Low Mains Voltage (~190-220v) - How to resolve?

[toontoonizer]

Cable size is probably 2.5mm, as to the other items I have no idea, I'm not an electrician sadly and didn't wire it up.

I've just checked the voltage at the main house kitchen socket and the annex. Main house is 218 and the annex is 216. 2v difference. 

 

[apprentice87]

Yup understand the relationship between current, voltage and resistance but there is no excessive load in the 205v example. No kitchen appliances - a maximum load of 20amps. 

I feel like I'm missing something obvious here

I think you are... WHERE are you measuring all these voltages?? You need to be measuring them at the supply cutout, anywhere else will tell you precisely NOTHING about the supply you have.. If you have a 3 phase supply, why not just connect the submains to different phases so instead of having your 100A load on the one phase, you could have the three annexes over three phases so 33A per phase.

Without being rude, if you have a building that pulls over 100A on a single phase, it was not the greatest design the world has ever seen, and if the same genius calculated the cable sizes from the buildings to the origin of the supply, then that is your problem..

If it were me, as you are obviouly not short of a bob or two, [or dim] i would buy my own loop tester and then you could test away to your hearts content

john..

 

[apprentice87]

  57 minutes ago, toontoonizer said:
Sure, understand a thorough analysis needs to be done, but in your example, let's ignore the annex. I'm talking about voltage in the main house. For example, the voltage at the kitchen socket in the main house, which is the shortest run of cable ~5m (to th consumer unit which is 30cm from the cutout) is 205v. The mains supply would have to be less than 216 for that to be the case - and this is what we experience.

Yes, but how far is the consumer unit from where the origin of the supply, [the suppliers cutout] and what size cable is that?? Far too small i would imagine..

john...

 

[toontoonizer]

I think you are... WHERE are you measuring all these voltages?? You need to be measuring them at the supply cutout, anywhere else will tell you precisely NOTHING about the supply you have.. If you have a 3 phase supply, why not just connect the submains to different phases so instead of having your 100A load on the one phase, you could have the three annexes over three phases so 33A per phase.

Without being rude, if you have a building that pulls over 100A on a single phase, it was not the greatest design the world has ever seen, and if the same genius calculated the cable sizes from the buildings to the origin of the supply, then that is your problem..

If it were me, as you are obviouly not short of a bob or two, [or dim] i would buy my own loop tester and then you could test away to your hearts content

john..

We have a three phase supply, but only a single phase meter. We cannot currently use 3 phases - we have a meter exchange scheduled so hopefully once that goes in (supplier engineers are really picky about what they will and won't do) we will be doing exactly that. Main house on one phase, the other main annex on another phase and the final phase will have the remaining annexes, gate, lights and electric car charger. Until then however, we still have to live.

Not being rude at all, we didn't design this house, it was bought like this and we are trying to make the best of it. Completely redesigning and rewiring an old house like this is not a cheap or quick affair - not something that can be done at the moment. 

I have a clamp ammeter on the way and can start checking at the supply point as you say. 

Yes, but how far is the consumer unit from where the origin of the supply, [the suppliers cutout] and what size cable is that?? Far too small i would imagine..

john...

Consumer unit is on a board literally next to the supplier cutout. The wire indeed may not be up to spec but I wouldn't be able to say. Our meter was installed years before I was born...so that should give you some indication as to what we are dealing with. 

 

[Geoff1946]

I would say that you are very lucky to have inherited the three phase supply.

It offers alleviation to at least some of your problems and would cost you a great deal to have installed if it wasn't already there.

The choice by a previous owner to only use one phase probably dates back to when they had a few  lights and a kettle!

As for your rural supply, are you on your own transformer or do you share it?  I'm wondering if your high unbalanced load may be upsetting some voltage controls along the line.

 

[SPECIAL LOCATION]

Cable size is probably 2.5mm, as to the other items I have no idea, I'm not an electrician sadly and didn't wire it up.

Do you have any electrical certificates for any of the circuits..

e.g. 

If you had a fuse-box replaced or a new circuit added an "Electrical Installation Certificate" should have been issued by the person doing the work..

If you have had an alteration / addition to an existing circuit then a "Minor Works Certificate" should have been issued by the person doing the work..

On these certificates there should be resistance values for the Live & Earth conductors, and the cable size used for the amended circuits...

from this you can calculate the cable length...

And if you know the circuit cable length / size of cable / load on cable..

You can calculate the volt-drop from tables in the regs that give the Millivolts per Amp per Metre for the common cable sizes..

These are some of the calculations you need to do if designing a new circuit from scratch to ensure you select the correct sized cables for your loads and volt-drop.

( It would appear that some parts of your installation may have been extended over the years beyond their initial design capacity..? )

Not that it helps much.. But I do think your problems are going to become more and more common at a lot of installations as everyone is encouraged to get electric cars!!

I have a regular customer who mentioned in conversation a few weeks ago that when they change their current diesel cars they will be looking to get an electric car charger fitted..

I was thinking..  oh err..  that's going to be tricky when their existing main fuse is 60A, and they are just on the borders of the countryside also with electric under-floor heating..

It may just tip the balance on their incoming cable!! 

Back to your situation..

have you considered any solar power and/or local power storage to supplement your incoming supply..

I'm no expert.. (one of our members @binky  would have better advice)..

But if you have a fair bit of land.. and/or a few buildings..

I am guessing a few solar panels could be installed to meet a bit more of your electrical demand?

Guinness   

ALSO..

how far away..

and how big are the neighbours properties..

i.e.  what other demand is there on the supply network locally?

 

[SPECIAL LOCATION]

Just to muddy the waters a bit more...

Wiring regs expect us to design circuits to meet a 3% volt-drop on lighting circuits

and a 5% volt drop on other circuits..

This is respect to the nominal voltage (230v)..

Which is 6.9v for lights  or 11.5v for other circuits..

Now if your circuits are on the limit of acceptable volt-drop..

But your supply has dropped to the lower limit of supply voltage..

216.2v-6.9v = 209.1v

or

216.2v-11.5v = 204.7v

make of that what you will in relation to voltages you have measured..

But maybe why the DNO haven't panicked so far!

 

[Murdoch]

Step 1 - do nothing until the 3 phase is up and running - make sure you have 3 meters and isolators fitted by the supplier

Step 2 - get a spark to separate out the 2 annexes onto separate phases

Step 3 - get spark to do tests on each of the installations

Also 13A sockets are unsuitable for car charging - so where do you plan to add a proper EV charger?#

PS maybe I missed this, but what are you using to do the voltage tests with?

 

[toontoonizer]

Do you have any electrical certificates for any of the circuits..

e.g. 

If you had a fuse-box replaced or a new circuit added an "Electrical Installation Certificate" should have been issued by the person doing the work..

If you have had an alteration / addition to an existing circuit then a "Minor Works Certificate" should have been issued by the person doing the work..

On these certificates there should be resistance values for the Live & Earth conductors, and the cable size used for the amended circuits...

from this you can calculate the cable length...

And if you know the circuit cable length / size of cable / load on cable..

You can calculate the volt-drop from tables in the regs that give the Millivolts per Amp per Metre for the common cable sizes..

These are some of the calculations you need to do if designing a new circuit from scratch to ensure you select the correct sized cables for your loads and volt-drop.

( It would appear that some parts of your installation may have been extended over the years beyond their initial design capacity..? )

Not that it helps much.. But I do think your problems are going to become more and more common at a lot of installations as everyone is encouraged to get electric cars!!

I have a regular customer who mentioned in conversation a few weeks ago that when they change their current diesel cars they will be looking to get an electric car charger fitted..

I was thinking..  oh err..  that's going to be tricky when their existing main fuse is 60A, and they are just on the borders of the countryside also with electric under-floor heating..

It may just tip the balance on their incoming cable!! 

Back to your situation..

have you considered any solar power and/or local power storage to supplement your incoming supply..

I'm no expert.. (one of our members @binky  would have better advice)..

But if you have a fair bit of land.. and/or a few buildings..

I am guessing a few solar panels could be installed to meet a bit more of your electrical demand?

Guinness   

ALSO..

how far away..

and how big are the neighbours properties..

i.e.  what other demand is there on the supply network locally?

Ha electrical certificates? No idea where those would be. If they didn't come with the house when we bought it then they don't exist.

Solar panels would help and probably in the future we will utilise some kind of solar/battery solution. 

Neighbour houses are the same size.. i.e. large, multiple annexes - some are farms. In terms of how far away..it's a long road but with very few houses. The last DNO engineer that came did mentioned that our house was the last on the end of a run. And well, that's why we get the lettuced volts. 

Just to muddy the waters a bit more...

Wiring regs expect us to design circuits to meet a 3% volt-drop on lighting circuits

and a 5% volt drop on other circuits..

This is respect to the nominal voltage (230v)..

Which is 6.9v for lights  or 11.5v for other circuits..

Now if your circuits are on the limit of acceptable volt-drop..

But your supply has dropped to the lower limit of supply voltage..

216.2v-6.9v = 209.1v

or

216.2v-11.5v = 204.7v

make of that what you will in relation to voltages you have measured..

But maybe why the DNO haven't panicked so far!

Perhaps indeed. 

Step 1 - do nothing until the 3 phase is up and running - make sure you have 3 meters and isolators fitted by the supplier

Step 2 - get a spark to separate out the 2 annexes onto separate phases

Step 3 - get spark to do tests on each of the installations

Also 13A sockets are unsuitable for car charging - so where do you plan to add a proper EV charger?#

PS maybe I missed this, but what are you using to do the voltage tests with?

3 meters? Isnt it just one 3 phase meter with a 3 phase isolator. The car is currently charged via 10amp 3pin plug. But the dedicated charge point would go on the spare phase of the 3 phase:

Phase 1: main house

Phase 2: upgraded annex

Phase 3: shed/annex, gate, driveway lighting, car charger. 

I'm using the uninterruptible power supplies I have - they display the input voltage at any given moment. 

 

[Murdoch]

I'm using the uninterruptible power supplies I have - they display the input voltage at any given moment. 

Ok - I think you need a local competent spark onsite to work with you.........

 

[Murdoch]

The car is currently charged via 10amp 3pin plug. But the dedicated charge point would go on the spare phase of the 3 phase:

Standard 13A sockets are unsuitable for EV chargers according to BS 7671

 

[toontoonizer]

Ok - I think you need a local competent spark onsite to work with you.........

Yeah I've spoken to a couple...I've not heard anything back after promising to send me quotes. So...not very professional or they just don't want to do the work.

Standard 13A sockets are unsuitable for EV chargers according to BS 7671

I think there might be a misunderstanding - there's no charger, it's just a cable which plugs directly in to the car and then directly to the socket. Nothing in between - it's designed to be used in a standard socket - that is its entire purpose.

Anyway, I can't charge the car on our current supply because it's too low and the car doesn't charge. So that's a major inconvenience. 

 

[Murdoch]

I think there might be a misunderstanding - there's no charger, it's just a cable which plugs directly in to the car and then directly to the socket. Nothing in between - it's designed to be used in a standard socket - that is its entire purpose.

BS 7671 suggests that standard 13A sockets should not be used to charging cars - which you will quite rightly think is MAD, seeing as most cars come with a "granny" changer but the numpties who write BS 7671 have declared standard 13A sockets in appropriate

 

[Sidney]

Putting the separate buildings on their own phases would not solve the problem IMHO. I would be looking at 3 phase for each installation and trying to balance as best as possible.

 

[toontoonizer]

BS 7671 suggests that standard 13A sockets should not be used to charging cars - which you will quite rightly think is MAD, seeing as most cars come with a "granny" changer but the numpties who write BS 7671 have declared standard 13A sockets in appropriate

Fair enough - at 10amps the car uses the same as a 2kw oil heater when it's charging!

Putting the separate buildings on their own phases would not solve the problem IMHO. I would be looking at 3 phase for each installation and trying to balance as best as possible.

I am inclined to agree with you that we would ideally have a fully distributed 3 phase supply across the whole installation which should address the issue. However, that would be a hugely significant investment that would require a lot of digging cabling and rewiring - not something feasible right now. 

We have to take it in steps - while having each building on its own phase may not fully address the issue, it will at least (hopefully) alleviate the issue to the point where it is not noticeable. 

 

[binky]

have you considered any solar power and/or local power storage to supplement your incoming supply..

I'm no expert.. (one of our members @binky  would have better advice)..

But if you have a fair bit of land.. and/or a few buildings..

I am guessing a few solar panels could be installed to meet a bit more of your electrical demand?

Sounds like you are just in an unfortunate location, or possibly the local transformer has a 'sticky tap' - they are supposed to alter voltages in line wth demand. But you've already had a data survey and this should have been shown by that.

Adding a large solar array may help as this will reduce the load on your supply, plus solar inverters are 'grid tied' and output a higher voltage than the grid, so, for example if the grid is at 240V they will output 245V so that you use energy from the solar array first (think of it as being like water at 2 levels, water from the higher level will always flow first). Now the down side of being grid tied is that if the grid voltage drops below an acceptanle level, the inverter shuts down, so a solar array may turn out to be an expensive frustration rather than helpful. From what has been discussed above, getting the 3 phase connected sounds like it would sort out most of your issues. However if you do have a large energy demand, then green tech may prove useful. Since the removal of the Feed in Tariff, only people with high energy demands get a decent payabck on going green. The aim being to put a large hole in your bills rather than meet full demand. By doing this every kWh you generate is worth the cost of buying electric from the grid, ie about 15/16p per kWh, so payback on the system would probably be around 6-8 years. Given you have so much land, a small wind turbine may prove useful as this will work through the night / windy winter months helping meet your demands 24/7 - bear in mind wind turbines have moving parts that wear out, so I'm not sure what the lifespan is. Solar panels will last about 30-40 years, the inverters around 15-20 years. A combination of wind and solar may be good for you? 

Now, one thing about solar, provided you aren't trying to export more than 16A per phase, is this may force the DNO to upgrade the local transformer, which sounds like it is not man enough for the job. This will cost you nothing if you maintain the 16A per phase limitation, the legal position is that you can install a system that complies with this limitation and it is upto the DNO to provide a suitable connection, and if that means upgrading the transformer that will be at their cost. A quick look at my fave wholesaler would suggest you could have something like 15-20kW on an inverter designed to do that. Some inverters also have the ability to maintain power to prime ccts eg your fridge / freezer, like wise battery packs. not sure I would go with batteries, your electric car already has a huge battery that will soak up a lot of 'spare electric' if you have it plugged in at the right time - some inverters are designed with a car charging facility.

Given that any money in a savings account is earning diddly squat these days, going green may well suite your needs financially, as well as help with the voltage drop, but I think I would persue the 3 phase first and go green second

 

[Murdoch]

Fair enough - at 10amps the car uses the same as a 2kw oil heater when it's charging!

I tend to agree with you but 

722.55.101.0.201.1 says we are both wrong

 

[Andy™]

I tend to agree with you but 

722.55.101.0.201.1 says we are both wrong

yep, its madness

 

[NozSpark]

BS 7671 suggests that standard 13A sockets should not be used to charging cars - which you will quite rightly think is MAD, seeing as most cars come with a "granny" changer but the numpties who write BS 7671 have declared standard 13A sockets in appropriate

I'm just reading through the "Electric Vehicle Charging Equipment Installation" COP and it says that you can use a standard socket, but that you have to be very careful about it siting and it's earthing arrangements, so it needs to be installed correctly, and it needs to designated for EV charging equipment

 

[Murdoch]

yep, its madness

How the authors of BS 7671 decide on what to put in and how to word it is beyond me.

I'm just reading through the "Electric Vehicle Charging Equipment Installation" COP and it says that you can use a standard socket, but that you have to be very careful about it siting and it's earthing arrangements, so it needs to be installed correctly, and it needs to designated for EV charging equipment

So if you have a EV, do you need to tell the owner to carry around the bits to add TT earths?

Nonsense .......