I have been corresponding with UKPN about the possibility of having a fuse upgrade. I must say that I am very impressed by their emails and phone calls - it's nice to deal with real people who are genuinely helpful. At the moment we have agreed that I will talk to my electrician again before he installs my new EV charger as he reckons that he can fit something so that my 60A fuse never risks a failure. UKPN have said that they can only guarantee a 60A supply in my area anyway but will do a site visit if needed. I have an OWL current monitor which shows kw but not amps. I have calculated that I can safely use 14 kw; is that correct? My voltage is 243v.
So if I stick to 14KW I don't need a new fuse
- Thread starter Vicario
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Near enough. Fuses don't blow, at exactly the stated rating, they have a time factor. The more you overload them, the sooner the blow. For a short period, your 60amp cut out fuse could probably sustain 100amps.
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What car are you planning to charge? It should charge at 20-30mph which means a full tank for most cars over night.
What other high-power electrical equipment do you have in your home?
A 60A fuse won't blow the instant you go over 60A, but running over 60A for long periods is likely to lead to failure. A cooker and a shower at max power put together are over 60A, but people rarely cook and shower at the same time showers are usually fairly short and cookers have thermostats that will make the elements cycle on and off once they get up to temperature. So overall the chances of an overload sustained long enough to blow a 60A service fuse are low.
Domestic EV chargers are normally 7KW (about 30A) which is lower than a cooker or shower. However unlike cookers and showers they can draw that current for many hours. A dumb EV charger plus an electric shower is a pretty much guaranteed recipe for an overload, perhaps the overload will be short enough not to blow the fuse but it's still something I wouldn't want to risk.
Most decent EV chargers nowadays have a "grid limit" feature which can be used to get around this problem. The EV charger is connected to a current transformer installed on the incoming connection from the grid, and if overloading of the grid connection is detected then the EV charger will reduce the current delivered to the car to get the current draw from the grid back within limits.
A 60A fuse won't blow the instant you go over 60A, but running over 60A for long periods is likely to lead to failure. A cooker and a shower at max power put together are over 60A, but people rarely cook and shower at the same time showers are usually fairly short and cookers have thermostats that will make the elements cycle on and off once they get up to temperature. So overall the chances of an overload sustained long enough to blow a 60A service fuse are low.
Domestic EV chargers are normally 7KW (about 30A) which is lower than a cooker or shower. However unlike cookers and showers they can draw that current for many hours. A dumb EV charger plus an electric shower is a pretty much guaranteed recipe for an overload, perhaps the overload will be short enough not to blow the fuse but it's still something I wouldn't want to risk.
Most decent EV chargers nowadays have a "grid limit" feature which can be used to get around this problem. The EV charger is connected to a current transformer installed on the incoming connection from the grid, and if overloading of the grid connection is detected then the EV charger will reduce the current delivered to the car to get the current draw from the grid back within limits.
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I still can't get my head around the phrase 'we only guarantee 60A per connection in your area' which has been quoted twice now by UKPN. I suppose they need to measure the total load and then make sure that their fuse (in the substation) won't blow. There are a lot of EV chargers being installed in my area too and I think that the electrician has to notify the DNO.
My electrician has said that he can set the charger to draw 16A or alternatively fit a device that measures the entire house's draw and calibrate accordingly whilst having the 32A load most of the time. We have 9KW shower which we wouldn't use when charging the car, so that sounds promising. Is that just a clip onto the live tail? My OWL clip is already there so would the two conflict?
We are looking to get a CorsaE or a Nissan Note, or possibly a Kia. A hybrid is also a possibility.
My electrician has said that he can set the charger to draw 16A or alternatively fit a device that measures the entire house's draw and calibrate accordingly whilst having the 32A load most of the time. We have 9KW shower which we wouldn't use when charging the car, so that sounds promising. Is that just a clip onto the live tail? My OWL clip is already there so would the two conflict?
We are looking to get a CorsaE or a Nissan Note, or possibly a Kia. A hybrid is also a possibility.
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You have answered your own question there - it is a local network limit. The substation, supply cables and etc. cannot sustain more than 60amps per customer.
One odd 100A, would not make much difference to the overall loading, but if everyone demanded 100A then it becomes an issue. The entire network end to end is specified for a fairly low average load and not able to support everyone trying to charge and heat their homes at the same time. As I keep predicting - there are major network capacity issues in the near future, as a result of the switch to EV's and air/ground sourced heating.
Fixing the shortfall is not going to be either a quick fix, nor a cheap one.
Yes, the lady from UKPN asked if I would be happy with 80A if they agreed to an upgrade. What rating is the fuse fitted to new builds then? Is 60A the norm in older houses and 100 in newer ones? I have been watching You Tube channels posted by EV fitters and they always seem to work on 100A systems.
I suspect that most chargers will be used overnight and this will stress the network eventually. Plus night owls like me who have been known to have a 9KW shower at 2 a.m.
I suspect that most chargers will be used overnight and this will stress the network eventually. Plus night owls like me who have been known to have a 9KW shower at 2 a.m.
The cut-out fuse carriers are all stamped 100amp on the side, but they accept 100, 80, 60 and 40amp fuses.
If they are offering an upgrade, take it - they will be much less willing to give upgrades in the near future..
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The big thing about EV car charging is the time it is on for, you get home and you put on charge so using power at same time as cooking dinner, etc. If it went on charge at say 9 pm by that time all the heavy use has stopped.
So the charger which monitors total use will auto reduce power being drawn when rest of house needs it, but with a cold fuse adding shower and cooker etc even if over 60 amp total it is unlikely to rupture, but if fuse already hot, then more likely, so you may already be exceeding the limit from time to time, but fuse will hold as cold to start with.
However 7 kW / 230 volt = 30 amp approx, so going from 60 to 80 only 10 amp more than already used, so unlikely to be a problem.
So the charger which monitors total use will auto reduce power being drawn when rest of house needs it, but with a cold fuse adding shower and cooker etc even if over 60 amp total it is unlikely to rupture, but if fuse already hot, then more likely, so you may already be exceeding the limit from time to time, but fuse will hold as cold to start with.
However 7 kW / 230 volt = 30 amp approx, so going from 60 to 80 only 10 amp more than already used, so unlikely to be a problem.
I agree that it doesn't make a lot of sense. It's obviously ultimately down to the capabilities/capacity of their network in your area, but if they are talking 'guarantees' (presumably to everyone, not just you), the implication would seem to be that their network could support every installation in the area drawing 60A simultaneously - which I very much doubt is the case.
Kind Regards, John
It will be based on an assumption that only a few customers at any one time, will need to draw the full 60amp capability, with the rest drawing an amp of two and thus keeping the average fairly low - that's how the whole network works and in fact all supply networks, based on an average maximum load.
As you say, that's how it works, with the assumption of a remarkably low "maximum average peak load" per installation.
However, as I asked, given the above, what on earth does a "guaranteed 60A supply" mean?
Kind Regards, John
I would make a guess that means that that is their limit of the maximum average current shared with everyone on the circuit and assumes that few of them will be drawing that 60amps. A guarantee, based on an expected average if you like. If they up everyone to 100amps, possibly the average maximum will be able to increase (well it will do that anyway soon with all the EV's).
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