Earth/neutral bond relay size

**Isetech** · 03-Mar-23, 10:11 AM

This is a question many people are asking.

I have been installing relay to suit the neutral conductor

5 kva = a 25 amp relay

8 KVA = 40 amp relay

Do you really need a 20/25 amp relay/contactor for a 5 kva unit?

or a 32/40 amp realy/contactor?

IF you have a 4 mm neutral wire then you should have a 32 amp relay.

**Justloadit** · 03-Mar-23, 10:30 AM

I think the question should rather be,
Will the relay contacts survive/support a fault current to allow the circuit breakers to trip.

**GCE** · 03-Mar-23, 12:28 PM

I agree with Justloadit
Need to size according to max possible fault current which would be normally be around 1,5 times the nominal current for 10sec

**Isetech** · 03-Mar-23, 12:36 PM

So my relays are correctly rated

**McGuywer** · 29-Aug-23, 02:26 PM

@Isetech

Do you mind sharing which relay you are using? Also how you are wiring said relay?

**Isetech** · 30-Aug-23, 07:55 PM

I use the din mount hager relays, yet to have one fail.

Originally Posted by McGuywer

@Isetech

Do you mind sharing which relay you are using? Also how you are wiring said relay?

**Leonsparky** · 03-Oct-24, 09:29 PM

Under no circumstance may you use an external relay or contactor to bond the neutral and earth

**Derlyn** · 04-Oct-24, 07:36 AM

@ Leonsparky. Most inverters have a dedicated output to energize an external relay for neutral earth bonding during islanding mode, so I do not agree with your statement above.
In fact, it is the only way to do it - by making use of an external relay.

**skatingsparks** · 13-Oct-24, 01:17 PM

Originally Posted by Derlyn

@ Leonsparky. Most inverters have a dedicated output to energize an external relay for neutral earth bonding during islanding mode, so I do not agree with your statement above.
In fact, it is the only way to do it - by making use of an external relay.

This story has been going on for ages. The AIA inspector catagorically says it must perminantly be bonded. I figure if ever anything ever goes really wrong and I end up in court the guy opposite me is going to be the AIA guy. I understand implications of permenant bond and implications of relays (should it fail) but if the main man, the guy from the AIA says permanent - I do permanent.

The ECA are a bit wishy washy on it(apparently I'm not reading it right) - depends on how you read the rules.

Haven't picked up my new copy yet but hopefully there is some clarity.

The basic argument is - if the relay fails will your earth leakage still operate.

**Leonsparky** · 13-Oct-24, 07:54 PM

An external relay is probably the most unsafe thing ever. I have posted a very long argument in another thread but can't seem to find it.
NRS chairman and I have done various test now too, we have given this info to the Working group, no changes as of yet but it will most probably say that no external contactor or relay/device may be used other than that of the manufacturer and supplied within a control panel such as the Sigenergy or Solaredge or Victron. Until then or anything else in SANS, permanent bond because that is what SANS says.