Junction box problems

[diy mad]

Hi,

Not sure if anyone will be able to help me with this.

I've been trying to make a junction box connection in the top of an underground garden rainwater storage tank. The SWA feed cable has had the correct gland fitted and screwed into a 20mm thread in the box. The flexible round cable from the pump has been fitted with a plastic gland and metal backnut.

I've used an IP66 junction box from Toolstation, ref 47979, which is a plastic box with the lid secured by 4 quarter-turn fastenings. (I was surprised to find there was no rubber or similar seal between the lid and box, but as it was rated IP66 assumed it must be OK).

After a week the RCCB trip in the house blew and the junction box had water droplets inside.

Am I missing something?

Many Thanks.

 

[davelx]

Water level covering the JB during heavy rain, unable to flow out of the overflow fast enough? Pictures of the installation would help.

 

[diy mad]

Thanks for that Davelx.

I'm due at the house next Wednesday so can take photo and post it then.

 

[diy mad]

Here are photos as requested. the tank is approx 600mm diameter and the JB is about 1800mm above water level, so there would need to be a huge volume of water to quickly fill it whilst outlet can't cope. Water has never been seen overflowing from under top drain cover. I'm thinking should the cable glands have been waterproof type - is there such a thing?

 

[333rocky333]

If you mean the armoured glands then yes there are BW and CW only the CW glands are watertight if done properly.
Could it just be condensation building up, what is the box actually for and does it need to be inside, maybe better located outside

 

[sparkwright]

Wiska outdoor junction boxes claim to be very watertight.

It used to be fairly common to fill outdoor junction boxes with electrical waterproof compound - no one seems to do that now.

It also helps for cable entries to be at the bottom of the box, if water and gravity are to be entered into the equation.

A CW SWA gland is a must, and the plastic stuffing glands are available with a seal that goes between the box and the gland.

 

[diy mad]

Thanks both.
The junction box connects the SWA feed to the flexible pump cable. The tank is in the middle of a lawn, so it’s not really possible to site it outside of the tank system Rocky.
I’m pretty sure it must be condensation and I did re-use the stuffing gland that was on the original flexible cable. Sparkright, I see Screwfix do a gland with a neoprene rubber seal (80851), I presume that’s what you mean, so I think I’ll try that with a BG Ip66 box.
Many thanks again for your comments chaps.

 

[bernardgreen]

The SWA feed cable has had the correct gland fitted

Is it an external gland or an internal gland ?

Internal glands are not water tight as they do not have a seal around the outer sheath of the SWA and are not suitable for use in damp or humid locations.

External gland have a seal around the outer sheath of the SWA which prevents moisture reaching the inside of the gland

 

[diy mad]

Thanks Bernard, I used the original gland but I’ll replace it with a new external.

 

[333rocky333]

There is a stuff called Magic Gel. never used it myself but I recall someone i knew filled a box with it and submerged it underwater and too my knowledge it still works fine.
To be honest the rubber ring on the stuffing gland is unlikely to make any difference

 

[sparkwright]

There is a stuff called Magic Gel. never used it myself but I recall someone i knew filled a box with it and submerged it underwater and too my knowledge it still works fine.
To be honest the rubber ring on the stuffing gland is unlikely to make any difference

I kind of agree about those rubber rings...