I’m seeking guidance regarding the incoming cable terminations on my Safe-T-Cut consumer unit (CU), specifically the bus-bar screw connectors that are meant to receive the incoming Live and Neutral conductors.

Both incoming conductors are the best to my knowledge made of aluminum, and their overall diameter appears slightly too large to fit properly into the brass bus-bar screw terminals. The only way they could be inserted is by trimming strands, which I understand is not considered good practice - especially for a main supply connection. (I am not an electrician, which is why I’m asking here.)

I am therefore considering replacing the incoming aluminum conductors with copper conductors, if appropriate.

Additional details:-
Main Breaker Model: CO12E
(Markings: SBJA-E – C63 – MX3 – Shunt Release)

Distance from meter/pole to CU: ~70 meters (generous estimate)

My main question:
Would a copper conductor of the correct rating have a smaller diameter than the equivalent aluminum conductor and therefore fit properly into the CU bus-bar connectors?
Or, would a different termination method (e.g., ferrules, reducers, etc.) be more suitable?

Any advice on the safe and compliant way to handle this situation would be greatly appreciated.

A copper pigtail would be a whole cable size smaller than the Al one. What size is your Al??

 

Also, unless your Safe-T-Cut says it's suitable for Al cable there's a risk of the terminations loosening over time leading to fizzing and potential conflagration.

 

Get your sparks to splice on a suitable length of copper and you're good to go. If you're lucky he may even use the correct Al-Cu bi-metal splices.

 

Personally, I would keep the splice outside the house.

17 minutes ago, Crossy said:

A copper pigtail would be a whole cable size smaller than the Al one. What size is your Al??

 

Also, unless your Safe-T-Cut says it's suitable for Al cable there's a risk of the terminations loosening over time leading to fizzing and potential conflagration.

 

Get your sparks to splice on a suitable length of copper and you're good to go. If you're lucky he may even use the correct Al-Cu bi-metal splices.

 

Personally, I would keep the splice outside the house.

Thank you for your feedback. There won't be any splicing of conductors and just bite the bullet ordering an additional 2x100 meters of IEC01 THW 1x25 sqmm copper cable.

That would be the best solution, however do consider that copper does have an annoying tendancy to develop a wunderlust late at night if it's not in a secure location.

 

Or even if it is in a secure location, the Red Line was stopped a couple of days back after copper cables were liberated!

 

21 minutes ago, Crossy said:

That would be the best solution, however do consider that copper does have an annoying tendancy to develop a wunderlust late at night if it's not in a secure location.

 

Or even if it is in a secure location, the Red Line was stopped a couple of days back after copper cables were liberated!

 

The electricity pole with meter is across the road and about 15 meters away from our fence. The rest of the cable (about 55 meters) will be on our land supported by 3 electricity poles. The cable is sheathed black and hopefully not too conspicuous.

FWIW, here's a handy ampacity chart comparing copper and aluminum wires in metric sizes.

 

Keep in mind the X axis is logarithmic.

 

 

 

On 12/7/2025 at 10:36 AM, Crossy said:

A copper pigtail would be a whole cable size smaller than the Al one. What size is your Al??

 

Also, unless your Safe-T-Cut says it's suitable for Al cable there's a risk of the terminations loosening over time leading to fizzing and potential conflagration.

 

Get your sparks to splice on a suitable length of copper and you're good to go. If you're lucky he may even use the correct Al-Cu bi-metal splices.

 

Personally, I would keep the splice outside the house.

I have revisited my original plan to install copper conductors throughout the entire supply run.

Given the significant cost difference between aluminum and copper conductors, I have reconsidered the feasibility of purchasing approximately 140–150 meters of copper cable. 
Based on this, I would like to go with your suggestion using copper pigtails.
I propose to run aluminum conductors from the PEA meter at the supply pole to a weatherproof junction box located outside the room housing the consumer unit (CU). From that junction box, a short copper run - pigtail (approximately 6 meters, or less if required) would connect directly to the CU. The junction box would be IP-rated, installed under cover, and protected from direct weather exposure.

For the aluminum-to-copper transition, I propose using bi-metal Al–Cu connectors, although I am unsure about the exact conductor sizes (mm²) required.

Based on preliminary calculations and guidance by A-I, the indicative conductor sizes would be:
Aluminum conductor: 50 mm²
Copper conductor: 25 mm²

Proposed cable requirements:
~150 m × 50 mm² THW-A aluminum conductor (supply pole to junction box)
~14 m × 25 mm² copper conductor (junction box to CU)

Materials envisaged for the Al–Cu transition include:
2 × bi-metal PG clamps (e.g. JBTL-10-70 or equivalent)
1 × IP65-rated junction box
Heat-shrink tubing or resin sealing kit
Anti-oxidant paste / compound for aluminum terminations

I would welcome feedback on:
The suitability of the proposed conductor sizing
Best practices for aluminum-to-copper transitions in this context
Any concerns regarding long-term reliability or local code compliance
Thank you in advance for your insights.

NOT that 25mm2 copper, it's not rated for mains use.

 

You need THW(f) / VSF for decent flexibility (25mm2 THW is a wrestle). In outdoor situations you should really use an insulated and sheathed cable but the locals happily use THW. 

 

Are you going to do this yourself or get a local sparks in (I suggest using a local man)?

 

You should be able to find these splices, add an adhesive-lined heatshrink and it's good to go.

 

 

12 minutes ago, Crossy said:

NOT that 25mm2 copper, it's not rated for mains use.

 

You need THW(f) / VSF for decent flexibility (25mm2 THW is a wrestle). In outdoor situations you should really use an insulated and sheathed cable but the locals happily use THW. 

 

Are you going to do this yourself or get a local sparks in (I suggest using a local man)?

A local handy-man who has experience installing electrics will do the work and I supply the goods.

I noted that 25 mm² THW-F / VSF would be the more practical choice and suppose you are okay with the 50 mm² THW‑A Aluminium conductor?

The THW-A should be fine.

 

Do you already have a permanent meter rather than a construction supply?

 

If not you will need to have a PEA inspection to get the permanent meter in which case a word with the inspectors at your local PEA office with your proposed solution may be a good idea just in case they have any "special" requirements.

20 minutes ago, Crossy said:

The THW-A should be fine.

 

Do you already have a permanent meter rather than a construction supply?

 

If not you will need to have a PEA inspection to get the permanent meter in which case a word with the inspectors at your local PEA office with your proposed solution may be a good idea just in case they have any "special" requirements.

No, we do not yet have a permanent meter - my wife will need to obtain the Tabien Baan (blue book) first.
I only require two copper conductors of up to 6 meters each and would appreciate guidance on the correct cable type/designation to use for this short run. Could you please advise which specific cable would be appropriate, with reference to the attached screenshots?
I will also confirm any PEA-specific requirements or instructions with the local PEA office before proceeding.

1 hour ago, Crossy said:

You should be able to find these splices, add an adhesive-lined heatshrink and it's good to go.

Don't these sleeves require to be crimped using a hydraulic crimping tool?

6 minutes ago, CharlesHolzhauer said:

Don't these sleeves require to be crimped using a hydraulic crimping tool?

 

Yup, and a decent contractor should have one.

 

The others don't need any special tools of course.

 

 

27 minutes ago, CharlesHolzhauer said:

No, we do not yet have a permanent meter - my wife will need to obtain the Tabien Baan (blue book) first.
I only require two copper conductors of up to 6 meters each and would appreciate guidance on the correct cable type/designation to use for this short run. Could you please advise which specific cable would be appropriate, with reference to the attached screenshots?
I will also confirm any PEA-specific requirements or instructions with the local PEA office before proceeding.

 

Screenshot 1  is aluminium cable

 

Screenshot 2 is Thai Yazaki, decent quality cable - I would use this, sellers on Lazada and Shopee do it in cut lengths.

 

Screenshot 3 is a cable company I've never heard of also noted as "battery cable"

 

Screenshot 4 is plain THW it would be fine but difficult to route.

 

A thought.

 

We used moonlighting PEA chaps to supply and place our poles and run the cables, they have all the gear.

 

 

3 minutes ago, Crossy said:

A thought.

 

We used moonlighting PEA chaps to supply and place our poles and run the cables, they have all the gear.

 

 

Thanks, this I will pursue.

8 minutes ago, CharlesHolzhauer said:

Thanks, this I will pursue.

 

The whole crew turned up on a Sunday, wearing PEA uniforms, driving a PEA crane truck, poles are marked "PEA". Cash to the team supervisor. Everyone happy.

 

When the inspector came he noticed the drops between the poles weren't all equal, so he got the guys back (on PEA time) to fix whilst he nattered with Madam and drank coffee.

 

All 100% above board Thailand style 

 

 

Bit late now, but if you can't get a mob with the correct crimping tool, they do have these screw ones.

 

On 12/14/2025 at 10:56 AM, Crossy said:

 

Screenshot 1  is aluminium cable

 

Screenshot 2 is Thai Yazaki, decent quality cable - I would use this, sellers on Lazada and Shopee do it in cut lengths.

 

Screenshot 3 is a cable company I've never heard of also noted as "battery cable"

 

Screenshot 4 is plain THW it would be fine but difficult to route.

 

#3 is what I would call welding leads 

On 12/14/2025 at 11:03 AM, CharlesHolzhauer said:

We used moonlighting PEA chaps to supply and place our poles and run the cables, they have all the gear.

Same here, 3 x 8 meter poles + pole & house fittings + THW-A 25 sq.mm - 

I was able to get in touch with the right contact person, and everything was installed in record time — it worked perfectly. Many thanks for the helpful hint.

In one of your earlier posts you mentioned, “Personally, I would keep the splice outside the house.”
Could you please elaborate on the reasoning behind this recommendation?

On 12/14/2025 at 10:58 AM, Crossy said:

A thought.

 

We used moonlighting PEA chaps to supply and place our poles and run the cables, they have all the gear.

 

 

On 12/7/2025 at 10:36 AM, Crossy said:

Personally, I would keep the splice outside the house.

Could you please elaborate on the reasoning behind this recommendation?

Just personal preference really.

Mainly I don't like Al wiring in the home, or at all to be honest. It can be difficult to work with and get right.

Also splices, particularly of dissimilar metals, if not done correctly, can be a source of heating and conflagration. I'd rather that was outside.

99.99% of the time there's no problem, it's usually my luck to get the 0.01%

I am facing an unexpected issue with conductor termination at the ground/earth bar of my SAFE-T-CUT consumer unit (CU).

Specifically, it is physically impossible to terminate a 25 mm² copper conductor into the existing proprietary ground/earth bar without resorting to undesirable practices such as cutting strands from the conductor or replacing the original earth bar with a non-OEM alternative. For reference, the main breaker itself is rated to accept 25 mm² conductors without issue.

Given this constraint, I am considering the following approach:

The neutral (N) copper pigtail is relatively short (less than 6 m).

Starting at the JBTL-10-70 Al–Cu bi-metal clamp in the external junction box, I would reduce the neutral conductor from 25 mm² to 16 mm².

This 16 mm² neutral would then terminate at the CU earth/neutral bar, with a 16 mm² link onward to the main breaker neutral connection.

The live (L) conductor would remain unchanged: a 25 mm² copper pigtail running from the JBTL-10-70 bi-metal clamp directly to the main breaker line input.

From a technical and safety standpoint, would this reduction of the neutral conductor to 16 mm² over such a short distance be considered acceptable practice?

Any guidance on code compliance, thermal considerations, or long-term reliability would be greatly appreciated.

A reducing link maybe?

Can you not fan out the end of the 25mm^2 and go into two of the openings?

I sent you a connectors picture on 15th Dec. Cu to Al. The Cu side is smaller.

This might work. It did for me when I couldn't get the 25mm2 Al cable into the AVR.

42 minutes ago, Yellowtail said:

A reducing link maybe?

Can you not fan out the end of the 25mm^2 and go into two of the openings?

According to AI:

Splitting the strands of a 25 mm² copper conductor and landing them in two holes of the ground bar is NOT acceptable and NOT safe.

Even though it may look mechanically secure, it violates basic electrical principles and creates long-term reliability and safety risks.

Let me (AI) explain why, then give you correct, practical solutions that work in Thailand.

Why splitting strands is not allowed

1️ - You lose guaranteed current sharing

There is no assurance that current divides evenly between the two halves.

One half may carry more current

The other may loosen or oxidize

This causes localized heating

2️ - You break the integrity of the conductor

A 25 mm² conductor is engineered to:

Be clamped as one solid bundle

Have uniform pressure and contact area

Splitting strands:

Reduces effective cross-section

Encourages strand breakage over time

Makes re-torque impossible to do correctly

3️ - It defeats inspection and compliance

Any competent electrician or inspector would immediately flag this as:

Improvised

Non-compliant

Unsafe on a service conductor

This is especially critical because:

This is your service neutral / MEN connection

4️ - Neutral integrity is critical in MEN systems

In MEN:

Neutral carries load current

Earth relies on neutral integrity

A poor neutral connection can cause:

Elevated touch voltages

RCD mis-operation

Appliance damage

So the neutral termination must be absolutely solid and singular.

38 minutes ago, carlyai said:

I sent you a connectors picture on 15th Dec. Cu to Al. The Cu side is smaller.

This might work. It did for me when I couldn't get the 25mm2 Al cable into the AVR.

This most probably will work but is code compliant? Please refer to the last sentence of my post.

Is there enough meat in the bar to drill out one hole to suit?

10 hours ago, Crossy said:

Is there enough meat in the bar to drill out one hole to suit?

Unfortunately not. There is insufficient material in the existing bar to safely drill out a termination and SAFE-T-CUT does not offer an oversized or alternative ground/earth bar for this CU model.

Given these constraints, and short of replacing the entire consumer unit, my remaining practical option is to revert to the earlier proposal to reduce the neutral (N) copper pigtail from 25 mm² to 16 mm² over the short run (less than 6 meters).

From a safety, thermal, and regulatory perspective, I would very much appreciate your expert view on whether this reduction would be acceptable and is compliant with Thai electrical code and any other applicable standards.

What size (amps) is your Safe-T-Cut main breaker?

16mm² THW is good for 92A in free air.

In reality I see no real issue in you using the smaller pigtail.