enthalpic exchanger helps balance humidity and prevents extreme fluctuations.
An enthalpic heat exchanger works on the principle of counterflow air streams. During ventilation, two separate airflows meet inside – the warm, humid exhaust air from indoors and the cold fresh air from outside. A special membrane transfers both heat and water vapor from the exhaust air to the incoming fresh air without mixing the two streams. This way, fresh air enters the home with a more comfortable temperature and humidity, improving comfort while saving energy.
The sealing tape must be applied around the perimeter of the exchanger, so that when inserted it presses firmly against the unit walls and prevents false air from being drawn in. The surface of the exchanger must be dry and clean before application. Always apply the tape straight, without gaps or folds, to ensure proper sealing.