Running cable for a submersible sump

Discussion in 'Electricians' Talk' started by Garym964, Oct 7, 2021.

  1. Garym964

    Garym964 New Member

    I have a sump pit in my garden where rainwater from land drains collects b4 being pumped by a submersible pump to rainwater storage butts. The cable from the submersible pump is plugged into a 13a socket inside a shed around 15 feet away but currently the cable is not protected from potential damage. Burying the cable is not an option so my intention is to route it through galvanised steel conduit surface mounted along railway sleepers that edge the gravel path under which the pump is located. My question is does the steel conduit through which the cable is routed need to be earthed & if so how can this be achieved given that the cable is the T&E that is wired into the pump by the manufacturer and is terminated with a standard 13a plug. NB the socket which the pump is plugged into is on a dedicated garden circuit with RCD protection at the CU.
     
  2. Bazza

    Bazza Screwfix Select

    Yes, it needs to be earthed. A better solution would be to use steel wire armoured cable (SWA). The armour being earthed. So much easier to install than steel conduit. You can just cleat the cable to your sleepers.
    Gland the SWA in to waterproof boxes at each end.

    Screwfix sell reels of SWA, and 1.5mm will be big enough for a pump
    https://www.screwfix.com/c/electric...agedredirect-_-electrical-_-armouredcable#_=p

    A local electrical supplier will probably sell a shorter cut length.
     
  3. Bob Rathbone

    Bob Rathbone Screwfix Select

    Or use black PVC conduit, that's even cheaper.
     
  4. Garym964

    Garym964 New Member


    Hi Bazza, thanks for ur reply. SWA is not really an option as the cable, or more correctly the flex on the pump is wired into the pump by the manufacturer to create the watertight seal needed so that it can sit underwater which means somewhere I wud need to connect that flex to the SWA. The only place to do that would be inside the sump chamber but that cud of course flood if the pump failed so that connection would need to be watertight too. I cud use a gel filled connector but that just complicates things should the pump need to be removed for servicing or to be replaced. Much easier just to thread the new flex thru the conduit so really think that steel conduit is the better way to go. The issue then is how do I earth the conduit given that the flex running through it just terminates with a 13a plug. My only thought was instead of plugging the pump into a socket in my shed I replace the socket with a metal outdoor switch, hard wire the pump flex to that switch then make the earth connection to the conduit inside that backbox
     
  5. Garym964

    Garym964 New Member

    On second thought it would need to be a fused outlet rather than a switch but earthing wud be same method.
     
  6. Bazza

    Bazza Screwfix Select

    Yes, as I said, you’d need the SWA to run between two weatherproof boxes. chop the plug off the pump and wire into one box. Connect the plug end to the box at the other end and you are done.
    If you go the conduit route you are going to have to remove the plug to get the cable through the conduit.
    PS, as above, if you decide on conduit, plastic will be way easier than steel. Unless you already have the bending and threading tools and skills)
     
  7. Lectrician

    Lectrician Screwfix Select

    Install an outside socket close to the pump, fed in SWA.
     
  8. Garym964

    Garym964 New Member

    Hi mate, thanks for taking the time to reply. The issue is that there is nowhere to install a socket where the sump pump is located. It sits inside a sump chamber under a gravel path which has concrete underneath, the path is edged by railway sleepers & on either side of the path is artificial grass which is why burying the cable is not an option. Currently the flex from the sump pump is just run in plastic conduit along the side of the railway sleepers under about 3 inches of gravel. I don’t consider that to offer sufficient protection to the flex so I want to replace the plastic conduit with metal conduit. I can run that metal conduit on the lawn side of the sleepers as there is enough of the sleeper exposed above the artificial grass to allow for conduit clips. Unfortunately this is the only way this works so my question was really just about earthing the metal conduit, specifically if it needs earthing given that the whole circuit has RCD protection. Cheers
     
  9. Bob Rathbone

    Bob Rathbone Screwfix Select

    Gary, use heavy duty PVC conduit, that will give adequate protection to the pump flex. With any conduit, steel or non metallic, you must provide additional protection when the chance of damage is greater, ie, in places where a fork lift truck may reverse into it. If you use steel conduit you are introducing a potential into the outside space that may differ from true earth, this is not a good idea. Keep it plastic, keep it safe.
     
    Bazza likes this.
  10. Garym964

    Garym964 New Member

    Hi Bob, ok I would love to go that route if that is acceptable. I have had a quick look at the Screwfix site, looks like they only stock standard plastic conduit, will I need to get heavy duty PVC conduit from an electrical supplier like CEF or TLC
     

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