Waterproof Electrical Junction Box

We can see from the photograph that the integrity of this junction box has been somewhat compromised. I cannot remember seeing such a large quantity of water inside any other junction box. The extension lead in this box was basically fully submerged in water ☹

1) What type of waterproof junction box do I need?

There are many different types of WATERPROOF ELECTRICAL JUNCTION BOX on the market with different purposes in mind and care should be taken selecting the correct one for your application. We can see from the photograph what happens when the incorrect type is selected or installed against manufacturer’s instructions. We select the correct type of outdoor equipment by examining, amongst other things, the IP rating.

2) What is an IP rating?

An IP rating is the rating applied to equipment so that consumer know its suitability for use in various locations. It is generally understood that IP stands for ‘Ingress Protection’ and points to the level of protection against water and particle ingress that an accessory provides to the electrical system. 

The IP rating consists of two numbers to a maximum of IP68. The first number relates to the ability of the enclosure to withstand the ingress of solids. The higher the number the better the enclosure prevents access to solids. Solids can be anything from a finger to dust particles. An IP6 rated enclosure should not allow any fine particles in whatsoever. The second number relates to the ability of the enclosure to withstand the ingress of water.

3) How do you waterproof an electrical box?

As an emergency electrician with many years of experience, I regularly see homeowners own Do-It Yourself electrical work that has been carried out poorly and in contravention of wiring regulations. It is a common misconception that in order to waterproof an electrical box you can:

• Wrap it in a plastic bag
• Silicone the edges
• Paint it with a waterproofing agent
• Use PVA to ‘seal it’

There is no good way to ‘waterproof’ an electrical box. The manufacturer is responsible for ensuring that the electrical junction box meets the relevant requirements for its stated IP rating. It is the electrician’s responsibility to ensure that the electrical box is installed in accordance with the manufacturer’s instructions such that the electrical box meets the requirements for its IP rating.

Covering electrics with a plastic bag does not ‘waterproof them’.

4) How do you install a waterproof junction box?

The answer is always in accordance with the manufacturer’s instructions. If these cannot be found or did not come with the product that you purchased then you should look them up online using the brand name and model of the product that you have to make sure that you have the correct instructions for your product.

Much will depend upon its installation location as to the best method for installation. Let’s assume that the junction box will be constantly exposed to the elements and is likely to continuously get wet. In this case, any electrician will tell you that you should always avoid using a top entry for any cables despite the quality of waterproof grommets or glands that you may use. 

Top entry connections (where the cable enters or exist the junction box through the top) should be avoided where water is likely to come into contact with the electrical box. This is because, water always runs down and will usually find its way in regardless of the IP rating of any glands or equipment. Many instructions will also tell you not to install a box or cable entry in this manner also.

5) How do you keep water out of a junction box?

In order to successfully keep water out of a junction box you must abide by the following 10 tips:

• Install in accordance with the manufacturer’s instructions
• Where possible remove all water sources from the installation location
• Install in a location where minimal water is likely to come into contact with the electrical junction box
• Ensure that the junction box is correctly IP rated for the environment in which you wish to install it
• Use entry and exit points for cables where water will not sit in joints
• Bottom entry is always best and side entry a close second
• Use a drip loop on any cables to allow water to drip away rather than running down the cable and into the junction box
• Make sure that the junction box is correctly closed or sealed according to the manufacturer’s instructions
• If the box is damaged, do not install it, instead just use a replacement
• Ensure that the box will not degrade in the sunlight, crack, and allow water in.

There are other tips that may be useful when installing a junction box but these will depend on the individual set of installation circumstances and site conditions where the box will be installed. 

6) Can you use silicone to waterproof electrical connections?

Generally, no you cannot. Silicone is not recommended unless it is supplied by the manufacturer for exactly that purpose. There are junction boxes that are designed to join cables together using special maintenance free connections and a resin that is then poured in to the box covering all connections. This is the absolute best way of ensuring that the electrical connections will not be subject to water. 

Should this joint or box be buried then eventually, no matter how brilliant the product might be, nature will find a way of getting some water in there for you to ruin your work. 😊

7) Are there industry standards for an electrical waterproof junction box?

The industry standards for preventing the passage of water into a junction box are the IP rating standards. As covered earlier in this blog, the IP rating will determine how well the junction box can withstand the entry of solid particles or water. 

The construction standards of the box should comply with BSEN 60670 for electrical junction boxes intended for installation in household premises in the UK. There are some other British Standards that apply to electrical accessories and installations products and you should ensure that any products that you install comply with the relevant British standard. Generally, this can be a headache to check and can be avoided by purchasing electrical equipment from your local reputable wholesaler.

Equipment and accessories purchased online can sometimes have questionable markings, dubious compliance with the relevant standards and may claim to fulfill the requirements of such standards but be of inferior quality and construction for purpose. Always use a reputable source for your electrical needs. 

8) Are there different sizes of outdoor electrical junction box?

There are many different sizes of outdoor electrical junction box in a variety of IP ratings. The sizes range from 85mm x 51mm x 49mm for the tiny WISKA 206 right up to 460mm x 380mm x 120mm for the GEWISS GW44011.  Beyond these sizes outdoor electrical boxes tend to start being manufactured with doors rather than lids and get rather expensive. 

The small WISKA boxes start from around £3.50 and the large GEWISS box is currently on one internet site at around £30. 
One of my favourite sizes is 95mm x 95mm which is ideal for many outdoor electrical purposes. WISKA is my favourite manufacturer and their WISKA BOX 308 is nearly the perfect size at 85mm x 85mm x 51mm. The construction is very durable on these boxes and installation is nice and easy with rubber membranes that can be broken to insert cables directly or the correct sizes IP rated gland used. 

9) Can a Waterproof Electrical Junction Box be used underground?

Certain junctions and joints can technically be used underground. Anything with an IP68 rating should theoretically survive the perils of underground moisture as this rating is sufficient for the electrical junction box to be submerged in water. 

In practice however things can turn out slightly differently. You see, the ground never actually stays still. We have to contend with tremors, ground heave, expansion and contraction, insects, rodents, and other ground disturbances. All of these issue need to be factored in to the equation when considering if you should bury the junction in the ground. 

It may be installed in the correct manner to the correct IP rating in accordance with manufacturer’s instructions but in my experience, they nearly always fail at some point and allow water in. This is not to say that the product is bad, the installation is bad or they are poorly manufactured but rather they have been subject to ‘external influences’ meaning that they no longer perform as intended. 

10) How do you properly seal cable entries in a waterproof electrical junction box?

The absolute best way of ensuring that no water enters the junction box at cable entry and exit points is to make sure that the correct IP rated glands are used and that any instructions provided by the manufacturer or the enclosure or box are followed. 
With WISKA boxes in particular, I ensure that when installed outside I use the relevant WISKA glands and the correct sized rubber inserts for the cable diameter that I will be using on that particular project. I also make sure that, where possible, I use bottom entry to take cables in and out of the enclosure so that water is highly unlikely to ever sit at entry points where the glands meet the box.

This WISKA box had been installed with too many cables inside and some of which were aluminium causing fractures in the metal, loose connections and burning.

11) Can you paint over a waterproof electrical junction box?

If intending to paint over a junction box you would need to ensure that any proposed paint product did not adversely affect the box construction material or any seals that prevent moisture or dust ingress. Each manufacturers (Paint and electrical box) instructions or technical helplines may need to be contacted to ensure that there are no compatibility issues with their products. 
Most outdoor electrical accessories have a very smooth coating meaning that a primer may be necessary in order to give the smooth surface an appropriate key for the paint to stick to. 

12) What maintenance is required with an outdoor rated junction box?

Generally, these boxes are maintenance free once installed correctly. Over time, outdoor plastics tend to become brittle so in many cases, the less interference with the equipment, the better as there is a risk of screws and lids breaking when opened. 
From a maintenance point of view, I have not seen an outdoor box that requires maintaining, rather the equipment inside is likely to need maintenance rather than the enclosure itself. 

13) Do waterproof junction boxes provide protection against dust and debris?

Yes, all outdoor junction boxes will provide a degree of protection against dust, debris, and moisture. The effectiveness of this protection against the elements is given by the IP rating of the junction box. 

14) What type of equipment can be installed in a waterproof electrical junction box?

Once equipment is installed in an environment that protects against the elements, the equipment installed in that box should only then have to suffer its surroundings. That is, often indoor equipment can be installed outdoors once the elements have been protected against. This is quite useful as extension leads are generally rubbish at preventing moisture and dust from entering themselves so once a suitable installation environment has been provided (IP RATED BOX) they are able to be used outdoors effectively. The picture at the top of this article proves that not all IP rated boxes are effective all of the time and installation practices do cause problems occasionally.

There are many different manufacturers of waterproof electrical junction box out there and many different products on the market. Each has its own IP rating, installations instructions, pros and cons. You should consider which meets your needs and budget for the work that is to be carried out.