An electrical connection may require additional protection against moisture, dirt and other external influences in certain situations. By filling a suitable junction box or electrical enclosure with casting resin, the connections are encapsulated by the resin. For potting electrical components, you can use a casting resin that has been specifically developed for this purpose. One example is Araldite DBF with Aradur HY 956 EN. This is a low-viscosity epoxy casting resin with a high dielectric strength of 24 kV/mm. A highly suitable epoxy resin for potting low-voltage and electronic components.
In this article, you will learn which casting resin you can use for a junction box, how to determine the required quantity and how to pot a junction box step by step.
Why fill a junction box with casting resin?
A suitable casting resin protects the potted components against external influences such as moisture, dirt and atmospheric exposure. Casting resin flows around cables, connections and other electrical components. After curing, it forms a solid, electrically insulating layer around the embedded parts. Potting electrical or electronic components is also known as potting or encapsulation.
It is important to distinguish between the casting resin and the complete electrical installation. The resin protects the components embedded in it, but it does not automatically make every junction box suitable for outdoor use, underground installation or prolonged contact with water.
Which casting resin should you use for a junction box?
For electrical applications, use a casting resin that is specifically intended for potting electrical or electronic components. For example, you can use Araldite DBF epoxy casting resin with Aradur HY 956 EN hardener.
This 2-component epoxy has a low mixed viscosity of approximately 1,800 mPa.s at 25°C. This allows the liquid epoxy to flow effectively around electrical components and through small openings.
After curing, Araldite DBF / Aradur HY 956 EN has a dielectric strength of 24 kV/mm under the test conditions specified in the technical data sheet. This system cures at room temperature and can be easily processed by casting or using an advanced vacuum injection method.
Can you pot any junction box?
No. The enclosure and electrical components used must be suitable for the intended application.
Check, among other things:
- whether the junction box or enclosure is suitable for the environment;
- whether the cables and connections are installed correctly;
- whether the cable entries and cable glands are suitable;
- whether the resin can flow around the components without leaking out;
- whether the electrical connection functions correctly before potting.
For underground cable connections or other applications with specific requirements, specially designed cable joints or complete connection systems are often used. Simply filling any junction box with epoxy does not automatically give the complete installation a specific IP rating or make it suitable for prolonged exposure to water.
Potting a junction box in 7 steps
What do you need?
To pot a junction box, you will need, among other things:
- A suitable junction box or electrical enclosure.
- Araldite DBF epoxy casting resin + Aradur HY 956 EN hardener.
- Digital scale.
- Mixing cups.
- Mixing spatulas.
- Nitrile gloves.
- Safety glasses.
- Protection for the work surface.
Prepare everything before you start mixing. As soon as the resin and hardener are combined, the curing process begins.
Step 1. Disconnect the power supply
Never work on electrical connections while they are live. Switch off the installation and check that it is actually de-energised.
Check the connections before you start potting. Once cured, the components are fixed in the epoxy and are much more difficult to access for adjustments or repairs.
Step 2. Check the junction box
Check that the enclosure, cables, glands and connections are suitable and correctly installed. Make sure the junction box is stable and preferably level. The epoxy is liquid during processing and must not be able to leak out through openings in the enclosure.
The components you are going to pot must be clean and dry.
Step 3. Determine how much epoxy you need
Calculate or estimate how much casting resin is needed to encapsulate the electrical components to the desired level.
Take into account the volume of cables, connectors and other components. Only mix the amount of epoxy you actually need and bear in mind the heat generated with larger casting volumes.
Step 4. Weigh the resin and hardener
For Araldite DBF and Aradur HY 956 EN, the mixing ratio is:
- 100 parts resin : 20 parts hardener by weight.
- Use an accurate digital scale.
- For example, if you use 250 grams of Araldite DBF, you need 50 grams of Aradur HY 956 EN.
- Do not change the mixing ratio to make the epoxy cure faster or slower.
Step 5. Mix the casting resin carefully
Add the hardener to the resin and mix both components thoroughly. Scrape along the bottom and sides of the mixing cup while mixing to minimise any unmixed material.
Mix gently. Stirring too vigorously can introduce unnecessary air into the epoxy. After mixing, you have approximately 70 minutes of working time until the mixture reaches a viscosity of 5,000 mPa.s. Temperature and the amount of material affect the processing time.
Step 6. Slowly fill the junction box
Slowly pour the mixed epoxy into the junction box. Preferably start at one point and allow the liquid resin to flow around the components by itself.
Pouring slowly reduces the risk of air becoming trapped between cables and electrical components.
While filling, check that the components you want to protect are sufficiently encapsulated by the resin. Afterwards, move the cables and connections as little as possible.
Step 7. Allow the epoxy to cure
Leave the junction box in place after casting while the epoxy cures. Araldite DBF has a minimum curing time of 24 to 48 hours at room temperature. The actual curing time is influenced by factors such as ambient temperature, casting volume and the shape of the casting.
Wait until the epoxy has cured sufficiently before putting any load on the potted components.
Potting a junction box with casting resin yourself
Potting a junction box starts with choosing a suitable enclosure and casting resin. Check the electrical connection before casting, determine how much resin you need and accurately follow the specified mixing ratio.
For potting low-voltage and electronic components, you can use Araldite DBF epoxy casting resin. This low-viscosity epoxy has been developed for potting and encapsulation and is easy to use.
Do you have questions about potting a junction box, the required amount of casting resin or choosing a suitable epoxy? Please contact our specialists! We are happy to help.
