Tesla Wall Connector - Type B / Type A-EV RCD

[pow216]

To all those who've installed a Tesla Wall Connector - what RCD have you used?

The installation manual doesn't mention a specific RCD, but the Home Charging Installation FAQ does... "an RCD Type B or a specific Type A-EV needs to be installed".

Home Charging Installation

So far I've found this
Doepke DFS4 040-2/0.03-A EV which is available from Rapid Electronics for £305+VAT ! What other options are there?

I'm interested to know what other people have used and if anybody has self-installed?

 

[MrBadger]

Ouch.

And it looks to be a big ole thing so wont fit in a single spare consumer unit slot.

 

[ACarneiro]

Ouch.

And it looks to be a big ole thing so wont fit in a single spare consumer unit slot.

Take 4 slots, apparently...

I'm slightly worried, as far as I can tell I have a "normal" RCD for each of my two Tesla Wall Connectors.
Is this unsafe? Should I worry? Should I "upgrade" my RCD?

 

[MrBadger]

What is normal?

The actual wording is

Which residual current device (RCD) should I use with my installation?
The standards for installing charge points state that every individual connector should be protected with an RCD that protects against direct current leaking. The Tesla Wall Connector does not measure DC current leaking, so an RCD Type B or a specific Type A-EV needs to be installed. National regulations can vary so always check with your local recommended electrician.

Do you have two separate circuits, one for each connector or are they daisy chained (and used in shared load mode)? Long term, that is what I am thinking I may do.

 

[Yev000]

This is what I had fitted:

IMG_20190702_121405

• Yev000
• Jul 26, 2019

RCB

 

[MrBadger]

Thats a RCBO (combined RCD and MCB [fuse/trip]) and by looks of it, it is a B type RCD. Which is kind of more like I was expecting and not some £300 thing. Presumably thats wired inline to the charge point from a Henley (junction) block from the main fuse (possibly by a main isolation switch which may also be new) rather than from the consumer unit?

Interestingly its rated right on 32A/7kW. I would have thought 40A may have given some overhead.

 

[ACarneiro]

What is normal?

The actual wording is


Do you have two separate circuits, one for each connector or are they daisy chained (and used in shared load mode)? Long term, that is what I am thinking I may do.

They have separate breakers.
The "daisy chaining" is probably a misnomer. You can simply make them "talk" to each other in order to share available load but each of them is connected to their own supply.
Mine are indeed communicating with each other because I was worried I wouldn't have enough juice to allow them both at full pelt, but fortunately I managed to get my main fuse upgraded to 100A so it's no longer an issue.

 

[MrBadger]

Thats interesting. I checked the Tesla instructions after posting and they use a separate breaker, going to a junction box and units wired from that. So in that config, its load balancing/protecting the breaker, where as with yours, its protecting the whole supply. I think in reality it doesn't matter which one you use so long as there is capacity in that part of the wiring. Advantage for me in using a single breaker is that I'm running low on available slots in my consumer units, although the option in #5 may help that.

 

[ACarneiro]

Thats interesting. I checked the Tesla instructions after posting and they use a separate breaker, going to a junction box and units wired from that. So in that config, its load balancing/protecting the breaker, where as with yours, its protecting the whole supply. I think in reality it doesn't matter which one you use so long as there is capacity in that part of the wiring. Advantage for me in using a single breaker is that I'm running low on available slots in my consumer units, although the option in #5 may help that.

To be fair, I had new wiring installed all the way from the consumer box, which explains why I chose to protect the whole supply
Also had the sparkies use 3Ph wire because eventually I think 100A single phase won't be enough and I may have to find the £10k that will cost me to get my supply upgraded to 3Ph.

 

[MrBadger]

100A not enough? Wow.

I was previously due to have a wall connector fitted as part of an EV trial and the suppliers initially refused to install, saying that I would overload my supply. I've got 100A supply and they simply tallied up the totals of all breakers already installed, added their one and came to the conclusion that it would overload my supply. After I pointed out that diversity would prevent this, and two of my breakers was supply from my PV and supply to my immersion which only functioned when I had excess PV they changed their tack and agreed to install. In the end, I pulled out as it became too much hassle as they also would also require a DNO supplied isolation switch which could only be fitted when I had a smart meter installed - which I didn't want as it would not work with my PV.

Long and short, by then I had worked out my historical power usage (I keep 5 minute generation and usage logs 24/7) and it was very small, around 1/4-1/3 my total capacity, which did surprise me - biggest load is electric range cooker with induction hobs - so you can guess when biggest load would be. Thats a Christmas gathering, so cooking full tilt, with induction and still only topping out around 25A.

So unless you are also running a heat pump and/or lots electrical heating, I would be very surprised if you are running risk of overloading 100A. 2 EV's at 32A would start to run it close for me, which is why I like the idea of load balancing and keeping things to max 32A.

And for anyone thinking they can charge their car using PV, the green line at the bottom shows the effectiveness of 4kWp of solar panels on a typical December day has.

 

[ACarneiro]

I also have a BMW i3 at home so both charging are 64A. Add about 5A baseload and throw in another 10 or 20A for a dishwasher, washing machine or tumble dryer (all of which I use at night to make use of Economy7) and it starts getting VERY tight. Having A/C fitted later in the year as well.
Eventually heat pumps will replace my boiler.
100A is really not as much as you think it is, in the "new world order"

 

[MrBadger]

64A yes I see. I thought you had the chargers load balancing - which would take 32A straight out of the equation and much cheaper than 3 phase. You probably find that white goods won't have significant impact - 100A is not a hard limit and diversity will probably cover those items. Our dishwasher and washer/tumble are around 3kW each and only peak for very short period, so 32A there, same as car. You won't be running AC and heat pump at same time will you.

Obviously everyone's usage patterns are different, but if you load balanced your EV charging, I think you will have capacity to spare.

 

[arg]

Thats a RCBO (combined RCD and MCB [fuse/trip]) and by looks of it, it is a B type RCD. Which is kind of more like I was expecting and not some £300 thing.

UK Regulations changed from January 1st 2019. Previously a Type-A RCD was acceptable (and the RCD component of that RCBO in the photo is Type A).

Now Type B is required, unless the chargepoint has internal DC fault detection, in which case a Type-A can still be used. Most manufacturers have been hurrying to add the DC fault detection to their chargepoints, but Tesla has not yet done so.

Here's one retailing for slightly less, but still mighty expensive:

Chint 63A 4Pole (3 phase + Neutral) DC earth leakage 30mA, Type B 10KA

 

[MrBadger]

Screwfix (random search) has got Type B 40A RCBO's for around £26 - what's the difference? I don't need 3 phase.

Edit changed to non discounted product.

 

[davidmc]

Screwfix (random search) has got Type B 40A RCBO's for around £8 - what's the difference? I don't need 3 phase.

Lol I was about to ask regards the same product at Screwfix! I have asked a Director at an Electrical subcontractor I use regularly who installs EV charge points all the time what I need etc but not answered my questions yet as he is away.

 

[MrBadger]

Lol I was about to ask regards the same product at Screwfix! I have asked a Director at an Electrical subcontractor I use regularly who installs EV charge points all the time what I need etc but not answered my questions yet as he is away.

I just changed the link - gone upmarket at £26! but its not a discounted unit now so probably more representative of general price.

Why are these units so expensive? Are they very different or just because they are 3 phase?

 

[arg]

Screwfix (random search) has got Type B 40A RCBO's for around £8 - what's the difference? I don't need 3 phase.

Unfortunately, that is NOT a TypeB, despite Screwfix incorrectly labelling it as such.

RCBOs are a pain to buy, since they have two parts to them - the overcurrent curve (which may be B, C, or D) and the RCD function (AC, A, or B), and catalogue listings are normally put together by people who don't understand the products they are listing.

If there's a genuine photo of the unit you can work it out (Type AC has a symbol with a sinewave in a box, Type A has the sinewave and a bumpy thing representing pulses underneath it inside the same box, Type B has two boxes, one with that symbol and one with a straight and a dotted line in it). However, catalogue listings often just have a 'representative' photo!

Type B RCDs are genuinely more expensive to make; £300 is a rarity premium, but £8 is too cheap to be real.

 

[Roy W.]

UK Regulations changed from January 1st 2019. Previously a Type-A RCD was acceptable (and the RCD component of that RCBO in the photo is Type A).

Now Type B is required, unless the chargepoint has internal DC fault detection, in which case a Type-A can still be used. Most manufacturers have been hurrying to add the DC fault detection to their chargepoints, but Tesla has not yet done so.

Here's one retailing for slightly less, but still mighty expensive:

Chint 63A 4Pole (3 phase + Neutral) DC earth leakage 30mA, Type B 10KA

With the new regulations from Jan 2019 what happens to all the old installations that predate the new regs? Are they now deemed unsafe if they don’t have the Type B RCD?

 

[arg]

With the new regulations from Jan 2019 what happens to all the old installations that predate the new regs? Are they now deemed unsafe if they don’t have the Type B RCD?

There is nothing compelling you to adopt the latest regulations other than for new work.

In general, changes to the regulations reflect perceived changes in the cost/risk balance. For example, RCDs used to be rare and expensive devices and only used in the highest risk situations; then they became cheaper and regulations began to require them in more situations; then one per house became the norm, then two per house. Quite a number of houses still don't have any RCDs, and vast numbers have none on the lighting circuits for example.

In this case, it's a risk that's always been known. A short-circuit in the charging cable from the pilot signal to neutral might not trigger a standard RCD. That fault in itself is harmless, but the DC current flowing might 'blind' other RCDs so that they don't trip if another more serious fault occurs around the same time. I have not heard of any accidents actually occurring, so my guess is the regulation writers perceive that this is now cheaper to protect against and so protection should be mandated, where they previously considered it a small risk not worth the cost of preventing.

 

[LEE3]

My electrician has ‘sourced’ a type B RCD for my charger install next week and claims it has come to £600. This is just for the unit itself and does not include the associated work. I cannot find any of these Type B units costing anywhere near this price. Would anyone else know if these things can reach this sort of cost or are we having a chat with Mr installer on Monday?