Meter tails across house to CU

[Mr Blobby]

The DNO here in Northern Ireland insists on a recessed meter box near the front of the house. 

The consumer unit in our house is not near the front, but about 15 metres away from the meter box and on the first floor.

Supply is three phase.

How do I run the meter tails from the recessed meter box to the Consumer unit?

 

Should I run the meter tails run through the masonry cavity and then chase up the wall to the ceiling void and run the tails across the house in ceiling void and up into the consumer unit?

(I know a fuse will be needed for meter tails > 2M, but AFAIK that fuse can be in the meter cabinet.)

Are there any building regs about chasing meter tails into walls to run up into ceeiling void?  Will I need to install some armoured ducting to do this?

 

The other option is to run some conduit from the meter box down into the KORE slab (within the insulation?) and run the tails in the slab to emerge under the comms room. 

Are there any regulations prohibiting running meter tails within the insulation because of heat or anything?

 

What should I do?  Run the meter tails through the wall or in conduit under the floor?

 

[ProDave]

Switch fuse in the meter box and steel wire armour from there to consumer unit.

[Nickfromwales]

10 hours ago, ProDave said:

Switch fuse in the meter box and steel wire armour from there to consumer unit.

Singles OK with PME, vs SWA?

25mm2 4C SWA is a whopper. Would 3C SWA suffice ( if singles not allowed ) with a separate 16mm PVC earth?

 

EDIT:

This was supposed to read 5C is a whopper. Would 4C SWA suffice. Already getting my coat, you'll see.

Edited April 2, 2023 by Nickfromwales
Tired / emotional

[Nickfromwales]

Assuming tails kept at 50mm depth, or more, of course.

[Mattg4321]

SWA is the only way to do this right imo. 

[Mattg4321]

8 hours ago, Nickfromwales said:

Singles OK with PME, vs SWA?

25mm2 4C SWA is a whopper. Would 3C SWA suffice ( if singles not allowed ) with a separate 16mm PVC earth?

Singles would need containment- way more work than swa. 
 

Meter tails could be buried in a wall deeper than 50mm or covered with thick steel plate. I wouldn’t do it though. 
 

3C SWA won’t work, as there are 3 phases and a neutral. 4C and a separate earth is the way to go. 

[Nickfromwales]

3 minutes ago, Mattg4321 said:

Singles would need containment- way more work than swa. 
 

Meter tails could be buried in a wall deeper than 50mm or covered with thick steel plate. I wouldn’t do it though. 
 

3C SWA won’t work, as there are 3 phases and a neutral. 4C and a separate earth is the way to go. 

My bad, I meant single tails, which are PVC / PVC so wouldn't need containment?

 

Same re number of cores. I need more sleep / fewer kids. Thanks for the observation!  

 

I'll get my coat....

[joth]

Depending how you're using the 3ph maybe you only need to bring one phase to the house CU and can have a separate distribution board near the meter (outside??) to split our other phases for big things outdoors like EV charger, ASHP or whatnot. Else the EV chargers' power maybe wrapping the house twice. Assuming cars park at the front. 

[ProDave]

The issue is usually you need a cable type/ method that can be routed without RCD protection.  You only want a switch fuse in the meter box not an rcbo.  Singles would need mechanical protection for that.

 

so 4C SWA and an earth is the best compromise.

[Nickfromwales]

38 minutes ago, joth said:

Depending how you're using the 3ph maybe you only need to bring one phase to the house CU and can have a separate distribution board near the meter (outside??) to split our other phases for big things outdoors like EV charger, ASHP or whatnot. Else the EV chargers' power maybe wrapping the house twice. Assuming cars park at the front. 

That's what I'm doing for 2 current clients ( both having 3ph Zappi's ). Biggest thing in a PH is the induction hob tbh, so what's the point in 3ph'ing the house?

If net metering is robust, then balancing the phases becomes far less of a consideration, if any at all.

 

On another project, 3 stories plus swimming pool in basement, I've installed ( in the process of finishing off this month ) 3x heat pumps ( house / swimming pool / A/C ), a whopper of 3ph solar PV + batteries + 3ph EV charging. It also has a self-contained  annex into which I've installed a 3ph 27kW Stiebel Eltron instantaneous water heater ( size of a large shoe box, performs like a 30kW gas combi!!!! ) .

As the annex gets fed from DB1 it was a no-brainer to go to a 3ph domestic install, but for my other projects there is simply no need to go to a full 3ph configuration for the house, in honesty, ( IMHO ). 

 

Maybe time to think of the validity, and consider what @joth says.

[Temp]

They usually want the meter box where it can be accesed without the owner present.  Sometimes they will allow it around the side if there is no side gate to block access.

[Mr Blobby]

Thank you everyone for your responses.  Through the cavity and up the wall it is then.  That's one less thing for me to worry about when the slab is laid.

Inner leaf block is 140mm so should be enogh depth, I hope, to bury the cable and make the thing airtight.  I know nothing about SWA and regs but hopefully this is fairly standard to chase the tails into the wall.  It would need to be SWA all the way to the CU I guess? 

 

4 hours ago, joth said:

Depending how you're using the 3ph maybe you only need to bring one phase to the house CU and can have a separate distribution board near the meter (outside??) to split our other phases for big things outdoors like EV charger, ASHP or whatnot. Else the EV chargers' power maybe wrapping the house twice. Assuming cars park at the front. 

 

Is it bad to be wrapping the house twice?

 

3 hours ago, Nickfromwales said:

That's what I'm doing for 2 current clients ( both having 3ph Zappi's ). Biggest thing in a PH is the induction hob tbh, so what's the point in 3ph'ing the house?

If net metering is robust, then balancing the phases becomes far less of a consideration, if any at all.

 

...Maybe time to think of the validity, and consider what @joth says.

 

Now here's a can of worms  just opened.  Single phase into the house with the three phases to an adjacent box and then the EV chargers at the front makes a lot of sense but, what about the PV?

 

I will have > 4 kW pv on the roof and I had assumed that I would need a 3-phase inverter to satisfy the DNO that there is <4kW per phase. Is that right? 

Also I figured I would need CT clamps on all 3 phases so that the EDDI could recognise the net postion and divert into the immersion/batteries properly.  (I think a lightbulb has just flickered on in my brain)

 

Yes I have made a rod for my own back here.  The meter box and EV chargers are on the left side of the house the inverter is in the garage on right-hand side of the house, and the consumer unit is in the middle of the house (The plan did start with everything in the same place 🙄)

 

The electricians have proposed a 3-phase CU.  Is this overengineered as house loads (hob+7kw ashp) would be small enough to run everything off a single phase?

 

The question is, I guess, do I need three phases to the PV invertor?  If so then would it be possible/sensible to bring the invertor/ batteries into the plant room on the same side of the house as the EV chargers and (with a DB here?) then take just a siingle phase from there up to the big house CU?  The reason I haven't done this already is because of concerns about the invertor/batteries generating heat I don't want inside the house.

 

 

Edited April 2, 2023 by Mr Blobby

[Nickfromwales]

3ph unnecessary in the da house, Capt. Blobby. Push back.

 

Why only 4kWp of solar? You spent too much money on anti-stress beer? Defo don't need 3ph inverter for 4kWp, that's a tiddly bit of solar!

[Mr Blobby]

16 hours ago, Nickfromwales said:

3ph unnecessary in the da house, Capt. Blobby. Push back.

 

Why only 4kWp of solar? You spent too much money on anti-stress beer? Defo don't need 3ph inverter for 4kWp, that's a tiddly bit of solar!

 

Sorry, I meant > 4kw.  Final number will be more like 8.5 kW total.  For a hybrid invertor with batteries to support this I need a 3-phase invertor right?

 

[Nickfromwales]

46 minutes ago, Mr Blobby said:

 

Sorry, I meant > 4kw.  Final number will be more like 8.5 kW total.  For a hybrid invertor with batteries to support this I need a 3-phase invertor right?

 

Nope. 

The hybrid I have my eye on is 8.8kW 1ph, and I can go all the ay down to zero export. Behind that, on the DC side, I can load this up with however much capacity I want without limit. Final plan ( just in the process of checking the roof structural integrity is ok for additional weight ) is 52 x 400w panels E/W split, between house roof and some very 'sunny' garden room / gazebo areas getting panelled too. Caveat is they all need Tigo's, but at least then I'll get panel by panel monitoring and can geek out ( prob once or twice than the novelty will wear off in favour of beer and BBQ time ).

[Mr Blobby]

5 minutes ago, Nickfromwales said:

Nope. 

The hybrid I have my eye on is 8.8kW 1ph...

 

The DNO is ok with that then? 

That would make my life simpler in splitting a single phase into the house.

Edited April 3, 2023 by Mr Blobby

[Nickfromwales]

Just now, Mr Blobby said:

 

The DNO is ok with that then? 

That would make my life simpler in keeping 3 phases out of the house.

Yup.You only ask for the inverter kW capacity with a hybrid. 🤜