How to reduce mains voltage from 245 to 220V or less?

kelper · Oct 29, 2019

My all-in-one brewer has a 1500W and an 1800W element - total 3300W. My mains voltage is 245V and so this draws almost 15A!

Is there a way to drop the voltage with a solid state device that won't damage the programmer? If I could supply 220V the amps would drop below 13A.

Alex.mc · Oct 29, 2019

I'm not a sparks of course.... but I think you need something akin to this?
They isolate supply from demand and usually clean and smooth the supply for equipment that needs a stable input. There must be varying models for different appliccations if you search.

https://uk.farnell.com/schneider-el...78108378549|&CMP=KNC-GUK-GEN-SHOPPING-2070180

kelper · Oct 29, 2019

That is only rated at 40VA. I need more like 4,000VA.

SteveH · Oct 29, 2019

Personally I'd get a 16A dedicated circuit installed - if you can't easily get a cable run to your brew location you could install it elsewhere and use a temporary extension cable like:

https://www.toolstation.com/extension-lead-16a/p12236?searchstr=16A

I think any kind of step-down transformer for this amount of current is likely to be huge, very heavy and very expensive?

kelper · Oct 29, 2019

That's why I said solid state.

peebee · Oct 29, 2019

You need have no control over the voltage, it's just pumped out 'tween acceptable tolerances. A "nominal" voltage if you like.

It was lowered fairly recently to match European standards. Dropping from 240V to 230V. But nothing actually changed. The alteration just played about with the accepted tolerances and it was all a paper exercise. 245v will certainly be in the upper limits, 220V inside the lower. Equipment for the UK must be able to handle these extremes. You calculate everything for 230V (nominal) mains voltage.

kelper · Oct 29, 2019

Maybe I will just wire a 300W immersion heater in series to drop the voltage. The dissipated heat will not be wasted if I put this into my sparging heater.

SteveH · Oct 29, 2019

kelper said:
Maybe I will just wire a 300W immersion heater in series to drop the voltage. The dissipated heat will not be wasted if I put this into my sparging heater.

I don't think this will work - if you were to wire it in parallel then it'd draw the nominal 300w but in series the kettle elements will try to pull 3kw+ through it ashock1

SteveH · Oct 29, 2019

Although I guess it won't drop the full 240v in series - probably would need to know the impedance of each element to calculate the actual power dissipated but I'd worry about overheating in such a high-current application (as the current has to be the same throughout the circuit when in series)

Ghillie · Oct 29, 2019

kelper said:
My all-in-one brewer has a 1500W and an 1800W element - total 3300W. My mains voltage is 245V and so this draws almost 15A!

Is there a way to drop the voltage with a solid state device that won't damage the programmer? If I could supply 220V the amps would drop below 13A.

Erm, other way round mate...

I = P/V = 3300/245 = 13.5A

if you had 220VAC

I = P/V = 3300/220 = 15A

Voltage comes down, current goes up.

Double gang sockets are rated at 20A (not continuous). If the appliance is fused by a 13A plugtop (which it is), then the terminals won’t be overloaded for very long at all before the fuse goes, <30 minutes. Instantaneous for short circuit.

I wouldn’t have any issues running your system through a 13A plug top in a standard socket outlet - but that’s not to say you shouldn’t either. We’re talking half an Amp, so I wouldn’t loose sleep. Whatsmore is you’ll likely only use both elements to get to strike temp and then ramp to a boil, so it’s not a real prolonged period. You won’t be drawing 3300W throughout your whole brewday.

Up to you but if ever in doubt, get a spark in.

Ghillie · Oct 29, 2019

kelper said:
Maybe I will just wire a 300W immersion heater in series to drop the voltage. The dissipated heat will not be wasted if I put this into my sparging heater.

No it doesn’t work that way.

simon12 · Oct 29, 2019

What is the problem you want to solve? I am guessing it has only 1 plug for everything so you don't want to plug it into a normal socket in which case installing one of these sockets https://www.screwfix.com/p/abb-surface-socket-16a-2p-e-250v-6h-ip44/1858f and one of these plugs https://www.screwfix.com/p/abb-straight-plug-16a-2p-e-250v-6h-ip44/3967x would do the job. And like Ghillie said higher voltage lowers the amps thata why in the US they need much thicker wire in circuits to get a decent current.

Sandimas · Oct 29, 2019

You need something called a Variac to lower mains voltage, you plug it in and can reduce the output voltage via a dial. Haven't seen one for decades but looks like you can still get them.

Ghillie · Oct 29, 2019

simon12 said:
What is the problem you want to solve? I am guessing it has only 1 plug for everything so you don't want to plug it into a normal socket in which case installing one of these sockets https://www.screwfix.com/p/abb-surface-socket-16a-2p-e-250v-6h-ip44/1858f and one of these plugs https://www.screwfix.com/p/abb-straight-plug-16a-2p-e-250v-6h-ip44/3967x would do the job. And like Ghillie said higher voltage lowers the amps thata why in the US they need much thicker wire in circuits to get a decent current.

I did think about this myself @simon12, but it's not entirely kosher (although tbh I'd do it).

Those industrial sockets are unfused which is the issue, so the appliance could overload up to 32A before a trip. There's upstream protection of course from the fuse box mccb, but at 32A you're talking serious overload potential before a trip - melted flex, melted socket, etc. Short circuit protection is still there.

Back in the day, I believe you could fit the 16A industrial sockets on a ring providing the ring mccb was reduced to 20A. I believe this is now outdated.

The Baron · Oct 29, 2019

If you are brewing in say a garage it is usually a simple job to put a dedicated 16a plug ( no plastering and trying to hide the wires just tag to the wall etc)in which would solve the problem in a safer way. I personally would not risk overloading a standard 13a ring circuit but everyone to their own. What size is the all in one as a 30ltr unit normally does not have elements that high or is it a higher volume or home made one?

kelper · Oct 29, 2019

If you reduce the voltage to a resistive load, the current goes down!

15 Amps through a 13A fuse heats it to over 70C (and that was with the plug top off) and the fuse will never blow at that current. But the plastic parts of the plug start to soften and char. I shudder to think how hot it would get with the plug top on.

But I agree, my immersion heater won't take 13A. So I'll scratch that idea!

kelper · Oct 29, 2019

darrellm said:
You need something called a Variac to lower mains voltage, you plug it in and can reduce the output voltage via a dial. Haven't seen one for decades but looks like you can still get them.

I'd love a variac butit would cost £400!

kelper · Oct 29, 2019

the baron said:
If you are brewing in say a garage it is usually a simple job to put a dedicated 16a plug ( no plastering and trying to hide the wires just tag to the wall etc)in which would solve the problem in a safer way. I personally would not risk overloading a standard 13a ring circuit but everyone to their own. What size is the all in one as a 30ltr unit normally does not have elements that high or is it a higher volume or home made one?

Agreed, but an electrician suggests I would need a new consumer unit and the costs all start to add up. My brewer is 45L. Plus, my garage is 30m from the house. I'm considering external 16A socket but the walls of my house are granite and very hard to drill through.

SteveH · Oct 29, 2019

Ghillie said:
Those industrial sockets are unfused which is the issue, so the appliance could overload up to 32A before a trip. There's upstream protection of course from the fuse box mccb, but at 32A you're talking serious overload potential before a trip

I think the only safe way to do that would be to have it locally fused e.g something similar to https://www.toolstation.com/hook-up-unit/p92936

Personally I'd prefer to have that on a dedicated (16a or 20a fused) radial circuit from the consumer unit to avoid potentially tripping the existing ring, but really this is something best advised by an electrician with up-to-date knowledge of the regs.

kelper · Oct 29, 2019

I could use a 30W 2 Ohm resistor in series.

How to reduce mains voltage from 245 to 220V or less?

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