Speak EV - Electric Car Forums banner
1 - 20 of 23 Posts

·
Registered
Joined
·
819 Posts
Discussion Starter · #1 ·
Hi all. Happy new year!

I’m shortly getting a new consumer unit fitted, but I want to make sure I’m future proofing it with enough spare ways.

We already have a switch for the car charger, another for the solar inverter and another for an immersion (not currently used but want to keep in case we ever add a solar diverter, or for emergency use if the boiler breaks so we still have hot water).

I’m allowing one spare way for a second car charger

If we added a home battery, does that require another way, or does it just feed off the existing inverter circuit?

Do heat pumps require more than one way?

My electrician is suggesting a 12 way RCBO unit, but that will only leave 2 spare ways. Allowing for a second car charger that would then only leave one spare.

The next size up is an 18 way RCBO unit. Price wise there is little difference, but the larger size of the 18 way presents some issues.

Do I need to go with the 18 way and resolve the space issue to allow for a battery and heat pump?

Thanks for any advice
 

·
Registered
Audi eTron 55
Joined
·
1,080 Posts
Can't really advise on no. of ways. Maybe buy some spare breakers now though, as electricians are rather anal about mixing up manufacturers.
Good advice, I've often really struggled to find the exact match (manufacturer / size) when adding additional circuits. Nothing screams "bodged diy job" quite like a mismatched breaker distorting the face of the consumer unit 😬
 

·
Registered
Joined
·
5,740 Posts
Depending on your space limitations I'd consider having two units. 2x10, 12+8, etc. Put the normal house stuff on one and put cars, solar, etc on the other.
That way work can be done on new charge/solar/etc installations without having to kill the whole house.
 

·
Registered
Joined
·
819 Posts
Discussion Starter · #5 ·
Can't really advise on no. of ways. Maybe buy some spare breakers now though, as electricians are rather anal about mixing up manufacturers.
The electrician did offer to populate the spare ways with RCBO’s. This will be a Hager unit. This would be a good idea, but I’d need to know the required size and type in advance and I‘m not sure. 32a for the second car charger, but not sure what size for a battery or heat pump. I’d guess 20a for a heat pump? Our solar is on a 32a as 6.3kW system, but again not sure what size, if at all, a battery would need. For a heat pump not sure if you need two ways, one for the outside unit and one for the inside unit....
 

·
Registered
Joined
·
819 Posts
Discussion Starter · #6 ·
Depending on your space limitations I'd consider having two units. 2x10, 12+8, etc. Put the normal house stuff on one and put cars, solar, etc on the other.
That way work can be done on new charge/solar/etc installations without having to kill the whole house.
Good idea, not sure this would work space wise though. The CU is going in a kitchen tower unit (CU mounted direct to the block work with the back of the tower removed, not mounted in the cabinet which would be rubbish)
 

·
Registered
Hyundai Ioniq 28
Joined
·
8,956 Posts
Many installers prefer to split the mains feed for a new charger, after the meter, into a small dedicated CU for that unit alone. And often locate that new CU alongside the meter in the outside access box. Which means that having extra breakers in the main CU is not a requirement for a new car charger.
 

·
Registered
Nissan LEAF30
Joined
·
9,616 Posts
Many installers prefer to split the mains feed for a new charger, after the meter, into a small dedicated CU for that unit alone. And often locate that new CU alongside the meter in the outside access box. Which means that having extra breakers in the main CU is not a requirement for a new car charger.
Good advice. There's a number of potential reasons for this:
  • It maybe easier to run the cable to the EVSE from there
  • The existing CU may not meet current regs and by ignoring it the installer avoids taking responsibility
  • Terminating large diameter cable in a populated CU can be tricky
Keeping the house wiring separate from the specialist wiring is generally sensible and allows non-specialist electricians to maintain the house side in the future.
 

·
Registered
Joined
·
5,740 Posts
This will be a Hager unit.
Highly unlikely that you won't be able to get suitable Hager breakers in the future. And most of this stuff is built to standard DIN rail sizes, doesn't change often, and is mostly interchangeable.
The main problem is usually space - RCBOs are taller above the exposed (switch) part and in many older CUs it's a squeeze to get the wiring in if you retrofit RCBOs. New CUs have much higher brows to allow for this.

Unless your spark is offering you spares for free I'd not bother - just have blanks.
 

·
Premium Member
Joined
·
11,980 Posts
If getting a new CU I would strongly recommend all circuits are protected by RCBOs as far more flexible and reliable. The cost isn't that much more now. Bear in mind that car charging circuits need dual pole RCBOs so are generally 2 spaces on DIN rail. They also need to be Type A or (in some cases) Type B tripping, not the usual AC for domestic circuits. IIRC you can't share a RCBO between two charging circuits in latest regs either.

A separate CU isn't necessary for car charging, that was introduced because few existing CUs had space for a dual pole RCBO and installers didn't want risks and potential liability of working on existing (often plastic) installations especially when trying to terminate SWA cable.
 

·
Registered
Joined
·
721 Posts
Good advice. There's a number of potential reasons for this:
  • It maybe easier to run the cable to the EVSE from there
  • The existing CU may not meet current regs and by ignoring it the installer avoids taking responsibility
  • Terminating large diameter cable in a populated CU can be tricky
Keeping the house wiring separate from the specialist wiring is generally sensible and allows non-specialist electricians to maintain the house side in the future.
It's also cheaper and easier when adding one circuit than upgrading the existing consumer unit. Like when electric showers were new and electricians would use the same arrangement to add a little consumer unit to provide a 32A or 40A supply for the shower without needing to upgrade the existing consumer unit.

But over time as electric showers become the norm and people upgrade their consumer units, they get fed from the consumer unit, I'd expect the same will happen with EV chargers and heat pumps as these become standard items. Otherwise we'll all have cupboards filled with lots of little consumer units, for the shower, the EV charger, the heat-pump etc.
 

·
Registered
Joined
·
819 Posts
Discussion Starter · #13 ·
Highly unlikely that you won't be able to get suitable Hager breakers in the future. And most of this stuff is built to standard DIN rail sizes, doesn't change often, and is mostly interchangeable.
The main problem is usually space - RCBOs are taller above the exposed (switch) part and in many older CUs it's a squeeze to get the wiring in if you retrofit RCBOs. New CUs have much higher brows to allow for this.

Unless your spark is offering you spares for free I'd not bother - just have blanks.
Thanks Mike, will just go for blanks for now then. Hager RCBO’s are not the cheapest so don’t want to go adding the wrong sizes!
 

·
Registered
Joined
·
819 Posts
Discussion Starter · #14 ·
If getting a new CU I would strongly recommend all circuits are protected by RCBOs as far more flexible and reliable. The cost isn't that much more now. Bear in mind that car charging circuits need dual pole RCBOs so are generally 2 spaces on DIN rail. They also need to be Type A or (in some cases) Type B tripping, not the usual AC for domestic circuits. IIRC you can't share a RCBO between two charging circuits in latest regs either.

A separate CU isn't necessary for car charging, that was introduced because few existing CUs had space for a dual pole RCBO and installers didn't want risks and potential liability of working on existing (often plastic) installations especially when trying to terminate SWA cable.
Thanks, yes, I’ve specified all RCBO with surge protection. Was offered Fuse Box by default but asked for Hager. A bit pricier but wanted to stick with a top known brand.

Our pod point has just one slot in the CU, a B40 (on the non RCD side of the board), but that feeds a mini CU in the garage which then has another switch on it, a C40.
 

·
Registered
Joined
·
721 Posts
If getting a new CU I would strongly recommend all circuits are protected by RCBOs as far more flexible and reliable. The cost isn't that much more now. Bear in mind that car charging circuits need dual pole RCBOs so are generally 2 spaces on DIN rail.
For the EV charger way, because the RCD requirements are evolving so quickly it might be better to have a simple 32A or 40A MCB to provide a supply, combined with either a stand-alone RCD or one integral to the chargepoint.
 

·
Registered
Joined
·
819 Posts
Discussion Starter · #16 ·
It's also cheaper and easier when adding one circuit than upgrading the existing consumer unit. Like when electric showers were new and electricians would use the same arrangement to add a little consumer unit to provide a 32A or 40A supply for the shower without needing to upgrade the existing consumer unit.

But over time as electric showers become the norm and people upgrade their consumer units, they get fed from the consumer unit, I'd expect the same will happen with EV chargers and heat pumps as these become standard items. Otherwise we'll all have cupboards filled with lots of little consumer units, for the shower, the EV charger, the heat-pump etc.
Yes, while I’m upgrading the CU would rather design it to take all future requirements than have add on boxes. I thought the outside meter cupboard was only for DNO kit too rather than user side mini CU’s?
 

·
Registered
Joined
·
819 Posts
Discussion Starter · #17 ·
For the EV charger way, because the RCD requirements are evolving so quickly it might be better to have a simple 32A or 40A MCB to provide a supply, combined with either a stand-alone RCD or one integral to the chargepoint.
Yes, that’s exactly how our pod point was done. Although I have specced an RCBO CU, I mentioned to the electrician about the charger switch and that it might need to remain as a MCB as presumably an RCBO at the board would interfere with the charger mini CU in the garage. He didn’t directly confirm but assume that’s what will be needed.
 

·
Registered
Joined
·
5,740 Posts
might need to remain as a MCB as presumably an RCBO at the board would interfere with the charger mini CU
It won't interfere as such. If there isn't sufficient discrimination (both will likely be 30mA residual trip*) then it and the downstream unit will trip on a fault, which may be undesirable. Eg. If you have a freezer fed off the mini-CU as well as the car.

( * You could probably spec a 100mA at the house end, but that's getting exotic.)
 

·
Premium Member
Joined
·
11,980 Posts
For the EV charger way, because the RCD requirements are evolving so quickly it might be better to have a simple 32A or 40A MCB to provide a supply, combined with either a stand-alone RCD or one integral to the chargepoint.
You have to protect a car charging circuit itself so RCD capability is required at the CU side, you can't rely on one in the charging point. Personally, I wouldn't actually fit anything initially, just makes sure there is sufficient space with blanks fitted.

Our house is under offer and I suspect installing a new CU will be high on the priorities when we get the next. Having seen the fire a forum member had, I would like to start with something safe and reliable before we start adding charging points. I would also prefer to put money towards a new CU rather than just an EICR...
 
1 - 20 of 23 Posts
Top