Fitting a Power Meter to a CU Part 1

[JS118m]

So that I can understand how the electrical energy that I consume is being used I want to fit one of these to my consumer unit (CU) - https://www.amazon.co.uk/EMPORIA-EN...37ML2R/ref=psdc_1938287031_t1_B00G5DZK8I?th=1 The power meter appears to be primarily produced for the USA market and its standards.

The CU is a Crabtree Starbreaker image attached/here - PXL_20211105_203526416.jpg - https://1drv.ms/u/s!AkQ39xZI1R4EkuBZw6HDW1Rud6QLbg?e=WMsdcU

The device is designed to be installed inside the consumer unit but there may be insufficient space for this so I have two sets of questions one for internal and external fitment. Other considerations i) the installation will be isolated prior to any work inside the CU using the isolator in the meter box, ii) my understanding is that this work isn’t notifiable as there are no new circuits and it doesn’t involve ‘Any addition or alteration to existing circuits in a special location’.

Internal Fitment

Is it acceptable to install such a device in the CU?

The wifi aerial may need to be fitted external to the CU, options i) mounted in a hole drilled in the CU case or ii) externally mounted to the adjacent wall with the aerial cable exiting the case via a hole/gland – are these options acceptable?

External Fitment

In this situation I would propose to bring the CT clamp leads out of the CU and mount the control box adjacent to the CU. In this situation is it necessary/appropriate to mount the control box in an enclosure? Part of the reason for this question is that the manufacturer supplied power lead appears to be single insulated which wouldn’t be acceptable without additional protection (conduit/enclosure etc).

The CT clamp lead/control box connections are 90 degrees which may make it tricky to pass 16 of them through a gland or conduit. For the gland situation I’d thought of cutting a slot lengthways to allow the cable to pass into the gland opening, is this acceptable are there any alternative options?

Power Supply

The power can be taken from an existing breaker for internal or external fitment – is this acceptable?

Fitting another breaker to provide a dedicated supply is another option but this method would I believe make this part of the work notifiable – is my understanding correct?

Many thanks

 

[Aaron b]

Cables within an enclosure with mains voltage should be rated to at least that voltage to be compliant with BS 7671. A doorbell transformer for example would either need to have cabling rated to above 230V or the transformer mounted remotely. Zappi car chargers can use a current transformer mounted over the double insulated tails. Those CT's don't look like they are rated to 230V so I don't think this system should be installed.

You are right that the cabling must be double insulated, You would need to mount the whole unit in an enclosure to protect the wires. YT3 trunking could be used to route the cables from the CTs.

 

[JS118m]

Cables within an enclosure with mains voltage should be rated to at least that voltage to be compliant with BS 7671. A doorbell transformer for example would either need to have cabling rated to above 230V or the transformer mounted remotely. Zappi car chargers can use a current transformer mounted over the double insulated tails. Those CT's don't look like they are rated to 230V so I don't think this system should be installed.

You are right that the cabling must be double insulated, You would need to mount the whole unit in an enclosure to protect the wires. YT3 trunking could be used to route the cables from the CTs.

Many thanks. I've messaged the company to determine the spec of the cables. Re the YT3 trunking are you saying that it could be possible to create a solution that uses the CT clamps even if they aren't compliant as supplied? Is there a sleeving product that could be used over the CT clamp cable that would make a compliant installation? A flexible sleeve would be easier to install than trunking..

 

[JS118m]

Possibly something like this - RS PRO Braided Acrylic Fibreglass Red Cable Sleeve, 4mm Diameter, 5m Length | RS Components - https://uk.rs-online.com/web/p/cable-sleeves/0398846

 

[Aaron b]

I don't think it would be possible to add anything to the cables that would make it compliant and with the main unit not being made to a British standard its not going to ever comply fully. Do you need to monitor each circuit? A second electricity meter could be added if you don't trust the suppliers unit. They are commonly referred to as check meters.

 

[JS118m]

I don't think it would be possible to add anything to the cables that would make it compliant and with the main unit not being made to a British standard its not going to ever comply fully. Do you need to monitor each circuit? A second electricity meter could be added if you don't trust the suppliers unit. They are commonly referred to as check meters.

Thanks again. There are two of us living in a 4000' sq ft dwelling, we use circa 7500 Kwh/year with LED lighting etc and I'm keen to know where its going so that we can reduce consumption hence the interest in the circuit level monitoring of the Emporia product.

Sorry to labour the point but if I install the control unit in a separate enclosure and the only components in the CU are the CT clamps with the addition of a sheath around their cable could this be compliant?

I’ve raised the point that you made about the cable spec with the supplier and await a response, they sell in many countries outside the USA so hopefully their cable will be okay. Your post has been very helpful.

​

 

[JS118m]

Just looked at the spec on the company website - Emporia Technical Specs - https://www.emporiaenergy.com/technical-specs#gen-2-vue The unit is certified to Energy monitor: EMCTV2 ( E506714) as per UL/IEC/EN 62368-1

Does this change the situation?
Many thanks

 

[Aaron b]

To be honest, I would generally just look for a CE mark unless I was looking for a device where I knew of a particular standard, I'm not familiar with the requirements of 62368-1. I don't think it would be likely to cause a real issue if you don't comply with the guidance on the proximity of electrical services. Most would code this a C3 on an EICR which would still be an acceptable report. Technically trunking, conduit or partition to separate the wires from the 230V wires are listed as method or compliance.

If I was doing this for my own property I would use something like 170-01012 TWIST-IN 08-PET-BK | HellermannTyton Braided PET Black Cable Sleeve, 8mm Diameter, 5m Length | RS Components - https://uk.rs-online.com/web/p/cable-sleeves/8026110 within the consumer unit to stop everything flapping about and to give some mechanical protection. Regarding the power, I would feed a fused spur from a socket circuit and change the fuse to 3A.

Have you hit the RCD test button recently? there looks like there is a lot of circuits on one.

 

[pc1966]

There are an astonishing number of circuits there for a UK domestic property! A guess is 9 RFCs and numerous others.

Personally I would look at putting it outside, and have it powered via a 13A plug or FCU with no more than a 3A fuse. Faults inside a CU are very bad news indeed!

You use is high but not really if you are using electric heating.

 

[JS118m]

There are an astonishing number of circuits there for a UK domestic property! A guess is 9 RFCs and numerous others.

Personally I would look at putting it outside, and have it powered via a 13A plug or FCU with no more than a 3A fuse. Faults inside a CU are very bad news indeed!

You use is high but not really if you are using electric heating.

Thank you for the reponse. Re the use our space heating and DHW is by gas/solar hence the desire to understand where all the eletricity is being used, if it was water I'd think there was a leak in a pipe!

For the power would it be acceptable to set up an FCU next to the CU and take a live feed from the same breaker that supplies the garage sockets? There are spare ways in the board so another option would be to fit a breaker specifically for the power meter, this approach I belive would bring the work within the scope of Part P by adding a new circuit.

There is a second CU (see image) which supplies the lighting control system this is on a different wall to the main CU. I intend to install a second power meter which will also need a power supply, is it possible to put an FCU next to this CU and take a live connection from one of the RCBOs? These RCBOs all supply lighting circuits.

THANKS

 

[brianmoooore]

Is all this fed from a single phase 'standard' 15kVA supply? If so, is the DNO fuse 80A or 100A?
If 100A, there's a real chance of those 80A RCDs being overloaded.

 

[JS118m]

Is all this fed from a single phase 'standard' 15kVA supply? If so, is the DNO fuse 80A or 100A?
If 100A, there's a real chance of those 80A RCDs being overloaded.

Thanks - I believe it's a 'standard' supply, I'm back home tomorrow and will have a look and let you know.

 

[Aaron b]

Thank you for the reponse. Re the use our space heating and DHW is by gas/solar hence the desire to understand where all the eletricity is being used, if it was water I'd think there was a leak in a pipe!

For the power would it be acceptable to set up an FCU next to the CU and take a live feed from the same breaker that supplies the garage sockets? There are spare ways in the board so another option would be to fit a breaker specifically for the power meter, this approach I belive would bring the work within the scope of Part P by adding a new circuit.

There is a second CU (see image) which supplies the lighting control system this is on a different wall to the main CU. I intend to install a second power meter which will also need a power supply, is it possible to put an FCU next to this CU and take a live connection from one of the RCBOs? These RCBOs all supply lighting circuits.

THANKS

Yes, an additional socket can be added to a ring final circuit or a radial circuit from the MCB.

 

[JS118m]

Thanks - I believe it's a 'standard' supply, I'm back home tomorrow and will have a look and let you know.

Thanks for alerting me to a potential problem, the main fuse is 80A so I guess all is fine.

 

[brianmoooore]

That raises the question as to why you have 596 amps worth of MCBs on the main fusebox, plus another 94 amps worth on the lighting box!