Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 8 replies
  • Subscribers 32 subscribers
  • Views 2193 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Earth Leakage - Boiler?

AncientMariner
Called at my friend's house where he is looking to run CAT6 underground today and he was telling me about his RCD tripping problem.


Virtually every day his RCD trips. Single phase overhead TT supply. Single 30mA RCD in Consumer Unit.

The problem started soon after a new oil fired CH boiler was fitted.

Putting a clamp meter around the meter tails, from 21 to 0mA unbalance step by step as the single pole MCBs were opened one by one.

Rather upsetting to find that with all MCBs in and 21mA unbalance there was only 2mA in the earth lead, could not find either the cable connection or the rod outside.

Hoping to find a convenient place on the boiler where I could access the L & N to check unbalance looked inside and nothing accessible within the time I had. Anyway out of "devilment" you could say, put the clamp meter around one of the CH pipes from the boiler and 21 mA flowing through the 22mm pipe! I'm guessing that assuming the cable and rod are ok, the earth leakage current will flow inversely proportional to the respective resistances.

He has been trying to get an Electrician in to sort out.

Besides ensuring a decent earth rod and cable to the MET I think the ideal would be a new Consumer Unit (metal of course) and Cobs.

To try and confirm the boiler being the main cause, since the CH system runs from a nearby 13a socket, have considered a short extension lead where the L, N & E are separated out for easy application of a clamp meter.

Any other checks to try before his Electrician gets in heavy style?


Clive



Parents
  • 0
    pop the clamp meter over the flex to the boiler as it is... see what that reads? If the 21mA is coming down the pipes... it won't be returning thru the CPC in the flex, it may be that the pipes have a better connection to true earth than the electrical system: Which would raise 2 issues, a) the bonding would have to be missing, and b) the earth rod connection is missing or poor.


    That's just wild guesswork of course, but I've known pumps to cause issues before, and of course any leakage (of water) inside the boiler will likely induce leakage of electricity sooner or later!


    I'd be tempted to go with an S type RCD up front, (time delayed), or possibly as suggested in another thread, a 300mA rcd, then a new 18th edition compliant board with either split load, or preferably, individual RCBOs. The cost of those is coming down.


    Being overhead TT, an SPD may be needed also, but that's a whole other worm can
Reply
  • 0
    pop the clamp meter over the flex to the boiler as it is... see what that reads? If the 21mA is coming down the pipes... it won't be returning thru the CPC in the flex, it may be that the pipes have a better connection to true earth than the electrical system: Which would raise 2 issues, a) the bonding would have to be missing, and b) the earth rod connection is missing or poor.


    That's just wild guesswork of course, but I've known pumps to cause issues before, and of course any leakage (of water) inside the boiler will likely induce leakage of electricity sooner or later!


    I'd be tempted to go with an S type RCD up front, (time delayed), or possibly as suggested in another thread, a 300mA rcd, then a new 18th edition compliant board with either split load, or preferably, individual RCBOs. The cost of those is coming down.


    Being overhead TT, an SPD may be needed also, but that's a whole other worm can
Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines