Electrician help - Can 32A Circuit handle ev 6.6kw draw + freezer?

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afe66

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#223540 5-Oct-2017 08:59

I after some advice from one of our resident electricians as I dont know how house fuses work.

Last year I got a caravan plug (16A) installed to charge my Leaf on a new circuit going back to the main fuse box. (I dont know what cable was installed although I can physically look at it easily enough)

At the time I said I would might like to draw up to 6.6kw (27.5A) via a dedicated charge box later and the electrician said he would install an appropriate cable so that later he would only need to change the main fuse and install the charge box rather than crawl round under the house. At the same time I got a couple of standard domestic power points put on this circuit for future proofing and to date they are essentially unused.

The issue is we are going to move a freezer (vertical, 1.8m size of fridge) onto this circuit in the next 6 months. Im not sure how the fuses work. Will the freezer clicking on/off in addition to the 16A draw from the leaf cause the fuses to pop if I'm charging?

Down the line if I put a 32A charging box (although drawing 6.6kw/27.5A) and freezer be too much for the cable? (If yes then how much fewer amps could I draw safely)

I can look at fusebox/cables for more information if that helps.

Thanks

PhantomNVD

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#1877623 5-Oct-2017 09:14

The cable will handle it fine if the sparky DID future proof your circuit with 32A cable, and should only need to upgrade the fuse box IF it trips with the freezer load too. If your charger is (like mine) actually a converted Jap original, it actually only draws/charges at 15A anyway, so I’d personally just ‘have a go’ and plug the freezer in while charging and see how it pans out... maybe a Friday or Sat evening when you likely stay up later anyway and don’t NEED the car to be ready ASAP in the morning for work?

The worst that will happen is the freezer trips the circuit and you get the sparky out to upgrade the trip switch before you load up your freezer and depend on it.

MikeAqua

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#1877651 5-Oct-2017 09:44

The cable should have the capacity printed on it.

Mike

mclean

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#1877693 5-Oct-2017 10:22

For 27.5A I would recommend a dedicated circuit. But to answer you question you need to tell us the cable conductor size, cable length, how the cable is installed (open air or enclosed in wall insulation, etc) and the circuit breaker rating. And if you really want to draw 27.5A continuous then I would also be checking the main supply into the house.

McLean

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#1877696 5-Oct-2017 10:25

Once was a sparkie..
We did a few 32A spa pools and ALWAYS had their own 6mm2 TPS+E cable and 32A breaker. Isolated circuit when dealing with high current.

Aredwood

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#1878213 6-Oct-2017 00:02

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If that cable was rated and installed such that it could safely handle 32A - then the sparky should have just put a 32A breaker on it at the time of install. The breaker is only intended to protect the cable. If an appliance draws more current than what it's plug is rated to - then that appliance is unsafe. So no need to put a 15A breaker on the circuit just because there happens to be a 15A socket wired to it. And you wouldn't have any worry about the freezer overloading the circuit.

The freezer will probably only draw 300W while running. But refrigeration compressors are terrible for drawing large surges of power at switch on. So when the leaf has it's full load on the circuit - the freezer could easily trip the breaker - I certainly wouldn't risk it. As loosing a freezer full of food or not being able to get to work because your car didn't charge are both big problems.

Assuming those power points are in your garage - They will still be really useful for running powertools. As no problem to temporally stop charging the car when you want to use powertools.

Linuxluver

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#1878643 6-Oct-2017 19:30

Aredwood:

The freezer will probably only draw 300W while running. But refrigeration compressors are terrible for drawing large surges of power at switch on. So when the leaf has it's full load on the circuit - the freezer could easily trip the breaker - I certainly wouldn't risk it. As loosing a freezer full of food or not being able to get to work because your car didn't charge are both big problems.

I once tried to get a 700L chest freezer to work with a car inverter. The inverter absolutely could support the running power requirements of the freezer....it was the startup surge it couldn't handle.

At the time, I was told the startup surge was just at startup....and it would then use very little power ongoing. I never did get a number or feel for the recurrence of any startup surge while it was operating indefinitely.

I'd be interested to get a sense of that. May be if the "startup surge" is very infrequent (weekly? monthly?) it won't matter much if charging an EV. But if it was any more frequent than roughly every 8 hours.....they could overlap.

I don't know.

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richms

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#1878656 6-Oct-2017 20:10

Old fridges had massive start up surges, modern ones have variable speeds and things so are much nicer on inverters.

Whenever I have had things added here, tame sparky has added up everything on the circuit with some list of what each thing counted as and worked out if it was good enough or needed more.

Richard rich.ms

gregmcc

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#1878687 6-Oct-2017 21:00

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MikeAqua:

The cable should have the capacity printed on it.

Wrong... it will have it's size, capacity depends length and installation method.

Aredwood

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#1878727 6-Oct-2017 23:03

Linuxluver:

I once tried to get a 700L chest freezer to work with a car inverter. The inverter absolutely could support the running power requirements of the freezer....it was the startup surge it couldn't handle.

At the time, I was told the startup surge was just at startup....and it would then use very little power ongoing. I never did get a number or feel for the recurrence of any startup surge while it was operating indefinitely.

I'd be interested to get a sense of that. May be if the "startup surge" is very infrequent (weekly? monthly?) it won't matter much if charging an EV. But if it was any more frequent than roughly every 8 hours.....they could overlap.

I don't know.

Fridge compressors also have terrible power factors. Easily as bad as 0.5 (my own fridge measured at 0.6PF) So that 300W freezer, If you measure the current and voltage going to it and multiply them together (to get Volt Amperes) You will instead get 500 to 600VA. If your inverter was rated at say 600W, it might still be running at it's limit on a 300W load. Even ignoring startup loads. Bad power factors also have to be considered when calculating how much load an appliance will place on a cable / circuit breaker / fuse

Even with inverter type fridges, it also depends on how the inverter circuit has been designed. The simple way is just place a bridge rectifier directly across the mains input, and then a filter capacitor to get your main high voltage DC supply rail. Simple but you end up with a power factor of 0.6 Sure, active power factor correction can get you 0.99 power factor. (1 is the best power factor) But that costs more to build.

Also beware capacitive loads when trying to use inverters. Especially power factor correction capacitors. They are common in magnetic ballast fluro lights. Such capacitors will instantly destroy most electronic inverters.

Scott3

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#1883186 13-Oct-2017 22:14

Any new installation almost certainly has circuit breakers rather than fuses.

With you current situation, the 3.3kW leaf will draw something like 15A. Fridge will draw something like 1A, so you will have masses of spare capacity on a 32A breaker. Don't worry to much about start up current surges. Domestic circuit breaker have two trip modes. Fast mode is intended to cut the power in milliseconds in the event of a short circuit. It takes a few hundred amps to trip this way. Slow mode is intended to trip before your wire gets so hot it melts, or catches on fire. It won't will trip if 64A is drawn for one second, but will if it is drawn for several minutes.

The above is why people have issues starting motors on Inverters. When running on grid power, motors will draw far more than their rating while they spin up. No issues, as the even skinny wires don't have time to overheat before the draw is back to normal, so they can provide heaps more power than their rating for startup. When running on an Inverter, most can only provide double their continuous rating as a surge, This is often not enough to start big motors.

Regarding your future setup, if you have a 32A EVSE on the end of the cable, I would want this cable to be dedicated. Seems to be the convention for large draws. Don't want it to trip out if somebody comes along with a 32A rated car (Tesla, BMW i3 etc), and plugs say an incandesent desk-lamp into your three pin plug...

Note some electrical equipment is quoted in output power (such as motors), as they are not 100% efficient input power is more. No idea if the leaf charger's rating is input or output. I think they are around 95% efficient at high currents.

afe66

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#1883537 14-Oct-2017 18:57

So if I change the circuit breaker from 16 to 32A and keep the leaf limited to 16A would it be reasonable to have freezer and leaf on same circuit?

An alternative would be to see if I could use the circuit which used to supply the hot water cylinder which is nearby and was decommissioned 2 years ago to power the freezer circuit and keep the new ev line for leaf only.

A.

gregmcc

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#1883544 14-Oct-2017 19:14

afe66: So if I change the circuit breaker from 16 to 32A and keep the leaf limited to 16A would it be reasonable to have freezer and leaf on same circuit?

An alternative would be to see if I could use the circuit which used to supply the hot water cylinder which is nearby and was decommissioned 2 years ago to power the freezer circuit and keep the new ev line for leaf only.

A.

Legally you cannot do any electrical work in a switch board, like changing a circuit breaker, you need to get an electrician out to sort this out instead of taking advice from this forum. There has not been enough information posted in this thread where someone with the relevant qualifications and experience can give you a certain answer.

sparkz25

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#1883552 14-Oct-2017 19:34

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you need to check the cable size and make sure that the sparky did do what he said he did, so if he has run a 6mm cable it would be fine depending on the distance and so on, as there are a few factors that will come to play with working out what the current carrying capacity of the cable that has been installed can handle, so measure it and find out what size the cable is and get the cable calculator and enter in the info and you will be given a result,

as for the freezer i dont know where you get the idea of a surge at start up, its actually the inrush current to start the motor from a stand still, the freezer will draw 6x its rated current at start up just as any electric motor would no matter its size weather it be a 1/2 hp or a 50hp, so for a split second the inrush current would be 6A roughly if the freezer would normally draw 1A when running, but this is only for a split second so shouldn't cause any problems

afe66

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#1883648 14-Oct-2017 22:50

gregmcc:
afe66: So if I change the circuit breaker from 16 to 32A and keep the leaf limited to 16A would it be reasonable to have freezer and leaf on same circuit?

An alternative would be to see if I could use the circuit which used to supply the hot water cylinder which is nearby and was decommissioned 2 years ago to power the freezer circuit and keep the new ev line for leaf only.

A.

Legally you cannot do any electrical work in a switch board, like changing a circuit breaker, you need to get an electrician out to sort this out instead of taking advice from this forum. There has not been enough information posted in this thread where someone with the relevant qualifications and experience can give you a certain answer.

Sorry wasn't clear in my reply.

By 'I', I mean I'd get an electrician.

My DIY courage doesn't go further than wiring plugs...

Scott3

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#1888296 23-Oct-2017 22:42

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Regarding running new circuits, when the board is full,

We were short a space in the board when we installed a new circuit for oven (new induction hob required the entire 32A circuit that previously did both the hobs and oven). Sparkie just doubled up two lighting circuits on one 10A breaker. Given the general move away from incandescent lighting to more efficient halogen / LED / CFL fittings, that can be done with no nuisance tripping. Could be worth a look if you want a new dedicated circuit.